Internal combustion engines  transforms about 25 to 35% of the chemical energy in the fuel in to mechanical energy.

About 35 percentage of the heat generated is lost in to the surroundings of combustion space, remainder being dissipated through exhaust and radiation from the engine.

The temperature of the burning gases reaches inside the engine cylinder about 2000 to 2500° C.

The engine components like cylinder head, cylinder wall piston and the valve absorb this heat.

Such high temperatures are objectionable for engine life.

I.C. ENGINE

It should remove only about 30% of the heat generated in the combustion chamber. Too much cooling reduces the thermal efficiency of the engine.

A good cooling system should remove heat at a faster rate when the engine is hot. During starting, the cooling should be very slow.

The components in the cylinder must be reasonably hot (250°C). Over-cooling of the engine results in insufficient vaporization of fuel,

loss of power, high fuel consumption, higher emissions, starting troubles, excessive formation of sludge, lower thermal efficiency and greater wear and tear of parts.

Requirements of a good Cooling System

1. Engine valves damage due to over heating.

2. Damage to the materials of cylinder body and piston.

3. Lubricating oil decomposes to form gummy and carbon particles.

4. Thermal stresses are set up in the engine parts and causes distortion and cracking of components.

5. Pre – ignition occurs (i.e. ignition occurs before it is required to igniter due to the overheating of spark plug).

6. Reduces the strength of the materials used for piston and piston rings.

7. Overheating reduces the efficiency of the engine.

Necessity For Engine Cooling

Demerits Of Overcooling

Starting of engine becomes difficult.

Engine life is reduced.

Greater frictional losses.

Economy and life of engine is reduced.

Demerits Of Undercooling

Engine seizure , distortion of cylinder block head.

Loss of power and damage to engine components

Friction and wear between piston and cylinder.

1. Air cooling System Have metal FINS on the outer perimeter of the engine. Heat is transferred from the engine, through these fins, into the

atmosphere.

Advantages:1. Design of engine becomes easy.

2. No danger of coolant leakage.

3. Low wears to the cylinder.

4. No coolant freezing problem.

Disadvantages:5. Non uniform cooling.

6. Produces noise.

7. Smaller useful compression ratio.

8. Output is less compared to liquid cooled engine.

Methods of cooling

1. water cooling System A liquid (coolant) is circulated around the cylinders and absorb heat

from the cylinder walls and cylinder head. Coolant absorbs heat by convection & conduction as it passes

through the engine and also lubricates the water pump. Hot coolant enters the radiator in which the heat is passed on to air

that is flowing through the radiator. Cooling system flush is recommended every two year in order to

remove any rust or contaminants.

Coolant must have these characteristics:1. Low freezing temp.

2. High boiling point.

3. Non corrosive

4. Cheap in cost

Methods of cooling

Application This system is used in light and heavy duty vehicles. It is

general in automobile engines such as buses, lorries, cars and trucks.

Advantages of water cooling Cooling is more efficient, thus engine efficiency is more. Uniform cooling is obtained. Water cooled engines can be installed anywhere. Chances of engine overheating are greatly reduced. Engine temperature can be controlled.

More weight, since it uses radiator, pump, fan etc.

Requires more maintenance. The engine may have to be stopped even if a small leakage of water is detected in the radiator.

In cold weather, freezing of water causes trouble. An electric heater may be required to heat the radiator.

Water circulating pump consumes more power.

Water causes scale formation in the water circulating jacket and corrosion of materials, hence greater maintenance is required

Disadvantages of water-cooling

1. Thermo syphon cooling2. Forced or pump cooling3. Cooling with thermostatic regulator4. Pressurized water cooling5. Evaporative cooling

Methods used to circulate water

CHASSIS SYSTEM OF AUTOMOBILE &

ITS REQUITEMNTS

CHASSIS

• Chassis is a french term which was initially used to denote the frame or main structure of a vehicle.

• The term chassis is now extensively used to denote the complete vehicle except the body for the heavy vehicles having a separate body.

COMPONENTS OF CHASSIS

• Frame• Steering system• Suspension system• Brake system• Front axle• Rear axle• Transmission • engine

CONSTRUCTION

• CONVENTIONAL CONSTRUCTION used in heavy vehicles . A separate frame is used in this case.

• UNITARY CONSTRUCTION used in cars and no separate frame is used in this case.

CLASSIFICATION OF CHASSIS

1. ACCORDING TO ITS CONTROL

(a) CONVENTIONAL CHASSIS: In this type of chassis , engine is fitted in front of the driver cabin or seat such as in cars and previous model of TATA trucks.

(b) SEMI FORWARD CHASSIS: This is such a chassis where half portion of engine in the driver cabin and remaining half out side the cabin. Such as in TATA trucks, Mercedes vans.

