Sudan University of science and technology

COLLEGE OF ENGINEERING

School of mechanical engineering

DEPARTMENT OF POWER

A Project Submitted In Partial Fulfillment for the Requirement

of the Degree of B.Sc. (Honor) In Mechanical Engineering

Measurement of Heat and

Mechanical Losses in Internal

Combustion engines

Prepared by:

1. Fayad Idris Ahmed Mohammed.

2. Mohammed Taj Elser Ali Abdallah.

3. M men Hassan Abdelrahman Taha.

Supervised by:

Eltayeb Hassan Elshaikh

(September 2015)

-I-

قال تعالى :

-II-

DEDICATION

We dedicate this research to all our friends and families, our

great teachers, and brothers in 27 mech.

-III-

صاحب انشكس و انعسفا انعزز اناانحد هلل أوال و أخسا

وانصالة وانسالو عهى يعهى انبشست و صاحب انخهق انسفع

عهه و عهى آل بته و أصحابه أتى انصالة و انتسهى

انطب حس انشخ \انشكس يىصىل نألستاذ

انري كا نه د انفضم بعد اهلل عز وجم بتىجهه وزعاته نهرا انبحث

أضا ندزست انهدست انكاكتوانشكس يىصىل

يثهت ف أساترتها انكساو

و ألساترة وزشت انسازاث بقسى انقدزة

وكم ي ساهى ف إخساج هرا انبحث

-IV-

ABSTRACT

This thesis focuses on measurement of the heat and mechanical losses

in I.C.engines based on a gasoline engine data operated on different engine

speeds. The objective is to determine the classic and modern methods of

measurement the heat and mechanical losses. The transfer of energy is

measured for losses to the engine coolant and exhaust, usable power output, as

well as friction losses. A major part of the energy is lost with the exhaust

gases. In addition, another major part of energy input is rejected in the form of

heat via the cooling system. Energy loss increases with increasing engines

speed and load and thus the mechanical efficiency decreases. Future

improvements to obtain distinguishable results are outlined.

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انتجسدة

ف يحزكاث انكاكتزارت تزكش ذ األطزحت عهى قباص انفقداث انح

اندف ي ذ األطزحت دراست األسانب انطزق انقدت .اإلحتزاق انداخه

انحدثت نقاص انفقداث انحزارت انكاكت ف يحزكاث اإلحتزاق انداخه . نحزك

،ادة انقدرة انفزيهت انستف ،دشل تى قاص انفقداث بسبب انتبزد غاساث انعادو

باإلضافت إنى جشء ،انقدرة اإلحتكاكت . جشء كبز ي انطاقت تى فقدا ف غاساث انعادو

كبز أضا باسطت ياة انتبزد .

انفقداث انحزارت انكاكت تشد بشادة انسزعت اندرات نهحزك يا ؤدي

اث ف انستقبم نهحصل عه تائج إنى قصا انكفاءة انكاكت . ال بد ي تحس

أفضم .

-VI-

LIST OF CONTENTS

Content Page

I االت

DEDICATION II

III شكز عزفا

ABSTRACT IV

V انتجزدة

LIST OF CONTENTS VI

LIST OF FIGURES VIII

LIST OF TABLES IX

CHAPTER ONE

INTRODUCTION

1.1 Research Importance 2

1.2 Research Problem 3

1.3 Research Objective 3

1.4 Research Methodology 3

CHAPTER TWO

LITERATURE REVIEW

2.1 Introduction 5

2.2 Internal combustion engines 5

2.3 Engine performance 7

2.4 Calorific value of fuels 8

2.5 Performance Parameters 9

Previous studies 15

CHAPTER THREE

METHODS OF MEASUREMENT OF HEAT AND

MECHANICAL LOSSES

3.1 Measurement of Heat Losses 23

3.1.1 Heat Balance Sheet 23

3.2 Measurement of mechanical losses 27

3.2.1 Measurement of brake power 27

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3.2.2 Important types of dynamometers 28

Content Page

3.2.3 Methods of measurement of mechanical losses 36

3.2.3.1 The Willan‘s line method 36

3.2.3.2 The Morse test 38

3.2.3.3 Motoring test 38

3.2.3.4 Difference between I.P. and B.P. 40

3.3 Engine Test cells 42

3.3.1 Overall size of individual test cells 44

3.3.2 General purpose automotive engine test cells 46

3.3.3 Research and development engine and

Power-train test cells

48

3.3.4 Automotive engine production test cells

(hot test)

50

3.3.5 Cold testing in production 51

3.3.6 Engine handling systems 52

CHAPTER FOUR

PRACTICAL TRAILS

4.1 Morse test 55

4.2 Engine heat balance sheet 61

CHAPTER FIVE

CONCLUSION AND RECOMMENDATION

5.1 Conclusion 66

5.2 Recommendations 67

References 68

-VIII-

LIST OF FIGURES

Figure Title page

2.1 Internal Combustion Engine 6

2.2 Indicator diagram 10

3.1 Heat balance diagram 26

3.2 Prony brake dynamometer 29

3.3 Rope brake dynamometer 31

3.4 Hydraulic dynamometer 33

3.5 Eddy current dynamometer 34

3.6 Transmission dynamometer 35

3.7 Willan‘s line for a diesel engine 37

3.8 Test cell 43

3.9 General Purpose test cell 46

3.10 Engine test cells with shared control rooms 47

4.1 Engine speed related with friction power 60

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LIST OF TABLES

Table Title Page

2.1 Heat balance sheet 25

2.2 Approximate percentage values of losses 26

3.1 Some actual cell dimensions found in UK industry 45

4.1 Morse test data recorded 56

4.2 Heat balance data recorded 62

4.3 Heat balance sheet 64

CHAPTER ONE

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INTRODUCTION

When it comes to Internal Combustion Engines and all types of engines

we as engineers our target is to reach for the maximum efficiency of the

engine, to achieve that we need to reduce losses in the engine, but we need

firstly to recognize and determine these losses, then define the methods and

devices which used to measure these losses in order to reduce them

eventually.

These losses reduce the engine power by a large rate and waste a lot of

energy which can be used, so by reducing these losses we will increase the

efficiency of the engine.

In this research we will study the losses in internal combustion engines

and the methods to measure them. In order to do that firstly we will collect

data from some references, search for previous researches, and finally we will

do some specific practical trails and tests to calculate the amount of the

losses.

