Engine Lubrication

Engine Technology & Lubrication

1SEHAM MANSOUR

Engine TechnologyAnengineormotoris amachinedesigned to convertenergyinto usefulmechanical motion.Heat engines, includinginternal combustion enginesandexternal combustion engines(such assteam engines) burn afuelto createheat, which then creates motion.Electric motorsconvert electrical energy intomechanical motion.Pneumatic motorconverts potential energy in the form ofcompressed airintomechanical work2

Evolution of Engine

Model of the Barsanti-Matteucci engine (1853) in theOsservatorio Ximenianoin FlorenceEarly internal combustion engines were used to power farm equipment similar to these models.This internal combustion engine was an integral aspect of the patent for the first patented automobile, made by Karl Benz on January 29, 18863

Evolution of EngineA brief outline of the history of the internal combustion engine includes the following highlights:1680- Dutch physicist,Christian Huygensdesigned (but never built) an internal combustion engine that was to be fueled with gunpowder.1807- Francois Isaac de Rivaz of Switzerland invented an internal combustion engine that used a mixture of hydrogen and oxygen for fuel. Rivaz designed a car for his engine - the first internal combustion powered automobile. However, his was a very unsuccessful design.1824- English engineer, Samuel Brown adapted an old Newcomen steam engine to burn gas, and he used it to briefly power a vehicle up Shooter's Hill in London.

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Evolution of Engine1858-Belgian-bornengineer,Jean Joseph tienne Lenoir invented and patented (1860) a double-acting, electric spark-ignition internal combustion engine fueled by coal gas.In 1863,Lenoir attached an improved engine (using petroleum and a primitive carburetor) to a three-wheeled wagon that managed to complete an historic fifty-mile road trip.1862- Alphonse Beau de Rochas, a Frenchcivil engineer, patented but did not build a four-stroke engine (French patent #52,593, January 16, 1862).1864-Austrian engineer,Siegfried Marcus, built a one-cylinder engine with a crude carburetor, and attached his engine to a cart for a rocky 500-foot drive. Several years later, Marcus designed a vehicle that briefly ran at 10 mph that a few historians have considered as the forerunner of the modern automobile by being the world's first gasoline-powered vehicle.

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Evolution of Engine1873- George Brayton, an American engineer, developed an unsuccessful two-stroke kerosene engine (it used two external pumping cylinders). However, it was considered the firstsafe and practical oil engine.1866- German engineers, Eugen Langen and Nikolaus August Otto improved on Lenoir's and de Rochas' designs and invented a more efficient gas engine.1876- Nikolaus August Otto invented and later patented a successful four-stroke engine, known as the "Otto cycle".1876- The first successful two-stroke engine was invented by Sir Dougald Clerk.1883 -French engineer, Edouard Delamare-Debouteville, built a single-cylinder four-stroke engine that ran on stove gas. It is not certain if he did indeed build a car, however, Delamare-Debouteville's designs were very advanced for the time - ahead of both Daimler and Benz in some ways at least on paper.

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Evolution of Engine1885- Gottlieb Daimler invented what is often recognized as the prototype of the modern gas engine - with a vertical cylinder, and with gasoline injected through a carburetor (patented in 1887). Daimler first built a two-wheeled vehicle the "Reitwagen" (Riding Carriage) with this engine and a year later built the world's first four-wheeled motor vehicle.1886- On January 29, Karl Benz received the first patent (DRP No. 37435) for a gas-fueled car.1889- Daimler built an improved four-stroke engine with mushroom-shaped valves and two V-slant cylinders.1890-Wilhelm Maybach built the first four-cylinder, four-stroke engine.

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Evolution of Engine1975 - Catalytic converters, unleaded fuelDetroit forced to buy technologyMore aromatics (e.g., benzene) in gasoline - high octane but carcinogenic, soot-producing1980s - Microcomputer control of enginesTailor operation for best emissions, efficiency, ...1990s - Reformulated gasolineReduced need for aromatics, cleaner(?)... but higher cost, lower miles per gallonThen we found that MTBE pollutes groundwater!!!Alternative oxygenated fuel additive - ethanol - very attractive to powerful senators from farm states

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Evolution of Engine2000s - hybrid vehiclesUse small gasoline engine operating at maximum power (most efficient way to operate) or turned off if not neededUse generator/batteries/motors to make/store/use surplus power from gasoline engineMore efficient, but much more equipment on board - not clear if fuel savings justify extra cost Plug-in hybrid: half-way between conventional hybrid and electric vehicleRecent study in a major consumer magazine: only 1 of 7 hybrids tested show a cost benefit over a 5 year ownership period if tax incentives removed

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Types of EnginesThough engines vary in design, but certain elements are common to all engines and are used for engine classification. Engines can be classified in several ways such as the number of cylinders, the geometry of the block, or type of ignition system used.The two major engine types in use are spark ignition (gasoline engine) and compression ignition (diesel engine) which use different types of fuel.10

Types of EnginesInternal Combustion Engines:Theinternal combustion engineis an engine in which thecombustionof a fuel (generally,fossil fuel) occurs with an oxidizer (usually air) in acombustion chamber. In an internal combustion engine the expansion of the hightemperatureand highpressuregases, which are produced by the combustion, directly appliesforceto components of the engine, such as the pistons or turbine bladesor anozzle, and by moving it over a distance, generates useful mechanicalenergy.11

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Internal Combustion Engines

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Types of EnginesExternal Combustion Engines:Anexternal combustion engineis aheat enginewhere an internal workingfluidis heated by combustion of an external source, through the engine wall or aheat exchanger. Thefluidthen, by expanding and acting on the mechanismof the engine produces motion and usablework.The fluid is then cooled, compressed and reused (closed cycle), or (less commonly) dumped, and cool fluid pulled in (open cycle air engine).13

External Combustion Engines

precursor of thesteam engine, with the boiler heated from beneath14

Classification of EnginesThere are different types of car engines and they can be classified according to:Type of FuelIgnition SystemBlock Geometry or Cylinder ArrangementNumber of CylindersStrokes per CycleCombustion ChamberCamshaft LocationCooling System15

Classification of EnginesType of Fuel:The most common classification of an engine could be done on the basis of the fuel which it runs on. The two types of fuels that engines use to convert energy to mechanical work are gasoline and diesel oil. Recently a number of alternate fuels like electricity, ethanol, methanol, hydrogen, propane and natural gas are being considered due to the rising prices of gasoline and diesel, however they are used in very limited situations.

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Classification of EnginesIgnition System:The term ignition relates to the medium by which the fuel is converted to energy. There are two ways by which the fuel is ignited inside the automobile engine, spark ignition and compression ignition. Gasoline engines use spark ignition while diesel engines use compression ignition.

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For gasoline and gas engines, the fire source for the combustion is spark plug therefore it is called spark ignition. For diesel engine the combustion is initiated by high temperature and pressure generated from the compressed air.

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Classification of EnginesBlock Geometry or Cylinder Arrangement:The cylinders of a car are arranged in the following ways: V type, inline horizontally opposed and slant In the case of an inline engine the cylinders are arranged in a row.In the V type the cylinders form two angled rows to form a V.In the horizontally opposed engine the cylinders are horizontal and opposing each otherIn the case of the horizontally slant engine the cylinders are arranged in a single row forming half a V.18

Cylinder Arrangement

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Classification of EnginesNumber of Cylinders:The number of cylinders in a car range from 3 to 12. The number of cylinders indicate how the smooth running of the car. The more the number of cylinders the smoother the car runs. A car that has 5 cylinders will run with more ease than a car with 3 cylinders. The number of cylinders also contributes to the amount power output; more cylinders, more power. However, this is not always a good indicator of power output. A turbocharged, four-cylinder engine can produce more power than a normally aspirated six-cylinder engine.20

Classification of EnginesStrokes per Cycle:Strokes per cycle are the number of times the pistons travel up and down during one cycle. Modern engines have four strokes per cycle: intake, compression, power, and exhaust. Two-stroke engines are not used due to their poor power output at low rpm, motor oil mixed with the fuel, less fuel efficient, generate an unacceptable amount of pollution, and require more maintenance.21

Strokes per CycleFour-stroke cycle used in gasoline/petrol engines.1- Intake,2- Compression,3- Power,4- Exhaust. The right blue side is the intake and the left brown side is the exhaust. The cylinder wall is a thin sleeve surrounded by cooling liquid.

