INTERNAL COMBUTION ENGINE

Made by:

Assistant Professor : NAPHIS AHAMAD

MECHANICAL ENGINEERING

6/10/2017 Naphis Ahamad (ME) JIT 1

6/10/2017 Naphis Ahamad (ME) JIT 2

UNIT IV

Cooling system for IC Engines

An automobile's cooling system is the collection of parts and substances (coolants)

that work together to maintain the engine's temperature at optimal levels. Comprising

many different components such as water pump, coolant, a thermostat etc. the system

enables smooth and efficient functioning of the engine at the same time protecting it

from damage

The following are the two main characteristics desired of an efficient cooling system

1. It should be capable of removing about 30% of heat generated in the combustion

chamber while maintain the optimum temp of the engine under all operating

conditions of engine.

2. It should remove heat at a faster rate when engine is hot. However during starting

of the engine the cooling should be minimum, so that the working parts of engine

Necessity of Cooling

The cooling system is provided in the IC engine for the following reasons:

• The temperature of the burning gases in the engine cylinder reaches up to

1500 to 2000°C, which is above the melting point of the material of the

cylinder body and head of the engine. (Platinum melts at 1750 °C, iron at

1530°C and aluminum at 657°C.) Therefore, if the heat is not dissipated, it

would result in the failure of the cylinder material.

• Due to very high temperatures, the film of the lubricating oil will get oxidized, thus

producing carbon deposits on the surface.This will result in piston seizure.

• Due to overheating, large temperature differences may lead to a distortion of the engine

components due to the thermal stresses set up. This makes it necessary for, the

temperature variation to be kept to a minimum.

• Higher temperatures also lower the volumetric efficiency of the engine

Effects of overcooling

(a) Increased cylinder wear.

(b) Dilution of oil due to poor vaporization of petrol

(c) Greater formation of sludge.

(d) Oil does not thin out properly and fluid friction losses are increased.

(e) Engine does not achieve full power.

(f) Burnt gases, which leak past piston, condense in the crankcase to form

corrosive acids in oil.

(g) Lower thermal efficiency i.e. more consumption of fuel

Type of cooling system

In order to cool the engine a cooling medium is required. This can be either air or

a liquid accordingly there are two type of systems in general use for cooling the

IC engine. They are…..

Liquid or indirect cooling system

Air or direct cooling system

Air Cooling

In this type of cooling system, the heat, which is conducted to the outer parts of

the engine, is radiated and conducted away by the stream of air, which is obtained

from the atmosphere. In order to have efficient cooling by means of air, providing

fins around the cylinder and cylinder head increases the contact area. The fins are

metallic ridges, which are formed during the casting of the cylinder and cylinder

head

The amount of heat carried off by the air-cooling depends upon the following

factors:

(i) The total area of the fin surfaces,

(ii) The velocity and amount of the cooling air and

(iii) The temperature of the fins and of the cooling air.

TYPES of Air Cooling

System

1. Natural flow type

2. Forced Convection type

Advantages of Air Cooled Engines

1. Its design of air-cooled engine is simple.

2. It is lighter in weight than water-cooled engines due to the absence of water

jackets, radiator, circulating pump and the weight of the cooling water.

3. It is cheaper to manufacture.

4. It needs less care and maintenance.

5. This system of cooling is particularly advantageous where there are extreme

climatic conditions in the arctic or where there is scarcity of water as in

deserts.

6. No risk of damage from frost, such as cracking of cylinder jackets or radiator

water tubes.

limitations of Air Cooled Engines

Can be applied only to small and medium sized engines.

Cooling is not uniform.

Higher working temperature compared to water-cooling.

Produce more aerodynamic noise.

Specific fuel consumption is slightly higher.

Lower maximum allowable compression ratios.

The fan, if used absorbs as much as 5% of the power developed by the engine.

liquid cooled system

In this system mainly water is used and made to circulate throughthe jackets provided around the cylinder, cylinder-head, valve portsand seats where it extracts most of the heat.

It consists of a long flat, thin-walled tube with an opening, facing thewater pump outlet and a number of small openings along its lengththat directs the water against the exhaust valves. The fits in thewater jacket and can be removed from the front end of the block.