1.1 Research Importance:

Measuring heat and mechanical losses in internal combustion engine to

be able to be reduced in order to contribute to the development of engine

performance and access the highest possible efficiency.

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1.2 Research Problems:

The main problem of this research is the thermal and mechanical losses

in the I.C. engine which reduce the engine efficiency.

1.3 Research Objectives:

The main objective of this research is to measure the heat and

mechanical losses in the I.C engine by determining:

1- Mechanical Losses (friction power).

2- Engine Heat Balance Sheet.

1.4 Research Methodology:

Data Collection: in our research we used scientific data that we had

collected from different references such as (internal combustion engines by

R.K Rajput, internal combustion engines by V Ganesan, engine testing by A.J

Martyr, M.A Plint)

Practical trails: in our research we will do some specific practical

trails and tests to calculate the amount of the losses (indicated power by

Morse method, Heat balance sheet)

CHAPTER TWO

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LITERATURE REVIEW

2.1 Introduction:

Generally we define heat engines as any type of engine or machine

which derives heat energy from the combustion of fuel or any other source

and convert this energy into mechanical work.

Heat engines may be classified into two main classes as follow:

I. External combustion engines.

II. Internal combustion engines.

2.2 Internal combustion engines:

In this case, combustion of fuel with oxygen of air occurs within the

cylinder of the engine. The internal combustion engines group includes

engines employing mixtures of combustible gases and air, known as gas

engines, those using lighter liquid fuel or spirit known as petrol engines and

those using heavier liquid fuels known as oil compression ignition or diesel

engines.

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Fig (2-1): Internal combustion engine

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2.3 Engine performance:

One ultimate measure of the performance of an internal combustion

engine is the proportion of the heat of combustion of the fuel that is turned

into useful work at the engine coupling. The thermal efficiency at full load of

internal combustion engines ranges from about 20 per cent for small gasoline

engines up to more than 50 per cent for large slow-running diesel engines,

which are the most efficient means currently available of turning the heat of

combustion of fuel into mechanical power.

It is useful to have some idea of the theoretical maximum thermal

efficiency that is possible, as this sets a target for the engine developer.

Theoretical thermodynamics allows us, within certain limitations, to predict

this maximum value. The proportion of the heat of combustion that is not

converted into useful work appears elsewhere: in the exhaust gases, in the

cooling medium and as convection and radiation from the hot surfaces of the

engine. In addition, there may be appreciable losses in the form of unburned

or late burning fuel. It is important to be able to evaluate these various losses.

Of particular interest are losses from the hot gas in the cylinder to the

containing surfaces, since these directly affect the indicated power of the

engine. The so-called ‗adiabatic engine‘ seeks to minimize these particular

losses.

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2.4 Calorific value of fuels:

The calorific value of a fuel is defined in terms of the amount of heat

liberated when a fuel is burned completely in a calorimeter.

Since all hydrocarbon fuels produce water as a product of combustion,

part of these products (the exhaust gas in the case of an I.C.Engine) consists

of steam. If, as is the case in a calorimeter, the products of combustion are

cooled to ambient temperature, this steam condenses, and in doing so gives up

its latent heat. The corresponding measure of heat liberated is known as the

higher or gross calorific value (also known as gross specific energy). If no

account is taken of this latent heat we have the lower or net calorific value

(also known as net specific energy). Since there is no possibility of an internal

combustion engine making use of the latent heat, it is the invariable practice

to define performance in terms of the lower calorific value.

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2.5 Performance Parameters:

The basic performance parameters of internal combustion engine

(I.C.E) may be summarized as follows:

2.5.1 Indicated power (I.P.):

It is the actual rate of work done by the working fluid on the piston. As

its name implies, the I.P. can be determined from an "indicator diagram" as

show in figure (1), by subtracting the pumping loop area (- ve) from the

positive area of the main diagram. I.P. power could be estimated by

performing a Morse test on the engine. The physical equation for the I.P. is:

I.P = PmLAN

Where N is the number of machine cycles per unit times, which is 1/2

the rotational speed for a four- stroke engine, and the rotational speed for a

two- stroke engine.

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Fig (2-2): Indicator diagram, four-stroke engine.

2.5.2 Brake power (B.P.):

This is the measured output of the engine. It is usually obtained by a

power absorption device such as a brake or dynamometer which can be loaded

in such a way that the torque exerted by the engine can be measured. The

break power is given by:

B.P = 2πNT

Where T is the torque.

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2.5.3 Friction power (F.P.) and Mechanical efficiency (ηm):

The difference between the I.P. and the B.P. is the friction power (F.P)

and is that power required to overcome the frictional resistance of the engine

parts,

F.P. = I.P. – B.P.

The mechanical efficiency of the engine is defined as:

ηm =

ηm is usually between 80% and 90%.

2.5.4 Indicated mean effective pressure (IMEP):

It is a hypothetical pressure which if acting on the engine piston during

the working stroke would results in the indicated work of the engine. This

means it is the height of a rectangle having the same length and area as the

cycle plotted on a p- v diagram.

IMEP (Pi) =

× Indicator scale

Consider one engine cylinder:

Work done per cycle = Pi AL

Where: A = area of piston; L = length of stroke

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Work done per min. = work done per cycle × active cycles per min.

I.P. = Pi AL× active cycles/ min

To obtain the total power of the engine this should be multiplied by the

number of cylinder n, i.e.:

Total I.P. = PiALNn/2 ) four- stroke engine (

And

= PiALNn ) Two- stroke engine (

2.5.5 Brake mean effective pressure (BMEP) and brake thermal

efficiency:

The BMEP (B.P) may be thought of as that mean effective pressure

acting on the pistons which would give the measured B.P., i.e.

B.P. = Pb AL × active cycles/ min

The overall efficiency of the engine is given by the brake thermal efficiency:

ηBT =

Where mf is the mass of fuel consumed per unit time, and Qnet is the lower

calorific value of the fuel.

-13-

2.5.6 Specific fuel consumption (S.F.C):

It is the mass of fuel consumed per unit power output per hour, and is a

criterion of economic power production.

Low values of S.F.C. are obviously desired. Typical best values of

B.S.F.C. for SI engines are about 270g/kw.h, and for C.I. engines are about

200g/kw.h.