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Strokes per CycleAtwo-stroke, ortwo-cycle,engineis a type ofinternal combustion enginewhich completes a power cycle in only one crankshaft revolution and with two strokes, or up and down movements, of thepistonin comparison to a "four-stroke engine", which uses four strokes

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Classification of EnginesCombustion Chamber:There are mainly 3 shapes of combustion chambers that are used in an engine: hemispherical, wedge, and pancake. The hemispherical shape is the most common out of all. The hemispherical, also called "hemi-head," is designed with the intake and exhaust valves angled and opposing each other. In the wedge shape the valves are side by side and slightly angled.In the pancake shape the valves are vertical.24

Combustion Chamber

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Classification of EnginesCamshaft Location:The camshaft in generally located in the cylinders head or engine block. Car engines which have the camshaft located in the cylinders head are called overhead cam (OHC) engine. There are two types of overhead cams engines, they are: Dual overhead cam and Single overhead cam. A dual overhead cam (DOHC) engine uses two camshafts, one for the intake valves and the other for the exhaust valves. Single overhead cam (SOHC) engines use one cam for both the intake and exhaust valves. Engines with the camshaft in the block make use of push rods to move the valves.26

Camshaft Location

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Classification of EnginesCooling System:Car engines could be liquid cooled or air cooled. Without a cooling system, car engines will quickly destroy themselves due to extreme temperatures. Air cooled engines have cooling fins surrounding the cylinders which carry away the heat which surrounds the cylinders. Liquid cooled engines are incorporated with water jackets in the cylinder block or cylinder head through which the coolant circulates and does away with the heat. Liquid cooled engines are more widely used in the modern day.28

Cooling System

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Main Components of Reciprocating Internal Combustion Engine

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Carburetor

A carburetor is a device that blends air and fuel for an internal combustion engine.31

Spark Plug

Automobile spark plug: electric part generating sparks to ignite an internal combustion engine.Ceramic insulator: pottery support for the parts that conduct electricity.Terminal: place where a current-conducting wire is attached.Spline: hollow channel.Resistance: device that controls the strength of the current.Ground electrode: current device that unites the electrodes.Spark plug gap: space separating the current conductors.Center electrode: central current conductor.Gasket: spot where two part join together.Spark plug body: metal part of the spark plug.Hex nut: hexagonal piece of metal used to screw in a spark plug.32

ValvesThe intake and exhaust valves open at the proper time to let in air and fuel and to let out exhaust. Note that both valves are closed during compression and combustion so that the combustion chamber is sealed.

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PistonA piston is a cylindrical piece of metal that moves up and down inside the cylinder.

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Types of Piston

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Piston Rings1. Piston rings provide a sliding seal between the outer edge of the piston and the inner edge of the cylinder. The rings serve two purposes:2. They prevent the fuel/air mixture and exhaust in the combustion chamber from leaking into the sump during compression and combustion.3. They keep oil in the sump from leaking into the combustion area, where it would be burned and lost.4. Most cars that "burn oil" and have to have a quart added every 1,000 miles are burning it because the engine is old and the rings no longer seal things properly.

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The piston rings serve three main purposes: Firstly, the top rings seal the combustion chamber to stop combustion gases passing down the side of the piston into the crankcase. These rings are called compression rings and can be two or more. Secondly, they transfer heat from the piston to the cylinder walls. Thirdly, the bottom ring controls the flow of oil from moving up the cylinder wall. This ring is usually called the oil ring.

The piston rings serve three main purposes: Firstly, the top rings seal the combustion chamber to stop combustion gases passing down the side of the piston into the crankcase. These rings are called compression rings and can be two or more. Secondly, they transfer heat from the piston to the cylinder walls. Thirdly, the bottom ring controls the flow of oil from moving up the cylinder wall. This ring is usually called the oil ring.

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Connecting RodThe connecting rod connects the piston to the crankshaft. It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates.

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Crankshaft

The crankshaft turns the piston's up and down motion into circular motion just like a crank on a jack-in-the-box does.

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Sump

The sump surrounds the crankshaft. It contains some amount of oil, which collects in the bottom of the sump (the oil pan).

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Engine OperationThe piston starts at the top, the intake valve opens, and the piston moves down to let the engine take in a cylinder-full of air and gasoline. This is the intake stroke. Only the tiniest drop of gasoline needs to be mixed into the air for this to work. (Part 1 of the figure) Then the piston moves back up to compress this fuel/air mixture. Compression makes the explosion more powerful. (Part 2 of the figure) When the piston reaches the top of its stroke, the spark plug emits a spark to ignite the gasoline. The gasoline charge in the cylinder explodes, driving the piston down. (Part 3 of the figure) Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tailpipe. (Part 4 of the figure) In an engine the linear motion of the pistons is converted into rotational motion by the crankshaft. The rotational motion is required because we plan to turn (rotate) the car's wheels with it.

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Engine Operation

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Conditions in Piston Ring Zone

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Engine Valve TrainThe valve train consists of the valves and a mechanism that opens and closes them. The opening and closing system is called a camshaft. The camshaft has lobes on it that move the valves up and down. This is a critical job, and can have a great impact on an engine's performance at different speeds.

Most modern engines have what are called overhead cams. This means that the camshaft is located above the valves, as you see in the Figure. The cams on the shaft activate the valves directly or through a very short linkage.43

On single and double overhead cam engines, the cams are driven by the crankshaft, via either a belt or chain called the timing belt or timing chain. These belts and chains need to be replaced or adjusted at regular intervals. If a timing belt breaks, the cam will stop spinning and the piston could hit the open valves.

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Double Overhead Cam in Pushrod Engine

two cams per headmore intake and exhaust valvesintake and exhaust gases can flow more freelyincreases the power of the enginethe camshaft on a pushrod engine is inside the engine blockthe speed of pushrod engines is limitedoften driven by gears or a short chain44

Cylinder LinerThe cylinder, or liner, has a microscopic film of oil that allows the piston to travel up and down freely. The combustion byproducts, or exhaust emissions, collect on this film of oil

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Exhaust EmissionIn addition to the emission deposits being carried into the oil, the oil on the liner that is exposed to the combustion flame ignites as well, contributing to the exhaust emissions and oil contamination

Oil on the cylinder burns and becomes part of emissionOil burns on every combustion cycle of the engine. 46

Blow-by Phenomenon of an EngineInternal oil leak (blow-by) will result in BLUE SMOKE at the tale pipe.

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Blow-by Phenomenon of an Engine

Blow-byoccurs when the explosion that occurs in your engines combustion chamber causes fuel, air and moisture to be forced past the rings into the crankcase.Engines rings must be maintained in an excellent fit in order to contain the pressure.The causes of blow-by: wear, soot and depositsThe effects of blow-by: loss of horsepower and oil contamination and dilution.Among the many gasses in your compression chamber are unburned fuel, moisture, sulfur dioxide and soot. Once these gasses slip into your crankcase they can dilute into your engine causing great damage.The detergents and Molybdenum Disulfide work together to clean the soot and deposits off of your rings allowing them to better seal the combustion chamber.

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Blow-by inhibits performance because it results in a loss of compression. When the expanding gases slip past the rings they cannot as effectively push the piston down and make the vehicle go. As a result the car will have less horsepower. This also results in a loss of fuel economy.48

Piston Rings Assembly

Only a small amount of lubricant gets past the oil control ring to lubricate the compression ring. Once it stays there for many cycles, being exposed to high temperatures and exhaust gases before returning to the sump, or going up into the combustion chamber where it is lost out of the exhaust.

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Key Temperature Readings

Temperature levelat designated spots ?

120 - 140 C1000 C270 - 300 C300 - 350 C110 - 150 C150 - 170 C300 - 350 C800 C

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Bearings in IC Engine

In apiston engine, themain bearings are the bearings on which the crankshaft rotates, usuallyplainorjournal bearings51

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IC Engine Family Tree

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Aramjet, sometimes referred to as aflying stovepipeor anathodydis a form ofair-breathing jet enginethat uses the engine's forward motion to compress incoming air without a rotary compressor.52

Ramjet EngineAramjet, sometimes referred to as aflying stovepipeis a form ofair-breathing jet enginethat uses the engine's forward motion to compress incoming air without a rotary compressor.A diffuser, a combustion chamber, and an exhaust nozzle.Most suitable for supersonic speeds.Compression by ram effect.Fuel injection into compressed flow - flame holders to stabilize flame.Combustion gases expand to high velocity in thenozzle.53

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Ramjet Engine

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Chemical Rockets

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Chemical Rockets

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Largest internal combustion engineWartsila-Sulzer RTA96-C turbocharged two-stroke diesel, built in Finland, used in container ships14 cylinder version: weight 2300 tons; length 89 feet; height 44 feet; max. power 108,920 hp @ 102 rpm; max. torque 5,608,312 ft lb @ 102 RPMPower/weight = 0.024 hp/lbAlso one of the most efficient IC engines: 51%

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Most powerful internal combustion engineWartsila-Sulzer RTA96-C is the largest IC engine, but the Space Shuttle Solid Rocket Boosters are the most powerful ( 42 million horsepower (32 hp/lb); not shaft power but kinetic energy of exhaust stream)Most powerful shaft-power engine: Siemens SGT5-8000H stationary gas turbine (340 MW = 456,000 HP) (0.52 hp/lb) used for electrical power generation

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Smallest internal combustion engineCox Tee Dee 010Application: model airplanesWeight: 0.49 oz.Displacement: 0.00997 in3(0.163 cm3)RPM: 30,000Power:5 wattsIgnition:Glow plugTypical fuel: castor oil (10 - 20%), nitromethane (0 - 50%), balance methanolGood power/weight (0.22 hp/lb) but poor performanceLow efficiency (< 5%)Emissions & noise unacceptable for many applications

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Gasoline or Petrol EngineAgasoline or petrol engine is aninternal combustion engine withspark-ignition, designed to run on petrol (gasoline) and similar volatile fuels. It was invented in 1876 in Germany by German inventorNikolaus August Otto.

