1. LOAD TEST ON A PERKINS DIESEL
ENGINE
EXPERIMENT NO.:
INSTRUCTED BY:
GROUP MEMBERS:
NAME :
COURSE : B.Sc. Engineering
INDEX NO. : 150131A
GROUP :
DATE OF PER. :
DATE OF SUB. :
2. ABSTRACT
There are two main types of engines in the use. They are IC engines and spark ignition engines. Here
we are going get an experiment with an IC engine. In this practical, used Diesel engine, that comes
under internal combustion engine. As an objective of this practical, we can get an idea of how the
internal combustion engine works. And also have to get an idea of the compression ignition internal
combustion engine works and operates, and also how the engine parameters affect to the power or
work that can get from it. The main parameters that we are going to use in this practical is, brake
power, indicated power, thermal efficiency, volumetric efficiency, mean effective pressure, specific
fuel consumption and swept volume.
Using the readings and also the observations through out the practical can get idea of the parameters
that is affected for the engine work. After the practical have to go through the analysis of the data that
we have got and also further improvements of the practical as well as the reading that will affect for
the work done and also to minimize the errors.
INTRODUCTION
In the world, there are several types of engines that are going to use in various applications. Among
them Ci engines and SI engines plays major role in the engineering world. Here we are focused on
diesel engine. This engine is also known as compression ignition or CI engine. The first CI engine
was invented by Rudolf Diesel so that the name is came from him.
The internal combustion engine ignites the fuel which is injected to the combustion chamber, because
of the temperature increment due to increment of the compression pressure. That pressure is
increased by mechanical procedure. Here as a reason for the increment of the temperature, the diesel
particles are atomized and then ignite spontaneously. There is no need of spark plug as Petrol
engines.
The Diesel engine has higher efficiency with comparative to other types. The main reason is higher
compression ratio. Mainly in low thermal diesel engines has higher efficiencies, as that exceed 50%.
In modern world Diesel engines are used in various applications, rather than transportation that we
know in general. As the higher efficiency, that kind of engines are economical. Apart from that there
are several other advantages as generate less carbon and carbon monoxide during exhaust,
comparatively noise is lower and require less maintenance.
3. THEORY
Breaking power is calculated by closing the exhaust system partially or completely. That is depends
on the speed of the engine as well as load of the engine.
π΅ππππ πππ€ππ =
π Γ π
πΎ
Where,
W = engine load
N = engine speed
K = 4500 (a constant)
To obtain the frictional losses, fuel consumption vs BP graph have to sketched. Using that graph, FP
can be calculated with the intercept and the data given in the lab sheet.
Intercept = C (kg/s)
Calorific value of the fuel = X (kJ/kg)
Friction power = CX (kW)
Indicated power that was produced by the engine is calculated as follows.
I.P = B.P +FP
Specific fuel consumption (SFC) is calculated using following equation.
ππππππππ πΉπ’ππ πΆπππ π’πππ‘πππ(ππΉπΆ) =
πΉπ’ππ πΆπππ π’πππ‘πππ
π΅ππππ πππ€ππ
β
3600 ππ
ππβ
Break mean of effective pressure is the average pressure which produces the brake power output
when applying uniformly on the piston.
π΅ππππ ππππ πΈπππππ‘ππ£π ππππ π π’ππ(π΅ππΈπ) =
π΅ππππ πππ€ππ
π
4
Γ π·2 Γ πΏ Γ (
π
2
) Γ
4
60
Where,
D - bore diameter = 98.4 mm
L- stroke = 127 mm
N - tested engine rpm
Volumetric efficiency is the ratio of actual amount of air the engine can ingests and the theoretical
maximum of it.
4. Volume inhaled
ππππ’ππ ππβππππ(ππ) =
4.193
35.22
Γ π2
Γ ββ Γ
π
π»
π3(min)β1
Where,
d - orifice diameter β 2.05 inches
h - Manometer water head in inches of water
H - atmospheric air pressure in inches of Hg
T- temperature at the orifice in intake air vessel
Swept volume
ππ€πππ‘ ππππ’ππ(ππ ) = 4 Γ
π
4
Γ π·2
Γ πΏ Γ
π
2
π3(min)β1
Where,
D - bore diameter = 98.4 mm
L- stroke = 127 mm
N - tested engine rpm
Volumetric efficiency
ππππ’πππ‘πππ πΈπππππππππ¦ =
ππππ’ππ ππβππππ
ππ€πππ‘ π£πππ’ππ
ππππ’πππ‘πππ πΈπππππππππ¦ =
ππ
ππ
Mechanical efficiency ratio is the ratio in between output work and total input work. In other words,
it is the ratio between BP and IP
πππβππππππ ππππππππππ¦ =
π΅ππππ πππ€ππ
πΌππππππ‘ππ πππ€ππ
Break thermal efficiency is the ratio between BP and rate of the heat input by the fuel.