2.5.7 Indicated thermal efficiency (ηIT):

It is defined in a similar way to ηBT

Dividing ηBT by ηIT gives

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2.5.8 Volumetric efficiency (ηv):

Volumetric efficiency is only used with four- stroke cycle engines. It is

defined as the ratio of the volume if air induced, measured at the free air

conditions, to the swept volume of the cylinder:

The air volume may be refereed to N.T.P. to give a standard

comparison.

The volumetric efficiency of an engine is affected by many variables such as

compression ratio, valve timing, induction and port design, mixture strength,

latent heat of evaporation of the fuel, heating of the induced charge, cylinder

pressure, and the atmospheric conditions.

-15-

2.6 Previous Studies:

Here are some examples of previous studies in Measurement of Heat

and Mechanical Losses in I.C.Engines:

2.6.1 First Study:

Title:

MEASUREMENT OF MECHANICAL LOSSES IN THE COMBUSTION

ENGINES

By:

Andre Drab, Stanislav Beroun, Robert Vozenilek (Technical University of

Liberec, Department of Vehicles and Engines /2011)

As the basis of the testing station for measuring mechanical losses in

piston combustion engine by induced revolution there serves a regulating

induction motor of the firm SIEI, type MA 133 K-62, with the output 28

kW/6000 1/min. The torque during induced revolution is measured by a shaft

pick-up HBM of the type T20WN (100 Nm, 0.2%, 10000 1/min), or by a

pick-up HBM T5 (50 Nm, 0.1%, 4000 1/min) – both pick-ups can be

overloaded statically to 200% of nominal value of Mt. Because of the required

range of r. p.m., the basic configuration of the testing rig is equipped with the

pick-up T20WN.

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Measurement system:

The testing rig for induced revolution of the engine is coupled with a data

logger MGC plus (Hottinger), allowing to record 2.400 samples of data per

second in the 8-channel version of the amplifier. Each sample comprehends

the data from the pick-up of the torque (Mt and revolutions) and from 13

temperature pick-ups (Pt 100 and thermocouples). The number of sensed

temperatures can be increased according to measuring needs. From the

effective values of the measured torque and r. p.m., the power loss is

calculated.

The operational environment for measuring passive resistances is generated

by means of the SW CAM-tan Easy. During measuring, on the PC monitor

there are displayed graphical values of measured temperatures and the time

courses of Mt and n. The values of all measured quantities (Mt, n and

temperatures) for each measured regime are established by statistic data

processing (as mean values of the data file in chosen time interval).

Results of measurement:

For the comparison of courses of the torque loss, two temperature

regimes have been chosen as the first temperature regime, 35° C have been

chosen for both media (lubrication oil and coolant/water) – for cold engine,

and as the second one, 90° C for both media (lubrication oil and

coolant/water) – for warm engine. The combustion engine has been resolved

in the range of 1.500 – 5.500 r. p.m. The step of a change of r. p.m. has been

chosen to amount to 250 r. p.m. The value at the highest measured velocity

5.500 r. p.m. is considered in the diagrams as 100 %, and other values of

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measured torque loss have been related to this value. The diagrams allow

noticing the tendency of the measured torque loss to increase with increasing

r. p.m. of the revolved combustion engine. With a cold combustion engine, the

measured torque loss for the highest measured r. p.m. (5.500 r. p.m.) is 1.82

time higher than at the lowest measured velocity (1.500 r. p.m.). With a

warmed-up combustion engine (warm engine – 90o C), the difference of the

measured torque loss between 1.500 r. p.m. and 5.500 r. p.m. increases to as

much as 2.13 multiple.

Conclusion:

The verifying measuring of mechanical losses of a piston combustion

engine by means of induced revolution on the testing rig have proved full

functionality of the testing rig, both concerning the requirement to measure

the torque loss with high precision and repeatability, and maintaining stable

temperature conditions during measuring by means of regulation of

temperatures of coolant and lubrication oil. The results of measuring carried

out until now show that by means of the testing station for measuring

mechanical losses in piston combustion engines by induced revolution it is

also possible to study such characteristics of the engine that other (calculation

or experimental) procedures do not show.

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2.6.2 Second Study:

Title:

ENERGY LOSSES IN A VEHICLE

Only about 15 percent of the energy from the fuel you put in your tank

gets used to move your car down the road or run useful accessories, such as

air conditioning. The rest of the energy is lost to engine and driveline

inefficiencies and idling. Therefore, the potential to improve fuel efficiency

with advanced technologies is enormous.

Engine Losses - 62.4 percent

In gasoline-powered vehicles, over 62 percent of the fuel's energy is

lost in the internal combustion engine (ICE). ICE engines are very inefficient

at converting the fuel's chemical energy to mechanical energy, losing energy

to engine friction, pumping air into and out of the engine, and wasted heat.

Advanced engine technologies such as variable valve timing and lift, turbo

charging, direct fuel injection, and cylinder deactivation can be used to reduce

these losses.

In addition, diesels are about 30-35 percent more efficient than gasoline

engines, and new advances in diesel technologies and fuels are making these

vehicles more attractive.

Idling Losses - 17.2 percent

In urban driving, significant energy is lost to idling at stop lights or in traffic.

Technologies such as integrated starter/generator systems help reduce these

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losses by automatically turning the engine off when the vehicle comes to a

stop and restarting it instantaneously when the accelerator is pressed.

Accessories - 2.2 percent

Air conditioning, power steering, windshield wipers, and other

accessories use energy generated from the engine. Fuel economy

improvements of up to 1 percent may be achievable with more efficient

alternator systems and power steering pumps.

Driveline Losses - 5.6 percent

Energy is lost in the transmission and other parts of the driveline.

Technologies, such as automated manual transmission and continuously

variable transmission, are being developed to reduce these losses.

Aerodynamic Drag - 2.6 percent

A vehicle must expend energy to move air out of the way as it goes

down the road—less energy at lower speeds and progressively more as speed

increases. Drag is directly related to the vehicle's shape. Smoother vehicle

shapes have already reduced drag significantly, but further reductions of 20-

30 percent are possible.

Rolling Resistance - 4.2 percent

Rolling resistance is a measure of the force necessary to move the tire

forward and is directly proportional to the weight of the load supported by the

tire. A variety of new technologies can be used to reduce rolling resistance,

-20-

including improved tire tread and shoulder designs and materials used in the

tire belt and traction surfaces.

