DARSHAN INSTITUTE OF ENGG. & TECH. · DARSHAN INSTITUTE OF ENGG. & TECH. Department of Mechanical...

DARSHAN INSTITUTE OF ENGG. & TECH.

Department of Mechanical Engineering

B.E. Semester – VI

Internal Combustion Engine (2161902)

List of Experiments

Sr.

No. Title

Date of Performance

Date of submission

Sign Remark

1. To determine valve timing diagram of 4-stroke diesel engine.

2. Study about Engine emissions and their control.

3. Study about various methods for measurement and testing of IC engine.

4. Performance test of single cylinder four stroke water cooled diesel engine.

5. To prepare heat balance sheet on Single-Cylinder, water cooled Diesel Engine.

6. Study of Willan’s line method for determination of friction power for single cylinder diesel engine.

7. Study about supercharging and turbocharging of IC engine.

8. Study about ignition and governing system of IC engine.

9. Study about different fuel injection pump and nozzles.

10. To study measurement of calorific value for solid/liquid fuel.

Valve Timing Diagram

Department of Mechanical Engineering Internal Combustion Engine (2161902) Darshan Institute of Engineering & Technology, Rajkot Page. 1.1

VALVE TIMING DIAGRAM

Objective: To determine valve timing diagram of 4-stroke diesel engine.

Theory:

Though theoretically the valves are supposed to open and close only at dead centers,

there is a large deviation in actual practice. The deviation is because of the following two

factors:

Mechanical factors:

The poppet valves of the reciprocating engines are opened and closed by cam mechanism.

The clearance between the cam and the poppet and valve must be slowly taken up and

valve slowly lifted at first if noise and wear is to be avoided. For the same reason, the

valve cannot be closed abruptly else it will become bounced on its seat. Thus the valve

opening and closing periods are spread over a considerable number of crank shaft

degrees. As a result the opening of the valve must commence ahead of the time at which

it is fully opened (i.e. before dead centre). The same reasoning applied for closing time

and the valve must close after dead centers.

Dynamic factors:

Besides mechanical factors of opening and closing the valves the actual valve timing is

set, taking into consideration the dynamic effects of gas flow.

Intake valve timing:

Intake valve timing has a bearing on the actual quantity of air sucked during the suction

stroke i.e. it affects the volumetric efficiency. For a variable speed engine, the chosen

intake valve setting is a compromise between the best setting for low and high speeds.

There is a limit to the high speed for advantage of ram effect. At very high speeds, the

effects of fluid friction may be more than offset, the advantage of ram effect and the charge

for cylinder per cycle falls off.

Exhaust valve timing:

The exhaust valve is set to open before BDC. If the exhaust valve does not start to open

until BDC, the pressures in the cylinder would be above atmospheric pressure, the overall

effect of opening the valve prior to the time, the piston reaches BDC , result in overall gain

in output. The closing time of the exhaust valve offsets the volumetric efficiency. The

period when both the intake and exhaust valves are open, at the same time, is called valve

overlap this overlap should not be excessive, it allows the burned gases to be sucked into

the intake manifold or the fresh charge to escape through exhaust valve.

Procedure:

1) The circumference of the wheel is measured with the help of scale and thread.

2) By turning the fly wheel, various events are marked on the fly wheel they are:

1 Experiment No.



Top dead centre (TDC)

Inlet valve opening (IVO)

Inlet valve closing (IVC)

Exhaust valve opening (EVO)

Exhaust valve closing (EVC)

Bottom dead centre (BDC)

TDC: The fly wheel is slowly rotated and the point where the piston reaches the top most

position in the cylinder is marked on the flywheel as top dead centre.

IVO: The fly wheel is slowly rotated with the help of handle. The piston moves in the

cylinder. There are push rods which operate with the help of a cam. These rods aid in

opening and closing of valves through spring loaded mechanisms. The inlet valve opens

before TDC position when the push rod tightens. This is marked as IVO.

BDC: The fly wheel is further rotated. BDC is taken as the point when the piston reaches

bottom most point in the cylinder.

IVC: The fly wheel is further rotated. The push rod then passes through the phase in

which it loosens from tight position. The point is marked as IVC.

EVO: The exhaust valve opening and closing are determined in the same way as that of

inlet valve.

Precautions:

1) The valve opening is to be taken as the point where it begins to open.

2) The valve closure is taken as the point where valve closes completely.

3) The flywheel is to be rotated in proper direction.

Observations

Circumference of the fly wheel =____________ in cm

Radius of flywheel = ___________ in cm



Observation Table:

Sr.

No.

Event Distance from the nearest

Dead centre in cm.

Angular distance in

degrees

1 Inlet valve opening

Before BDC

2 Inlet valve closing

After BDC

3 Exhaust valve opening

Before BDC

4 Exhaust valve closing

After TDC

5 Valve overlap



Calculations:



Actual Valve Timing Diagram:

Engine Emissions

Department of Mechanical Engineering Internal Combustion Engine (2161902)

Darshan Institute of Engineering & Technology, Rajkot Page. 2.1

Experiment No: 2

ENGINE EMISSIONS

Objective: Study about Engine emissions and their control.

Theory:

Air pollution can be defined as an addition of any material which will have a

deteterious effect on life upon the earth. The main pollutants contributed by l.c. engines

are CO, NOX unburned hydro-carbons (HC) and other particulate emissions. Other

sources such as Electric power stations industrial domestic fuel consumers also add

pollution like NOx, S02 and particulate matters. An addition to this, all fuel burning

systems emit C02 in large quantities and this is more concerned with the Green House

Effect which is going to decide the health of Earth. A noted meteorologist recently

predicted that polluted air could put an end to life on the earth within a century. In

advanced countries like USA, the air pollution by vehicles is about 50 to 60% of the total

air pollution in the country. The pollution from automobiles is concerned is small in

urban areas whereas pollution from power stations is usually outside the populated

area. Therefore the air-pollution from automobile is more concerned as it directly

affects the human health.

As per the data available in 1973, USA had 10 crore petrol vehicles and total

pollutants emitted were 110 million tones of CO, 20 million tones of HC and 10 million

tones of NOx. It is also estimated that the number of vehicles will be 20 crore by the end

of 2000. As per the data available in 1979, Fig. shows the percentage contribution of

pollution by different sources of combustion. The figure shows the high pollution due to

petrol vehicles. There is growing realization of the seriousness of this problem over last

25 years. As a result of research efforts made to reduce these emissions, the emission

level has brought to a considerable low level in many advanced countries.

1. S.I. Engine-Emissions

S.I. engine emissions are divided into three categories as exhaust emission,

evaporative emission and crank case emission.

The major constituents which contribute to air pollution are CO, Nox and HC coming

from S.I. engine exhaust. The percentages of different constituents coming out from the

above three mentioned sources are shown as fig.

Engine Emissions



Fig.2.1 Distribution of emission by source

The relative amounts depend on engine design and operating conditions but are of

order, NOX → 500 to 1000 ppm (20 g/kg of fuel), CO → 1 to 2% (200 g/kg of fuel) and

HC→ 43000 ppm (25 g/kg of fuel). Fuel evaporation from fuel tank and Carburetor

exists even after engine shut down and these are unburned hydrocarbons. However

most modern engines, these non-exhaust unburned HC are effectively controlled by

returning the blow by gases from the crank case to the engine intake system by venting

the fuel tank and through a vapour absorbing carbon canister which is purged as some

of the engine intake air during normal engine operation.

A. Exhaust Emission

i) Hydrocarbons:

The unburnt hydrocarbon emission is the direct result of incomplete combustion.