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Applications of Gasoline EngineGasoline engines can be built to meet the requirements of practically any conceivable power-plant application, the most important being passengerautomobiles, smalltrucksand buses, general aviation aircraft, outboard and small inboard marine units, moderate-sized stationary pumping, lighting plants, machine tools, and power tools. Four-stroke gasoline engines power the vast majority ofautomobiles, lighttrucks, medium-to-large motorcycles, and lawn mowers.Two-stroke gasoline engines are less common, but they are used for small outboard marine engines and in many handheld landscaping tools such as chain saws, hedge trimmers, and leaf blowers.61

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Types of Gasoline EngineGasoline engines can be grouped into a number of types depending on several criteria, including their application, method of fuel management, ignition, piston-and-cylinder or rotor arrangement, strokes per cycle, cooling system, and valve type and location.Two basicgasoline engine types include: Piston-and-Cylinder engines Four-stroke CycleTwo-stroke CycleRotary or Wankel engines62

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Piston-and-Cylinder EngineMost gasoline engines are of thereciprocating piston-and-cylinder type. The essential components of thepiston-and-cylinderengine are shown in thefigure. Almost all engines of this type follow either the four-stroke cycle or the two-stroke cycle.

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Four-Stroke CycleOf the different techniques for recovering the power from the combustion process, the most important so far has been thefour-stroke cycle, a conception first developed in the late 19th century.The four-stroke approach is also known as theOtto cycle, in honor of Nikolaus Otto, who invented it in 1867.Each combustion cycle requires four strokes of the piston intake, compression, power, and exhaustand two revolutions of the crankshaft to convert gasoline into motion.

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Four-Stroke SI Operating CycleIntake stroke: starts with piston at TC and endswith piston BC, which draw fresh mixture intocylinder. To increase mass inducted, inlet valveopens shortly before stroke starts and closes afterit ends.Compression stroke: both valves are closed andthe mixture inside the cylinder is compressed toa small fraction of its initial volume. Toward theend of the compression stroke, combustion is initiatedand the cylinder pressure rises more rapidly.

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Four-Stroke SI Operating CyclePower stroke: or expansion stroke:- starts with the piston at TC and ends at BCas the high-temp., high-pressure, gases pushthe piston down and force the crank to rotate.- About five times as much work is done onthe piston during the power stroke as the pistonhad to do during compression.- As the piston approaches BC the exhaustvalve opens to initiate the exhaust processand drop the cylinder pressure to close to theexhaust pressure.

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Four-Stroke SI Operating CycleExhaust stroke: where the remaining burned gasesexit the cylinder:- first, because the cylinder pressure may besubstantially higher than the exhaust pressure;- then as they are swept out by the piston as itmoves toward TC.- As the piston approaches TC the inlet valveopens. Just after TC the exhaust valve closesand the cycle starts again.

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Four-Stroke SI Operating Cycle

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Disadvantage of Four-Stroke CycleA disadvantage of the four-stroke cycle is that only half as many power strokes are completed as in the two-stroke cycle (see below) and only half as much power can be expected from an engine of a given size at a given operating speed. The four-stroke cycle, however, provides more positive clearing out of exhaust gases (scavenging) and reloading of the cylinders, reducing the loss of fresh charge to the exhaust.

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Main Components of 4-Stroke Engine

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Main Components of 4-Stroke EngineEngine components shown in earlier slide are defined as follows: Block : Body of the engine containing cylinders, made of cast iron or aluminium.Cylinder : The circular cylinders in the engine block in which the pistons reciprocate back and forth.Head : The piece which closes the end of the cylinders, usually containing part of the clearance volume of the combustion chamber.Combustion chamber: The end of the cylinder between the head and the piston face where combustion occurs.The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC.

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Main Components of 4-Stroke EngineCrankshaft : Rotating shaft through which engine work output is supplied to external systems. The crankshaft is connected to the engine block with the main bearings.It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft, offset from the axis of rotation. This offset is sometimes called crank throw or crank radius.Connecting rod : Rod connecting the piston with the rotating crankshaft, usually made of steel or alloy forging in most engines but may be aluminum in some small engines. Piston rings: Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls.

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Main Components of 4-Stroke EngineCamshaft : Rotating shaft used to push open valves at the proper time in the engine cycle, either directly or through mechanical or hydraulic linkage (push rods, rocker arms, tappets) .Push rods : The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase.Crankcase : Part of the engine block surrounding the crankshaft.In many engines the oil pan makes up part of the crankcase housing.Exhaust manifold : Piping system which carries exhaust gases away from the engine cylinders, usually made of cast iron .

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Main Components of 4-Stroke EngineIntake manifold :Piping system which delivers incoming air to the cylinders, usually made of cast metal, plastic, or composite material.In most SI engines, fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor.The individual pipe to a single cylinder is called runner.Carburetor : A device which meters the proper amount of fuel into the air flow by means of pressure differential.For many decades it was the basic fuel metering system on all automobile (and other) engines.Spark plug : Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap.

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Accessories of 4-Stroke EngineExhaust System: Flow system for removing exhaust gases from the cylinders, treating them, and exhausting them to the surroundings.It consists of an exhaust manifold which carries the exhaust gases away from the engine, a thermal or catalytic converter to reduce emissions, a muffler to reduce engine noise, and a tailpipe to carry the exhaust gases away from the passenger compartment.Flywheel : Rotating mass with a large moment of inertia connected to the crank shaft of the engine.The purpose of the flywheel is to store energy and furnish large angular momentum that keeps the engine rotating between power strokes and smoothes out engine operation.

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Accessories of 4-Stroke EngineFuel injector : A pressurized nozzle that sprays fuel into the incoming .Fuel pump : Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine.Starter : Several methods are used to start engines. Most are started by use of an electric motor (starter) geared to the engine flywheel. Energy is supplied from an electric battery.

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Basic Engine Terminologies

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Basic Engine Terminologies

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Basic Engine TerminologiesTop Dead Center (TDC): Position of the piston when it stops at the furthest point away from the crankshaft.Top because this position is at the top of the engines (not always), and dead because the piston stops as this point. Because in some engines TDC is not at the top of the engines(e.g: horizontally opposed engines, radial engines, etc,.)Bottom Dead Center (BDC): Position of the piston when it stops at the point closest to the crankshaft.

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Basic Engine TerminologiesStroke : Distance traveled by the piston from one extreme position to the other : TDC to BDC or BDC to TDC.Bore :It is defined as cylinder diameter or piston face diameter; piston face diameter is same as cylinder diameter( minus small clearance).Swept volume/Displacement volume : Volume displaced by the piston as it travels through one stroke.Swept volume is defined as stroke times bore.Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders).

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Basic Engine TerminologiesClearance volume : It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle. Minimum volume of combustion chamber with piston at TDC.Compression ratio : The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine. Typically compression ratio for SI engines varies form 8 to 12

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Valve and Ignition TimingYou want the piston to be moving up with both valves closed when the sparkplug ignites.You want the intake valve to open when the piston starts its descent in the cylinder. Everything needs to be in time in order for this to work.

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Piston DisplacementPiston Displacement identifies the volume of air which a piston moves (displaces) in one complete stroke.It is used to describe the size of an engine in cubic inches (in3), cubic centimeters (cc), or in liters (L)BoreIdentifies the measurement of the cylinder diameter in inches or millimeters.StrokeDetermined by the number of inches or millimeters the piston moves from BDC (Bottom Dead Center) to TDC (Top Dead Center).

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Piston Displacement

One complete cycle of a four-cylinder, four-stroke engine. The volume displaced is marked in orange.84

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Calculating Piston DisplacementV=A x hV is volume of a cylinder in cubic inches or cubic centimetersA is the area of a cylinder in square inches or square centimetersh is the stroke of the piston in inches or millimetersd is the bore or diameter of cylinder

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Calculating Piston Displacement

If the bore is 10cm and the stroke is 5cm with four cylinders, the calculation is:

3.1416/4 (10cm)2 5cm 4= 1,570cc = 1.57litres

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Compression RatioCompression Ratio (CR) is defined as the total volume (TV) of the cylinder when the piston is at BDC to the cylinder volume when the piston is at TDCTDC is called Clearance Volume (ClV)The difference is generally expressed as the ratio of the total cylinder volume to the clearance volumeA mixture with less air and more fuel is fuel-rich, and a ratio with more air and less fuel is fuel-lean.Control of the air-fuel ratio (A/F) is critical to good emissions performance in an engine. Because emission of carbon monoxide (CO) and volatile organic compounds (VOCs) increases under fuel-rich operation and emission of nitrogen oxides (NOX) rises during fuel-lean operation.

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Compression RatioMost Gasoline Engines will have a lower compression ratio (6:1 or 10:1)Diesel Engines will usually have a much higher Compression Ratio. (19:1)

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The CR can be as high as 13.5:1 (2013Ferrari LaFerrari) in engines with a'ping' or 'knock'sensorand anelectronic control unit. In 2012,Mazdareleased new petrol engines under the brand nameSkyActivwith a 14:1 compression ratio88

Compression Ratios of Other IC EnginesPetrol/gasoline engine with pressure-chargingIn aturbochargedorsuperchargedgasoline engine, the CR is customarily built at 10.5:1 or lower. This is due to the turbocharger/supercharger already having compressed the fuel/air mixture considerably before it enters the cylinders.Petrol/gasoline engine for racingMotorcycle racing engines can use compression ratios as high as 14:1, and it is common to find motorcycles with compression ratios above 12.0:1. F1 engines come closer to 17:1, which is critical for maximizing volumetric/fuel efficiency at around 18000 RPM.

