Automobile Engineering

Engine - Components and Functions and Materials, Emission

Automobile Engineering 05ME72 Dr. A. S. Krishnan

Department of Mechanical Engineering Coimbatore Institute of Technology

Working of a 4-s engine

Main body of the engine 1. Cylinder block - Comprises

1. Cylinders in which the pistons slide up and down 2. Ports or openings for valves 3. Passages for cooling water

2. Cylinder head comprises 1. Combustion chamber 2. Spark plug or fuel injector 3. Valves (in case of I-head and F-head) 4. Coolant water passages

3. Crank case 1. Attached to bottom face of cylinder block 2. Acts as base of engine 3. Supports crankshaft and camshaft in suitable bearings 4. Provides arms for supporting the engine on to the frame 5. Contains the oil sump

Cylinder block

Separate cylinder block and crankcase restricted to stationary & marine engines Separate aluminium crankcase will help in weight reduction, cheaper and quicker replacement

Integral cylinder block and crankcase Most modern engines Rigid structure, sometimes ribs are cast in the crankcase to enhance strenght

Engine components

1. Cylinder block

2. Cylinder head

3. Crank case

4. Piston

5. Piston rings

6. Piston pin

7. Connecting rod

8. Crank shaft 9. Flywheel 10.Valves and valve

actuating mechanisms 11.Rocker arm 12.Cam shaft 13.Air induction system 14.Fuel system 15.Exhaust system

Materials [1]

S No. Component Material

1 Cylinder block 1. Gray Cast Iron with addition of nickel and chromium 2. Aluminium with cast-iron or steel sleeves

2 Cylinder Head 1. Aluminium alloy 2. Gray iron

3 Piston 1. Aluminium alloy 2. Cast iron

4 Piston rings Fine-grained alloy cast iron

5 Connecting rod 1. Forged steel 2. Alumnium alloy

6 Crank shaft Casting or forging of heat treated alloy steel

7 Flywheel Steel

8 Valves Austenitic stainless steel

Engine Emission Control

3 way catalytic controller

Emission measuring instruments for CO, HC and NOx

Catalytic Convertor [2]

Most effective after-treatment for reducing engine emission

Used in most automobiles and other modern engines of medium or large size

CO and HC can be oxidized to CO2 and H2O in exhaust and thermal system if 600C T 700C.

Use of catalysts reduces oxidation temperature to 250C T 300C.

Catalyst substance that accelerates a chemical reaction without being consumed

Catalytic convertor mounted in the flow system in the passage of exhaust gases Generally 3 way convertors: reduce concentrations of CO, HC

and NOx

Catalytic convertor [2] Convertor - a stainless steel container housing a porous ceramic structure; mounted in the path of exhaust gases

Ceramic honeycomb structure (Unit) with many flow passages

Loose Granular Ceramic with Gas passing through the packed spheres

Volume of the ceramic structure half the engine displacement volume

5 to 30 changeovers of gas each second through the convertor

Catalytic convertors for CI engines require larger flow passages owing to solid

soot in the exhaust gases

Catalytic particles (which promote oxidation reaction) are embedded in the

ceramic passages

Catalytic convertors for SI engines

Catalysts Catalyst Reactants / Reaction

Aluminium Oxide (Alumina)

Base material for most catalytic convertors Withstand high temperatures, chemically inert Does not thermally degrade with age

Platinum & Palladium

Oxidation of CO and HC

Rhodium Reaction of NOx

Cerium Oxide Water-gas shift

yxz

OyHxCOzOHC yx

25.0

222

222

1COOCO

OHONHNO

OHNHHNO

OHNHNO

COONCONO

CONHOHCONO

CONCONO

222

232

222

22

232

22

2

2252

2

1

2

53352

2

1

222 HCOOHCO

Conversion efficiency of catalytic convertors

Catalytic convertor efficiency

Degradation Of Catalytic Activity

Effective life time 2,00,000km Loss of efficiency due to thermal degradation (500C

- 900 C), poisoning of active catalyst material Source of impurities

Fuel: lead and sulphur Lubricating oil: zinc, phosphorous, antimony, calcium, and

magnesium from oil additives Air

Cold start up Contributes from 70 to 90 % emission Artificial heating:

locating convertor close to engine Electric preheating Incorporating thermal batteries Using flame heating

