INTERNAL COMBUSTION ENGINE

REPORT

Name: Hossam Gamal Mahmoud Khalil

ID:18010553
 Engine friction
Objective
Understanding the engine friction concept, and studying some empirical
methods to calculate engine friction.

Discussion
What is friction work?
The friction work, defined as the difference between the work delivered to the
piston while the working fluid is contained within the cylinder (i.e., during the
compression and expansion strokes) and the usable work delivered to the drive
shaft, is expended as follows:

1. To draw the fresh mixture through the intake system and into the cylinder,
and to expel the burned gases from the cylinder and out of the exhaust
system. It is usually called the pumping work Wp.

2. To overcome the resistance to relative motion of all the moving parts of

the engine. This includes the friction between the piston rings, piston skirt,
and cylinder wall; friction in the wrist pin, big end, crankshaft, and
camshaft bearings; friction in the valve mechanism; friction in the gears,
or pulleys and belts, which drive the camshaft and engine accessories. It
is usually called the rubbing friction work Wrf.

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3. To drive the engine accessories. These can include: the fan, the water
pump, the oil pump, the fuel pump, the generator, a secondary air pump
for emission control, a power-steering pump, and an air conditioner. It is
usually called the accessories work Wa.
Total friction work Wtf: The total friction work is the sum of these three
components,
Wtf =Wa +Wrf +Wp
The total friction work per cycle for a given engine geometry will vary with the
speed.

There are different methods to calculate Friction:

A. Measurement of fmep from imep
B. Direct motoring test
C. Willans line
D. Morse test
In our experiment we use Willans line method:
A plot of fuel consumption versus brake output obtained from engine tests at a
fixed speed is extrapolated back to zero fuel consumption.

Calculating the engine friction using Willians line method:

We will fix the speed N

Procedure:
1. Start the engine, let it to warm up and reach steady state.
2. Load the engine with 5 Lb with respecting the const. N(rpm) and measure fuel
mass flow rate.
3. Increase the load to 10Lb and also make sure that the speed is constant
and measure the fuel mass flow rate.
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4. Repeat for 15Lb and 20Lb and put the results in the table.
ρfuel = 830 Kg/m3 V ol=50 mL
V ol
Vool,fuel= t m ofuel = ρfuel×Vool,fuel

0.746
BP(KW) = 2800 ×load(lb) × N(rpm)

For N=1000

load(Ib) 5 10 15
time(sec) 82 72 63
Qf(m3/s) 6.1E-07 6.9E-07 7.9E-07
m°f(Kg/s) 0.00051 0.00058 0.00066
pb(KW) 1.33214 2.66429 3.99643
pb(KW) VS m°f(Kg/s)
0
f(x) = 0 x + 0
R² = 1
0

0
m°f(Kg/s)

0
1 1.5 2 2.5 3 3.5 4 4.5
B.P

 When mass flow rate=0

Friction power=-Brake power=6.67 KW
 Friction power is constant when N(rpm) is constant

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 Energy Balance
Objective
To know what is the benefit of Engine Energy Balance and how we made engine
test and knowing its performance.

Engine Energy Balance

There are many reasons to perform an energy balance study on an engine. The
knowledge of how the energy is lost will help in finding means to improve the
performance of the engine in terms of efficiency and power output. This seems to
be the main reason behind most energy studies performed on engines. By
improving the efficiency of the engine, the result is a higher percentage of the
fuel’s energy getting converted into power output. This is noticed as improved
performance. Although the goal of understanding engine operation to improve
efficiency is common, there are many different reasons an energy balance study
helps to reach this goal. Energy balances studies help characterize the impact a
change has on the overall system. Once the impact is identified by the energy
balance, one can attempt to either maximize or oppose its use due to the benefits
and drawbacks. These changes include variations in fuel, physical changes to
engine design, or adjustments of engine settings.
Energy balance Equation Surrounding power

Exhaust power

Fuel power
Brake power

Coolant power

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mf×H.V=Q Coolant+ Q Exhaust+ Q Surrounding+ B.p

Fuel Power
This is the Power which we take from the Fuel. This power is resulted from the
chemical reaction of fuel which gives us the heat and explosion we need. We
calculate it from the product of mass flow rate multiplied by the Heating value of
the fuel .
Fuel Power = m f×H.V
H.V (diesel) = 43.1 MJ/Kg
Density of diesel fuel = 830 Kg/m3
How to measure Fuel Power
Fuel flow rates (mf) were measured with flow meters or else by measuring the
volume of fuel consumed and the specific time of consumption.

Brake Power (Pb)

Brake power is the measure of an engine's power without the loss in power
caused by the gearbox, alternator, differential, water pump, and other auxiliary

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components. We get it from the product of the torque multiplied by the RPM of
the Engine.
Brake Power=τb× ω
0.746
BP(KW) = 2800 ×load(lb) × N(rpm)

How to measure Brake Power

In order to measure the brake Torque (τb) of the engines dynamometers were
used. Hydraulic brake dynamometers were used in most cases examined,
however, it should be noted that other dynamometers such as water brake, fan
brake, prony brake, eddy current, direct current, or electric motor/generator.