The emission amount of hydrocarbon is closely related to design variables as induction

system and combustion chamber design and operating variables as A : F ratio, speed

load and mode of operation as idling, running or accelerating. Induction system

determines the optimum operating A : F ratio on the basis of evenness of fuel

distribution to the cylinders. The engine wear, lubrication, cooling and wall deposits are

likely to affect A : F ratio and indirectly emission of HC. The effect of A:F ratio on HC

emission is exactly similar to CO emission. Near stoichiometric A:F mixture, both HC and

CO emissions are higher and lean mixture has substantially low emissions of HC and CO.

The design of combustion chamber is important as fuel air mixture when comes in

contact with the walls get quenched and do not burn this unburned quenched mixture is

forced out of the combustion chamber during the exhaust. Because of high local

concentration of hydrocarbon leads to exhaust unburned hydrocarbons.

The following factors affect HC emission:

a. Surface/Volume Ratio.

b. Wall Quenching

c. Complete Combustion

d. Spark Plug Timing.

e. Effect of compression Ratio

ii) Carbon Monoxide (CO)

Carbon monoxide, being an intermediate product of combustion, remains in the

exhaust if the oxidation of CO to C02 is not complete. Theoretically, it can be said that

Engine Emissions



the petrol engine exhaust can be made free from CO by operating it at A : F ratio =15.

However, some CO is always present in the exhaust even at lean mixture and can be as

high as 1%. The percentage of CO increases during engine idling but decreases with

speed.

iii) Oxides of Nitrogen.

Oxides of N2 generally occur mainly in the form of NO and NO2. These are generally

formed at high temperature. Hence higher temperature and availability of free O2 are

the main two reasons for the formation of NO and N02. Many other nitrogen oxides, like

N2O4 , N2O, N203 , N205 are also formed in low concentrations but they decompose

spontaneously at ambient conditions to NO2.

B. Evaporative Emission

As mentioned earlier, here are two main sources of evaporative emissions, the fuel

tank and the main factors governing the tank emissions are fuel volatility and ambient

temperature but the tank design and location can also influence the emissions as

location affects the temperature. Insulation of fuel tank and vapour collection systems

have all been explored with a view to reduce the tank emissions. Carburetor emission

may be divided into two categories as running losses and parking losses. Although most

internally vented carburetors have an external vent which open at idle throttle position.

The existing pressure forces prevent outflow of vapours to the atmosphere. Internally

vented carburetor may enrich the mixture which in turn increases exhaust emission.

Carburetor losses are significant only during hot condition when the vehicle is in

operation. The fuel volatility also affects the carburetor emissions.

C. Crankcase Emission

It consists of engine blow by-gases and crank case lubricant fumes. From pollution

point of view, blow by gases are most important. The blow-by is the phenomenon of

leakage past the piston from the cylinder to the crankcase because of pressure

difference. The blow of HC emissions are about 20% of total HC emission from the

engine. This is further increased to 30% if the piston-rings are worn.

D. Lead Emission

Lead emissions come only from S.I. engines. The lead is present in the fuel as lead

tetraethyl or tetra methyl, to control the self-ignition tendency of fuel-air mixtures that

is responsible for knock (to improve the octane rating of the fuel). Most of the lead that

enters the engine is emitted from the exhaust to from very small particles of oxides and

oxyhalides in the atmosphere. A portion of the lead particles falls to the ground very

quickly, others are small enough to remain suspended in the atmosphere for some time,

before they fall out, usually after coagulation with other dusty material in the air. The

largest fraction of all man-made emissions of lead into atmosphere comes from vehicles.

2. C.I. ENGINE EMISSIONS

The diesel engine is used more than any other type of engine for transportation,

thermal power generation and many other industrial and agricultural applications. The

exhaust emissions from combustion in diesel engine are no different from those of

combustion processes in petrol engine, the difference being only in the level of

Engine Emissions



concentration of individual pollutants. The sample of diesel exhaust may be free from

smoke, odour and HC or may be heavily smoke laden highly malodorous and can have

heavy concentration of unburned HC.

The pollutants from diesel engine can be classified into two types as visible and

invisible emissions. Visible emission is the smoke which is objected more by the public:

The invisible emissions include, CO, HC, NOX , SO2 partially oxidized organics (as

aldehydes and ketones) and odours. An unpleasant odour is also heavily objected by the

public. The smoke and odour are not harmful to the public health but they are

objectionable because of its unsightliness, unbearable smell and possible reduction in

visibility. Other invisible emissions mentioned above have similar effect on health as

they are also emitted by petrol engines.

3. Emission (Euro & Bharat) norms

Emission norms are prescribed CO, HC and NOx levels set by the government which

a vehicle would emit when running on roads. All the manufacturers need to implement

the same for vehicles being manufactured from the date of implementation. Euro norms

refer to the permissible emission levels for both petrol and diesel vehicles, which have

been implemented in Europe. However in India, the government has adopted the Euro

norms for available fuel quality and the method of testing. Euro norms are set in

following categories:

EURO-1 (1993) - for passenger car

EURO-II (1996) - for passenger car

EURO-III (2000) - any vehicle

EURO-IV (2005) - any vehicle

EURO-V (2008) - for heavy good vehicle

Bharat norms are translated from Euro norms. The first Indian emission regulations

were idle emission limits which became effective in 1989. These idle emission

regulations were soon replaced by mass emission limits for both petrol (1991) and

diesel (1992) vehicles, which w ere gradually tightened during the 1990’s. Since the

year 2000, India started adopting European emission and fuel regulations for four

wheeled light-duty and for heavy duty vehicles. Indian emission regulations still apply

to two and three-wheeled vehicles. On October 6, 2003, the National Auto Fuel Policy

was announced, which planed a phased program for introducing EURO II to EURO IV

emission and fuel regulations by 2010. Current requirement is that all transport

vehicles carry a fitness certificate that is renewed each year after the first two years of

new vehicle registration.

The implementation schedule of emission standards in India is summarized in Table

1. The Euro/ Bharat state emission standards for different vehicles in India is given in

Table 2, 3, 4, 5, 6 and 7.

For 2 and 3-wheelers, Bharat Stage II applied from April 1, 2005 and Stage III

standards came into force in April 1, 2010. The roll out of Bharat Stage IV limits

nationwide was delayed by the challenge of convincing fuel producers to make the

necessary investments required to supply 50 ppm sulfur fuel nationwide. Potential

solutions that have been suggested include deregulation of diesel prices, an

Engine Emissions



environment compensation charge on diesel vehicles and an additional levy on diesel

fuel. Even in cities with Bharat Stage IV limits, there have been challenges ensuring the

dominance of compliant vehicles. Some of these challenges include: exemptions granted

to some speciality vehicle (e.g. taxis) manufacturers, registration of Bharat Stage III

vehicles by vehicle owners outside of their place residence due to loopholes in

residential proof, registration of commercial vehicles outside of the Bharat Stage IV

zones and insufficient availability of some speciality vehicles (e.g. garbage trucks ) in

Bharat Stage IV configurations.

Attempts to set fuel economy standards started in 2007, but it were delayed due to

inter-ministerial conflicts and pressure from the automobile industry. In January 2014,

the Ministry of Power the Bureau of Energy Efficiency notified minimum fuel efficiency

norms for passenger vehicles that are sold in India. Two sets of standards were

announced: one set for fiscal years 2016-17 to 2020-21 and another for fiscal year

2021-22 onwards [3037]. The Road Transport Ministry objected by claiming the new

emission levels were being mandated a year ahead of an earlier agreed to deadline.

Euro 5/6 norms are planned to be introduced across the country by the year 2020.