Poisoning Lead Poisoning Sulphur poisoning

* Some catalyst promote conversion of SO2 to SO3 * Eventually converted to sulphuric acid degradation of catalytic convertor ; acid rain * Development of new catalyst, which produce no SO3 if Tcat

References

1. Gupta, R. B., Automobile Engineering, Tech India Publications, 7th edition, New Delhi, 2011.

2. Ganesan, V., Internal Combustion Engines, 2nd edition, Tata McGraw Hill, New Delhi, 2004.

Engine Auxiliary Systems



Topics for discussion Carburettor Working Principle

Electronic Fuel Injection Mono Point Injection systems Construction

Operation and Maintenance of Lead Acid Battery

Electrical Systems

Battery Generator

Starting Motor and Drives

Lighting and Ignition (Battery, Magneto coil and electronic type)

Regulators

Cut outs

7/10/2012 18 05ME72 Automotive Engineering

Carburetor

Introduction

Construction & defects in Simple Carburetor

Classification

Typical Carburetors

Disadvantages


Introduction SI engine

Use volatile fuel; Mixture preparation outside cylinder

Formation of homogenous mixture not completed in inlet manifold

Fuel droplets continue to evaporate during suction and compression

Carburetion Definition: process of formation of a combustible fuel-

air mixture by mixing proper amount of fuel with air before admission to engine cylinder

Purpose: provide combustible mixture of required quality and quantity for efficient operation of the engine under all conditions


Air fuel mixtures Types

o Chemically correct (stoichiometric) ~15:1

o Rich mixture (limited to > 9:1) o Lean Mixture (limited to < 19:1)

At full open throttle and constant speed

Anticipated Carburetor Performance


Ranges of throttling operation 1. Idling

o No load and with nearly closed throttle o Exhaust gas dilution of fresh charge - prominent

2. Cruising o Maximum fuel economy prime objective o Exhaust gas dilution of fresh charge relatively insignificant

3. Power o To provide best power o To prevent overheating of exhaust valve and area near it

enriched mixture results in lower flame temperature


Factors affecting Carburetion 1. Engine speed

o Modern engines are of high speed o Little time for mixture formation: 10ms for 3000rpm and

5ms for 6000rpm

2. Vaporization characteristic of the fuel o presence of highly volatile components ensure high

quality carburetion

3. Temperature of incoming air o Higher atmospheric air temperature aids fuel

vaporization o However reduced o/p due to reduced vol due to

reduced mass flow rate 4. Design of the carburetor

o Proper design alone ensures supply of desired composition of mixture for different operating conditions of the engine


The Simple Carburetor Float vented to atmosphere

or upstream side of venturi

Carburetor depression

pressure difference between

the float chamber and throat

of the venturi

Throat Pressure @ fully open

throttle ~ 5 cm Hg below atm

Liquid level in float < tip of

discharge jet

SI engine quantity governed

i.e., power o/p at constant

speed is varied by varying the

amount of charge to the

cylinder


The Simple Carburetor Main components of a Carburetor

Fuel Strainer prevent entry of dust particles and consequently

blockage of nozzle; serviceable

Float Chamber supply fuel to nozzle at constant pressure

Main Fuel metering System

Idling System

Choke and throttle cold starting; speed and power output of engine

Compensating devices

Air-bleed jet

compensating jet

emulsion tube

Back suction & control mechanism

auxiliary air valve and air port

Simple Carburetor provides the necessary AFR only at one throttle

position 7/10/2012 25 05ME72 Automotive Engineering

Carburetor - Classification Based on flow direction

Up-draught

Down draught

Cross draught

Constant choke

Constant vacuum

emulsion tube

Back suction & control mechanism

auxiliary air valve and air port

Multiple Venturi

Multi-jet

Multi-barrel Venturi


Solex Carburetor

1 float 2 main metering jet 3- venturi 4 emulsion tube with lateral holes 5 air correction jet 6 spraying orifice / nozzles 7 throttle valve 8 bi-starter valve (disc) 9 starter gasoline jet 10 starter air jet 11 starter lever 12 dashboard control 13 pilot jet 14 small pilot air bleed orifice 15 idling volume control screw 16 idle port; 17 by-pass orifice