We can measure engine

speed (ω) by using tachometers

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Coolant Losses (QCoolant)
This is the heat loss to the coolant. We may name it losses but actually we need to
do it to reduce the temperature of the engine. To measure the energy transferred
through conduction of engine components, the losses to the coolant, are
calculated by:
Coolant Losses=mc.w×cp,c.w×(Tc.w,o-Tc.w,in)
mc.w= 0.0533292×√ h
cp,c.w= 4.186 KJ/Kg.k
h is manometer reading in ( mm )
How to measure Coolant Losses (QC)
Heat loss to the engine coolant was usually measured by finding the difference in
coolant temperature at the engine’s inlet and outlet.

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Exhaust Losses (QExhaust)
It is the heat that is released from the exhaust system which contains heat that
can be used in any other process in the car. The losses through the exhaust were
determined by measuring the air and fuel flow rates, and determining the exhaust
gas temperature
Exhaust Losses= mex×cp,ex×(Tex-Tamb)
mex= mf+ mair
ρw
√
mair= ρair× Cd×Ao× 2 gh
ρair

cp ex is the specific heat at constant pressure (if not given assume it = 1.13
KJ/Kg.k)
Cd is coefficient of discharge ( 0.658 )
ρair assume 1.23 kg/m3
Ao is area of orifice ( value is 0.001353 m2)

How to measure Exhaust Losses (Qex)

For measuring losses to the exhaust, finding the mass flow rate of the exhaust by
direct measurement or from adding the air and fuel flow rates into the engine,
then maximum heat can be found from cooling the exhaust to ambient
temperature. Air flow rates were measured with either some kind of flow meter
or by a pressure change (manometer) in a flow element.

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Losses to surrounding (Q surrounding)
This term we can not measure it but we can calculate it from the difference of the
fuel power and the other losses. This type of losses may go to the oil or friction or
by radiation from the cylinder block or anything we cannot calculate easily.

Energy balance for the Engine

We will make a variable load test for the engine. All sensors are connected to the
engine and all indicators are working.
Procedure:
1. Start the engine
2. Open the throttle valve until the speed reach 1000 rpm
3. Wait while the engine is running until you reach steady state
4. Read all the data shown in the table from the indicators
5. Repeat the same procedures with load varying between (0, 5, 10, 15, and 20)lb
H.V(MJ/Kg)= 43.1
ρfuel(Kg/m3)= 830
Cp,C.W(KJ/Kg)= 4.186
ρair(Kg/m3)= 1.23
Cd=0.658
Ao(m2)= 0.001353
ρw(Kg/m3)=1000
Cp,ex(KJ/Kg)= 1.13
Tamb(°C)= 25

load(Ib) 5 10 15

N(rpm) 1200 1200 1200

hc.w(mm) 55 55 55

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 Tc.w,c(°C) 33 38.2 41.7

Tc.w,h(°C) 35.5 40.4 43.8

hair(cm) 5 5 5

Tex(°C) 40 57.6 70.6

Vol(ml) 50 50 50

time(sec) 85.4 72.3 70

 
mfuel(Kg/s 0.00048594 0.0005739 0.00059285
) 8 97 7

mC.W(Kg/s 0.3955 0.3955 0.3955

)
0.30925074 0.3092507 0.30925074
mair(Kg/s) 1 41 1
 
20.9443793 24.739280 25.5521428
Qfuel(KW) 9 77 6
1.59857142 3.1971428 4.79571428
B.P(KW) 9 57 6
4.13890679 3.6422379 3.47668170
QC.W(KW) 2 77 5
5.25003689 11.413323 15.9656209
Qex(KW) 5 73 5
9.95686427 6.4865762 1.31412591
Qsurr(KW) 5 15 5
 
%B.P 8% 13% 19%

%QC.W 20% 15% 14%

%Qex 25% 46% 62%

%Qsurr 48% 26%

LOAD 5%
VS FUEL POWER
30

25 f(x) = 0.46 x + 19.14

R² = 0.88
20
Qfuel(KW)

15

10

5
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0
4 6 8 10 12 14 16
Load(Ib)
 LOAD VS BREAK POWER
6

5
f(x) = 0.32 x − 0
4 R² = 1

0
4 6 8 10 12 14 16

LOAD VS COOLANT LOSSES

4.2

4 f(x) = − 0.07 x + 4.41

R² = 0.92
3.8
QC.W(KW)

3.6

3.4

3.2

3
4 6 8 10 12 14 16
Load(Ib)

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 f(x) = 0
R² = 0 LOAD
LOADVS
VSEXHAUST LOSSES
SURROUNDING
18
12
16
10
14 f(x) = 1.07 x + 0.16
R² = 0.99
12
8
Qsurr(KW)
Qex(KW)

10
6
8
6
4
4
2
0
04 6 8 10 12 14 16
0 2 4 6 8 10 12
Load(Ib)
Load(Ib)

30

25
fuel power
20 Linear (fuel power)
brake power
15 Polynomial (brake
power)
10 coolant losses
Linear (coolant
5 losses)
exahaust losses
0
4 6 8 10 12 14 16

Conment:
 As the load increases Qfuel & B.P & Qex increases

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  As the load increases QC.W & Qsurr decreases
If load =5 Ib

0.8
%B.P
2.0
%QC.W

%Qex 2.5
10.0

4.7
%Qsurr

1.3

1.5 %B.P

%QC.W

4.6 10.0

%Qex

2.6

%Qsurr
If load =10 Ib

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If load =15 Ib

1.9
%B.P
1.4
%QC.W

10.0

6.2
%Qex

0.5
%Qsurr

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