The heat is transferred from the cylinder walls and other parts byconvection and conduction. The liquid becomes heated in itspassage through the jackets and is in turn cooled by means of anair-cooled radiator system. The heat from liquid in turn is transferredto air. Hence it is called the indirect cooling system.

TYPES OF WATER COOLED SYSTEMS

•Direct or non-return system

•Thermo siphon system

•Forced circulation cooling system

•Evaporative cooling system

•Pressure cooling system

Thermo-siphon system

This system works on the principle that hot water

being lighter rises up and the cold water being

heavier goes down. In this system the radiator is

placed at a higher level than the engine for the easy

flow of water towards the engine. Heat is conducted

to the water jackets from where it is taken away due

to convection by the circulating water. As the water

jacket becomes hot, it rises to the top of the radiator.

Cold water from the radiator takes the place of the

rising hot water and in this way a circulation of water

is set up m the system. This helps in keeping the

engine at working temperature.

Disadvantages of Thermo-Siphon System

1 Rate of circulation is too slow.

2. Circulation commences only when there is a marked

difference in temperature.

FORCED or PUMP system

This system is similar in construction to the thermo-siphon system except that it makes use of a centrifugal pump to circulate the water throughout the water jackets and radiator

The water flows from the lower portion of the radiator to the water jacket of the engine through the centrifugal pump. After the circulation water comes back to the radiator, it loses its heat by the process of radiation.

Advantages

Cooling is ensured in all conditions

Disadvantages

Cooling is not temperature dependent

Cooling stops as soon as the engine is stopped, which is undesirable

Thermostat cooling

Thermostat

Placed between the cylinder head and top radiator

hose.

Regulates engine coolant temperature

The temperature that the thermostat opens is called

thermostat rating. (85-900 C most common)

Solid Expansion design – wax pellet expands as

temp increases, valve begins opening at rating & is

completely open within 10 degrees

If it fails in open position, engine runs cold resulting

in poor mileage and high wear & tear. If it fails

closed, creates temperature in the engine well

beyond normal limits. Many types of damage may

occur. (Can be checked by placing in the boiling

water)

Pressurized cooling In pressure cooling system moderate

pressure, say up to 2 bar, are commonly

used. As shown in fig a cap is fitted with

two valves which are loaded by a

compression spring and a vacuum valve.

When the coolant is cold both valves are

shut but as the engine warm up the

coolant temperature rises until it reaches a

certain preset value corresponding to the

desired pressure when the safety valve

open. But if the coolant temperature falls

during the engine operation the valve will

close again until the temperature rises to

equivalent pressure value. When the

engine is switched off and the coolant cool

down vacuum begin to form in the cooling

system but when the internal pressure fall

below atmosphere the vacuum valve is

opened by the higher outside pressure

and the cooling system then attains

atmosphere pressure

ADVANTAGES

1. Can take overload very easily

2. The placement of radiator is

not critical

3. Corrosion is lo because of the

pressurized coolant

4. No loss of water due to boiling

or evaporation

Evaporative cooling

This is predominately used in stationary

engine. In this the engine will be cooled

because of the evaporation the water in

the cylinder jackets into the steam.

Here the advantage is taken from the

high latent heat of vaporizing of the

water by allowing evaporating in the

cylinder jackets. If the steam is formed

at a pressure above atmospheric the

temperature will be above the normal

permissible temperature.

Components of water cooling system

Water cooling system mainly consists of :

(a) Radiator,

(b) Thermostat valve,

(c) Water pump,

(d) Fan,

(e) Water Jackets,

(f) Antifreeze mixtures.

Radiator It mainly consists of an upper tank and lower

tank and between them is a core. The upper

tank is connected to the water outlets from

the engines jackets by a hose pipe and the

lover tank is connect to the jacket inlet

through water pump by means of hose pipes.

There are 2-types of cores :

(a) Tubular

(b) Cellular

(c) Gilled tube radiator:

When the water is flowing down through the

radiator core, it is cooled partially by the fan

which blows air and partially by the air flow

developed by the forward motion of the

vehicle.

As shown through water passages and air

passages, wafer and air will be flowing for

cooling purpose.

It is to be noted that radiators are generally

made out of copper and brass and their joints

are made by soldering.

Water pump

It is used to pump the circulating water.

Impeller type pump will be mounted at the front

end.

Pump consists of an impeller mounted on a

shaft and enclosed in the pump casing.