For passenger cars, a 5-7 percent reduction in rolling resistance

increases fuel efficiency by 1 percent. However, these improvements must be

balanced against traction, durability, and noise.

Overcoming Inertia; Braking Losses - 5.8 percent

To move forward, a vehicle's drive train must provide enough energy to

overcome the vehicle's inertia, which is directly related to its weight. The less

a vehicle weights, the less energy it takes to move it. Weight can be reduced

by using lightweight materials and lighter-weight technologies (e.g.,

automated manual transmissions weigh less than conventional automatics).

In addition, any time you use your brakes, energy initially used to

overcome inertia is lost.

Source: www.fueleconomy.gov/feg/atv.shtml

Comment:

This study about ENERGY LOSSES in vehicles as general, because it

deals with all energy losses in vehicle at all, but our research is about heat and

mechanical losses in internal combustion engine only which mean energy

losses inside the engine.

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2.6.3 Third Study:

Title:

Mechanical Losses in an Engine

Science Daily (Jan. 12, 2012)

• No less than one third of a car's fuel consumption is spent in

overcoming friction.

• This friction loss has a direct impact on both fuel consumption and

emissions.

• New technology can reduce friction by anything from 10% to 80% in

various components of a car, according to a joint study by VTT

Technical Research Centre of Finland and Argonne National

Laboratory (ANL) in USA.

It should thus be possible to reduce car's fuel consumption and emissions by

18% within the next 5 to 10 years and up to 61% within 15 to 25 years.

Source: (University of IITDELHI)

P M V Subarea

Professor

Mechanical Engineering Department

CHAPTER THREE

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METHODS OF MEASUREMENT OF HEAT

AND MECHANICAL LOSSES

3.1 Measurement of Heat Losses:

The thermal performance of an engine is usually studied by heat

balance-sheet.

3.1.1 Heat Balance Sheet:

The main components of the heat balance are:

• Heat equivalent to the effective (brake) work of the engine,

• Heat rejected to the cooling medium,

• Heat carried away from the engine with the exhaust gases, and

• Unaccounted losses.

The unaccounted losses include the radiation losses from the various

parts of the engine and heat lost due to incomplete combustion. The friction

loss is not shown as a separate item to the heat balance-sheet as the friction

loss ultimately reappears as heat in cooling water, exhaust and radiation.

To draw heat balance sheet for I.C.E, it is run at constant load. Indicator

diagram is obtained with the help of indicator. The quantity of fuel used in a

given time and its calorific value, the amount, inlet and outlet temperature of

cooling water and the weight of exhaust gases are recorded. After calculating

I.P. and B.P. the heat in different items is found as follows:

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(i) Heat supplied by fuel:

Heat supplied = mf × C.V.

Where:

mf mass of fuel used per minute (kg)

C.V. lower calorific value of fuel (kJ)

(ii) Heat absorbed in I.P:

Heat equivalent of I.P. (per minute) = I.P. × 60 kJ

(iii) Heat taken away by cooling water:

Heat taken away by cooling water = mw × cw × (t2 – t1)

Where:

mw = Mass of cooling water used per minute.

cw = Specific heat of water.

t1 = Initial temperature of cooling water

t2 = Final temperature of cooling water.

(iv) Heat taken away by exhaust gases:

Heat taken away by exhaust gases = me × cpg × (te -tr )

Where:

me = Mass of exhaust gases per minute (kg/min)

Cpg = Specific heat of exhaust gases

-25-

te = Exhaust gases temperature

tr = Room temperature

* Mass of exhaust gases can be obtained by adding the mass of fuel supplied

with the mass of air supplied.

Item kJ/min Per cent

Heat supplied by fuel … …

(i) Heat absorbed in I.P

(ii) Heat taken away by cooling

water

(iii) Heat taken away by exhaust

gases

(iv) Unaccounted losses

…

...

...

…

…

…

…

…

Total … …

Table (2-1) Heat balance sheet table

-26-

Fig (3-1): Heat balance diagram

The following table gives the approximate percentage values of various

losses in SI and CI engines:

Engine % B.P. % Heat cooling

water

% Heat to exhaust

gases

% unaccounted

losses

S.I. 21-28 12-27 30-55 0-15

C.I. 29-42 15-35 25-45 10-20

Table (2-2): approximate percentage values of losses

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3.2 Measurement of mechanical losses:

It is a curious fact that, in the long run, all the power developed by all the

road vehicle engines in the world is dissipated as friction: either mechanical

friction in the engine and transmission, rolling resistance between vehicle and

road or wind resistance.

Mechanical efficiency, a measure of friction losses in the engine, is

thus an important topic in engine development and therefore engine testing. It

may exceed 80 per cent at high power outputs, but is generally lower and is of

course zero when the engine is idling.

To measure friction loss we have to measure both of indicated and

brake power.

3.2.1 Measurement of brake power:

Brake power is the power output of the engine or the power developed

in crankshaft. To measure brake power we need to measure the torque and

angular speed of the engine.

The device which we use to measure the torque is called Dynamometer,

the Dynamometer is always be loaded then we can measure the generated

torque

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3.2.2 Important types of dynamometers:

A- 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.

1- Prony brake:

This type is consist of frame with brake shoes , often made of two

blocks of wood , each of which embraces slightly less than one-half of the

rotating drum rim . The drum is attached to the output shaft of the engine. The

two blocks can be drawn together by means of nuts and bolts, cushioned by

springs, so as to increase the pressure on the drum. A load bar extends from

the top of the brake and a weight is hanged to the end of the load bar.

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Fig (3-2): Prony brake dynamometer

W = weight

Torque = w × r

Brake power =

This type of dynamometer must be cooled since the power absorbed is

converted into heat.

This way is not suitable for absorption of large amount of power as

wear of blocks and reduction in the coefficient of friction between drum and

the friction material with the rise in temperature require continues tightening

of the bolts

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2- Rope Brake :

This type is directly coupled to the engine output shaft. In this

brake two or more ropes rest on the rim of pulley. The ropes are spaced

evenly across the width of the rim by means of wooden blocks

positioned at different points around the rim. The total pull on the slack

end of the ropes is registered on a spring balance, while the pull on the

tight end is provided by dead weights. The power absorbed is due to

friction between rope and the drum .Friction torque on the pulley

maybe increased by increasing the dead load by addition of weights.