Table 1: Indian Emission Standards (4-Wheel Vehicles)

Standard Reference Year Region

India 2000 Euro I 2000 Nationwide

Bharat Stage II Euro II

2001 Delhi, Mumbai, Kolkata, Chennai

2003 Delhi, Mumbai, Kolkata, Chennai,

Bangalore, Hyderabad, Secunderabad,

Ahmadabad, Pune, Surat, Kanpur and Agra

2005 Nationwide

Bharat Stage III Euro III

2005 Delhi, Mumbai, Kolkata, Chennai,



2010 Nationwide

Bharat Stage IV Euro IV

2010 Delhi, Mumbai, Kolkata. Chennai,



Engine Emissions



Table 2: Emission Standards for Light-Duty Gasoline Vehicles (gross vehicle

weight < 3500 kg), g/km

Year. Reference CO HC HC+NOx NOx PM

2000 Euro I

2.72-6.90 - 0:97-1.70 - -

2005 Euro II 2.2-5.0 - 0.5-0.7 - -

2010 Euro III

2.3

4.17

5.22

0.20

0.25

0.29

-

0.15

0.18

0.21

-

2010 Euro IV

1.0

1.81

2.27

0.1

0.13

0.16

-

0.08

0.10

0.11

-

Table 3: Emission Standards for Light-Duty Diesel Vehicles (gross vehicle weight

<3500 kg), g/km

Year

Reference CO HC HC+NOx NOx PM

2000 Euro I 2.72-6.90 - 0.97-1.70 0.14-0.25 2005 Euro II 1.0-1.5 - 0.7-1.2 - 0.08-0.17

2010 Euro III

0.64

0.80

0.95

-

0.56

0.72

0.86

0.50

0.65

0.78

0.05

0.07

0.10

2010 0.50 - 0.30 0.25 0.025

Euro IV 0.63 0.39 0.33 0.04 0.74 0.46 0.39 0.06

Table 4: Emission Standards for Diesel Truck and Bus Engines (gross vehicle

weight > 3500 kg), g/kWh

Year Reference Test CO HC NOx PM

2000 Euro I ECE

R49

4.5 LI 8.0 0.36

2005 Euro II ECE

R49

4.0 1.1 7.0 0.15

2010 Euro HI ESC 2.1 0.66 5.0 0.10

ETC 5.45 0.78 5.0 0.16

2010 Euro IV ESC 1.5 0.46 3.5 0.02

ETC 4.0 0.55 3.5 0.03

Engine Emissions



Table 5: Emission Standards for two wheelers gasoline vehicle, g/km

Year Standard CO HC HC+NOx PM 2000 2.0 - 2.00 - 2005 BS II 1.5 - 1.5 - 2010 BS III 1.0 - 1.0 -

Table 6: Emission Standards for three wheelers gasoline vehicle, g/km

Year Standard CO HC HC+NOx PM

2000 4.00 - 2.00 -

2005 BS II 2.25 - 2.00 -

2010 BS III 1.25 - 1.25 -

Table 7: Emission Standards for two-three wheelers diesel vehicle, g/km

Year Standard CO HC HC+NOx PM

2005 BS II 1.00 - 0.85 0.10

2010 BS III 0.50 - 0.50 0.05

4. COTROL OF EMISSION FROM S.I. ENGINES

To reduce atmospheric pollution, two different approaches are followed:

1. To reduce the formation of pollutants in the emission by redesigning the engine system,

fuel system, cooling system and ignition system.

2. By destroying the pollutants after these have been formed.

In petrol engines, the main pollutants which are objectionable and are to be reduced are

HC, CO and NOx. The methods used are

a) Modifications in the Engine design.

b) Modifying the Fuel used.

c) Exhaust gas treatment devices.

d) Evaporative emissive control devices.

e) Catalytic Converters.

Measurement and Testing of IC Engine



Experiment No. 3

MEASUREMENT AND TESTING OF IC ENGINE

Objective: Study about various methods for measurement and testing of IC

engine.

Theory:

The important performance parameters of I.C. engines are as follows:

a) Power and Mechanical Efficiency.

b) Mean Effective Pressure and Torque.

c) Specific Output.

d) Volumetric Efficiency.

e) Fuel-air Ratio.

f) Specific Fuel Consumption.

g) Thermal Efficiency and Heat Balance.

h) Exhaust Smoke and Other Emissions.

i) Specific Weight.

1. MEASUREMENT OF INDICATED POWER

The power developed in the cylinder is known as Indicated Horse Power and is

designated as IP. The IP of an engine at a particular running condition is obtained from

the indicator diagram. The indicator diagram is the p-v diagram for one cycle at that

load drawn with the help of indicator fitted on the engine. The construction and use of

mechanical indicator for obtaining p-v diagram is already explained.

A typical p-v diagram taken by a mechanical indicator is shown in Figure

Fig.3.1 p-v diagram taken by mechanical indicator

The areas, the positive loop and negative loop, are measured with the help of a

planimeter and let these be Ap and An cm2 respectively, the net positive area is (Ap –




An). Let the actual length of the diagram as measured be L cm, then the average height

of the net positive area is given by

H = (Ap-An)/L in centimeter

The height multiplied by spring-strength (or spring number) gives the indicated

mean effective pressure of the cycle.

Imep = (Ap – An)*S/L

Where, S is spring scale and it is defined as a force per unit area required to compress

the spring through a height of one centimeter (N/m2/cm).

Generally the area of negative loop An is negligible compared with the positive loop

and it cannot be easily measured especially when it is taken with the spring used for

taking positive loop.

Special light springs are used to obtain the negative loop. When two different

springs are used for taking the p-v diagram of positive and negative loop, then the net

indicated mean effective pressure is given by

Pm=Ap*Sp/L-An*Sn/L

Where,

Sp = Spring strength used for taking p-v diagram of positive loop, (N/m2 per cm)

Sn = Spring strength used for taking p-v diagram of negative loop, (N/m2 per cm)

Ap = Area in Cm2 of positive loop taken with spring of strength Sp

An = Area in Cm2 of positive loop taken with spring of strength Sn

Sometimes spring strength is also noted as spring constant.

The IP developed by the engine is given by

IP=PmLAn/L

Where ,‘n’ is the number of working strokes per second.

2. MEASUREMENT OF B.P

Part of the power developed in the engine cylinder is used to overcome the internal

friction. The net power available at the shaft is known as brake power and it is denoted

by B.P. B.P. can be measured with the help of prony brake dynamometer, hydraulic

dynamometer, electric dynamometer, eddy current type dynamometer and swinging

field dynamometer. The arrangement used for measuring the BP of the engine with the

help of prony brake dynamometer is described below:

a) Prony Brake:

The arrangement of the braking system is shown in Figure. It consists of brake

shoes made of wood and these are clamped on to the rim of the brake wheel by means




of the bolts. The pressure on the rim is adjusted with the help of nut and springs as

shown in Fig.

A load bar extends from top of the brake and a load carrier is attached to the end of

the load bar. Weight kept on this load carrier is balanced by the torque reaction in the

shoes. The load arm is kept horizontal to keep the arm length constant.

The energy supplied by engine to the brake is eventually dissipated as heat.

Therefore, most of the brakes are provided with a means of supply of cooling water to

the inside rim of the brake drum.

Fig.3.2 Prony brake dynamometer

The BP of the engine is given by

B.P (brake power) = 2*p*N*T/60 watts =2*p*N*T/60*1000 Kw ….. (9)

Where T = (W.L) (N-m)

Where W = Weight on load carrier, (N)

And L = Distance from the centre of shaft to the point of load-meter in meters.