Carter Carburetor


Introduction

Construction

Operation

Maintenance

7/10/2012 05ME72 Automotive Engineering 29

Lead Acid Battery

Introduction - Battery


Need for Battery four main circuits 1. Generating 2. Starting 3. Ignition 4. Light

Types of Battery 1. Lead Acid 2. Alkaline

a. Nickel Iron b. Nickel - Cadmium

3. Zinc - Air

Branch Circuits Special Purpose Lights, Radio, Gasoline Gauge, Heater, Cigar Lighter, Windshield wiper, defogger, etc

Ignition, lighting and Branch Circuits receive current from the generator when it is operating; energy supplied from battery during excess load

Construction Lead Acid Battery


1. Container 2. Plates 3. Separators 4. Cell covers 5. Electrolyte 6. Grids 7. Cell connectors 8. Tapered

terminals 9. Sealing

compounds

)(22 424422 energyQPbSOOHPbSOPbSOHPbO

Chemicals used 1. Sponge Lead (solid) 2. Lead Oxide (paste) 3. Sulfuric Acid

(liquid)

1. Positive Plate: Lead Peroxide (PbO2)

2. Negative Plate: Lead (porous spongy lead)

3. Electrolyte: Sulfuric Acid (40%) 4. Separators 5. Sealing compounds

Construction Lead Acid Battery [3]


Lead Acid Battery Construction

Source: http:// www.tpub.com/neets/book1/chapter2/1e.htm

Container Houses individual cells rubber, plastic etc., resistant to

electrolyte and mechanical shock, withstand high temperatures

Vent plugs allows the gases from within the

cells to escape

Plates Anode (positive plate group) Cathode (negative plate group) Interlaced with a terminal attached

to each plate group

Cells Connected in series

Terminals Individual cell terminals connected by link connectors +ive terminal of one end cell becomes +ive terminal of the

battery -ive terminal of opposite end cell becomes +ive terminal of

the battery

http://pvcdrom.pveducation.org/BATTERY/operlead.htm

Overall reaction

Negative terminal reaction

Positive terminal reaction

Factors Affecting Battery Life

Overcharging Decomposition of electrolyte into H2 & O2 gas Decomposition results in acid concentration, harmful to separators

and ive electrode Softening and distortion of container

Undercharging Liable to freeze in severe winter Development of lead sulphate over the plates dense, hard &

crystalline, cannot be electrochemically converted to normal active material again, leads to shorting, distortion of plates

Lack of water Lead to high concentrations of acid which may charge and

disintegrate the separators, permanently sulphate the plates and impair the performance

[Sulfuric acid must never be added to a cell unless it has been lost due to spillage]

Factors Affecting Battery Life

Loose hold-downs

Excessive Loads

Never use battery to propel car by using starting motor with clutch engaged

Produce extremely high internal battery temperature and damage the starting motor

Freezing of Electrolyte

Crack the container and damage the positive plates

Battery testing

Specific Gravity test

Open volt test

High Discharge test

Cadmium test

Battery troubles

1. Self discharging

2. Sulphation

3. Internal short circuiting

4. Deterioration

5. Cracking of container

6. Corrosion of battery terminals and clamps

7. Loss of water

8. Variation in specific gravity of electrolyte

Maintenance of Batteries

Electrolyte Sulphation Battery size and Design Performance Shock and vibration Charging System A.C/ D.C system Charger output Fast charging Maintenance of Acid level Laying up of batteries

Charging System - Generator [4]


1. Restores to the battery the charge removed to crank the engines 2. Handles the load of the ignition, lights, radio and other electrical and electronic components while the engine is running Regulator prevents the alternator from producing excess current Rectifier converts ac to dc

Position of the Generator / Alternator


Alternator Principle


The current in the loop can be increased by increasing i. magnetic field

strength ii. speed of rotation iii. number of loops

Alternator stator and rotor [4]


Alternator rectifier [4]