Brake Power =

W = dead weight

S = spring balance

N = engine speed r.p.m

R = effective radius of pulley

-31-

Fig (3-3): Rope brake dynamometer

This dynamometer is easy to fabricate but is not very accurate because

of changes in friction coefficient of the rope with temperature.

-32-

3- Hydraulic Dynamometer:

This type of dynamometer works on the principle of dissipating

the power in fluid friction rather than in dry friction.

•In principle its construction is similar to that of a fluid flywheel.

•It consists of an inner rotating member or impeller coupled to the output shaft

of the engine.

•This impeller rotates in a casing filled with fluid.

•This outer casing, due to the centrifugal force developed, tends to revolve

with the impeller, but is resisted by a torque arm supporting the balance

weight.

•The frictional forces between the impeller and the fluid are measured

By the spring-balance fitted on the casing.

•The heat developed due to dissipation of power is carried away by a

continuous supply of the working fluid, usually water.

•The output can be controlled by regulating the sluice gates which can

Be moved in and out to partially or wholly obstruct the flow of water between

impeller, and the casing.

-33-

Fig (3-4): Hydraulic Dynamometer

4- Eddy Current Dynamometer:

It consists of a stator on which are fitted a number of

electromagnets and a rotor disc made of copper or steel and coupled to

the output shaft of the engine. When the rotor rotates eddy currents are

produced in the stator due to magnetic flux set up by the passage of

field current in the electromagnets. These eddy currents are dissipated

in producing heat so that this type of dynamometer also requires some

cooling arrangement. The torque is measured exactly as in other types

-34-

of absorption dynamometers, i.e. with the help of a moment arm. The

load is controlled by regulating the current in the electromagnets.

Fig (3-5): Eddy Current Dynamometer

B- Transmission Dynamometers:

Transmission dynamometers, also called torque meters, mostly

consist of a set of strain-gauges fixed on the rotating shaft and the

torque is measured by the angular deformation of the shaft which is

indicated as strain of the strain gauge. Usually, a four arm bridge is

used to reduce the effect of temperature to minimum and the gauges are

-35-

arranged in pairs such that the effect of axial or transverse load on the

strain gauges is avoided.

Transmission dynamometers are very accurate and are used where

continuous transmission of load is necessary. These are used mainly in

automatic units.

Fig (3-6): Transmission dynamometer

-36-

3.2.3 Methods of Measurement of Mechanical Losses:

The friction force power of an engine is determined by the following

methods:

(a)Willan‘s line method.

(b) Morse test.

(c) Motoring test.

(d) Difference between Indicated power and Brake power.

3.2.3.1 The Willan’s line method:

This is applicable only to un-throttled compression ignition engines.

It is a matter of observation that a curve of fuel consumption rate against

torque or B.M.E.P. at constant speed plots quite accurately as a straight line

up to about 75 per cent of full power, This suggests that for the straight line

part of the characteristic, equal increments of fuel produce equal increments

of power combustion efficiency is constant.

At zero power output from the engine, all the fuel burned is expended

in over-coming the mechanical losses in the engine, and it is a reasonable

inference that an extrapolation of the Willan‘s line to zero fuel consumption

gives a measure of the friction losses in the engine. Strictly speaking, the

method only allows an estimate to be made of mechanical losses under no-

load conditions. When developing power the losses in the engine will

undoubtedly be greater.

-37-

Fig (3-7): Willan‘s line for a diesel engine

-38-

3.2.3.2 The Morse test

In this test, the engine is run under steady conditions and ignition or

injection is cut off in each cylinder in turn: it is of course only applicable to

multi-cylinder engines.

On cutting out a cylinder, the dynamometer is rapidly adjusted to restore

the engine speed and the reduction in power measured. This is assumed to be

equal to the indicated power contributed by the non-firing cylinder. The

process is repeated for all cylinders and the sum of the reductions in power is

taken to be a measure of the indicated power of the engine.

A modification of the Morse test makes use of electronically controlled

unit injectors, allowing the cylinders to be disabled in different ways and at

different frequencies, thus keeping temperatures and operating conditions as

near normal as possible.

3.2.3.3 Motoring Test:

• In the motoring test, the engine is first run up to the desired speed by

its own power and allowed to remain at the given speed and load conditions

for some time so that oil, water, and engine component temperatures reach

stable conditions.

• The power of the engine during this period is absorbed by a swinging

field type electric dynamometer, which is most suitable for this test.

-39-

• The fuel supply is then cut-off and by suitable electric-switching

devices the dynamometer is converted to run as a motor to drive for ‗motor‘

the engine at the same speed at which it was previously running.

• The power supply to the motor is measured which is a measure of the

F.H.P of the engine. During the motoring test the water supply is also cut-off

so that the actual operating temperatures are maintained.

• This method, though determines the F.P. at temperature conditions

very near to the actual operating temperatures at the test speed and load, does,

not give the true losses occurring under firing conditions due to the following

reasons.

(a) The temperatures in the motored engine are different from those in a

firing engine because even if water circulation is stopped the incoming air

cools the cylinder. This reduces the lubricating oil temperature and increases

friction increasing the oil viscosity. This problem is much more severing in

air-cooled engines.

(b) The pressure on the bearings and piston rings is lower than the firing

pressure. Load on main and connecting road bearings are lower.

(c) The clearance between piston and cylinder wall is more (due to cooling).

This reduces the piston friction.

(d) The air is drawn at a temperature less than when the engine is firing

because it does not get heat from the cylinder (rather loses heat to the

cylinder). This makes the expansion line to be lower than the compression line

on the P-v diagram. This loss is however counted in the indicator diagram.

-40-

(e) During exhaust the back pressure is more because under motoring

conditions sufficient pressure difference is not available to impart gases the

kinetic energy is necessary to expel them from exhaust.

Motoring method, however, gives reasonably good results and is very

suitable for finding the losses due to various engine components. This insight

into the losses caused by various components and other parameters is obtained

by progressive stripping-off of the under progressive dismantling conditions

keeping water and oil circulation intact. Then the cylinder head can be

removed to evaluate, by difference, the compression loss. In this manner

piston ring, piston etc. can be removed and evaluated for their effect on

overall friction.

3.2.3.4 Difference between I.P and B.P.:

(a) The method of finding the F.P by computing the difference between

I.P, as obtained from an indicator diagram, and B.P., as obtained by a

dynamometer, is the ideal method. However, due to difficulties.