The prony brake is inexpensive, simple in operation and easy to construct. It is,

therefore used extensively for testing of low speed engines. At high speeds, grabbing

and chattering of the band occur and lead to difficulty in maintaining constant load. The

main disadvantage of the prony brake is its constant torque at any one band pressure

and therefore its inability to compensate for varying conditions.

3. MEASUREMENT OF AIR-CONSUMPTION

One can say the mixture of air and fuel is the food for an engine. For finding out the

performance of the engine accurate measurement of both is essential.

In IC engines, the satisfactory measurement of air consumption is quite difficult

because the flow is pulsating, due to the cyclic nature of the engine and because the air a

compressible fluid. Therefore, the simple method of using an orifice in the induction

pipe is not satisfactory since the reading will be pulsating and unreliable.




All kinetic flow-inferring systems such as nozzles, orifices and venturies have a

square law relationship between flow rate and differential pressure which gives rise to

severe errors on unsteady flow. Pulsation produced errors are roughly inversely

proportional to the pressure across the orifice for a given set of flow conditions.

The various methods and meters used for air flow measurement include

(a) Air box method, and

(b) Viscous-flow air meter.

4. MEASUREMENT OF FUEL CONSUMPTION

Fuel consumption is measured in two ways:

a) 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.

b) Another method is to measure the time required for consumption of a given mass of

fuel.

Accurate measurement of fuel consumption is very important in engine testing

work. As already mentioned two basic types of fuel measurement methods are :

Volumetric type

Gravimetric type.

Volumetric type flow meter includes Burette method, Automatic Burette low meter

and Turbine flow meter.

Gravimetric Fuel Flow Measurement

The efficiency of an engine is related to the kilograms of fuel which are consumed

and not the number of liters. The method of measuring volume flow and then correcting

it for specific gravity variations is quite inconvenient and inherently limited in accuracy.

Instead if the weight of the fuel consumed is directly measured a great

improvement in accuracy and cost can be obtained. There are three types of

gravimetric type systems which are commercially available include Actual weighing of

fuel consumed, Four Orifice Flow meter, etc.

Performance Test



Experiment No. 4

PERFORMANCE TEST

Objective: Performance test of single cylinder four stroke water cooled

diesel engine.

EQUIPMENT:

1. 4- Stroke, single cylinder Diesel engine with a rope break dynamometer.

2. Tachometer (0-2000 rpm.)

3. Stopwatch.

SPECIFICATIONS:

Bore : 110 mm

Stroke : 140 mm

Rated Speed : 700 rpm

Rated Power : 6 HP / 4.4 kW

Cubic Capacity : 1331 cc

Pulley Dia. : 12 inch

Rope Dia, : 1.5 inch

Spring Balance : Max. 100 kg

Apparatus:

This is a water cooled single cylinder vertical diesel engine is coupled to a rope pulley

break arrangement to absorb the power produced. Necessary weights and spring

balances are included to apply load on the break drum. Suitable cooling water

arrangement for the break drum is provided. Separate cooling water lines are provided

for the engine cooling. Thermocouples are provided for measuring temperature. A fuel

measuring system consists of a fuel tank mounted on a stand, burette, and a 3-way cock.

Theory:

Single cylinder stationary, constant speed diesel engines are generally quality governed.

As such the air supplied to the engine is not throttled as in the case of S.I. engines. To

meet the power requirements of the shaft, the quantity of fuel injected into the cylinder

is varied by the rack in the fuel pump. The rack is usually controlled by a governor or by

a hand. The air flow rate of single cylinder engine operating at constant speed does not

vary appreciably with the output of the engine. Since the fuel flow rate varies more or

less linearly with output, the fuel air ratio increases with output. Performance tests can

be conducted either at constant speed (or) at constant throttle. The constant speed

method yields the F.P. of the engine.

Procedure:

1. Calculate maximum load to be applied for a selected engine

Performance Test



2. Check the fuel supply, water circulation in the water system and lubricating oil in

the oil sump.

3. Ensure no load condition

4. The engine is started and allowed to run on idle speed for a few minutes.

5. Gradually the engine is loaded by mechanical brake method and the speed is

maintained constant.

6. Make sure the cooling water is supplied to the brake drum.

7. Load the engine in steps of 0%, 25%, 50%, 75% & 100% of maximum load to be

applied.

8. Note the corresponding readings of spring balance, fuel consumption,

manometer reading.

9. After taking the readings, unload the engine, allow it to run for few minutes and

then stop the engine.

Observations:

1. Calorific Value of Fuel =……………….

2. Density of fuel = …………………

3. Dia. of Pulley (D) = ……………. m

4. Dia. of Rope (d) = ……………. m

Sr. No.

Dead Weight

(W in kg)

Spring balance reading (S in kg)

Net Load (S-W) (kg)

RPM (N)

Time for 10 ml fuel consumption, t

(s)

1

2

3

4

5

6

7

8

Calculations:

1. Volume of fuel consumed = ……….. ml = ………….. m3

2. Volume of fuel consumed per unit time = ..............f

VolumeV

t

3. Mass flow rate of fuel = ....................f f fm V kg/s

4. Brake Power

Performance Test



2 ( )2

60000

D dN S W g

BP

..................BP kW

5. Brake Thermal Efficiency

bth

f

BP

m CV

..............bth

6. Brake Specific Fuel Consumption

fmBSFC

BP

................. /BSFC kg kW hr

Performance Test



Result Table:

Sr. No.

Net Load (kg)

RPM Brake power Brake Thermal Efficiency (%)

Brake specific fuel

consumption (kg/kWhr)

1

2

3

4

5

6

7

8

Heat Balance Sheet



Experiment No. 5

HEAT BALANCE SHEET

Objective: To prepare heat balance sheet on Single-Cylinder, water cooled

Diesel Engine.

Theory and Description:

The thermal energy produced by the combustion of fuel in an engine is not

completely utilized for the production of the mechanical power. The thermal efficiency

of I. C. Engines is about 33 %. Of the available heat energy in the fuel, about 1/3 is lost

through the exhaust system, and 1/3 is absorbed and dissipated by the cooling system.

It is the purpose of heat balance sheet to know the heat energy distribution, that

is, how and where the input energy from the fuel is is distributed.

The heat balance sheet of an I.C. Engine includes the following heat distributions:

a) Heat energy available from the fuel burnt.

b) Heat energy equivalent to output brake power.

c) Heat energy lost to engine cooling water.

d) Heat energy carried away by the exhaust gases.

e) Unaccounted heat energy loss.

Procedure:

1. Before starting the engine check the fuel supply, lubrication oil, and availability of

cooling water. 2. Set the dynamometer to zero load and run the engine till it attain the working

temperature and steady state condition. 3. Note down the fuel consumption rate, Engine cooling water flow rate, inlet and

outlet temperature of the engine cooling water, Exhaust gases cooling water flow

rate, Air flow rate, and Air inlet temperature. 4. Increase the load on dynamometer from no load to 20 %, 40 %, 60% and 80 % and

full load. 5. Note down the fuel consumption rate, Engine cooling water flow rate, inlet and

outlet temperature of the engine cooling water, Exhaust gases temperature, Air flow

rate, and Air inlet temperature. 6. Disengage the dynamometer and stop the engine. 7. Do the necessary calculation and prepare the heat balance sheet.