Rectification of alternator current


References


2. Ganesan, V., Internal Combustion Engines, 2nd edition, Tata McGraw Hill, New Delhi, 2004.

3. Rajput, R. K., A text book of Automotive Engineering, Laxmi Publications, New Delhi, 2007.

4. William H. Crouse and Donald L. Anglin, Automotive Mechanics, 10th edition, Tata McGraw Hill, New Delhi, 2004.


Transmission Systems



Topics

1. Clutch Construction & Types

2. Gear Box Manual & Automatic

3. Simple Floor Mounted Shift

4. Overdrives Transfer box and Fluid Flywheel

5. Propeller shaft, U-Joint & Slip Joint

6. Hotchkiss and Torque Tube Drive

7. Differential & Rear Axle

Clutch [3] Location - Between engine flywheel and Transmission or

Transaxle Functions

While disengaged Allow engine cranking, permits engine to run freely without delivering

power to transmission Permit shifting transmission to various gears

While engaging Slip momentarily, for smooth engagement and lessens shock on gears,

shafts and other drive-train parts

While engaged Transmit engine power to transmission

Construction - Flywheel + Pressure Plates + Friction disc Operation Pressing / releasing of Pressure plate against

friction disc Types Coil Spring, Diaphragm Spring, Double disc

Clutch - Location

Clutch parts

Clutch linkage

Clutch operation

http://www.tpub.com/basae/89.htm

Clutch

Friction Plate Cushion Springs & Dampening Springs Cushion Springs slightly waved springs attached to plate (compresses slightly to take up shock of engagement) dampening springs torsional springs drives the hub and reduces torsional vibrations caused by engine power impulses Facings provided with grooves to prevent sticking of facings by breaking vacuum Facings cotton & asbestos, woven or moulded, saturated with resins or binders

Cover assembly

Types of Clutches

Single Plate

Multi Plate

Coil spring

Diaphragm Spring

Single Plate Clutch

Multi Plate Clutch

Diaphragm Spring Clutch

Coil Spring Clutch


Gears[5]

Power transmission

Change angular velocity and torque

Teeth provide a positive driving action, no slippage

Many types of gears almost every type used in automobile Straight tooth spur: transmit high torque 1st & reverse

Helical spur: progressive meshing axial load transmission

Straight tooth bevel: noisy as type1 - differential

Spiral Bevel: final drives to connect interconnecting shafts

Hypoid: final drives to connect shafts which are neither parallel nor intersecting

The table below shows some example gear ratios for a 5-speed manual gearbox (in this case a Subaru Impreza) Read more: http://www.carbibles.com/transmission_bible.html#ixzz1S3dsajeA

Gear Ratio

RPM of gearbox output shaft when the engine is at 3000rpm

1st 3.166:1 947

2nd 1.882:1 1594

3rd 1.296:1 2314

4th 0.972:1 3086

5th 0.738:1 4065

http://www.mekanizmalar.com/menu_gear.html

Types of Gears [5] Straight spur gears: straight teeth parallel to the axis of rotation engagement - instantaneously along the tooth face; sudden meshing - results in high impact stresses and noise; replaced with helical gears in most transmissions. do not generate axial (or thrust) loads along the shaft axis. easier to manufacture; transmit high torque loads; many transmissions use spur gears for first and reverse gears - This accounts for the distinctive "whine" when a car is reversed rapidly.

Helical gears: teeth cut in the form of helix on a cylindrical surface engagement contact begins at leading edge, progresses along tooth face greatly reduced impact load and noise, but generates a thrust load that must be absorbed at the end of shaft with suitable bearing

Types of Gears [5] Straight tooth bevel gears: Straight teeth cut on conical surface Power transmission between intersecting non-parallel shafts Noisy; In differential, they rotate only when axles are rotating at different speeds

Spiral bevel gears: Helix teeth cut on conical surface Final drives to connect intersecting shafts

Hypoid gears: Helical teeth cut on hyperbolic surface Final drives to connect non-intersecting, non-parallel shafts; high tooth loads & greater sliding - specially lubricated less efficient than spiral bevel; however allow driveshaft to be lowered; hence smaller transmission tunnel in body

Power transmission through Gears a review [5]