(b) In obtaining accurate indicator diagrams, especially at high engine

speeds, this method is usually only used in research laboratories. Its use at

commercial level is very limited.

-41-

Comments on Methods of Measuring F.P.:

• The Willan‘s line method and Morse tests are very cheap and easy to

conduct.

• However, both these tests give only an overall idea of the losses

whereas motoring test gives a very good insight into the various causes of

losses and is a much more powerful tool.

• As far as accuracy is concerned the I.P– B.P method is the most

accurate if carefully done.

• Motoring method usually gives a higher value for F.H.P as compared

to that given by the Willian‘s line method.

The four standard methods of estimating mechanical losses in an

engine and its auxiliaries have been briefly described. No great accuracy can

be claimed for any of these methods and it is instructive to apply as many of

them as possible and compare the results. Measurement of mechanical losses

in an engine is still something of an ‗art’.

-42-

3.3 Engine Test Cells:

An engine test cell is a facility used to develop, characterize and test

engines. The facility, often offered as a product to automotive, allows engine

operation in different operating regimes and offers measurement of several

physical variables associated with the engine operation.

Engine test cell houses has several sensors (or transducers), data

acquisition features and actuators to control the engine state. The sensors

would measure several physical variables of interest which typically include:

*Crank shaft torque and angular velocity

*Intake air and fuel consumption rates, often detected using volumetric and/or

gravimetric measurement methods

*air-fuel ratio for the intake mixture, often detected using an exhaust gas

oxygen sensor

*environment pollutant concentrations in the exhaust gas such as carbon

monoxide, different configurations of hydrocarbons and nitrogen oxides,

sulfur dioxide, and particulate matter

*temperatures and gas pressures at several locations on the engine body such

as engine oil temperature, spark plug temperature, exhaust gas temperature,

intake manifold pressure

*atmospheric conditions such as temperature, pressure, and humidity

Information gathered through the sensors is often processed and logged

through data acquisition systems. Actuators allow for attaining a desired

engine state (often characterized as a unique combination of engine torque and

-43-

speed). For gasoline engines, the actuators may include an intake throttle

actuator, a loading device for the engine such as an induction motor. The

engine test cells are often custom-packaged considering requirements of the

OEM customer. They often include microcontroller-based feedback control

systems with following features:

*closed-loop desired speed operation (useful towards characterization of

steady-state or transient engine performance)

*closed-loop desired torque operation (useful towards emulation of in-vehicle,

on-road scenarios, thereby enabling an alternate way of characterization of

steady-state or transient engine performance)

Fig (3-8): Test cell

-44-

3.3.1 Overall size of individual test cells:

One of the early considerations in planning a new test facility will be

the space required. The areas to be separately considered are

• The engine or power train test cell;

• The control room;

• The space required for services and support equipment;

• The support workshop or engine rig and derig area;

• The storage area required for engine rig items and consumables.

A cramped cell, in which there is not room to move around in comfort,

is a permanent source of danger and inconvenience. The smaller the volume

of the cell the more difficult it is to control the ventilation system under

conditions of varying load .As a rule of thumb, there should be an

unobstructed walkway 1 meter wide all round the test engine. Cell height is

determined by a number of factors including the provision or not of a crane

beam in the structure. In practice, most modern automotive cells are between

4 and 4.5 meters internal height.

-45-

Table (3-1): Some actual cell dimensions found in UK industry:

QA test cell for small automotive

diesels fitted with eddy-current

dynamometer

6.5m long × 4m wide × 4m high

ECU development cell rated for

250kW engines, containing work

bench and some emission equipment

7.8m long × 6m wide × 4.5m high

Gasoline engine development cell

with

A.C. dynamometer, special coolant

and

Inter-cooling conditioning

6.7m long × 6.4m wide × 4.7m

High

Engine and gearbox development bed

with two dynamometers in ‗Tee‘

configuration. Control room runs

along 9.0 meter wall

9.0m wide × 6m × 4.2m high

(to suspended ceiling)

It is often necessary, when testing vehicle engines, to accommodate the

exhaust system as used on the vehicle, and this may call for space and extra

length in the cell. It must be remembered that much of the plant in the cell

requires calibration from time to time and there must be adequate access for

the calibration engineer, his instruments and in some cases ladder. The major

layout problem may be caused by the calibration of the dynamometer,

involving accommodation of a torque arm and dead weights.

-46-

3.3.2 General purpose automotive engine test cells:

This figure represents general purpose automotive engine test cells as

follow:

Fig (3-9): General Purpose test cell arranged against an outside wall with

control desk ‗side on‘ to engine

-47-

Fig (3-10): Engine test cells with shared control rooms running down the

length of the cell

Such cells are often built in multiples, side-by-side and in a line with a

common control room that is shared by two cells on either side. Engines enter

the cell by way of a large door in the rear wall while the operator may enter by

way of a door in the front wall to one side of the control desk. Typically there

is a double-skinned toughened glass window in front of the control desk. Most

wall-mounted instrumentation, smoke meters, fuel consumption meters, etc.,

is carried on the side wall remote from the cell access door.

In cells rated at above about 150kW where engine changes and rigging

were carried out in the cell it was usual to provide a crane rail located above

-48-

the test bed axis with a hoist of sufficient capacity to handle engines and

dynamometer. The penalty of such a lifting beam is that the structure has to be

built to take the full rated crane load plus its plant support load. In modern

cells where the engine is rigged outside the cell and trolley or pallet mounted,

in-cell cranes are not usually included as the cost benefit of a crane structure

may be judged as marginal.

3.3.3 Research and development engine and power-train test

cells:

The term ‗power-train‘ testing is used to cover engine plus direct

mounted transmission, but does not cover vehicle transmissions complete with

vehicle shafting; these are considered as ‗transmission test rigs‘.

Power-train rigs are often designed to be able to take up different

configurations, on a large bedplate, as required by the unit under test (UUT).

The typical configurations catered for are:

• Transverse engine plus gearbox driving two dynamometers;

• In-line engine and gearbox driving one dynamometer;

• In-line engine plus gearbox driving two dynamometers (‗Tee‘ set-up).

To allow fast transition times, the various UUT have to be pallet

mounted in a system that presents a common height and alignment to the cell

interface points.