Heat Balance Sheet



Observation: 1. Engine Speed (N) = ………. Rpm

2. Calorific Value of fuel (CV) = ………….. kJ/kg

3. Specific heat of water = ……………. kJ/kgK

4. Maximum load on the Engine (S-W) = …………….. kg

5. Pulley dia. (Dp) = …………….. m

6. Rope dia. (dr) = …………… m

7. Air inlet temperature (T1) = …………˚C = ………… K

8. Cooling water inlet temperature (T2) = …………˚C = ………… K

9. Cooling water outlet temperature (T3) = …………˚C = ………… K

10. Exhaust gas temperature (T4) = …………˚C = ………… K

11. Velocity of air (Va) = ………… m/s

12. Dia. of air inlet pipe (d) = ………….

13. Volume of the fuel consumed (Vf) = ……………. ml

14. Time for consumption of fuel (s) = ……….. s

15. Density of Fuel (𝜌𝑓) = ………….. kg/m3

16. Water flow rate (Vw) = …………. lph

17. Density of water (𝜌𝑤) = ………….. kg/m3

Calculations:

a) Mass flow rate of fuel

f f

f

Vm

t

b) Heat energy input by burning of fuel

Heat Input fm CV

c) Brake Power

2 (S W)g2

60000

P rD dN

BP

Heat Balance Sheet



d) Heat carried by cooling water

Mass flow rate of water (kg/s)

f w wm V

Heat carried by cooling water

3 2( )w Pwm C T T

e) Heat Carried by exhaust gases

Mass flow rate of air a aAV

A = area of inlet pipe 2

4d

A = …………… m2

am ………………. kg/s

Mass flow rate of exhaust gases = g a fm m m = …………. kg/s

Heat carried by exhaust gases = 4 1( )g Pgm C T T

f) Unaccounted heat losses

= Heat Input – (Brake Power + Heat carried by cooling water + Heat carried by

exhaust gases)

= ……………. kW

Heat Balance Sheet



Result

Heat Balance Sheet for Load = …………. kg

Energy Input kJ/s % Heat expenditure per second kJ/s %

Heat supplied by

combustion of fuel

(a) Heat in BP

(b) Heat carried by jacket

cooling water

(c) Heat carried by exhaust

gases

(d) Unaccounted heat loss

Total

Willan’s Line Method



EXPERIMENT NO. 6

WILLAN’S LINE METHOD

Objective: Study of Willan’s line method for determination of friction

power for single cylinder diesel engine.

Theory:

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.

Friction power includes the frictional losses and the pumping losses. During suction

and exhaust strokes the piston must move against a gaseous pressure and power

required to do this is called the “pumping losses”. The friction loss is made up of the

energy loss due to friction between the piston and cylinder walls, piston rings and

cylinder walls, and between the crank shaft and camshaft and their bearings, as well as

by the loss incurred by driving the essential accessories, such as water pump, ignition

unit etc.

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. One of the method for measurement of frictional

power is Willan's Line Method or Fuel Rate Extrapolation.

In Willan’s line method, gross fuel consumption vs. BP at a constant speed is plotted

and the graph is extrapolated back to zero fuel consumption as illustrated in Figure 6.1

The point where this graph cuts the BP axis in an indication of the friction power of the

engine at that speed. This negative work represents the combined loss due to

mechanical friction, pumping and blow by.

In petrol engine, we keep the air-fuel mixture constant and vary the amount of the

mixture intake for required torque or power. This is called quantitative governing. In

diesel engine, we draw a constant volume of air (compressed) and vary the fuel injected.

Technically, we alter the quality of the air - fuel mixture, this is called qualitative

governing.

In SI engine, at low speeds, the air mixture intake is very low (quantitative

governing). Hence, there will be a low pressure region created inside the cylinder due to

which, there will be pumping losses. Therefore, there will be more friction power than

actual, we get erroneous output if we use Willan’s line test for SI engine.

If we use the same test for CI engines, there is qualitative governing and hence, there

will be fixed amount of air entering the cylinder and no negative pressure and pumping

losses occurs. So, we get a relatively closer value of friction power, the errors are greatly

minimized.

So, Willan's line method is applicable only to Diesel (C.I) engines.

Willan’s Line Method



Fig.6.1 Willan’s line method

The main drawback of this method is the long distance to be extrapolated from data

measured between 5 and 40% load towards the zero line of fuel input.

The directional margin of error is rather wide because of the graph which may

not be a straight line many times.

The changing slope along the curve indicates part efficiencies of increments of

fuel. The pronounced change in the slope of this line near full load reflects the

limiting influence of the air-fuel ratio and of the quality of combustion.

Similarly, there is a slight curvature at light loads. This is perhaps due to

difficulty in injecting accurately and consistently very small quantities of fuel per

cycle.

Therefore, it is essential that great care should be taken at light loads to establish

the true nature of the curve.

The Willan’s line for a swirl-chamber CI engine is straighter than that for a direct

injection type engine.

The accuracy obtained in this method is good and compares favorably with other

methods if extrapolation is carefully done.

Supercharging

Department of Mechanical Engineering Internal Combustion Engine (2161902) Darshan Institute of Engineering & Technology, Rajkot Page.7.1

EXPERIMENT NO: 7

SUPERCHARGING

Objective: Study about supercharging and turbocharging of IC engine.

Theory: The power output of an engine depends upon the amount of air indicated per unit

time, the degree of utilization of this air and the thermal efficiency of the engine. The

amount of air inducted per unit time can be increased by increasing the engine speed or

by increasing the density of air at intake. The increase in engine speed calls for rigid and

robust engine as the inertia loads increase. The engine friction and bearing loads also

increase and the volumetric efficiency decreases when the speed is increased. The

method of increasing the inlet air density, called supercharging, is usually employed to

increase the power output of the engine. This is done by supplying air at a pressure higher

than the pressure at which the engine naturally aspirates air from the atmosphere by

using a pressure boosting device called a supercharger.

The power output can also be increased by increasing the thermal efficiency of the

engine, say, by increasing' the compression ratio. However, this increases the maximum

cylinder pressure. The rate of increase of maximum cylinder pressure is less than the rate

of increase of break mean effective pressure in case of a supercharged engine. This means

that for a given maximum cylinder pressure more power can be obtained by

supercharging as compared to that obtained by increase in compression ratio. The rate

of increase of maximum temperature is also low in case of supercharging. This results in

lower thermal loads.

Fig.7.1 Supercharging

Objective of supercharging

The increase in the amount of air inducted per unit time by supercharging is obtained

mainly to bum a greater amount of fuel in a given engine and thus increase its power

output. The objects of supercharging include one or more of the following:

1. To increase the power output for a given weight and bulk of the engine. This is

important for aircraft, marine and automotive engines where weight and space

are important.

Supercharging


2. To compensate for the loss of power due to altitude. This mainly relates to aircraft

engines which lose power at an approximate rate of one per cent 100 meters

altitude. This is also relevant for other engines which are used at high altitudes.

3. To obtain more power from an existing engine.

Thermodynamic cycle

The schematic arrangement is shown in figure 1.The theoretical operating cycle for

both natural aspirated and supercharges petrol engines can be compared on p-v diagram.

The larger upper loop is a measure of the positive power develops in the cylinder while

the lower loop is represents the negative power needed to fill the cylinder with fresh

charge.

Naturally aspirated cycle of operation:

The larger area enclosed in the upper loop is propos ional to the useful work perform

by the combustion on the piston whereas the small loop area which is below the

atmosphere line is measure of the work done in inducing the fresh charge into the

cylinder.

Fig.7.2 Otto cycle on P-V diagram

Supercharged cycle of operation:

With this pressurized charge system the larger upper loop area represents a measure

of the work done in moving the piston to and fro so that crank shaft rotates. Small loop

area represents pumping work of the fresh charge into the cylinder.

Types of Superchargers.

There are two main types of superchargers defined according to the method of

compression

I. Positive displacement

II. Dynamic compressors

The former deliver a fairly constant level of pressure increase at all engine speeds

(RPM), whereas the latter deliver increasing pressure with increasing engine speed.