Summing moments about the centre,

Tangential force at the point of meshing must be equal and opposite, so:

Pitch diameter proportional to number of teeth (N), angular velocity inversely related to diameter leads to the gear law

A gear train

Extension of gear law [5]

Where, n number of meshing

For gaining torque ratio, a compound gear train needs to be used:

A compound gear train

Types of Transmissions [1]

Manually operated

Overdrive

Chrysler semi-automatic

Automatic

Sliding Mesh Gear Box [1]

Sliding Mesh 1st and Reverse Gears

Sliding Mesh 2nd and Top Gears

Constant Mesh Gear Box

Dog Clutch

Gear Boxes[5]

Power transmission through various gears

http://www.carbibles.com/transmission_bible.html

Read more: http://www.carbibles.com/transmission_bible.html#ixzz1S3dktg3u

http://auto.howstuffworks.com/sequential-gearbox1.htm

Manual Gear Box[6]

Cross-section of a front-wheel drive manual gear box

Simple floor mounted shift mechanism

Overdrives

Transfer box, Fluid Flywheel, Torque convertor

Propeller shaft, Slip Joint, Universal Joint

Hotchkiss and Torque Tube Drive

Overdrives[4]

Top gear position (generally) direct drive between clutch shaft and main shaft; gear ratio 1:1

Overdrive main shaft of gear box revolves faster than clutch shaft

Fitted to rear of the gear box, between gear box and propeller shaft

Advantages of Overdrive Permits an engine to run at lower speed while the car is

running at high speed

Engine runs at slower speed, producing less power, consequently lesser fuel consumption, lesser wear and tear on the engine and accessories

Construction & Operation of an Overdrive[4]

Two shafts input and output shafts Input shaft Main shaft of gear box Output shaft connected to propeller shaft Epicyclic train - sun + planet gear Sun gear free to rotate on input shaft Carrier moves on splines of the input shaft Free wheel clutch attached to splines Ring gear connected to output shaft

Sun gear locked to casing becomes stationary, overdrive engaged, o/p shaft speed increases Sun gear locked to carrier solid drive through gear train achieved, normal drive obtained Sun gear locked to ring same as the previous

http://www.buckeyetriumphs.org/technical/jod/JOD1/JOD1.htm

A: Sun gear

B: Planet gears

C: Outer ring gear or annulus

D Planet gear carrier

1. Input rotary power is applied to the planet gear carrier (D). 2. Output rotary power is taken from the annulus (C). 3. For direct drive (no speed change) the sun gear (A) is locked to the

annulus (C). 4. For an output that is a higher speed than the input (overdriven) the sun

gear (A) is locked stationary.

Mekanizmalar.com

Deceleration Power input: ring gear Power output: planetary carrier Stationary: sun gear When the sun gear is held stationary, only the pinion gear rotates and revolves. Therefore, the output shaft decelerates in proportion to the input shaft only by the rotation of the pinion gear.

Direct Coupling

Power input: sun gear, ring gear Power output: planetary carrier

Ring gear rotates with the locked planetary carrier, the input and output shafts rotate at the same rate.

Reverse Rotation Power input: sun gear Power output: ring gear Stationary: Planetary carrier When the planetary carrier is fixed in position and the sun gear turns, the ring gear turn on its axis and the rotational direction is reversed.

http://www.servocity.com/html/planetary_gearbox.html

Fluid couplings and Torque Convertors

Fluid flow path in a fluid coupling

Propeller shaft, Slip Joint and Universal Joint

Hotchkiss Drive and Torque Tube Drive Types of Drive

Rear End Torque Torque transmission: transmission box propeller shaft

differential rear wheels; causes wheels to rotate, attempts to rotate differential housing in opposite direction

Propeller shaft turns pinion, forces (side thrust of pinion) ring gear & wheels to rotate

Side thrust causes pinion to push against shaft bearing, push opposite to side thrust

Pinion bearings held in differential housing, housing tries to rotate in a direction opposite to ring gear and wheel

Methods of bracing the housing to prevent excessive movement of differential housing Hotchkiss Drive Torque Tube Drive