Automotive engine test and development facilities built since the mid-

1990s will have the following features, additional to those found in general

purpose cells:

-49-

1. Exhaust gas analysis equipment.

2. Dedicated combustion air treatment plant.

3. Ability to run ‗in vehicle‘ exhausts systems.

4. High dynamic four-quadrant dynamometers.

Such requirements increase both the volume of the cell and of the space

required to house plant such as combustion air treatment equipment and the

electrical drive cabinets associated with the A.C. dynamometers. The

positioning and condition in which such ‗service‘ plant operates is as

important and as demanding as those of the contents of the test cell.

While plant such as the A.C. drive cabinets are usually positioned

outside the cell, for reasons of ambient temperature and noise, they need to be

as close to the dynamometer as practical to avoid higher than necessary costs

for the connecting power cable.

Modern dynamometer drive cabinets tend to be large, heavy and

difficult to maneuver within restricted building spaces. Therefore, expert

planning is required, as is anti-condensation heating if there is a long period

between installation and commissioning. Combustion air units also need to be

close to the engine to prevent heat loss or gain through the delivery trucking.

They are often positioned in the service room immediately above the engine,

with the delivery duct running via a fire damper through the cell ceiling to a

flexible duct attached to the engine as part of the rigging process. If the

humidity of the combustion air is being controlled, the unit will require

condensation and steam drains out of the building or into foul water drains.

-50-

Typical applications are:

• Development departments of vehicle and engine manufacturers and major

oil companies;

• Motor-sport developers;

• Specialist consultancy companies;

• Government testing and monitoring laboratories.

3.3.4 Automotive engine production test cells (hot test):

These cells are highly specialized installations forming part of an

automation system lying outside the scope of this research. The objective is to

check, in the minimum possible process time, that the engine is complete and

runs. Typical ‗floor-to-floor‘ times for small automotive engines range

between 5 and 8 minutes.

The whole procedure – engine handling, rigging, clamping, filling,

starting, draining and the actual test sequence – is highly automated, with

interventions, if any, by the operator limited to dealing with fault

identification. Leak detection may be difficult in the confines of a hot test

stand therefore it is often carried out at a special (black-light) station

following test.

The test cell is designed to read from identity codes on the engine and

recognize variants to adjust the pass or fail criteria accordingly.

Typical measurements made during a production test include:

• Time taken for engine to start.

-51-

• Cranking torque.

• Time taken for oil pressure to reach normal level.

• Exhaust gas composition.

Most gasoline engines are no longer loaded by any form of

dynamometer during a hot test, but in the case with diesel engines load is

applied with power output measured and recorded.

3.3.5 Cold testing in production:

In addition to rotational testing in processes of subassemblies, cold

testing is sometimes applied to (near) completely built engines. This is a

highly automated process.

Cold test rigs are invariably situated within the assembly process line

fed by a ‗power and free‘ or similar conveyor system. The mechanical layout,

based on docking on to a drive motor and transducer pick-up system, is

physically simpler than a hot test cell since it does not require fuel supplies or

hot gas and fluid evacuation.

Cold test areas also have the cost advantage of being without any

significant enclosure other than safety guarding.

3.3.6 Engine handling systems:

A considerable number of connections must be made to any engine

before testing can proceed. These include the coupling shaft, fuel, cooling

water, exhaust and a wide range of transducers and instrumentation. It is

-52-

obviously cost-effective when dealing with high throughput of small

automotive units to carry out such work in a properly equipped workshop

rather than use expensive test cell space. Once rigged the engines have to be

transported to the cell.

The degree of complexity of the system adopted for transporting,

installing and removing the engine within the cell naturally depends on the

frequency with which the engine is changed. In some research or lubricant test

cells the engine is more or less a permanent fixture, but at the other extreme

the test duration for each engine in a production cell will be measured in

minutes, and the time taken to change engines must be cut to an absolute

minimum.

There is a corresponding variation in the handling systems:

• Simple arrangements when engine changes are comparatively infrequent.

The engine is either craned into the cell and rigged in situ or mounted on a

suitable stand such as that shown in Fig. 4.4 which is then lifted, by crane or

forklift, into the cell. All connections are made subsequently by skilled staff

with workshop back-up.

• The pre-rigged engine is mounted on a wheeled trolley or truck maneuvered

pallet carrying various transducers and service connections which are coupled

to the engine before it is moved into the cell. An engine rigging workshop

needs to be fitted with a dummy test cell station that presents datum

connection points identical in position and detail to those in the cells,

particularly the dynamometer shaft in order for the engine to be pre-aligned.

Clearly to gain maximum benefit, each cell in the facility needs to be built

with critical fixed interface items in identical positions from a common

-53-

datum. These positions should be repeated by dummy interface points in any

pre-rigging stand, in the workshop.

• For production test beds it is usual to make all engines to pallet connections

prior to the combined assembly entering the cell. An automatic docking

system permits all connections (including in some cases the driving shaft) to

be made in seconds and the engine to be filled with liquids.

Workshop support in the provision of suitable fittings and adaptors

should always be made available. All pipe connections should be flexible and

exhaust connections can be particularly troublesome and short-lived at high

temperatures; they should be treated as consumable items.

Rigging of exhaust systems often requires a welding bay; this must

obey regulations concerning shielding. Electrical arc welding must not be

allowed within the test cell because of the danger of damage to

instrumentation by stray currents.

The workshop area used for derigging should be designed to deal with

the inevitable spilled fluids and engine wash activities. Floor drains should

run into an oil intercept unit.

CHAPTER FOUR

-55-

PRACTICAL TRAILS

In this chapter we will discuss the practical trails that we have done

and show the results of these tests.

4.1 Morse test:

Tools:

1-Diesel Engine:

(4stroke engine, 4cylender)

2-Dynamometer:

(Hydraulic Dynamometer/ H-P-A TEST)

3-Water Pump:

(0.5HP)

4-Water Tank

Theory:

Brake Power =

I1 = B.P – B1

Where:

B1 = B.P. when cylinder 1 is cut off.

-56-

I1 = I.P. of cylinder 1

I2 = B.P. – B2

I3 = B.P. – B3

I4 = B.P. – B4

IT = I1 + I2 + I3 + I4

F.P = I.P – B.P

Ƞmech =

Methodology:

We ran the engine at stable speed 1000 r.p.m., then we applied

load and the result torque was recorded, then we cut off the first cylinder, the

torque was measured by keeping the speed constant, then the same for the

other cylinders, and for different speeds.