The pump casing has inlet and outlet

openings. The pump is driven by means of

engine output shaft only through belts. When it

is driven water will be pumped.

FAN

•It is driven by the engine output shaft through same belt that drives the pump.

It is

provided behind the radiator and it blows air over the radiator for cooling

purpose.

WATER JACKETS

Cooling water jackets are provided around

the cylinder, cylinder head, valve seats

and any hot parts which are to be cooled.

Heat generated in the engine cylinder,

conducted through the cylinder walls to the

jackets. The water flowing through the

jackets absorbs this heat and gets hot.

This hot water will then be cooled in the

radiator

Purpose of LUBRICATION

Lubrication produces the following effects: (a) Reducing friction effect (b)

Cooling effect (c) Sealing effect (d) Cleaning effect.

(a) Reducing frictional effect: The primary purpose of the lubrication is to

reduce friction and wear between two rubbing surfaces. Two rubbing

surfaces always produce friction. The continuous friction produce heat

which causes wearing of parts and loss of power. In order to avoid friction,

the contact of two sliding surfaces must be reduced as far a possible. This

can be done by proper lubrication only. Lubrication forms an oil film

between two moving surfaces. Lubrication also reduces noise produced

by the movement of two metal surfaces over each other.

(b) Cooling effect: The heat, generated by piston, cylinder, and bearings is

removed by lubrication to a great extent. Lubrication creates cooling effect

on the engine parts.

(c) Sealing effect: The lubricant enters into the gap between the cylinder

liner, piston and piston rings. Thus, it prevents leakage of gases from the

engine cylinder.

(d) Cleaning effect: Lubrication keeps the engine clean by removing dirt or

carbon from inside of the engine along with the oil.

Dry Sump Lubrication System

FUELS

Introduction

The increase in energy consumption particularly in the past several decades has raised fears of exhausting vital natural resources

Rapid industrialization and massive growth in population has increased the dependence and use of natural fuels

Approximately 90% of our energy requirement are met by fossil fuels

Alternative Fuel Sources

Ethanol

Hydrogen

Natural Gas

Propane

Methanol

Ethanol

• Ethanol is an alcohol-based alternative fuel produced by fermenting and

distilling starch crops that have been converted into simple sugars. Feedstock

for this fuel include corn, barley, and wheat.

• Ethanol can also be produced from "cellulosic biomass" such as trees and

grasses and is called bioethanol. Ethanol is most commonly used to increase

octane and improve the emissions quality of gasoline.

Hydrogen

•It is the simplest and lightest fuel with atomic no. 1.

•Hydrogen burns more efficiently and creates energy more than gasoline.

•Hydrogen is extremely reactive with oxygen and makes it highly flammable

•Hydrogen mixed with natural gas can be used in internal combustion engine.

•Hydrogen is the perfect fuel to run fuel cells cause pure hydrogen reacts only

with oxygen releasing water thus no emissions.

Properties

Does not occur to any significant extent on earth in its free, elemental form.

Found in chemical compositions such as water and hydrocarbons, and dry coal.

Pure hydrogen contains no carbon thus burns to form water with no CO2 or CO emissions.

One kg of hydrogen contains roughly equivalent energy to one gallon of gasoline.

Can be stored as compressed hydrogen at 5,000 – 10,000 psi or liquid hydrogen (cooled to -4230F, -2520C).

There are two types of Hydrogen engine

Hydrogen IC engine

Hydrogen fuel cell engine

Hydrogen IC engine emits zero CO2 and minimal Nox when compared to other

engines. The SI engine can be used for it.

Generation of Hydrogen – Electrolysis of water

H2OH2 + ½ O2

Supply Hydrogen gas to intake valve of SI engine

Vary voltage of DC supply to control electrolysis process.

• Natural gas is a mixture of hydrocarbons, mainly methane, and is

produced either from gas wells or in conjunction with crude oil

production.

• Natural gas is consumed in the residential, commercial, industrial, and

utility markets.

• Natural gas can either be stored onboard a vehicle as compressed

natural gas (CNG) or as liquefied natural gas (LNG). Natural gas can

also be blended with hydrogen.

Natural Gas

CNG

In India CNG costs are at Rs. 40/kg much cheaper than petrol at Rs. 70/ltr.

The cost saving is immense along with reduced emissions and environment

friendly.