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Compression Ratios of Other IC EnginesEthanol and methanol enginesEthanol and methanol can take significantly higher compression ratios than gasoline. Racing engines burningmethanolandethanol fueloften incorporate a CR of 14.5-16:1.Gas-fueled engineThe CR may be higher in engines running exclusively onLPGorCNG, due to the higher octane rating of these fuels.Kerosene engineA compression ratio of 6.5 or lower is desired for operation on Kerosene.

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Calculating Compression Ratio

The total volume is obtained by adding the piston displacement volume and the clearance volume

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Calculating Compression Ratio

Piston Displacement = 13.36Clearance Volume = 2.67

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Ignition SystemElectricignition systemsmay be classified asmagneto, battery-and-coil, and solid-state ignition systems Although these are similar in basic principle, the magneto is self-contained and requires only the spark plugs and connecting wires to complete the system, whereas thebattery-and-coiland solid-state ignition systems involve several separate components.

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Ignition System

Theignition system(Figure -L) produces a high-voltage electrical charge and transmits it to the spark plugs viaignition wires. The charge first flows to adistributor, which you can easily find under the hood of most cars. The distributor has one wire going in the center and four, six, or eight wires (depending on the number of cylinders) coming out of it. Theseignition wiressend the charge to each spark plug. The engine is timed so that only one cylinder receives a spark from the distributor at a time. 94

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Ignition System TimingThe ignition system on your car has to work in perfect concert with the rest of the engine. The goal is to ignite the fuel at exactly the right time so that the expanding gases can do the maximum amount of work. If the ignition system fires at the wrong time, power will fall and gas consumption and emissions can increase.In order to get the mosttorque and powerfrom the engine, the goal is to maximize the pressure in the cylinder during thepower stroke. Maximizing pressure will also produce the best engine efficiency, which translates directly into better mileage. The timing of the spark is critical to success.

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When you need less than the maximum torque available from a premixed-charge engine (which is most of the time), a throttle is used to control torque & powerThrottling adjusts torque output by reducing intake density (of premixed mixture of fuel and gas) through decrease in pressure95

Ignition System TimingThere is a small delay from the time of the spark to the time when the fuel/air mixture is all burning and the pressure in the cylinder reaches its maximum. If the spark occurs right when the piston reaches the top of the compression stroke, the piston will have already moved down part of the way into its power stroke before the gases in the cylinder have reached their highest pressures.To make the best use of the fuel,the spark should occur before the piston reaches the top of the compression stroke, so by the time the piston starts down into its power stroke the pressures are high enough to start producing useful work.

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The timing of the spark is important, and the timing can either beadvancedorretardeddepending on conditions.The time that the fuel takes to burn is roughly constant. But the speed of the pistons increases as the engine speed increases. This means that the faster the engine goes, the earlier the spark has to occur. This is calledspark advance: The faster the engine speed, the more advance is required.

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Ignition System Timing

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Effect of Ignition Timing on EmissionBy retarding the spark timing (moving the spark closer to the top of the compression stroke), maximum cylinder pressures and temperatures can be reduced. Lowering temperatures helps reduce the formation of nitrogen oxides (NOx), which are a regulated pollutant. Retarding the timing may also eliminate knocking; some cars that have knock sensors will do this automatically.

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Fuel InjectionIn most petrol engines, the fuel and air are usually pre-mixed before compression (although some modern petrol engines now use cylinder-direct petrol injection). The pre-mixing was formerly done in acarburetor, but now it is done by electronically controlledfuel injection, except in small engines where the cost/complication of electronics does not justify the added engine efficiency.

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Speed and efficiencyPetrol engines run at higher speeds than diesels, partially due to their lighter pistons, connecting rods and crankshaft and due to petrol burning more quickly than diesel. Because pistons in petrol engines tend to have much shorter strokes than pistons in diesel engines, typically it takes less time for a piston in a petrol engine to complete its stroke than a piston in a diesel engine. However the lower compression ratios of petrol engines give petrol engines lower efficiency than diesel engines.

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Combustion in SI EngineMixture preparation:- Carburation (no longer used in North American markets)- Port injection - fuel is sprayed into the air stream just before the inlet valve.- Direct injection - fuel is injected into the cylinder (DISI).Ignition: spark plugFlame kernel initiation and propagation model

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In spark ignition engines, the mechanism of transferring electrical energy from an ignition system into the mixture in the spark gap is controlled by many aspects. The major parameters of these aspects are inputs of electrical energy, combustion energy release, and heat transfers. Heat caused by combustion energy is transferred to the spark plug, cylinder head, unburned mixture, and others.101

Combustion in SI EngineEngine knock:- Fuel octane number- Engine compression ratioPollutant formation:- Nitric oxides, NOx- Carbon dioxide, CO- Unburned hydrocarbons, UHCExhaust treatment:- Catalytic converters

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Acatalytic converteris avehicle emissions controldevice that converts toxicpollutantsinexhaust gasto less toxic pollutants by catalyzingaredoxreaction(oxidation or reduction). Catalytic converters are used ininternal combustion enginesfueled by eitherpetrol(gasoline) ordieselincludinglean burnengines.102

Exhaust SystemCombustion products exit the engine cylinder through the exhaust valves in the cylinder head. anexhaust manifoldcollects theexhaust gasesfrom multiplecylindersinto one pipe.For many engines, there are aftermarket tubular exhaust manifolds known asheaders

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Exhaust manifolds are generally simplecast ironor stainless steel units which collect engine exhaust from multiple cylinders and deliver it to the exhaust pipe. The most common types of aftermarket headers are made of mild steel or stainless steel tubing103

Catalytic ConverterA catalytic converter is a vehicle emissions control device that converts toxic pollutants in exhaust gas to less toxic pollutants by catalyzing redox reaction (oxidation or reduction).Catalytic converters are used in internal combustion engines fueled by either gasoline or diesel-including lean burn engines.

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Cooling SystemThecooling systemin most cars consists of the radiator and water pump. Water or coolant circulates through passages around the cylinders and then travels through the radiator to cool it off.Usually a thermostat is located in the circulating system to maintain the designed jacket temperatureapproximately 88 C (190 F).

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Cooling SystemIn a few cars (most notably Volkswagen), as well as mostmotorcyclesand lawn mowers, the engine is air-cooled instead .Air cooling is accomplished by forming thin metalfins on the exterior surfaces of the cylinders to increase the rate of heat transfer by exposing more metal surface to the cooling air. Air is forced to flow rapidly through the spaces between the fins by ducting air toward the engine.Air-cooling makes the engine lighter but hotter, generally decreasing engine life and overall performance.

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But why is air circulation so important? Most cars arenormally aspirated, which means that air flows through an air filter and directly into the cylinders. High-performance engines are eitherturbochargedorsupercharged, which means that air coming into the engine is first pressurized (so that more air/fuel mixture can be squeezed into each cylinder) to increase performance. The amount of pressurization is calledboost. Aturbochargeruses a small turbine attached to the exhaust pipe to spin a compressing turbine in the incoming air stream. Asuperchargeris attached directly to the engine to spin the compressor.106

Cylinder Configuration

Common cylinder configurations include thestraight or inline configuration, the more compactV configuration, and the wider but smootherflat or boxer configuration.straight or inlineV-Shapedflat or boxer

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Cylinder Configuration

Inline the cylinders are arranged one after the other in a straight line (vertical orientation) in one bank.A Inlineengine is considerably easier to build than an otherwise equivalent Flat or V type engines because the cylinder bank and crankshaft can be milled from a single metal casting and it requires fewer cylinder heads and camshafts.This ultimately means lower production and maintenance costs.Also due to their smaller and more lightweight construction, this is the preferred EnginedesignforFFcars (Front Wheel Drive).The design can be extremely fuel efficient compared toV type,FlatandRotaryengine designs.The engines are not generally thought to be as smooth as the V type and Flat engine designs and the structure has it's limitations in terms of durability and strength.

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Cylinder Configuration

V-ShapedThe V-type of engine has two rows of cylinders set normally at aninety degree angle to each other in two banks. Advantages include it's short length, great rigidity of the block, its heavy crankshaft, and attractive low profile. This is a tried and tested engine design with huge performance potential.In sports applications, having the engine as low to the floor as possible increases the car's handling characteristics, as it will naturally have a lower centre of gravity.With this type of engine it is possible to have a very high compression ratios, without block distortion under load.Another attribute for this compact engine design is a shorter car length without losing passenger room.

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You can find, for example, inline 6 cylinder engines, flat 6 cylinder engines and V-6 engines. If you built all three of these six cylinder engines to the exact same specifications -- same displacement, same valves, same intake and exhaust systems, etc. -- they would likely perform nearly identically109

Cylinder Configuration

Flat (also known as horizontally opposed or a boxer) the cylinders are arranged in two banks on opposite sides of the engine.The two pistons join together in the middle ofTDC ( Top Dead Centre).Flat engines have a lower center of gravity than any other common configuration, so vehicles using them should benefit from better stability and control during cornering. But they are also wider than more traditional configurations and the extra width causes problems fitting the engine into the engine bay of a front-engined car.Flat engines are one of only three cylinderlayouts that have a natural dynamic balance; the others being the Straight/Inline6cylinderand the V12 design.