(c) FULL FORWARD CHASSIS: In this type of chassis the complete engine is mounted inside the driver cabin. Driver can see the full frontal side of wheel. Increased floor area.

CLASSIFICATION OF CHASSIS

2. ACCORDING TO FITTING OF ENGINEa) FRONT ENGINE REAR DRIVE: Weight is balanced on all wheels, Easier to

inspect , repair and adjust the engine, clutch and gear box. Increased efficiency of cooling system because radiator is placed just front of the chassis.

b) FRONT ENGINE FRONT DRIVE: The vehicle has more adhesion on road since more weight is placed on the driving wheels. The cost is less. While accelerating , the weight of the vehicle shifts to the rear wheels reducing tractive effort. Understeer can also happen.

c) ENGINE FITTED AT CENTER OF THE CHASSIS Royal tiger world master buses plied by delhi transport corporation.

d) ENGINE FITTED AT BACK: Renault , volkswagon uses this type of chassis. Good brake capacity. Reduce the traction on hill climbing. Good braking

effort.

CLASSIFICATION OF CHASSIS

3. ACCORDING TO NO. OF WHEELS ATTACHED AND DRIVING WHEELS(a)4*2 drive chassis vehicle(b) 4*4 drive chassis vehicle(c) 6*2 drive chassis vehicle(d) 6*4 drive chassis vehicle

FRAME

• The frame is the main part of the chassis on which the remaining parts of the chassis are mounted.

• Engine is mounted in the forward end of the frame and the rear axle attached at the rear end.

TYPES OF FRAMES

(a) Channel section - is used in long members of the frame. It has a good bending strength.(b) Box section - is used in short members of the frame. It has a good torsion and bending strength.(c) Tubular section - is used in scooters , three- wheelers etc. it has a good torsion strength .

Basically frames are of following three types

(a) Conventional frame - also called non load carrying frame. Load on the vehicle is transferred to the suspension by the frame.

SEMI INTEGRAL FRAME

• The rubber body mounts are replaced by stiff mounts so part of the frame load is transferred to the body structure .

• This type of frame is popular in small european cars and american cars.

• Frame is heavy

INTEGRAL FRAME

• No frame is used. All assembly units are attached to the body.

• Reduces weight , lowers production cost and allows floor space.

• Modern form of construction for lighter commercial vehicles.

Various loads acting on FRAMES

• Various load acting on the frames are1. Short duration load – while crossing a broken

patch2. Momentary duration load – while taking a

curve.3. Impact load - due to collision of vehicle 4. Inertia load – while applying the brakes5. Static load – load due to chassis parts6. Overload – load is over the design capacity

REQUIREMENTS OF THE BODY OF VEHICLE

• Light in weight.

• Cheap and easy to manufacture.

• Minimum resistance to air.

• Minimum vibrations during running of vehicle.

• Adequate space for passengers.

• Clear all- round vision through glass area.

• Good access space for passengers and luggage.

AUTOMOBILE AIR-CONDITIONING

WHAT IS AIR-CONDITIONING

Air conditioning is the process of altering the properties of air. An air conditioner (often referred to as AC) is the mechanism

designed to change the air temperature and humidity within an area.

TYPE REFRIGERATION CYCLE

OPEN REFRIGERATION CYCLE CLOSE REFRIGERATION CYCLE

COMPONENTS OF AUTOMOTIVE AIRCONDITIONER

1. COMPRESSOR This is the heart of our a/c system. The compressor is what takes the refrigerant (the gas) and pressurizes

it so it will cool the air. Runs by an engine belt.

2. CONDENSOR The condenser is like a miniature radiator. Mounted at the front of the car right next to radiator. The hot, compressed air passes through the condenser and cooled. As

it cools, it becomes a liquid.

COMPONENTS OF AUTOMOTIVE AIRCONDITIONER

3. EVAPORATORThe evaporator is another little radiator that does just the opposite task as the condenser. As the super-cool liquid is passed through its tubes, air is forced through and gets really cold, right before it hits our face. As it warms up again, the refrigerant starts turning back into a gas.

4. THERMAL EXPANSION VALVE

5. DRIER OR ACCUMULATOR

TYPES OF AIR CONDITIONING SYSTEM USED IN CARS

There are two main types of air conditioning systems in use in the automobile industry. The main difference between each system is the type of device that is used to lower the refrigerant pressure.

The expansion valve system 2. The fixed orifice tube system

HEATING SYSTEM IN A CAR

A car heater is designed to warm the passenger cabin of our car.

This system makes use of excess heat from the engine's internal combustion process.

The engine's excess heat is absorbed by a circulating liquid coolant.

The heated liquid coolant is carried from the engine through the hoses to the radiator often called the heater core .

A fan is positioned in front of the heater core to blow cold outside air over the fins so that it heats up and becomes the hot air which blows out through heater vents.