engine design2014-lecture2.pdf
Post on 14-Apr-2018
221 Views
Preview:
TRANSCRIPT
-
7/27/2019 engine design2014-lecture2.pdf
1/30
Vehicle Design II
Vehicle Design I ILecture 2
Dr. Nouby M. GhazalyAutomotive and Tractor Engineering Dept.
College of Engineering,Minia University-61111
Nouby.Ghazaly@mu.edu.eg
-
7/27/2019 engine design2014-lecture2.pdf
2/30
Outline of Presentation
1. Introduction
2. Engine construction overview
3. Classification of engines4. Engine information
-
7/27/2019 engine design2014-lecture2.pdf
3/30
Introduction
Energy is used to produce power.
The chemical energy in fuel is converted to heat by the burning of
the fuel at a controlled rate.
This process is called combustion. If engine combustion occurswithin the power chamber, the engine is called an internal
combustion engine.
-
7/27/2019 engine design2014-lecture2.pdf
4/30
ENGINE CONSTRUCTION
OVERVIEW
-
7/27/2019 engine design2014-lecture2.pdf
5/30
ENGINE CONSTRUCTION OVERVIEW
A blockis constructed of cast iron or aluminumand provides the foundation for most of the
engine components and systems.
Pistons are installed in the block and move up
and down during engine operation.
-
7/27/2019 engine design2014-lecture2.pdf
6/30
ENGINE CONSTRUCTION OVERVIEW
The cylinder head also contains valves that allow air and fuel intothe cylinder, called intake valves and exhaust valves
Crankshafts are generally made of cast iron, forged steel, or
nodular iron and machined for bearing fit and balance.
Air and fuel enters the engine through an intake manifold and exitsthe engine through the exhaust manifold.
-
7/27/2019 engine design2014-lecture2.pdf
7/30
ENGINE CLASSIFICATION
-
7/27/2019 engine design2014-lecture2.pdf
8/30
ENGINE CLASSIFICATION
Engines are classified by several characteristics including:
Cylinder arrangement
Operational cycles
Valve location
Type of fuel
Combustion Chamber Design
Cooling method
Application
-
7/27/2019 engine design2014-lecture2.pdf
9/30
CLASSIFICATION of ENGINESCylinder arrangement
1. Reciprocating (a) Single Cylinder
(b) Multi-cylinder
(I) In-line
(ii) V
(iii) Radial(iv) Horizontally opposed
(v) Opposed Piston
2. Rotary: (a) Single Rotor
(b) Multi-rotor
-
7/27/2019 engine design2014-lecture2.pdf
10/30
Types of Reciprocating
Engines
Automotive engine
cylinder arrangements.
A horizontally opposed
engine design helps to lower
the vehicles center of
gravity.
-
7/27/2019 engine design2014-lecture2.pdf
11/30
Rotary Piston Engine
A successful alternative engine design is the rotary engine, also
called the Wankel engine after its inventor.
The Mazda RX-7 and RX-8 represents the only longterm use of the
rotary engine.
Rotary engine operates on the four-stroke
cycle but uses a rotor instead of a piston
and crankshaft to achieve intake,compression, power, and exhaust stroke.
-
7/27/2019 engine design2014-lecture2.pdf
12/30
Chapter 8
CLASSIFICATION of ENGINES
Operational Cycle
Four-Stroke Gasoline
Requires two complete turns of the crankshaftto complete its cycle.
Two-Stroke Gasoline
Requires only one crankshaft revolution tocomplete its cycle.
Due to the lack of a complete intake stroke theintake charge must be forced into the cylinder.
continued
-
7/27/2019 engine design2014-lecture2.pdf
13/30
4-Stroke Engines
Each cycle of events requires that the engine
crankshaft make two complete revolutions or
720.
The greater the number of cylinders, the
closer together the power strokes occur.
Angle with three cylinders = 720/3 = 240
Angle with four cylinders = 720/4 = 180
Angle with five cylinders = 720/5 = 144
Angle with six cylinders = 720/6 = 120
Angle with eight cylinders = 720/8 = 90
Angle with ten cylinders = 720/10 = 72
-
7/27/2019 engine design2014-lecture2.pdf
14/30
4-Stroke Engines Operation
-
7/27/2019 engine design2014-lecture2.pdf
15/30
4-Stroke Engines Operation
Valve timing for low and high speed four-stroke SI engine
-
7/27/2019 engine design2014-lecture2.pdf
16/30
2-StrokeEngines
2-stroke
Reed
Valve
intake
-
7/27/2019 engine design2014-lecture2.pdf
17/30
CLASSIFICATION of ENGINES
Valve Location
The F-headThe L-headThe I-head
-
7/27/2019 engine design2014-lecture2.pdf
18/30
CLASSIFICATION of ENGINESValve Location
The I-head: (i) Over head Cam (OHC)
(ii) Over head Valve (OHV)
Overhead Camshaft (OHC) or Dual/ Double Overhead
camshaft (DOHC) Both intake and exhaust valves are located in
the cylinder head.