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In 1896, Karl Benz invented the first internal combustion engine with it's horizontally opposed pistons. This is similar to two boxers touching gloves at the beginning of a bout and is the origins of the name appointed to the engine design.When you combine the engine configuration with the number of cylinders, the resulting references are as follows: I-4, I-5, I-6, V-6, V-8, V-10, V-12, H-4, H-6, etc.

Porsches and Subarus have Flat engines. You can find, for example, inline 6 cylinder engines, flat 6 cylinder engines and V-6 engines. If you built all three of these six cylinder engines to the exact same specifications -- same displacement, same valves, same intake and exhaust systems, etc. -- they would likely perform nearly identically110

Increasing Engine PowerThere are a few ways to increase engine horsepower:Larger engine displacementBut its costly and adds unwanted weightNitrous oxideShort duration of increased powerTurbochargers and SuperchargersLightweight, relatively cheap, continuous supply of power

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One of the surest ways to get more power out of anengineis to increase the amount of air and fuel that it can burn. One way to do this is to add cylinders or make the current cylinders bigger. Sometimes these changes may not be feasible -- a turbo can be a simpler, more compact way to add power.ANitrous oxide engineis an engine in which the oxygen required for burning the fuel stems from the decomposition ofnitrous oxide(N2O) rather than air. The system increases theinternal combustion engine's power output by allowing fuel to be burned at a higher rate than would normally be the case, because of the higherpartial pressureof oxygen injected into the fuel mixture. When you heat nitrous oxide to about 570 degrees F (~300 C), it splits into oxygen and nitrogen. So the injection of nitrous oxide into an enginemeans thatmore oxygen is available during combustion.Because you have more oxygen, you can also inject more fuel, allowing the same engine to produce morepower. Nitrous oxide has another effect that improves performance even more. When it vaporizes, nitrous oxide provides a significantcooling effect on the intake air. When you reduce the intake air temperature, you increase the air's density, and this provides even more oxygen inside the cylinder.The only problem with nitrous oxide is that it is fairly bulky, and the engine needs a lot of it. Like any gas, it takes up a fair amount of space even when compressed into a liquid. A 5-liter engine running at 4,000 rotations per minute (rpm) consumes about 10,000 liters of air every minute (compared to about 0.2 liters of gasoline), so it would take a tremendous amount of nitrous oxide to run a car continuously.111

Turbocharged & Supercharged EnginesMost cars arenormally aspirated, which means that air flows through an air filter and directly into the cylinders. High-performance engines are either turbocharged or supercharged, which means that air coming into the engine is first pressurized (so that more air/fuel mixture can be squeezed into each cylinder) to increase performance. The amount of pressurization is calledboost. Aturbochargeruses a small turbine attached to the exhaust pipe to spin a compressing turbine in the incoming air stream. Asuperchargeris attached directly to the engine to spin the compressor.

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Brief History of Turbocharger & Supercharger1st forced induction patent in 1885 to Gottlieb Daimler1st turbocharger patent given in 1905 to Alfred BchiInstalled on French WW-I fighter planes to limited successGE installed a turbocharger on a plane in 1918Began being used on diesels in the 1920sIn 1860, brothersPhilandrandFrancis Marion Roots, founders ofRoots Blower Companypatented the design for an air mover for use inblast furnacesThe world's first functional, actually testedengine supercharger was made byDugald Clerk, who used it for the firsttwo-stroke enginein 1878The world's first series-produced carswith superchargers wereMercedes6/25/40hp and Mercedes 10/40/65hp in 1921

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Forced Induction Principle

All naturally aspirated engines use the down stroke of the piston to create a low pressure area, drawing in the air and fuel mixture into the cylinder.However, most engines cannot inhale the full displacement of the atmospheric-density fuel mixture.This volumetric efficiency varies from engine to engineForced induction is when air is forced into the cylinder to increase the volumetric efficiency.All turbochargers and superchargers work on this principle.

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TurbochargerAturbocharger, orturbofrom Latin "turbo" ("spinning top"), is a turbine-drivenforced inductiondevice that increases an engine's efficiency and power by forcing extra air into the combustion chamber.This improvement over anaturally aspirated engine's output results because the turbine can force more air, and proportionately more fuel, into the combustion chamber than atmospheric pressure alone.Turbochargers are commonly used on truck, car, train, aircraft, and construction equipment engines. They are most often used withOtto cycleandDiesel cycleinternal combustion engines.

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Working of TurbochargerThe objective of a turbocharger is to improve an engine's volumetric efficiency by increasing density of the intake gas (usually air).The turbocharger's compressor draws in ambient air and compresses it before it enters into theintake manifoldat increased pressure.This results in a greater mass of air entering the cylinders on each intake stroke. The power needed to spin the centrifugal compressoris derived from the kinetic energy of the engine's exhaust gases.A turbocharger may also be used to increase fuel efficiency without increasing power. This is achieved by recovering waste energy in the exhaust and feeding it back into the engine intake.

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In normally aspiratedpiston engines, intake gases are "pushed" into the engine by atmospheric pressure filling the volumetric void caused by the downward stroke of the piston, similar to drawing liquid using a syringe. The amount of air actually inspirated, compared to the theoretical amount if the engine could maintain atmospheric pressure, is calledvolumetric efficiency.The objective of a turbocharger is to improve an engine's volumetric efficiency by increasing density of the intake gas (usually air).

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Turbocharger

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With air being pumped into the cylinders under pressure by the turbocharger, and then being further compressed by the piston, there is more danger of knock.Knockinghappens because as you compress air, the temperature of the air increases. The temperature may increase enough to ignite the fuel before thespark plugfires. Cars with turbochargers often need to run on higheroctanefuel to avoid knock. If the boost pressure is really high, the compression ratio of the engine may have to be reduced to avoid knocking.117

Turbocharger

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Location of Turbocharger in a Car

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The typical boost provided by a turbocharger is 6 to 8 pounds per square inch (psi). Since normal atmospheric pressure is 14.7 psi at sea level, you can see that you are getting about 50 percent more air into the engine.It's not perfectly efficient, so you might get a30- to 40-percent improvementinstead.119

SuperchargerAsuperchargeris an aircompressorthatincreases the pressureordensity of airsupplied to aninternal combustion engine. This gives each intake cycle of the engine more oxygen, letting it burn morefueland do morework, thus increasing power.Power for the supercharger can be provided mechanically by means of a belt, gear, shaft, or chain connected to the engine's crankshaft.They are most often used withOtto cycleandDiesel cycleinternal combustion engines.Operating principle remains the same as in Turbocharger as both use forced induction to increase engine performance

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Supercharger

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Types of SuperchargerThere are two main types of superchargers defined according to the method of gas transfer:Positive displacementcompressorDynamic compressorPositive-displacement pumps deliver a nearly fixed volume of air per revolution at all speeds (minus leakage, which is almost constant at all speeds for a given pressure).Major types of positive-displacement pumps include:RootsLysholm twin-screwSliding vaneScroll-type supercharger

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Types of SuperchargerDynamic compressors rely on accelerating the air to high speed and then exchanging that velocity for pressure by diffusing or slowing it down.Major types of dynamic compressor are:CentrifugalMulti-stage axial-flowPressure wave supercharger

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Turbocharger Vs Supercharger

A turbocharger is simply an air compressor driven by an exhaust gas turbine.A turbocharger runs off waste energy created by the engine.Turbochargers power increase contains a lag.

A supercharger is an air compressor driven by the crankshaft of an engine, usually connected with a belt.A supercharger requires engine power to run.The increased power using a supercharger is immediate.

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The lag is because the turbine in the turbocharger needs to increase in speed using the exhaustLag can be reduced by reducing the moment of inertia of the turbine

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Turbocharger Vs Supercharger

EXHAUSTGASESAIR INAIR IN

EXHAUSTGASESTURBOCHARGINGSUPERCHARGINGCOMPRESSOR DRIVEN FROM CRANKSHAFTTURBINE DRIVEN BY EXHAUST GAS

COMPRESSOR DRIVENBY TURBINE

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The lag is because the turbine in the turbocharger needs to increase in speed using the exhaustLag can be reduced by reducing the moment of inertia of the turbine

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Turbocharger Advantages and Disadvantages

Pros:Significant increase in horsepower.Power vs size: allows for smaller engine displacements to produce much more power relative to their size.Better fuel economy: smaller engines use less fuel to idle, and have less rotational and reciprocating mass, which improves fuel economy.Higher efficiency: turbochargers run off energy that is typically lost in naturally-aspirated and supercharged engines (exhaust gases), thus the recovery of this energy improves the overall efficiency of the engine.

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Turbocharger Advantages and Disadvantages

Cons:Turbo lag: turbochargers, especially large turbochargers, take time to spool up and provide useful boost.Boost threshold: for traditional turbochargers, they are often sized for a certain RPM range where the exhaust gas flow is adequate to provide additional boost for the engine. They typically do not operate across as wide an RPM range as superchargers.Power surge: in some turbocharger applications, especially with larger turbos, reaching the boost threshold can provide an almost instantaneous surge in power, which could compromise tyre traction or cause some instability of the car.Oil requirement: turbochargers get very hot and often tap into the engines oil supply. This calls for additional plumbing, and is more demanding on the engine oil. Superchargers typically do not require engine oil lubrication.