Torque Tube Drive [1] Propeller shaft enclosed in a hollow tube Hollow tube

rigidly bolted to differential housing at one end fastened to transmission through a marginally flexible joint incorporates bearing to support propeller shaft

Sliding joint not required for propeller shaft Pair of truss rods attached between rear axle housing and transmission end of torque tube Torque tube + truss rods brace differential housing to prevent excessive differential housing movement Springs - take side thrusts and weight of the body

Hotchkiss Drive [1]

Propeller shaft (not enclosed), 2 universal joints and a slip joint Springs

front end rigidly fixed to frame, rear supported on a shackle absorbs rear end torque

Forward movement of car front half of springs compressed, rear expanded

Two universal joint unlike the torque tube drive Used in most cars

References




4. Srinivasan, S., Automotive Mechanics, 2nd Edition, Tata McGraw Hill, New Delhi, 2003.

5. Richard Stone and Jeffery, K. Ball, Automotive Engineering Fundamentals, ISBN 0-7680-0987-1, SAE International, Warrendale, 2004.

6. David, A. Crolla (Editor), Automotive Engineering Power Train, Chassis and Body, Butterworth Heinemann, Oxford, 2009.


Steering, Brakes and Suspension Systems



Topics

1. Wheels 1. Types 2. Alignment Parameters

2. Steering 1. Geometry 2. Types of Steering Gear Box 3. Power Steering

3. Types of Front Axle 4. Suspension 5. Brakes

1. Hydraulic 2. Vacuum Assisted Servo Brakes

Wheels [4] Types of wheels i. Pressed Steel Disc Wheel

mostly used in LMVs some rims are attached using bolt & nut or rivets; tyres rest on rim; wheels fit to axle by bolting to flange attached to axle

ii. Wire Wheel Comprises hub, spoke and rim made of iron Spokes connected between hub and rim Tyre-tube rests on rim Mostly used in motor-cycles

iii. Alloy Wheel Light wheels, less bouncing, faster cooling, better braking Made from aluminium or magnesium alloys Magnesium alloy wheel half the mass of steel wheel, 70% mass of

aluminium alloy wheel for the same strength

Cast wheels for cars Forged wheels for heavy vehicles

Wheels requirements [1]

Strong enough to withstand weight of the vehicle

Flexible to absorb road shocks

Able to grip the road surface

Static and dynamic balance

Light and easy to replace

Pressed Steel Disc Wheel [4,3]

Wire Wheel[4]

Alloy Wheel[4]

Wheels - Attachment & Covers [4]

Attached to brake drum or disc by 5 or 3 wheel nuts or lug nuts

Lug nuts tapered at wheel that matches its seat in wheels; helps tightening lug nuts to centre the wheel

Hub caps / wheel covers attached by clips; locks to protect theft, removed by key wrench

Aluminium wheels have locking lug nut as anti-theft device

Wheel Alignment Parameters [5]

Wheel Alignment Parameters

Wheel alignment positioning of front wheels and steering mechanism that gives directional stability, reduces tire wear to minimum [1]

Camber

Steering Axis Inclination

Toe

Caster

Steering system to allow for Turning of the vehicle To track straight ahead without steering effort from the driver

Camber[5]

Angle made by the tire/wheel with respect to the vertical in the front view of the vehicle

Approximately 1 Types

Positive top of wheel tilted away from vehicle; used in most vehicles

Negative top of wheel tilted towards the vehicle; used in off-road vehicles and race vehicles (which sometimes use zero camber also)

Steering Axis Inclination[5] Angle from the vertical defined by the centerline

passing through the upper and lower ball joints (as viewed from front of the vehicle)

Upper ball joint is closer (usually) to the vehicle centerline than the lower

Inclined Steering Axis with Positive Camber

Vertical Steering Axis

SAI + Positive Camber

Reduced - Scrub Radius during turning, Tire wear & Steering Effort

Wheel arc no longer parallel to the ground turning of wheel causes it to arc toward the ground ground immovable, causing the front of the vehicle to be raised not the position of minimum potential energy weight of vehicle tends to turn the wheel back to straight ahead position

Toe[5]

Defined as the difference of the distance between the leading edge of the wheels and the distance between the trailing edge of the wheels when viewed from above