ππ£πππππ ππππππππππ¦ =
π΅ππππ πππ€ππ
π ππ‘π ππ βπππ‘ ππππ’π‘ ππ¦ π‘βπ ππ’ππ
5. APPARATUS
β’ 4-cylinder 4 stroke naturally aspired 3.86-liter Perkins diesel engine.
β’ Fraud hydraulic dynamometer
β’ Thermometers
β’ Venture flow meter
β’ Intake air controlling vessel
β’ Stopwatch
β’ Manometer
PROCEDURE
Open the inlet valve fully and the outlet valve slightly
All valves in the piping between the source of water supply and the dynamometer inlet are fully open.
Fuel availability is checked, otherwise make sure that the valve is open and let the fuel fill into the
tank.
The engine was started.
The rpm is adjusted using accelerator.
Load is regulated by opening the sluice gate by means of the hard wheel and simultaneous opening
the engine throttle, until the desired load and speed obtained.
Water was sufficiently applied through the piping system to maintain the temperature of the engine.
The applying load is measured and balanced using hand-wheel that is placed on the top of the balance
frame to adjust the height of the balance arm. The pin point at the bottom of the adjustment has to be
in position in order to maintain readable load.
Fuel consumption was measured using stopwatch, the time that is taken to decrease between the two
points in the indicator.
Temperature values of the cooling water inlet temperature, outlet temperate, and also engine exhaust
temperature is measured using thermometers and thermocouples.
Manometer reading was read in the air intake vessel.
The procedure was repeated for other readings that relevant to the different rpm of the engine.
6. CALCULATION
Calculation for 1100 rpm
For 30 lbs load,
Data:
D - 98.4 mm
L- 127 mm
N - 1100 rpm
T- 300
C
H - 758 mmHg = 29.843 inchHg
h - 1.3*0.826 inchWater = 1.0738 inchWater
C- higher calorific value of diesel = 44290 kJ/kg
For the braking power
π΅π =
π Γ π
πΎ
π΅π =
30 Γ 1100
4500
π΅π = 7.33 ππ
To plot the graph
Load(lbs) Break Power(kW)
NL 0
15 3.667
30 7.333
45 11
Fuel consumption
πΉπΆ =
π£πππ’ππ ππ ππ’ππ ππππ π’πππ
π‘πππ
πΉπΆ =
50 ππ
52.29 π
πΉπΆ = 0.9562 πππ β1
7. Friction Power =
0.6083
0.0428
kW
Friction Power = 14.213 kW
IP = BP + FP
IP = 7.333 + 14.213 kW
IP = 21.546 kW
Specific fuel consumption
SFC =
Fuel consumption
Break Power
Γ
3600 kg
kWh
SFC =
50 Γ 10β6
Γ 880
52.29 Γ 7.333
Γ 3600 kg(kWh)β1
SFC = 0.4130 kg(kWh)β1
Break mean effective pressure(BMEP),
BMEP =
Break Power
(
Ο
4
ΓΓ D2 Γ L Γ
N
2
Γ
4
60
)
BMEP =
7.333
(
Ο
4
Γ 0.09842 Γ 0.127 Γ
1100
2
Γ
4
60
)
BMEP = 207.083 kPa
y = 0.0428x + 0.6083
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
-20 -15 -10 -5 0 5 10 15
fuelconsumption(cc/s)
Break Power(kW)
Fuel consumption Vs Break Power
8. Volume inhaled,
Vi =
4.193
35.22
Γ d2
Γ βh Γ
T
H
Vi =
4.193
35.22
Γ 2.052
Γ β1.0738 Γ
(273 + 30)
29.843
Vi = 1.6519 m3(min)β1
Swept Volume,
Vs = 4 Γ
Ο
4
Γ D2
Γ L Γ
N
2
Vs = 2.1247 m3(min)β1
Volumetric efficiency,
Ξ·v =
Vi
Vs
Ξ·v =
1.6519
2.1247
Ξ·v = 0.7775
Mechanical efficiency,
Ξ·M =
B. P
I. P
Ξ·M =
7.33
21.546
Ξ·M = 0.3403
Rate of heat input by the fuel,
QΜ = mΜ Γ C
QΜ =
V Γ Ο
t
Γ C
QΜ =
50 Γ 10β6
Γ 880
52.29
Γ 44290
QΜ = 37.2683 kW
Overall efficiency,
Ξ·M =
B. P
QΜ
Ξ·M =
7.33
37.2683
Ξ·M = 0.1968
12. DISCUSSION
β’ Applications of CI engine
Mainly CI engine is used for transportation system. The advantages as well as applications are
based in the characteristics of the engine.