The use of CNG is mandatory for public transport in New Delhi as well as

for Ahmedabad.

The Delhi Transport Corporation operates the world’s largest fleet of CNG

buses.

Natural

GasProperties

• Lower emissions

• Lower smog producing gases (60-90% Light-Duty use, 90% in Mid to Heavy-

duty use)

• Can be used to make hydrogen to power the future fuel cell technology

Future of natural gas

• Natural gas is now being installed in 1 out of 5 transit buses today

• Fueling systems are being installed in home or public facilities

• Gradually the automobiles shift to natural gas fuel.

Propane

• Propane is a liquefied gas made up of propylene, butane, and butylene

from petro chemicals.

• By-product of natural gas processing and crude oil refining.

What are the benefits?

• A 98% reduction in toxic emissions in light-duty bi-fuel vehicles

• In the quantities needed it costs less than gasoline

• Very accessible compared to other alternative fuels.

Propane Properties

• HD5, the automotive propane standard, a mixture of 90% propane and

other hydrocarbons(proplyene).

• Contains 33% - 41% less energy content per gallon than gasoline.

• Vehicles can demonstrate a 60% reduction in ozone-forming emissions

compared to gasoline.

• High octane properties (~104) allow vehicles to operate with higher

compression ratios; leads to higher efficiency/fuel economy

• Methanol is wood alcohol, which can be made from natural gas, coal, or

wood.

• Methanol is produced from natural gas in production plants with 60% total

energy efficiency.

• Methanol can be made with any renewable resource containing carbon such

as seaweed, waste wood and garbage.

• Methanol fuel cells will greatly reduce carbon dioxide emissions for vehicles

and virtually eliminate smog and particulate pollution.

Methanol

Methanol

Properties

• Lower emissions

• Higher performance

• Lower risk of flammability

• Methanol can be used to easily make hydrogen

Conclusion

• The biggest is the lack of vehicles to use it, manufactures have stopped making

vehicles to run on Methanol

Characteristics of IC Engines

1. Brake Thermal Efficiency

2. Indicated Thermal Efficiency

3. Specific Fuel Consumption

4. Mechanical Efficiency

5. Volumetric Efficiency

6. Air Fuel Ratio

7. Mean Effective Pressure

Brake thermal efficiency

Brake thermal efficiency is defined as break power of a heat engine as a

function of the thermal input from the fuel. It is used to evaluate how well

an engine converts the heat from a fuel to mechanical energy

Indicated thermal efficiency

The thermal efficiency is a dimensionless performance measure of a device that

uses thermal energy, for example engine, a steam turbine, a steam engine, a

boiler, a furnace, etc, . Thermal efficiency indicates the extent to which the energy

added by work is converted to net heat output.

Mechanical efficiency

Mechanical efficiency is the measure of effectiveness of a machine's energy

and power that is input into the device into an output that makes force and

movement. Mechanical advantage by comparing the input and output force

you can find the advantage of a machine

Specific fuel consumption

Thrust specific fuel consumption (TSFC) or sometimes simply specific fuel

consumption, SFC, is an engineering term that is used to describe the fuel

efficiency of an engine design with respect to thrust output.

Volumetric Efficiency

Volumetric efficiency in internal combustion engine is defined as the ratio of the

mass density of the air-fuel mixture drawn into the cylinder at atmospheric

pressure (during the intake stroke) to the mass density of the same volume of

air in the intake manifold.

Air Fuel Ratio

Air–fuel ratio (AFR) is the mass ratio of air to fuel present in a combustion

process such as in an internal combustion engine

Mean Effective Pressure

Mean effective pressure is a quantity relating to the operation of a

reciprocating engine and is a valuable measure of an engine's capacity

to do work that is independent of engine displacement.

The performance of an engine is evaluated

on the basis of the following;

(a) Specific Fuel Consumption.

(b) Measurement of brake Power

(c) Specific Power Output.

Fuel consumption measurement

Fuel consumption is measured in two ways:

The fuel consumption of an engine is measured by determining the

volume flow in a given time interval and multiplying it by the specific

gravity of the fuel which should be measured occasionally to get an

accurate value.

Another method is to measure the time required for consumption of a

given mass of fuel

Measurement of brake power

The brake power measurement involves the determination of

the torque and the angular speed of the engine output shaft.