Toe-in front of the wheels are closer than the rear

Toe-out rear of the wheels are closer than the front

Rear wheel drive: front wheels have slight amount of toe-in

Front wheel drive: require slight toe-out

Toe-in & Toe-out[5] Rear wheel drive

Front wheels have slight toe in As vehicle begins to roll, rolling

resistance produces a force through the tire contact patch rolling axis

Existence of scrub radius causes this force to produce a torque about the steering axis causing wheels to toe-out

Front wheel drive Tractive force on wheels

produces a moment about the steering axis

This moment tends to toe the wheel inward

Caster Caster is the angle of the

steering axis from the vertical as viewed from the side

Positive caster is defined as the steering axis inclined toward the rear of the Vehicle.

Positive caster

Tire contact patch after the intersection of steering axis and ground

During turn, cornering force acts to wheel axis through contact patch

Creates torque about the steering axis tending to centre the wheel

Example shopping cart, wheels free to turn around the axis, self-align to move in straight-ahead position when cart is pushed straight

Factors aiding in self-straightening[5]

Steering

Horse carriage steering [5]

High forces required by the driver

Unstable at high speeds

Ackerman Steering System[5]

Developed by German engineer Lankensperger (1817); patented in the name of British lawyer Rudolph Ackerman

Each end of axle has a spindle that pivots around a kingpin Linkages connecting spindle form a trapezoid Base of trapezoid rack and tie rods

Parallelogram steering linkages [5]

Steering System (Simplified diagram)[1]

References




4. Srinivasan, S., Automotive Mechanics, 2nd Edition, Tata McGraw Hill, New Delhi, 2003.




ALTERNATIVE ENERGY SOURCES Use of Natural Gas, LPG, Biodiesel,

Gasohol and Hydrogen in Automobiles Electric and Hybrid

Vehicles, Fuel Cells (9)



Topics

1. Use of the following fuels in automobiles 1. Natural Gas

2. LPG

3. Bio-diesel

4. Gasohol

5. Hydrogen

2. Electrical and Hybrid Vehicles

3. Fuel Cells

Natural Gas Constituents 80 to 90% methane; rest higher HCs, primarily

ethane Advantages

Clean, non-toxic and non-corrosive, safer produces lesser CO2, CO and volatile than any other fossil fuel combustion produces no significant aldehydes or other air toxins as petrol CNG tanks suffer less damage, high self-ignition temperature (540C)

Economical cheaper than diesel and much cheaper than petrol

Performance More efficient than SI engine Low energy density, compressed to a pressure of 200 to 250 ksc On energy basis, 1 kg of natural gas is equivalent to

1.349 liters of Petrol 1.18 liters of Diesel

Layout of CNG system [1]

CNG System [5]

LPG

Primarily Propane and Butane (more in winter and more in summer respectively) [6]

Heavier than air

LPG system[1]

LPG System [5]

Fuel properties[1]

Optimization points CNG System LPG System

Emission Compression ratio

Mixer flow diameter Valve and Valve seat

Air-Fuel ratio ECU

Location of the mixer Air-Gas valve

Vehicle drivability Ignition timing

Vehicle performance

Gasohol[4]

WHY HYDROGEN ?

Potentially an inexhaustible supply of energy

Can be produced from several primary energy sources

Reduced dependence on petroleum imports if produced from coal or renewables

Potential environmental benefits

High energy conversion efficiency by use of H2 in Fuel Cells(UPTO 90%) in place of I.C. engines (30-35%)

HYDROGEN GENERATION

PROCESSES

Steam reforming of Natural Gas/Naphtha

Partial oxidation of hydrocarbons

Thermal cracking of Natural Gas

Coal/Bio mass Gasification

Electrolysis Electricity from renewable sources like solar, wind, hydel etc.

HYDROGEN PRODUCTION

World wide production

From Natural gas (mostly steam reforming) - 48%

Oil (mostly consumed in refineries) 30%

Coal 18%

Electrolysis 4%

Nearly all H2 production is based on fossil fuels at present.