Table(4-1): Data Recorded:

N (r.p.m.) TBP

(N.m)

T1 T2 T3 T4

1000 75 53.2 53.6 53.4 53.3

1500 84.8 60.2 58.1 57.6 60.5

2000 90.8 63.5 63.7 63.3 63.7

2500 93.6 66.4 67.2 66.9 66.5

3000 95.3 66.3 67 66.7 66.7

-57-

Calculations:

1- At 1000 r.p.m:

B.P. =

=

= 7.86 kW

B1 =

=

= 5.57 kW

B2 =

=

= 5.61 kW

B3 =

=

= 5.59 kW

B4 =

=

= 5.58 kW

I1 = B.P. – B1= 2.29 kW

I2 = B.P. – B2 = 2.25 kW

I3 = B.P. – B3 = 2.27 kW

I4 = B.P. – B4 = 2.28 kW

IT = I1 + I2 + I3 + I4 = 9.09 kW

F.P. = I.P. – B.P.

= 9.09 – 7.86 = 1.23 kW

-58-

Ƞmech =

=

= 86.46 %

2- at 2000 r.p.m:

B.P. =

=

= 19.02 kW

B1 =

=

= 13.3 kW

B2 =

=

= 13.34 kW

B3 =

=

= 13.26 kW

B4 =

=

= 13.34 kW

I1 = B.P. – B1= 5.72 kW

I2 = B.P. – B2 = 5.68 kW

I3 = B.P. – B3 = 5.76 kW

-59-

I4 = B.P. – B4 = 5.68 kW

IT = I1 + I2 + I3 + I4 = 22.84 kW

F.P. = I.P. – B.P.

= 22.84 – 19.02 = 3.82 kW

Ƞmech =

=

= 83.27 %

3- at 3000 rpm:

B.P. =

=

= 29.94 kW

B1 =

=

= 20.83 kW

B2 =

=

= 21.05 kW

B3 =

=

= 20.95 kW

B4 =

=

= 20.95 kW

I1 = B.P. – B1= 9.11 kW

I2 = B.P. – B2 = 9.89 kw

-60-

I3 = B.P. – B3 = 8.99 kW

I4 = B.P. – B4 = 8.99 kW

IT = I1 + I2 + I3 + I4 = 36.98 kW

F.P. = I.P. – B.P.

= 36.98 – 29.94 = 7.04 kW

Ƞmech =

=

= 80.96 %

Results:

Fig (4-1): Engine speed related with friction power

Where:

X= engine speed (r.p.m.)

Y=friction power (kW)

0

1

2

3

4

5

6

7

8

0 500 1000 1500 2000 2500 3000 3500

speed(r.p.m)

F.P. (kw)

-61-

4-2 Engine Heat Balance Sheet:

*On this experiment we only calculated the loss by cooling water.

Tools:

1-Diesel Engine:

(4stroke engine, single cylinder, 499C.C. srtoke 80mm, bore 85mm,

5.5kW, Cr 17.5/1, 28.5Nm)

2-D.C. Generator:

(320V, 8.0kW)

3-Water Pump:

(0.5HP)

4-Water Tank

5-Thermometer

6-Stop Watch

Theory:

Brake Power =

Heat supplied by fuel = mf × C.V.

Heat equivalent of B.P. = B.P. × 60

Heat carried away by cooling water = mw × cpw × (tw2 – tw1)

-62-

Methodology:

We ran the engine at stable speed 1000 r.p.m., then we recorded the

values of engine speed, torque, fuel consumption, quantity of cooling water

used, water inlet temperature, water outlet temperature, then we calculated the

brake power, heat supplied by fuel, heat equivalent of brake power, in order to

calculate the heat loss, then we repeated that for different speeds.

Table (4-2): Data recorded:

Item Value

Speed(rpm) 1000 1200 1400

Fuel consumption(kg/min) 0.00789 0.00882 0.00993

Torque(Nm) 16.8 17.2 16.9

Quantity of cooling water

(kg/min)

22.167 22.167 22.167

Water inlet temperature(°C) 36 37 39

Water outlet temperature(°C) 37 38 40

-63-

Sample of calculations (at 1000 rpm):

Brake Power =

=

= 1.759 kW

Heat supplied by fuel = mf × C.V.

= 0.00789 ×43300 = 341.637 kJ/min

Heat equivalent of B.P. = B.P. × 60

= 1.759 × 60 = 105.56 kJ/min

Heat carried away by cooling water = mw × cpw × (tw2 – tw1)

= 22.167 × 4.18 × (37 - 36) = 92.658 kJ/min

-64-

Results:

Table (4-3): Heat lost to cooling water table:

Item Value

Speed(rpm) 1000 1200 1400

Heat supplied by fuel(kJ/min) 341.637 381.906 429.97

Heat absorbed in B.P.

(kJ/min)

105.56

(30.9%)

129.68

(33.9%)

152.18

(35.3)

Heat taken away by cooling

water(kJ/min)

92.658

(27.12%)

92.658

(24.26%)

92.658

(21.55%)

CHAPTER FIVE

-66-

CONCLUSION AND RECOMMENDATIONS

5.1. Conclusion:

We had studied the methods of measuring the thermal and mechanical

losses in I.C.engines, and then we calculated these losses practically, the

mechanical efficiency was 83.56% in average.

And the heat lost to cooling water were (27.12% at 1000 r.p.m)

,(24.26% at 1200 r.p.m.) ,(21.55% at 1400 r.p.m.).

-67-

5.2. Recommendations:

In order to reduce the thermal and mechanical losses in I.C.engines we

have to make sure about the fuel quality, and the purity of air used, and the

suitable lubricant of engine, also we recommend with the periodic

maintenance of injectors to avoid delay period in combustion.

We also have to avoid over tying in engine parts such as crankshaft to

reduce the power losses.

-68-

REFERENCES

[1] A.J. Martyr and M.A. Plint, ―Engine Testing Theory and Practice‖,

Elsevier, Oxford, 2007.

[2] V Ganesan, ―Internal combustion engines‖, McGraw-Hill, India, 2006.

[3] R.K. Rajput, ―Internal combustion engines‖, Laxmi Publications, India,

2007.