Supercharging


Dynamic Compressors rely on accelerating the air to high speed and then exchanging that

velocity for pressure by diffusing or slowing it down.

Effect of supercharging

Air is supplied at high pressure which increases volumetric efficiency.

Supercharged engines develop more power

Mechanical efficiency is more than that of naturally aspirated engines.

Supercharging gives better turbulence, proper air fuel ratio and efficient

combustion of fuel

The specific fuel consumption of super charged engines is less due to better

turbulence and proper air fuel mixture.

Super charging tends to increase the possibility of detonation in SI engines.

Super-charging tends to decrease the possibility of knocking in CI engines.

At high altitudes, it is possible to obtain sufficient air by supercharging only.

Super-charging shortens the 'delay period'.

Different methods/arrangements of supercharging

Fig.7.3 Different arrangements for super charging

Supercharging


TURBOCHARGERS:

Turbochargers are a type of forced induction system whose function is same as that

of Supercharger. They compress the air flowing into the engine. A turbocharged engine

produces more power overall than the same engine without the charging. This can

significantly improve the power-to-weight ratio for the engine.

In order to achieve this boost, the turbocharger uses the exhaust flow from the engine

to spin a turbine, which in turn spins an air pump. The turbine in the turbocharger spins

at speeds of up to 150,000 RPM. The turbocharger is bolted to the exhaust manifold of

the engine. The exhaust from the cylinders spins the turbine, which works like a gas

turbine engine. The turbine is connected by a shaft to the compressor, which is located

between the air filter and the intake manifold. The compressor pressurizes the air going

into the pistons.

The exhaust from the cylinders passes through the turbine blades, causing the

turbine to spin. The more exhaust that goes through the blades, the faster they spin. On

the other end of the shaft that the turbine is attached to, the compressor which pumps air

into the cylinders. The compressor is a type of centrifugal pump; it draws air in at the

centre of its blades and flings it outward as it spins. In order to handle speeds of up to

150,000 rpm, the turbine shaft has to be supported very carefully. Most turbochargers

use a ‘Fluid Bearing’. This type of bearing supports the shaft on a thin layer of oil that is

constantly pumped around the shaft. This serves two purposes: It cools the shaft and

some of the other turbocharger parts and it allows the shaft to spin without much friction.

Some turbochargers use ‘Ball Bearings’ instead of fluid bearings to support the turbine

shaft. But these are not your regular ball bearings, they are super-precise bearings made

of advanced materials to handle the speeds and temperatures of the turbocharger.

Fig.7.4 Otto cycle with turbocharging

Ceramic turbine blades are lighter than the steel blades used in most turbochargers.

When air is compressed, it heats up; and when air heats up, it expands. So some of the

Supercharging


pressure increase from a turbocharger is the result of heating the air before it goes into

the engine. An intercooler or charge air cooler is an additional component that looks

something like a radiator, except air passes through the inside as well as the outside of

the intercooler. The intake air passes through sealed passage ways inside the cooler,

while cooler air from outside is blown across fins by the engine cooling fan.

Methods of Turbocharging and their Advantages and Limits:

1. Constant Pressure Turbocharging:

The exhaust from various cylinders discharge into a common manifold at pressure at

pressures higher than the atmospheric pressure. The exhaust gasses from all the

expanded in the exhaust valves to an approximately constant pressure in common

manifold from here it passes to turbine. Thus the blow-down energy, in the form of

internal energy, is converted into work in the turbine. The exhaust gases are maintained

at constant pressure during the whole cycle so that a pure Reaction turbine can be used.

Advantages:

The exhaust piping is very simple for a multi-cylinder engine as well as single-

cylinder; highly efficient turbine can be used.

Engine speed is not limited by the pressure waves in the exhaust pipes.

Disadvantages:

Scavenging is not efficient.

At part load the efficiency of turbine reduces due to partial admissions to the

turbine.

2. Pulse Turbocharging:

Considerable part of the blow-down energy is converted into exhaust pulses as soon

as the exhaust valve opens. Towards the end of exhaust the pressure in the exhaust pipe

drops below the scavenging and large air pressure making scavenging quite easy. The

rate of the exhaust gas at the various turbine inlets is different and variable in time.

Advantages:

The space required is less due to short and smaller diameter pipes.

Comparatively better scavenging is obtained at low loads due to reduced pressure.

Disadvantages:

With large number of cylinders complicated inlet and exhaust pipe arrangements

are needed.

The length of the pipe or engine speed is limited.

3. Two Stage Turbocharging:

Two –stage turbocharging is defined as use of two turbochargers of different sizes In

series; for example a high-pressure stage operating on pulse system and a low-pressure

stage on constant pressure operation.

Supercharging


Fig.7.6 Two Stage Turbocharging

Advantages:

Better matching of the turbochargers to engine operating conditions possible.

The efficiency of two-stage turbocharger is higher than that of a single stage

turbocharger having a high boost ratio.

Disadvantages:

The space requirement is higher.

The total system is heavier.

Limitations of Turbocharging:

The use of turbochargers requires special exhaust manifolds.

Fuel injection has to be modified to inject more fuel per unit time.

The efficiency of the turbine blades is very sensitive to gas velocity so that it is

very difficult to obtain good efficiency over a wide range of operations.

One of the main problems with turbochargers is that they do not provide an

immediate power boost. It takes a second for the turbine to get up to speed before

boost is produced. This results in a lag known as ‘Turbo Lag’.

Ignition and Governing System


Darshan Institute of Engineering and Technology, Rajkot Page. 8.1

Experiment No. 8

IGNITION AND GOVERNING SYSTEM

Objective: Study about ignition and governing system of IC engine.

Theory: In S.I. engines the combustion process is initiated by a spark between the two

electrodes of spark plug. This occurs just before the end of compression stroke. The

ignition process must add necessary energy for starting and sustaining burning of the

fuel till combustion takes place.

Ignition is only a prerequisite of combustion. It does not influence the gross

combustion process. It is only a small scale phenomenon taking place within a specified

small zone in the combustion chamber. Ignition only ensures initiation of combustion

process and has no degree intensively or extensively.

Energy requirements for ignition

A spark energy below 10 mill joules is adequate to initiate combustion for A / F ratio

12-13:1 ("Range of mixtures normally used); the duration of few micro-seconds is

sufficient to start combustion.

A spark can be struck between the gap in the two electrodes of the spark plug by

sufficiently high voltage. There is a critical voltage called breakdown voltage below

which no sparking would -occur. In practice the pressure, temperature and density

have a profound influence on the voltage required to cause the spark. Also, the striking

voltage is increased due to the fouling factor of the electrodes owing to deposits and

abrasion.

For automotive engines, in normal practice, the spark energy to the tune of 40 mill

joules and duration of about 0.5 millisecond is sufficient over entire range of operation.

Requirements of an ignition system

For an ignition system to be acceptable it must be moderately priced, reliable and its

performance must be adequate to meet all the demands imposed on it by various

operating conditions.

An ignition system should fulfill the following requirements:

1. It should have an adequate reserve of secondary voltage and ignition energy over

the entire operating speed range of the engine.

2. It should consume the minimum of power and convert it efficiently to a high-energy

spark across the spark-plug electrode gap.

3. It should have a spark duration which is sufficient to establish burning of the air-fuel

mixture under all operating conditions.

4. It should have the ability to produce an ignition spark when a shunt (short) is

established over the spark-plug electrode insulator surface, due possibly to carbon,

oil or lead deposits, liquid fuel or water condensation.

5. Good performance at high speeds.




6. Longer life of breaker points and spark plug.

7. Good starting when the breaker points open slowly at cranking speed.

8. Good reproducibility of secondary voltage rise and maximum rise.

9. Adjustment of spark advance with speed and load.

The basic source of electrical energy is either battery, a generator or a magneto.