In transportation systems, the diesel engine plays major role. In passenger cars is the famous
application of Diesel engine. The Diesel engines have been introduced about 1980s in Europe.
Diesel engines tends to be more economical at regular speeds, that cars are normally used.
With comparision to the SI engines the life span is increased and so that will cause for more
economical point of view. Another thing is the CO2 content that emits form the engine is
lesser amount, so that eco friendliness is higher. And also, diesel engine has cheaper.
In another mode of transportation systems such as aircrafts, marine applications, motorcycles.
But now a day the application in aircraft industries as well as marine they tend to use another
power sources. In aircrafts, in smaller sizes had use piston engines. Now Cessna aircrafts, that
can carry about 2 or 3 number of passengers have horizontal oppose cylinder engines, that use
diesel as the fuel. In second world war, the aircrafts that run from diesel engines played major
role.
The advantages of the using the Diesel engine in marine and aircraft applications are same as
car industries. Also for the use of other transportation systems that has used to transport
agricultural equipment as well as roadway construction equipment are use Diesel engine
powered vehicles, in most of the times.
In military uses, diesel engines have used in the vehicles, that is a trend to improve the
efficiency of the vehicle. As an example, NATO army is used diesel power motor cycle in the
middle east operations.
And also, the non-transportation such as systems that use power generation, act as a generator
that can be categorized as portable or non-portable systems, use diesel engines. Also for
irrigation pumps that use in large irrigation projects, and large grinders that use for grind the
stones in the mills can be used the diesel engines.
β’ Characteristics of a CI engine with comparative to a SI engine
There are several characteristics in SI engines and CI engine that can use to compare the two
different engines. Mainly, type of fuel, weight, efficiency, emission gases types and
composition are in concern.
Description SI engine CI engine
Thermodynamic
cycle
Otto cycle Diesel of duel cycle
Fuel Petrol (expensive) Diesel (cheaper)
Compression ratio 6-10 (average 7-8) 12-22 (average 16-
17)
Combustion or
ignition of charge
Spark ignition Compression ignition
Thermal
efficiency
Lower thermal efficiency
due to low compression
ratio
Higher thermal
efficiency due to
higher compression
ratio
Weight Lighter in weight due to
low compression ration
and lower peak pressure
value
Heavier due to high
compression ratio and
high peak pressure
In thermal cycle, SI engine is used OTTO cycle that addition of heat or fuel combustion
occurs at a constant volume. In CI engine Diesel cycle is used and here addition of heat and
fuel is occurred at constant pressure.
13. In SI engine, mix of fuel and air is introduced in to the piston via carburetor that control the
quantity as well as quality of the air fuel mixture. In CI engine fuel is added to the combustion
chamber towards the end of the compression stroke. Here use fuel pump and injector.
β’ Dynamometer and types of engine dynamometer
That is a device that is to measure torque and brake power required to operate a driven
machine. Mainly there are two types of dynamometers, power absorption dynamometer and
power transmission dynamometer.
Power absorption dynamometer measure and absorb the power output that is coupled. Power
absorption is usually dissipated as heat. There are several power absorption dynamometers
such as Prony break dynamometer, Rope brake dynamometer, Eddy current dynamometer,
Hydraulic dynamometer etc.
In power transmission dynamometer that transmitted the load couple to the engine after it is
indicated on some scale. Also known as torque meters.