The torque measuring device is called a dynamometer.

Dynamometers can be broadly classified into two main types,

power absorption dynamometers and transmission

dynamometer.

Measurement of friction power

The difference between indicated power and the brake power output of

an engine is the friction power.

Almost invariably, the difference between a good engine and a bad

engine is due to difference between their frictional losses.

The frictional losses are ultimately dissipated to the cooling system (and

exhaust) as they appear in the form of frictional heat and this influences

the cooling capacity required. Moreover, lower friction means availability

of more brake power; hence brake specific fuel consumption is lower.

Types Of Dynamometers

Absorption Dynamometers

These dynamometers measure and absorb the power output of the

engine to which they are coupled. The power absorbed is usually

dissipated as heat by some means. Example of such dynamometers

is prony brake, rope brake, hydraulic dynamometer, etc.

Transmission Dynamometers: In transmission dynamometers, the

power is transmitted to the load coupled to the engine after it is

indicated on some type of scale. These are also called torque-

meters.

Characteristics of IC Engines

1. Brake Thermal Efficiency

2. Indicated Thermal Efficiency

3. Specific Fuel Consumption

4. Mechanical Efficiency

5. Volumetric Efficiency

6. Air Fuel Ratio

7. Mean Effective Pressure

Brake thermal efficiency

Brake thermal efficiency is defined as break power of a heat engine as a

function of the thermal input from the fuel. It is used to evaluate how well

an engine converts the heat from a fuel to mechanical energy

Indicated thermal efficiency

The thermal efficiency is a dimensionless performance measure of a device that

uses thermal energy, for example engine, a steam turbine, a steam engine, a

boiler, a furnace, etc, . Thermal efficiency indicates the extent to which the energy

added by work is converted to net heat output.

Mechanical efficiency

Mechanical efficiency is the measure of effectiveness of a machine's energy

and power that is input into the device into an output that makes force and

movement. Mechanical advantage by comparing the input and output force

you can find the advantage of a machine

Specific fuel consumption

Thrust specific fuel consumption (TSFC) or sometimes simply specific fuel

consumption, SFC, is an engineering term that is used to describe the fuel

efficiency of an engine design with respect to thrust output.

Volumetric Efficiency

Volumetric efficiency in internal combustion engine is defined as the ratio of the

mass density of the air-fuel mixture drawn into the cylinder at atmospheric

pressure (during the intake stroke) to the mass density of the same volume of

air in the intake manifold.

Air Fuel Ratio

Air–fuel ratio (AFR) is the mass ratio of air to fuel present in a combustion

process such as in an internal combustion engine

Mean Effective Pressure

Mean effective pressure is a quantity relating to the operation of a

reciprocating engine and is a valuable measure of an engine's capacity to do

work that is independent of engine displacement.

The performance of an engine is evaluated

on the basis of the following

(a) Specific Fuel Consumption.

(b) Measurement of brake Power

(c) Specific Power Output.

Fuel consumption measurement

Fuel consumption is measured in two ways:

The fuel consumption of an engine is measured by determining the

volume flow in a given time interval and multiplying it by the specific

gravity of the fuel which should be measured occasionally to get an

accurate value.

Another method is to measure the time required for consumption of a

given mass of fuel

Measurement of brake power

The brake power measurement involves the determination of the

torque and the angular speed of the engine output shaft. The

torque measuring device is called a dynamometer.

Dynamometers can be broadly classified into two main types,

power absorption dynamometers and transmission

dynamometer.

Measurement of friction power

The difference between indicated power and the brake power output

of an engine is the friction power.

Almost invariably, the difference between a good engine and a bad

engine is due to difference between their frictional losses.

The frictional losses are ultimately dissipated to the cooling system

(and exhaust) as they appear in the form of frictional heat and this

influences the cooling capacity required. Moreover, lower friction

means availability of more brake power; hence brake specific fuel

consumption is lower.

Types Of Dynamometers

Absorption Dynamometers

These dynamometers measure and absorb the power output of the

engine to which they are coupled. The power absorbed is usually

dissipated as heat by some means. Example of such dynamometers is

prony brake, rope brake, hydraulic dynamometer, etc.

Transmission Dynamometers: In transmission dynamometers, the

power is transmitted to the load coupled to the engine after it is indicated

on some type of scale. These are also called torque-meters.