The valves are operated directly by thecamshaft or through cam followers.
Some engines use separate intake and exhaustcamshafts.
f
-
7/27/2019 engine design2014-lecture2.pdf
19/30
CLASSIFICATION of ENGINES
Valve Location
Overhead Valve (OHV)
The intake and exhaust valves are mounted in the cylinder head
and operated by a camshaft located in the cylinder block.
This requires the use of valve lifters, pushrods and rocker arms
to transfer camshaft motion to the valves.
-
7/27/2019 engine design2014-lecture2.pdf
20/30
CLASSIFICATION of ENGINES
Fuel
1.Conventional: (a) Crude oil derived (i) Petrol
(ii) Diesel
(b) Other sources: (i) Coal
(ii) Wood (includes bio-mass)
(iii)Tar Sands
(iv)Shale
2. Alternate: (a) Petroleum derived (i) CNG
(ii) LPG
(b) Bio-mass Derived (i) Alcohols (methyl and ethyl)
(ii) Vegetable oils
(iii) Producer gas and biogas
(iv) Hydrogen3. Blending
4. Dual fueling
-
7/27/2019 engine design2014-lecture2.pdf
21/30
CLASSIFICATION of ENGINES
Cooling
1. Direct Air-cooling
2. Liquid Cooling
-
7/27/2019 engine design2014-lecture2.pdf
22/30
CLASSIFICATION of ENGINES
Application
1. Automotive: (i) Car(ii) Truck/Bus
(iii) Off-highway
3. Light Aircraft
4. Marine: (i) Outboard
(ii) Inboard
(iii) Ship5. Power Generation: (i) Portable (Domestic)
(ii) Fixed (Peak Power)
6. Agricultural: (i) Tractors
(ii) Pump sets
7. Earthmoving: (i) Dumpers
(ii) Tippers(iii) Mining Equipment
8. Home Use: (i) Lawnmowers
(ii) Snow blowers
(iii) Tools
9. Others
-
7/27/2019 engine design2014-lecture2.pdf
23/30
Engine Information
-
7/27/2019 engine design2014-lecture2.pdf
24/30
Engine Information
ENGINE DISPLACEMENT
Engine size is described as displacement.
Displacement is the cubic inch (cu. in.) or cubic centimeter(cc) volume displaced or swept by all of the pistons.
The formula to calculate the displacement of an engineis basically the formula for determining the volume of acylinder multiplied by the number of cylinders.
Bore x bore x stroke x number of cylinders
-
7/27/2019 engine design2014-lecture2.pdf
25/30
Swept and Displaced Volumes
Swept Volume/cylinder:
sAsd4=V p
2Bs
Vs
= swept volume dB
= bore diameter
s = stroke
s
s x Ap
Inlet Port
Note: In valve design the Volume which flows into thecylinder must equal the volume which flows through
the inlet port. The velocity past the valve must then be
considerably greater than the velocity in the cylinder.
-
7/27/2019 engine design2014-lecture2.pdf
26/30
Engine Information
COMPRESSION RATIO
The compression ratio of an engine is an
important consideration when rebuilding or
repairing an engine.
Compression ratio (Cr) is the ratio of the
volume in the cylinder above the piston
when the piston is at the bottom of the
stroke to the volume in the cylinder above
the piston when the piston is at the top of
the stroke.
-
7/27/2019 engine design2014-lecture2.pdf
27/30
Engine Information
COMPRESSION RATIO
FIGURE Combustion chamber
volume is the volume above thepiston with the piston at top dead
center.
-
7/27/2019 engine design2014-lecture2.pdf
28/30
Engine Information
Crankshaft Throw
The distance from the centre of the crankshaft main
bearing journal to the centre of the crankshaft connecting
rod bearing journal is called crank radius ( throw).
The crank radius determines the stroke of the engine.
2 X crank radius = Stroke.
-
7/27/2019 engine design2014-lecture2.pdf
29/30
Engine Information
Stroke to Bore
Stroke to Bore (L/D) Ratio = (0.75-0.9) Engines that have a larger bore than stroke are called oversquare.
Theseengines offer the opportunity to fit larger valves in thecombustion chamber and use shorter crank throws and connecting
rods, which means oversquare engines are capable of runningat higher engine speeds.
Engines with a larger stroke than bore are referred to as beingundersquare. (L/D) Ratio = (1.1- 1.85)
Undersquareengines have long crank throws and connecting rods
that aid in the production of more powerat lower engine speeds.
A square engine has equal bore and stroke measurements and is acompromise between the two designs
-
7/27/2019 engine design2014-lecture2.pdf
30/30
Questions?
top related