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Supercharger Advantages and Disadvantages

Pros:Increased horsepower: adding a supercharger to any engine is a quick solution to boosting power.No lag: the superchargers biggest advantage over a turbocharger is that it does not have any lag. Power delivery is immediate because the supercharger is driven by the engines crankshaft.Low RPM boost: good power at low RPM in comparison with turbochargers.Price: cost effective way of increasing horsepower.

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Superchargers are easier to install but tend to be more expensive.128

Supercharger Advantages and Disadvantages

Cons:Less efficient: the biggest disadvantage of superchargers is that they suck engine power simply to produce engine power. Theyre run off an engine belt connected to the crankshaft, so youre essentially powering an air pump with another air pump. Because of this, superchargers are significantly less efficient than turbochargers.Reliability: with all forced induction systems (including turbochargers), the engine internals will be exposed to higher pressures and temperatures, which will of course affect the longevity of the engine. Its best to build the engine from the bottom up to handle these pressures, rather than relying on stock internals.

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Summary

Turbochargers are one of the best ways to increase power Theyre lighter and cost less than a larger engineDo not place as much stress on the engine as a supercharger doesThey actually help to increase efficiency as they use the "wasted" energy in the exhaust stream for its power source

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In theory, a turbocharger is more efficient because it is using the "wasted" energy in the exhaust stream for its power source. On the other hand, a turbocharger causes some amount of back pressure in the exhaust system and tends to provide less boost until the engine is running at higher RPMs. Turbochargers simply make more sense, as they improve the efficiency of the engine in multiple ways. Superchargers are an extra demand on the engine, even if they are capable of producing useful boost at low RPM. But if you find yourself unable to decide, it is possible to use both simultaneously, and its called twincharging.Electric turbos will likely be more common in future vehicles, where an electric motor spools up the turbo at low RPMs, producing useful boost until the exhaust gases are sufficient enough to power the turbo. This is exactly whats happening in Formula 1 with the ERS (Energy Recovery System), and its the solution to the turbos biggest disadvantage - turbo lag.

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Twincharger

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Twincharger

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Airflow in VW Twincharged TSI (twincharger and Fuel Stratified Injection) engine. Besides being very expensive, the twin charger engine also only operates withpremium gasoline132

Applications of Turbochargers & Turbochargers

High altitudes:Aircraft and automobilesAir pressure is less at high altitudes, so there is less air in naturally aspirated enginesThis leads to less powerTurbochargers will increase the pressure, reducing altitude induced power loss

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Applications of Turbochargers & Turbochargers

Increasing Power:Used on heavy trucks, ships, etcMuch better power: weight ratio than just putting in a large engine

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Two-Stroke Cycle (SI) Engines

Spark-ignition two-strokes are small and light for their power output and mechanically very simple. However, they are also generally less efficient and more polluting than their four-stroke counterparts. However, in single-cylinder small motor applications, cc for cc, a two-stroke engine produces much more power than equivalent 4 strokes, due to the enormous advantage of having 1 power stroke for every 360 degrees of crankshaft rotation (compared to 720 degrees in a 4 stroke motor).

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Two-Stroke Cycle (SI) Engines

Most designs have fuel-air mixture flowing first into CrankcaseFuel-air mixture must contain lubricating oil Two-stroke engines do not have valves, which simplifies their construction and lowers their weightOn down-stroke of pistonExhaust ports are exposed & exhaust gas flows out, crankcase is pressurizedReed valve prevents fuel-air mixture from flowing back out intake manifoldIntake ports are exposed, fresh fuel-air mixture flows into intake portsOn up-stroke of pistonIntake & exhaust ports are coveredFuel-air mixture is compressed in cylinderSpark & combustion occurs near top of piston travelWork output occurs during 1st half of down-stroke137

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Two-Stroke Cycle (SI) EnginesPower/exhaust: This stroke occurs immediately after the ignition of the charge. The piston is forced down. After a certain point, the top of the piston passes the exhaust port, and most of the pressurized exhaust gases escape. As the piston continues down, it compresses the air/fuel/oil mixture in the crankcase. Once the top of the piston passes the transfer port, the compressed charge enters the cylinder from the crankcase and any remaining exhaust is forced out.

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Two-Stroke Cycle (SI) Engines

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Two-Stroke Cycle (SI) EnginesIntake/Compression: The air/fuel/oil mixture has entered the cylinder, and the piston begins to move up. This compresses the charge in the cylinder and draws a vacuum in the crankcase, pulling in more air, fuel, and oil from the carburetor. The compressed charge is ignited by the spark plug, and the cycle begins again.

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Two-Stroke Cycle (SI) Engines

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Different Two-Stroke Design Types

The design types of the two-stroke cycle engine vary according to the method of intake of fresh air/fuel mixture from the outside, the method of scavenging the cylinder (exchanging burnt exhaust for fresh mixture) and the method of exhausting the cylinder. They may be:Piston Controlled Inlet Port Inlet Valve Rotary Inlet Valve Cross flow-Scavenged Loop-Scavenged Uniflow-Scavenged Power Valve Systems Stepped Piston Engine Direct Injection 143

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Lubrication in Two-Stroke (SI) Engines

Two-cycle motors are considered total-loss type lubricating systems. Because the crankcase is part of the intake process, it cannot act as an oil sump as is found on four-cycle engines.Lubricating traditional two-cycle engines is done by mixing the oil with the fuel. The oil is burned upon combustion of the air/fuel mixture.Direct Injection engines are different because the fuel is directly injected into the combustion chamber while the oil is injected directly into the crankcase. Direct injection engines have a higher power density than traditional two-cycle engines. They also require more lubricity than traditional two-cycle motors. 144

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Applications of Two-Stroke (SI) Engines

Some of the devices that might have a two-stroke engine include:Lawn and garden equipment (chain saws, leaf blowers, trimmers)Dirt bikesMopedsJet skisSmall outboard motorsRadio-controlled model planes

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Some Pros and Cons of Two-Stroke (SI) Cycle Engines

Because two-cycle engines can effectively double the number of power strokes per unit time when compared to four-cycle engines, power output is increased. However, it does not increase by a factor of two. The outputs of two-cycle engines range from only 20 to 60 percent above those of equivalent-size four-cycle units.This lower than expected increase is a result of the poorer than ideal charging efficiency, or in other words, incomplete filling of the cylinder volume with fresh fuel and air. The higher frequency of combustion events in the two-cycle engine results in higher average heat transfer rates from the hot burned gases to the motor's combustion chamber walls.Traditional two-cycle engines are also not highly efficient because a scavenging effect allows up to 30 percent of the unburned fuel/oil mixture into the exhaust. In addition, a portion of the exhaust gas remains in the combustion chamber during the cycle.146

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Other Variants of SI EnginesFive-stroke Engines based on the five-stroke cycle are a variant of the four-stroke cycle. Normally the four cycles are intake, compression, combustion, and exhaust. The fifth cycle added by Delautour is refrigeration.Engines running on a five-stroke cycle are claimed to be up to 30 percent more efficient than equivalent four-stroke engines. Six-stroke The six stroke engine captures the wasted heat from the 4-stroke Otto cycle and creates steam, which simultaneously cools the engine while providing a free power stroke. This removes the need for a cooling system, making the engine lighter while giving 40% increased efficiency over the Otto Cycle.

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Compression Ignition (CI) EnginesThediesel engine(also known as acompression-ignition engine) is aninternal combustion enginethat uses theheat of compression to initiateignitionand burn thefuelthat has been injected into thecombustion chamber.The diesel engine has the highestthermal efficiencyof any standardinternalorexternal combustionengine due to its very high compression ratioand inherentleanburn which enables heat dissipation by the excess air.Diesel engines are manufactured intwo-strokeandfour-strokeversions.

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History of Diesel EnginesRudolf Diesel developed the idea for the diesel engine and obtained the German patent for it in 1892.His goal was to create an engine with high efficiency.Gasoline engines had been invented in 1876 and, especially at that time, were not very efficientBoth the gasoline and diesel engine utilize the process of internal combustion for power

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Applications of (CI) EnginesCI engines were originally used as a more efficient replacement for stationarysteam engines. Since the 1910s they have been used insubmarinesand ships. Use in locomotives, trucks,heavy equipment and electricity generation plants followed later. In the 1930s, they slowly began to be used in a fewautomobiles. Since the 1970s, the use of diesel engines in larger on-road andoff-road vehiclesincreased.The world's largest diesel engine is currently aWrtsil-Sulzer RTA96-CCommon Rail marine diesel of about 84.42MW (113,210hp) at 102rpmoutput.Prototype of Ronald Valentine's 2006 Mini Bee 0.021 ccm diesel engine. Thisis the worlds smallest running model diesel engine.

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Applications of (CI) Engines

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Wrtsil-Sulzer RTA96-CRonald Valentine's 2006 Mini Bee

Technical Data:

Bore 3.0 mmStroke 3.0 mmRpm14,800 rpmTotal combustion0.021 ccmWeight 3gramIntake Front Rotor

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Operating principleThe diesel IC engine differs from the gasoline powered Otto cycle by using highly compressed hot air to ignite the fuel rather than using a spark plug.In the true diesel engine, only air is initially introduced into the combustion chamber. The air is then compressed with a compression ratio typically between 15:1 and 22:1.This high compression heats the air to 550C.