H2 OPTIONS FOR INDIA

Hydrocarbon Liquid Fuels

Natural Gas

Solar / Wind power for electrolysis

Coal

Bio-mass

Other options like Chlor-Alkali Units & Co-generation electricity from Bagasse at sugar mills

STORAGE OPTIONS

Storage as gas under pressure (250 350 bar)

Cryogenic storage as liquid hydrogen

(Temp. 253 0 C)

Storage as metallic hydrides

Carbon adsorption and glass microsphere

storage techniques (under development)

WHY FUEL CELL TECHNOLOGY IS FAVOURED ?

Batteries are the cleanest automotive energy source.

To liberate electric cars from electro-chemical battery.

Electric cars have a limit range and slow charging.

GMs EV-1 and Hondas EV- Plus have limited range.

Decades of research and investment on electro-chemical batteries.

Power density required for effective automotive propulsion havent attained.

Hybrid Electric Vehicle (HEV) approach followed to increase range of vehicle.

Toyota Prius and Honda Insight have been introduced.

HEVs are having high efficiency internal combustion engines with batteries.

Batteries supplement power to the engine during acceleration and hill climbing.

Combined electric and mechanical drives make them costly and complex.

FUEL CELL THEORY

First demonstrated in principle by British Scientist Sir Willliam Robert Grove in 1839.

Groves invention was based on idea of reverse electrolysis.

In electrolysis, an electric current is introduced in to electrolyte.

This flow between two electrodes causes the splitting of water.

FUEL CELL THEORY

A fuel cell consists of two electrodes - Anode and Cathode.

Hydrogen and Oxygen are fed into the cell.

Catalyst at Anode causes hydrogen atoms to give up electrons leaving positively charged protons.

Oxygen ions at Cathode side attract the hydrogen protons.

Protons pass through electrolyte membrane.

Electrons are redirected to Cathode through external circuit.

Thus producing the current - power

FUEL CELLS FOR DIRECT ENERGY

CONVERSION

TYPES OF FUEL CELLS

Temp.C Application Alkaline (AFC) 70-90 Space

Phosphoric Acid 150-210 Commercially available

(PAFC)

Solid Polymer 70-90 Automotive application

(PEMFC)

Moltan Carbonate 550-650 Power generation

(MCFC)

Solid Oxide 1000-1100 Power generation

(SOFC)

Direct Methanol 70-90 Under development

(DMFC)

FUEL CELL CARS

Start to look real

Fuel cell car - the long awaited

Prototype vehicles have been displayed

Clear personal transportation of the future

Moving from laboratory vision to technical reality

FUEL CELL APPLICATION FOR AUTOMOTIVE USE

Proton exchange membrane (PEM) variety has emerged as the best design

GM has obtained nearly 400 patents in PEM technology

SOFC together with and on-board gasoline fuel processor or reformer would be suited as auxiliary power units (APUs)

Replacement of low efficiency alternator in automobiles

BMW, Renault and Delphi are pursuing this approach

Fuel Fuel

Cell

Batteries

Accessories

Power

conditioner AC/DC

Drive

motor

Wheels

Wheels

FUEL CELL VEHICLE CONFIGURATION

General Motors and Adam Opel AGs View (GAPC)

Long term vision : Hydrogen

Problem : H2 - Storage

H2 -Infrastructure

Bridging Strategy : Fuel Cell Systems for vehicles using

conventional / Pump Grade Fuels

Establishing infrastructure and storage technology for

hydrogen in between co-operation of

OEMs with mineral oil companies GM / Exxon / Mobil / BP

Gasoline tank

Fuel Cell Drive System

FUELS FOR FUEL CELL SYSTEMS

References




4. http://upload.wikimedia.org/wikipedia/commons/c/c8/Common_ethanol_fuel_mixtures.gif

5. http://www.btautomotive.com.my/VSI-CNG-s-LPG.aspx 6. http://en.wikipedia.org/wiki/Liquefied_petroleum_gas 7. HYDROGEN ACTIVITIES IN THE OIL & GAS SECTOR, 15th April,

2004, R & D Centre, NTPC, Noida. Slides 12-29.


Automobile Engineering

Documents

cylinder head

separate cylinder block

face of cylinder block

convertor catalytic

alloy steel

base of engine

engine components

nox catalytic convertor