In Prony break dynamometer, it is the simplest dynamometer, that attempts to stop the engine
using brake on the flywheel. The Rope brake dynamometer consists of some turns of rope
rotating around a drum. The power is absorbed in friction of the rope and drum.
In eddy current dynamometer there are several advantages like that is high brake power per
unit weight of dynamometer. That is offered highest ratio of constant power speed range. It
has higher torque under low speed condition.
in hydraulic dynamometer, the construction is similar to that of a fluid flywheel. That is
consists of an impeller or inner rotating member coupled to the output shaft of the engine. The
friction forces generated between the impeller and the fluid is measured using spring balance
fitted on the casting.
The absorption dynamometers are called as torque meters. They are mostly consisting of a set
of strain gauges, that is fixed on the rotating disk. The angular deformation of the strain
gauges is measured of the shaft.
β’ Components of heat balance equation of a CI engine
The equation for the heat balance of the CI engine is defined as
π»πππ‘ πππππππ‘ππ ππ πππππ’π π‘πππ ππ π‘βπ ππ’ππ
+ πππβππππππ πππ€ππ ππππ’π‘ πππ πππππππ π πππ
= πππβππππππ ππππππ¦ ππ’π‘ππ’π‘ + ππππππ¦ πππ π ππ
The energy losses can be categorized under three categories as follows.
o Heat loss to coolant
o Heat loss to exhaust
o Frictional losses
So that the total energy losses are described as
ππππππ¦ πππ π = βπππ‘ πππ π π‘π πππππππ‘ + βπππ‘ πππ π π‘π ππ₯βππ’π π‘ + πππππ‘πππ πππ π
In the coolants, the energy is loss in order to increase the temperature of the coolants. So
that the coolants are carried out energy that generated.
In heat loss in exhaust, because exhausting gas carried some part of the energy that is
generated during the thermodynamic cycle. That cannot be recoverable. In engines that
cannot be used as air preheater, specially in locomotives so that, that energy is wasted.
The frictional losses are undesirable. We cannot avoid that but using coolants as well as
well maintaining the engine via services, can reduce frictional losses.
β’ Importance of calculating the above performance indices of the engine
Basically, mechanical efficiency provides and indicates how much mechanical work that
gives by the engine with respect to the energy that we have supplied. By using that values we
14. can say that how the engine is worked and is the engine works during profitable region. We
can compare general values with the values that get from the engine and decide what are the
improvements to take to increase the efficiency.
In specific fuel consumption values, indicated how much fuel use in order to get the work. If
the fuel consumption is higher, sometimes the work will have reduced. So that we can get an
idea of the fuel consumption with the amount of work. If the work is low with respect to the
work done, we have to take some actions to reduce the specific fuel consumption and get the
higher work. That is an indictor of the energy losses due to less maintenance.
The volumetric efficiency gives us how much air get filled into the cylinder during stroke.
That will help us to get an idea about the combustion in low oxygen condition or higher
oxygen condition. So, have to consider about the best air to fuel ration in order to increase the
efficiency of the engine.
In overall efficiency of the that is the indicator of the mechanical work output respect to the
chemical energy input to the engine. By changing the parameters of the engine have to get the
optimum efficiency from the engine.
β’ Error minimization of the experiment
o Readings must take after some times that will take for the engine to settle under some
set of constant variables.
o Maintain the load applied on the engine constant, and get corrected load values.
o Use horizontal indicator to read the manometer readings in the air tank
o Maintain the constant rpm during the process, have to correct acceleration as fast as
we can if there any changes.
o Can minimize the time measuring errors, by taking time for 100cc values rather than
50cc values.
References
Swagatam, H. K. (2008, 5 11). Comparison of Spark Ignition (SI) and Compression Ignition (CI) engines.
Retrieved from Bright hub engineering: http://www.brighthubengineering.com/machine-design/1537-
comparison-of-spark-ignition-si-and-compression-ignition-ci-engines/
15. y = 0.0428x + 0.6083
y = 0.0383x + 0.7679
y = 0.0428x + 0.818
-0.5
0
0.5
1
1.5
2
-25 -20 -15 -10 -5 0 5 10 15 20
fuelconsumption(cc/s)
Break power(kW)
Fuel Consumption Vs Break Power
Linear (1100 rpm)
Linear (1300 rpm)
Linear (1500 rpm)