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In a four cylinder, 2-liter engine, each cylinder would have a 500 cc capacity. "As the piston moves down the cylinder, it draws in 500 cc of air and fuel. The valves close and the piston moves up, compressing the 500 cc charge. If that charge is compressed into 50 cc, the compression ratio of the engine would be 10:1.octane ratings are a measurement of a gas's ability to resist detonation.The higher the octane number, the morecompressionthe fuel can withstand before detonating (igniting). Cetane numberor CN is an indicator of thecombustionspeed ofdiesel fuel. It is an inverse of the similaroctane ratingforgasoline. Generally, diesel engines operate well with a CN from 40 to 55.In contrast, fuels with lower octane numbers (but highercetane numbers) are ideal fordiesel engines, because diesel engines (also referred to as compression-ignition engines) do not compress the fuel but rather compress only air and then inject the fuel into the air heated up by compression.152

Four-Stroke Cycle of CI EngineIntake stroke: Intake valve opens while the piston moves down from its highest position in the cylinder to its lowest position, drawing air into the cylinder in the process.Compression stroke: Intake valve closes and the piston moves back up the cylinder.This compresses the air & therefore heats it to a high temperature, typically in excess of 1000F (540C).Near the end of the compression stroke, fuel is injected into the cylinder.After a short delay, the fuel ignites spontaneously, a process called auto ignition.

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The fuel injector ensures that the fuel is broken down into small droplets, and that the fuel is distributed evenly. The heat of the compressed air vaporizes fuel from the surface of the droplets.The vapour is then ignited by the heat from the compressed air in the combustion chamber, the droplets continue to vaporise from their surfaces and burn, getting smaller, until all the fuel in the droplets has been burnt.153

Four-Stroke Cycle of CI EngineCombustion stroke: The hot gases produced by the combustion of the fuel further increase the pressure in the cylinder, forcing the piston down.Exhaust stroke:Exhaust valve opens when the piston is again near its lowest position, so that as the piston once more moves to its highest position, most of the burned gases are forced out of the cylinder.

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Since only air is compressed in a diesel engine, and fuel is not introduced into the cylinder until shortly before top dead centre (TDC), premature detonation is not an issue and compression ratios are much higher. The rapid expansion of combustion gases then drives the piston downward, supplying power to the crankshaft. 154

Four-Stroke Cycle of CI Engine

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Diesel Engine Vs Gasoline Engine

In theory, diesel engines and gasoline engines are quite similar. Both diesel engines and gasoline engines covert fuel into energy through a series of small explosions or combustions. The major difference between diesel and gasoline is the way these explosions happen. In a gasoline engine, fuel is mixed with air before intake and injected in the cylinder, compressed by pistons and ignited by sparks from spark plugs. In a diesel engine, however, the air is compressed first, and then the fuel is injected. Because air heats up when it's compressed, the fuel ignites.156

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Diesel Engine Vs Gasoline EngineSpark ignition: Gasoline engines use spark plugs to ignite fuel/ air Mixture Compression ignition:Diesel engines uses the heat of compressed air to ignite the fuel (intakes air, compresses it, then injects fuel)Fuel injection:-Gasoline uses port fuel injection or carburetion;-Diesel uses direct fuel injection or pre combustion chambers (indirect injection)Glow plug:- is an electrically heated wire that helps heat pre combustion chambers fuel when the engine is cold-when a diesel engine is cold, compression may not raise air to temperature needed for fuel ignition157

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Diesel Engine Vs Gasoline Engine

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Gasoline engineDiesel engineSpark-ignitionHomogeneous air/fuel mixtureCompression-ignitionVariable air/fuel mixtureMixture air-gasoline

AirGasoline

Air/Fuel : 8:1 -12:1Carbureters : Fuel/Air mix prior to the cylinderAir/Fuel : 12:1 -24:1No Spark PlugFuel injected directly into the cylinder (DI)

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Diesel Engine Vs Gasoline EngineDIESELVARIABLE AIR / FUEL RATIO(ALWAYS RUNS IN EXCESS AIR)HIGH COMPRESSION RATIO 14-20:1CHEAP FUELMORE FUEL EFFICIENTLONGER LIFE SPANGOOD RELIABILITYCHEAP TO RUNLOW CO AND H/C LEVELS

159GASOLINEAIR TO FUEL RATIO ABOUT 14.6:1(STOICHIOMETRIC)LOW COMPRESSION RATIO 9.5:1HIGH POWER TO WEIGHT RATIO LOW PARTICULATE LEVELSSMALL IN SIZE, AND LIGHTCHEAP TO BUYGENERALLY QUIETEREMISSIONS CONTROLLED BY CATALYST

GASOLINE OFFERS GOOD POWER TO WEIGHT RATIO, SMALL SIZE, CHEAPER TO BUY AND GENERALLY QUIETER, THEREFORE MORE APPEALING FOR THE PASSENGER CAR MARKET DIESEL IS MORE COST EFFECTIVE IN THE LONG TERM, HAS A LONGER LIFE SPAN, LOW MAINTENANCE, AND GOOD EFFICIENCY, WHICH APPEALS TO THE COMMERCIAL MARKET

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Compression Ratio

160This is defined as the ratio of the volume of the cylinder at the beginning of the compression stroke (when the piston is at BDC) to the volume of the cylinder at the end of the compression stroke (when the piston is at TDC).The higher the compression ratio, the higher the air temperature in the cylinder at the end of the compression stroke.Higher compression ratios, to a point, lead to higher thermal efficiencies and better fuel economies.Diesel engines need high compression ratios to generate the high temperatures required for fuel auto ignition.In contrast, gasoline engines use lower compression ratios in order to avoid fuel auto ignition, which manifests itself as engine knock or pinging sound.Common spark ignition compression ratio: 8:1 to 12:1Common compression ignition ration: 14:1 to 25:1

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Diesel Fuel Injection

161One big difference between a diesel engine and a gas engineis in the injection process.Most car engines use port injection or a carburetor.Diesel engines use direct fuel injection -- the diesel fuel is injected directly into the cylinder.The injector on a diesel engine is its most complex component.The injector has to be able to withstand the temperature and pressure inside the cylinder and still deliver the fuel in a fine mist.Some diesel engines contain aglow plug that heats the combustion chambers and raises the air temperature when the engine is cold so that the engine can start.

All functions in a modern engine are controlled by the ECM communicating with an elaborate set of sensors measuring everything from R.P.M. to engine coolant and oil temperatures and even engine position (i.e. T.D.C.). Glow plugs are rarely used today on larger engines. The ECM senses ambient air temperature and retards the timing of the engine in cold weather so the injector sprays the fuel at a later time.161

Direct and Indirect Injection

162Diesel engines are also produced with two significantly different injection locations. "Direct" and "Indirect.

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Direct and Indirect Injection

163Direct-Injection (DI) or Open Chamber Engine:Direct injection engines have two design philosophies:-High-swirl design, which have a deep bowl in the piston, a low number of holes in the injector and moderate injection pressures.-Low-swirl or quiescent engines are characterized by having a shallow bowl in the piston, a large number of holes in the injector and higher injection pressures.Smaller engines tend to be of the high-swirl type, while bigger engines tend to be of the quiescent type

Pressure activated injectors can produce harsh engine noise. Fuel consumption is about 1520% lower than indirect injection diesels163

Direct and Indirect Injection

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Direct-Injection (DI)

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Direct and Indirect Injection

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Indirect-Injection (IDI)

This design has the advantage of less noise and faster combustion, but typically suffers from poorer fuel economy. Indirect injection engines are cheaper to build and it is easier to produce smooth, quiet-running vehicles with a simple mechanical system.165

Diesel Ignition System

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Direct injection:quiescent chamberDirect injection:swirl in chamberIndirect injection: turbulent and swirl pre-chamber

Orifice -plateGlow plug

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Diesel Ignition SystemIgnition Delay:Ignition delay is defined as the time (or crank angle interval) from when the fuel injection starts to the onset of combustion.Both physical and chemical processes must take place before a significant fraction of the chemical energy of the injected liquid is released.Physical processes are fuel spray atomization, evaporation and mixing of fuel vapor with cylinder air.Good atomization requires high fuel-injection pressure, small injector hole diam., optimum fuel viscosity, high cylinder pressure.Chemical processes involves heterogeneous reactions on the liquid fuel drop surface.

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Diesel Ignition SystemIgnition Quality of Fuel:The ignition characteristics of the fuel affect the ignition delay.The ignition quality of a fuel is defined by its Cetane Number CN.For low cetane fuels the ignition delay is long and most of the fuel is injected before auto-ignition and rapidly burns, under extreme cases this produces an audible knocking sound referred to as diesel knock.For high cetane fuels the ignition delay is short and very little fuel is injected before auto-ignition, the heat release rate is controlled by the rate of fuel injection and fuel-air mixing smoother engine operation.