The battery and generator normally provide 6 V or 12 V direct current, while the

magneto provides an alternating current of higher voltage.

The low voltage (6 V or 12 V) is boosted to a very high potential of about 10 kV to 20

kV, in order to overcome the spark gap resistance and to release enough energy to

initiate self-propagating flame from within the combustible mixture.

Basic ignition systems

The following basic ignition systems are in use:

1. Battery ignition system—Conventional, transistor assisted.

2. Magneto ignition system—Low tension, high tension.

3. Electronic ignition system.

The difference between Battery and Magneto ignition systems lies only in the source

of electrical energy. Whereas 'Battery ignition system' uses a battery, 'Magneto ignition

system' uses a magneto to supply low voltage, all other system components being

similar

1. Battery (or coil) ignition system

It is a commonly used system because of its combined cheapness, convenience of

maintenance, attention and general suitability.

Construction: This system consists of the following components:

1. Battery (6 or 12 volts)

2. Ignition switch

3. Induction coil

4. Circuit/contact breaker

5. Condenser

6. Distributor.

Working:

A cam mounted on cam shaft causes the contact breaker point to open and close.

When the ignition switch is on and the primary circuit is closed by the contact

breaker, a current begins to flow through the primary coil and magnetize the core of the

coil. Therefore, e.m.f. is induced in the secondary circuit. The e.m.f. induced in the

secondary coil is proportional to the rate at which the magnetic flux increases. The

e.m.f. produced in the secondary due to the growth of current in the primary is not

sufficient to produce, a spark at the spark plug because the primary circuit has to

establish the magnetic flux.




When the primary circuit is opened by the contact breaker, the magnetic field

collapses. Electromotive force is induced in the secondary which is directly

proportional to the rate at which the magnetic field of the core collapses which in turn

depends on the rate of decrease of the primary current. A condenser is connected

across the contact breaker in the primary circuit. This helps to collapse the field very

rapidly by absorbing part of the energy of the magnetic field which is thrown back into

the primary winding and produces a very high voltage in the secondary. This e.m.f. in

the secondary is sufficient to ignite the charge by producing the spark.

As magnetic field collapse rapidly, high voltage of the order of 10,000 to 20,000 V

induced. This high voltage current from secondary windings is supplied to the

individual spark plug through distributor. This process is repeated continuously when

contact breaker open and close and every time high voltage generated which is

distributed by distributor and supplies to each spark plug according to firing order.

Fig.8.1 Battery (or coil) ignition system

Advantages:

1. It offers better sparks at low speeds, starting and for cranking purposes.

2. The initial cost of the system is low.

3. It is a reliable system and periodical maintenance required is negligible except

for battery.

4. Items requiring attention can be easily located in more accessible position than

those of magnetos.

5. The high speed engine drive is usually simpler than magneto drive,

6. Adjustment of spark timing has no detrimental effect over the complete ignition

timing range.

Disadvantages:

1. With the increasing speed, sparking voltage drops.

2. Battery, the only unreliable component of the system needs regular attention. In

case battery runs down, the engine cannot be started as induction coil fails to

operate.

3. Because of battery, bulk of the system is high.




2. Magneto ignition system

The magneto ignition system is similar in principle to the battery system except that

the magnetic field in the core of the primary and secondary windings is produced by a

rotating permanent magnet. As the magnet turns, the field is produced from a positive

maximum to a negative maximum and back again. As this magnetic field falls from a

positive maximum value, a voltage and current are induced in the primary winding.

The primary current produces a magnetic field of its own which keeps the total

magnetic field surrounding the primary and secondary windings approximately

constant. When the permanent magnet has turned for enough so that its contribution to

the total field is strongly negative, the breaker points are opened and the magnetic field

about the secondary winding suddenly goes from a high positive value to a high

negative value. This induces a high voltage in the secondary winding which is led to the

proper spark plug by the distributor.

Fig.8.2 Magneto ignition system

The magneto is an efficient, reliable, self-contained unit which is often preferred for

aircraft engines because storage batteries are heavy and troublesome. Special starting

means are required, however, as the magneto will not furnish enough voltage for

ignition at low speeds.

Variation in ignition timing is more difficult with the magneto, since the breaker

point must be opened when the rotating magnets are in the most favorable position. It

is possible to change the engine crank angle at which the magneto points open without

disturbing the relationship between point opening and magnet position by designing

the attachment pad so that the entire magneto body may be rotated a few degrees

about its own shaft. Obviously this method is not as satisfactory as rotating a timer cam-

plate.




Advantages:

1. The system is more reliable as there is no battery or connecting cable.

2. The system is more suitable for medium and very high speed engines.

3. With use of cobalt steel and nickel-aluminum magnet metals very light and

compact units can be made which require very little room.

4. With recent development this system has become fairly reliable.

Disadvantages

1. At low speeds and during cranking the voltage is very low. This has been

overcome by suitable modifications in the circuit.

2. Adjustment of the spark timing i.e. advance or retard, has detrimental effect

upon the spark voltage or energy. The powerful sparks at high engine speeds

cause burning of the electrodes. Low tension magneto ignition system.

Governing of IC engines

The purpose of governing is to maintain the speed of the engine constant regardless

of the changes in the load on the engine. The mechanism used for this purpose is known

as governor and method used is kwon as governing.

If the load on the engine decreases, the speed of the engine will begin to increase if

the fuel supply is not decreased. On the other hand, if the load on the engine increases,

the speed of the engine will begin to decrease if the fuel supply is not increased. The

purpose of governing is to supply the fuel to the engine according to the load on the

engine and to maintain the speed of the engine constant.

The methods of governing: The governing of speed of the engine according to the load is done by one of the

following methods:

i) The fuel supplied to the engine is completely cut off during few cycles of the

engine. This is known as Hit and Miss Governing. This is generally used for gas

engine.

ii) The fuel supplied per cycle of the engine is varied according to the load on the

engine. This is known as Quality Governing. The A : F ratio is changed according

to the load on the engine. Rich mixture is supplied at high loads and lean mixture

is supplied at low loads. This is used for diesel engines.

iii) The quantity of air-fuel mixture supplied is varied according to the load on the

engine. The A : F ratio of the mixture supplied to the engine at all loads remain

merely constant, therefore it is known as Quantity Governing. This is used for

petrol engine.

Fuel Injection Pumps & Nozzles


Experiment No. 9

FUEL INJECTION PUMPS & NOZZLES

Objective: Study about different fuel injection pump and nozzles.

Theory: The fuel-injection system is the most vital component in the working of Cl engines.

The engine performance viz., power output, economy etc. is greatly dependent on the

effectiveness of the fuel-injection system. The injection system has to perform the

important duty of initiating and controlling the combustion process. The main elements

of fuel injection system is fuel pump and nozzle.

1. Fuel-injection pumps The high-pressure fuel-injection pump is one of the main and most complicated

units of the fuel-injection system in a CI engine. It meters out the fuel in conformity with

the engine duty and supplies fuel to the injector at the proper time. Fuel pumps in which

every working section delivers fuel to individual cylinders of the engine arc known as

multi-sectional pumps. These are generally of jerk type. The other types are single- or

double-plunger distributing pumps in which one working section feeds fuel to several

cylinders.

a. Jerk Type Bosch Fuel-injection Pump

Fig. 9.1 shows the jerk type Bosch high-pressure fuel-injection pump. It consists of a

barrel in which a plunger reciprocates. The pump plunger is lifted by a cam on a camshaft

driven by the engine. There is a very small clearance between the barrel and the plunger,

which is of the order of 2 to 3 thousandths of a millimeter. It provides perfect scaling even

at very high pressures and low speeds.

