Engine Design Lecture2

8/3/2019 Engine Design Lecture2

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Vehicle Design II

Vehicle Design IILecture 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 ENGINES

4. 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 block is 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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Wankel Rotary Piston Engine


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Types of Rotary Engines


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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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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

f


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Chapter 8


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.

continued


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Chapter 8

CLASSIFICATION of ENGINESValve Location

The I-head: (i) Over head Valve (OHV)

(ii) Over head Cam (OHC)

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 the camshaft or through cam followers.

Some engines use separate intake and exhaust camshafts.


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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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Combustion Chamber Design

1. Open Chamber: (i) Disc type

(ii) Wedge

(iii) Hemispherical

(iv) Bowl-in-piston

(v) Other design

2. Divided Chamber: (For CI): (i) Swirl chamber

(ii) Pre-chamber

(For SI) (i) CVCC

(ii) Other designs


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Combustion Chamber Designs


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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 anengine is basically the formula for determining thevolume of a cylinder multiplied by the number ofcylinders.

Bore x bore x stroke x number of cylinders


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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 10-18 Combustion

chamber volume is thevolume above the piston

with the piston at top dead

center.


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Engine Information

The stroke of an engine is thedistance the piston travels from top

dead center (TDC) to bottom dead

center (BDC).

This distance is determined by the

throw of the crankshaft.

FIGURE 10-19 The distance between the centerline

of the main bearing journal and the centerline of the

connecting rod journal determines the stroke of theengine. This photo is a little unusual because this is

from a V-6 with a splayed crankshaft used to even

out the impulses on a 90, V-6 engine design.


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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 throw.

The throw determines the stroke of the engine.

2 X Throw = Stroke.

continued


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Engine Information

Bore to Stroke Ratio Engines that have a larger bore than stroke are called

oversquare.

Theseengines offer the opportunity to fit larger valves in the

combustion chamber and use shorter crank throws andconnecting rods, which means oversquare engines are capableof running at higher engine speeds.

Engines with a larger stroke than bore are referred to as beingundersquare.

Undersquareengines have long crank throws and connectingrods that aid in the production of more power at lower enginespeeds.

A square engine has equal bore and stroke measurements and is

a compromise between the two designs


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Swept and Displaced Volumes

Swept Volume/cylinder:

sAsd4=V p

2Bs

Vs = swept volume dB = bore diameters = stroke

s

s x Ap

Inlet Port

Note: In valve design the Volume which flows intothe cylinder 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 Design Lecture2

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