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Diesel Ignition SystemCetane Number of Diesel:The method used to determine the ignition quality in terms of CN is analogous to that used for determining the antiknock quality using the ON.Cetane numberor CN is an indicator of the combustion speed ofdiesel fuel.Generally, diesel engines operate well with a CN from 40 to 55. Fuels with higher cetane number have shorter ignition delays, providing more time for the fuel combustion process to be completed.Alkyl nitrates(principally 2-ethylhexyl nitrate) anddi-tert-butyl peroxideare used as additives to raise the cetane number.

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Diesel Ignition System

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Diesel Fuel System

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Diesel Engine Fuel RequirementThe Fuel Must Ignite in the EngineThe Fuel Must Release Energy When It BurnsThe Fuel Must Provide A Large Amount of Energy Per GallonThe Fuel Must Not Limit The Operability of the Engine at Low TemperaturesThe Fuel Must Not Contribute to CorrosionThe Fuel Must Not Contain Sediment that Could Plug Orifices or Cause WearThe Fuel Should Not Cause Excessive PollutionThe Fuel Should Not Deviate from the Design FuelThe Fuel Should be Intrinsically Safe172

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Diesel Fuel PropertiesOne of the most important properties of a diesel fuel is its readiness to auto-ignite at the temperatures and pressures present in the cylinder when the fuel is injected.The cetane number is the standard measure of this property.High cetane means the fuel will ignite quickly at the conditions in the engine (does not mean the fuel is highly flammable or explosive).Most fuels have cetane numbers between 40 and 60.173

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1742-stroke Diesel engineUsed in large engines, e.g. locomotivesMore differences between 2-stroke gasoline vs. diesel engines than 4-stroke gasoline vs. dieselAir comes in directly through intake ports, not via crankcaseMust be turbocharged or supercharged to provide pressure to force air into cylinder No oil mixed with air - crankcase has lubrication like 4-strokeExhaust valves rather than ports - not necessary to have intake & exhaust paths open at same timeBecause only air, not fuel/air mixture enters through intake ports, short circuit of intake gas out to exhaust is not a problemBecause of the previous 3 points, 2-stroke diesels have far fewer environmental problems than 2-stroke gasoline engines

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2-stroke Diesel engineWhy cant gasoline engines use this concept? They can in principle but fuel must be injected & fuel+air fully mixed after the intake ports are covered but before spark is firedAlso, difficult to control ratio of fuel/air/exhaust residual precisely since intake & exhaust paths are open at same time - ratio of fuel to (air + exhaust) critical to premixed-charge engine performance Startup, variable RPM performance problematicSome companies have tried to make 2-stroke premixed-charge engines operating this way, e.g175

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Advantages of Diesel engineDiesel engines have several advantages over other internal combustion engines:They burn less fuel than a petrol engine performing the same work, due to the engine's higher temperature of combustion and greater expansion ratio.Gasoline engines are typically 30% efficient while diesel engines can convert over 45% of the fuel energy into mechanical energy.They have no high voltage electrical ignition system, resulting in high reliability. The absence of coils, spark plug wires, etc., also eliminates a source ofradio frequency emissionswhich can interfere with navigation and communication equipment.The longevity of a diesel engine is generally about twice that of a petrol enginedue to the increased strength of parts used. 176

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Advantages of Diesel EngineDiesel fuel has better lubrication properties than petrol as well.Diesel fuel is considered safer than petrol in many applications. Although diesel fuel will burn in open air using awick, it will not explode and does not release a large amount of flammable vapor.They generate less waste heat in cooling and exhaust.Diesel engines can accept super- or turbo-charging pressure without any natural limit, this is unlike petrol engines, which inevitably suffer detonation at higher pressure.The carbon monoxide content of the exhaust is minimal.Biodieselis an easily synthesized, non-petroleum-based fuel (throughtrans-esterification) which can run directly in many diesel engines, while gasoline engines either need adaptation to runsynthetic fuelsor else use them as an additive to gasoline.

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Disadvantages of Diesel EngineDespite their many advantages, diesel engines are not perfect. The characteristics that make them more durable than gasoline engines also make them more expensive to build. Diesel fuel injection pumps and injectors must be built to precise tolerances, a requirement that also adds to the initial cost of the engine.When compared to a diesel engine, a gasoline engine delivers usable torque through a much wider rpm range.Gasoline engines also run quieter and offer faster acceleration than diesel engines.Diesel fuel attracts water, which can cause bacteria to form in the fuel system.

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Disadvantages of Diesel EngineIn addition, diesel engines have been subject to escalating emission control standards that have led to changes in engine design and emission control systems.The power output of the diesel engine can also be affected by the temperature of the fuel. At lower temperatures, wax in diesel fuel begins to solidify into crystals that can block fuel flow through filters, lines, and injectors.High fuel temperatures above 38C can also thin out the diesel fuel and reduce power output. At temperatures above 66C, diesel fuel loses much of its lubricating ability. When this occurs, damage to the injectors and other parts can result.179

Many diesel engines are equipped with fuel heaters to help prevent this problem.179

Technological Developments Use of turbochargers and superchargers to increase power output and engine responsiveness under load. Changes in combustion chamber, piston, and valve designs to increase fuel burning efficiency and power output.Use of high-efficiency air-to-air after-coolers resulting in a 3%-5% improvement in fuel mileage and a reduced exhaust emissions.Computerized fuel management systems and variable injection timing.Low-flow cooling systems and extended life coolants.Introduction of ultra-low sulfur diesel fuel,exhaust gas recirculation systems, catalytic converters, oxidation catalysts, and particulate trap filters.180

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Basic Size Groups of Diesel EngineThere are three basic size groups of diesel engines based on power small, medium, and large.

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LargeMediumSmall

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Basic Size Groups of Diesel EngineSmall:Small engines have power-output values of less than 188 kilowatts, or 252horsepower.This is the most commonly produced diesel engine type. These engines are used inautomobiles, lighttrucks, and some agricultural and construction applications and as small stationary electrical-power generators and as mechanical drives. They are typically direct-injection, in-line, four- or six-cylinder engines. Many are turbocharged with after-coolers.182

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Basic Size Groups of Diesel EngineMedium:Medium engines have power capacities ranging from 188 to 750 kilowatts, or 252 to 1,006 horsepower. The majority of these engines are used in heavy-duty trucks. They are usually direct-injection, in-line, six-cylinder turbocharged and after-cooled engines. Some V-8 and V-12 engines also belong to this size group. 183

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Basic Size Groups of Diesel EngineLarge:Large diesel engines have power ratings in excess of 750 kilowatts. These unique engines are used for marine,locomotive, and mechanical drive applications and for electrical-power generation. In most cases they are direct-injection, turbocharged and after-cooled systems. They may operate at as low as 500 revolutions per minute when reliability and durability are critical.184

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Diesel Engine SpeedsWithin the diesel engine industry, engines are often categorized by their rotational speeds into three unofficial groups:High-speed engines (> 1,000 rpm),Medium-speed engines (300 - 1,000 rpm), andLow-speed engines (< 300 rpm).High- and medium-speed engines are predominantly four-stroke engines; except for theDetroit Dieseltwo-stroke range. Medium-speed engines are physically larger than high-speed engines and can burn lower-grade (slower-burning) fuel than high-speed engines.Low-speed engines are predominantly large two-stroke crosshead engines.185

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High Speed Diesel EnginesHigh-speed engines are used to power truck lorries, buses, cars, yachts, compressors, pumps and smallelectrical generators. As of 2008, most high-speed engines havedirect injection. Many modern engines, particularly in on-highway applications, havecommon raildirect injection, which is cleaner burning.186

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Medium Speed Diesel EnginesMedium-speed engines are used in large electrical generators, ship propulsion and mechanical drive applications such as large compressors or pumps. Medium speed diesel engines operate on either diesel fuel or heavy fuel oil by direct injection in the same manner as low-speed engines.Engines used in electrical generators run at approximately 300 to 1000rpm and are optimized to run at a setsynchronous speed.Typical synchronous speeds for modern medium-speed engines are 500/514rpm, 600rpm, 720/750rpm, and 900/1000rpm.There are also dual (diesel/natural gas/coal gas) fuel versions of medium and low speed diesel engines

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It should also be noted that most major manufacturers of medium-speed engines makenatural gas-fueled versions of their diesel engines, which in fact operate on theOtto cycle, and require spark ignition, typically provided with a spark plug. There are also dual (diesel/natural gas/coal gas) fuel versions of medium and low speed diesel engines using a lean fuel air mixture and a small injection of diesel fuel (so-called "pilot fuel") for ignition. In case of a gas supply failure or maximum power demand these engines will instantly switch back to full diesel fuel operation187

Low Speed Diesel EnginesAlso known asslow-speed, the largest diesel engines are primarily used to powerships, although there are a few land-based power generation units as well. These extremely large two-stroke engines have power outputs up to approximately 85MW (114,000hp), operate in the range from approximately 60 to 200rpm and are up to 15m (50ft) tall, and can weigh over 2,000 short tons (1,800t).They typically use direct injection running on cheap low-grade heavy fuel, also known asbunker Cfuel.At least three cylinders are required withtwo-strokeengines and at least six cylinders withfour-strokeengines to providetorqueevery 120 degrees.Companies such asMAN B&W Diesel andWrtsildesign such large low-speed engines.188

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Wankel EnginesTheWankel engineis a type ofinternal combustion engineusing aneccentricrotary designto convert pressure into rotating motion.Over the commonly used