The pump barrel has two radially opposing ports. These are the inlet port and the spill

or bypass port. The plunger moves vertically in the band with a constant stroke. To enable

the pump to vary the quantity of fuel delivered per stroke, the plunger is provided with a

vertical channel extending from its top edge to an annular groove, the upper edge of

which is formed as a helix. The helix runs a little way down the plunger length the

effective stroke is varied by means of the helix on the plunger which permits the by-

passing of fuel at any position of the delivery stroke, thereby controlling the quantity

delivered. This is accomplished by means of a control rod or rack, which turns a toothed

control sleeve that turns the plunger to the desired position.



b. Distributor Type Pump

This pump has only a single pumping element and the fuel is distributed to each

cylinder by means of a rotor (Fig. 9.2)

The rotor has a central longitudinal passage two sets of radial holes (each equal to the

number of engine cylinders) located at different heights. One set is connected to pump

inlet via central passage whereas the second set is connected to delivery lines leading to

injectors of the various cylinders.

The fuel is drawn into the central rotor passage from the inlet port when the pump

plunger move away from each other. Wherever, the radial delivery passage in the rotor

coincides with the delivery port for any cylinder the fuel is delivered to each cylinder in

turn.

Fig. 9.1 BOSCH Fuel-injection Pump



Main advantages of this type of pump lies in its small size and its light weight.

Fig. 9.2 Principle of working of distributor type fuel-injection pump

2. Nozzles The combustion chamber design dictates the type of nozzle, the droplet size and

the spray required to achieve complete combustion within a given time and space. There

is a wide variety of nozzle designs to provide the spray characteristics required for each

type of combustion chamber. The most common types illustrated in Figure 9.3 are:

a. The single-bole (orifice) nozzle

b. The multi-hole (orifice) nozzle

c. The pintle nozzle

d. The pintaux nozzle.

a) The single-bole (orifice) nozzle

This is the simplest type of nozzle and is used in open combustion chambers. It

consists of a single hole bored centrally through the nozzle body and closed by the needle

valve. The size of the hole is usually larger than 0.2 mm. Its spray cone angle varies from

5 to 15°. In some cases, a cone is given a series of spiral grooves in order to impart a

rotational motion to the fuel for better mixing with the air.

b) The multi-hole (orifice) nozzle

This type of nozzle finds extensive use in automobile engines, particularly having

open combustion chambers. It mixes the fuel with air properly even with slow air

movement available with open combustion chambers. The number of holes varies from



4 to 18; the greater number provides better fuel distribution. The hole diameter lies

between 0.25 to 0.35 mm and hole angle lies between 20° to 45°. Usually the holes are

drilled symmetrically but many times they are non-symmetrical to meet certain specific

requirements of the combustion chamber.

Fig. 9.3 Types of nozzles

c) The pintle nozzle

The stem of the nozzle valve is extended to form a pin or pintle which protrudes

through the mouth of the nozzle body. It may be either cylindrical or conical in shape. The

size and shape of the pintle can be varied according to requirement. The spray core angle

is generally 60°. When the valve lifts, the pintle partially blocks the orifice and thus does

not allow the pressure drop to be greater. As the lift of the valve increases the entire

orifice is uncovered and full area for flow is available. Thus dribbling is avoided. The spray

obtained by the pintle nozzle is hollow conical spray.

d) The pintaux nozzle.

It is a type of pintle nozzle which has an auxiliary hole drilled in the nozzle body. It

injects a small amount of fuel through this additional hole which is called pilot injection

in the upstream direction slightly before the main injection. The needle valve does not lift

fully at low speeds and most of the fuel is injected through the auxiliary hole.

Calorimeter


Darshan Institute of Engineering & Technology, Rajkot Page 10.1

Experiment No. 10

CALORIMETER

Objective: To study measurement of calorific value for solid/liquid fuel.

Theory:

The “heating value or calorific value” of the fuel is defined as the energy liberated by

the complete oxidation of a unit mass or volume of a fuel. It is expressed in kJ/kg for

solid and liquid fuels and kJ/m3 for gases.

The higher calorific value, HCV, is obtained when the water formed by combustion is

completely condensed. The lower calorific value, LCV, is obtained when the water

formed by combustion exists completely in the vapour phase.

1. Bomb calorimeter:

The calorific value of solid and liquid fuels is determined in the laboratory by ‘Bomb

calorimeter’. It is so named because its shape resembles that of a bomb. Fig. 1 shows the

schematic sketch of a bomb calorimeter.

Fig.10.1 Bomb calorimeter

The calorimeter is made of austenitic steel which provides considerable resistance

to corrosion and enables it to withstand high pressure. In the calorimeter is a strong

cylindrical bomb in which combustion occurs. The bomb has two valves at the top. One

supplies oxygen to the bomb and other releases the exhaust gases. A crucible in which a

Calorimeter



weighted quantity of fuel sample is burnt is arranged between the two electrodes as

shown in Fig. 10.1.

The calorimeter is fitted with water jacket which surrounds the bomb. To reduce the

losses due to radiation, calorimeter is further provided with a jacket of water and air. A

stirrer for keeping the temperature of water uniform and a thermometer to measure the

temperature up to an accuracy of 0.001°C are fitted through the lid of the calorimeter.

Procedure:

To start with, about 1 gm of fuel sample is accurately weighed into the crucible and a

fuse wire (whose weight is known) is stretched between the electrodes. It should be

ensured that wire is in close contact with the fuel. To absorb the combustion products of

sulphur and nitrogen 2 ml of water is poured in the bomb. Bomb is then supplied with

pure oxygen through the valve to an amount of 25 atmosphere. The bomb is then placed

in the weighed quantity of water, in the calorimeter. The stirring is started after making

necessary electrical connections, and when the thermometer indicates a steady

temperature fuel is fired and temperature readings are recorded after 1/2 minute

intervals until maximum temperature is attained. The bomb is then removed; the

pressure slowly released through the exhaust valve and the contents of the bomb are

carefully weighed for further analysis.

The heat released by the fuel on combustion is absorbed by the surrounding water

and the calorimeter.

From the above data the calorific value of the fuel can be found in the following way:

Let ,

Wf = Weight of fuel sample (kg),

W = Weight of water (kg),

CV = Calorific value (higher) of the fuel (kJ/kg),

We = Water equivalent of calorimeter (kg),

T1 = Initial temperature of water and calorimeter,

T2 = Final temperature of water and calorimeter,

Tc = Radiation corrections, and

c = Specific heat of water.

Heat released by the fuel sample = Wf × C

Heat received by water and calorimeter

= (Ww + We) × c × [(T2 – T1) + Tc].

Heat lost = Heat gained

W𝑓 × CV = (W + W𝑒) × c × [(T2 + T1) + T𝑐]

[Value of c is 4.18 in SI units and unity in MKS units.]

Calorimeter



Corrections pertain to the heat of oxidation of fuse wire, heat liberated as a result of

formation of sulphuric and nitric acids in the bomb itself.

It should be noted that bomb calorimeter measures the higher or gross calorific

value because the fuel sample is burnt at a constant volume in the bomb. Further the

bomb calorimeter will measure the H.C.V. directly if the bomb contains adequate

amount of water before firing to saturate the oxygen. Any water formed from

combustion of hydrogen will, therefore, be condensed. The procedure of determining

calorific values of liquid fuels is similar to that described above. However, if the liquid

fuel sample is volatile, it is weighed in a glass bulb and broken in a tray just before the

bomb is closed. In this way the loss of volatile constituents of fuels during weighing

operation is prevented.

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