engine design2014-lecture2.pdf

7/27/2019 engine design2014-lecture2.pdf

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Vehicle Design II

Vehicle Design I ILecture 2

Dr. Nouby M. GhazalyAutomotive and Tractor Engineering Dept.

College of Engineering,Minia University-61111

[email protected]


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Outline of Presentation

1. Introduction

2. Engine construction overview

3. Classification of engines4. Engine information


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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.


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ENGINE CONSTRUCTION

OVERVIEW


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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.


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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.


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ENGINE CLASSIFICATION


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ENGINE CLASSIFICATION

Engines are classified by several characteristics including:

Cylinder arrangement

Operational cycles

Valve location

Type of fuel

Combustion Chamber Design

Cooling method

Application


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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


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Types of Reciprocating

Engines

Automotive engine

cylinder arrangements.

A horizontally opposed

engine design helps to lower

the vehicles center of

gravity.


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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.


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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


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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


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4-Stroke Engines Operation


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4-Stroke Engines Operation

Valve timing for low and high speed four-stroke SI engine


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2-StrokeEngines

2-stroke

Reed

Valve

intake


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Valve Location

The F-headThe L-headThe I-head


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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


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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.


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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


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Cooling

1. Direct Air-cooling

2. Liquid Cooling


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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


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Engine Information


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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


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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.


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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.


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Engine Information

COMPRESSION RATIO

FIGURE Combustion chamber

volume is the volume above thepiston with the piston at top dead

center.


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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.


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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


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Questions?

engine design2014-lecture2.pdf

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