MORSE TEST
Introduction: - The basic task in the design and development of I.C.Engines is to reduce the cost of production and improve the efficiency and power output. In order to achieve the above task, the engineer has to compare the engine developed by him with other engines in terms of its output and efficiency. Hence he has to test the engine and make measurements of relevant parameters that reflect the performance of the engine. In general the nature and number of tests to be carried out depend on a large number of factors. In this chapter only certain basic as well as important measurements and tests are described.
Important Performance Parameters of I.C.Engines:- The important performance parameters of I.C. engines are as follows:
Friction Power,
Indicated Power,
Brake Power,
Specific Fuel Consumption,
Air – Fuel ratio
Thermal Efficiency
Mechanical Efficiency,
Volumetric Efficiency,
Exhaust gas emissions,
Noise
1.3. Measurement of Performance Parameters in a Laboratory
1.3.1. Measurement of Friction Power:- 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.
Following methods are used in the laboratory to measure friction power:
Willan’s line method;
From the measurement of indicated power and brake power;
Motoring test;
Retardation test;
Morse Test.
1.3.1.2.From the Measurement of Indicated Power and Brake Power:- This is an ideal method by which friction power is obtained by computing the difference between the indicated power and brake power. The indicated power is obtained from an indicator diagram and brake power is obtained by a brake dynamometer. This method requires elaborate equipment to obtain accurate indicator diagrams at high speeds.
1.3.1.3.Morse Test:- This method can be used only for multi – cylinder IC engines. The Morse test consists of obtaining indicated power of the engine without any elaborate equipment. The test consists of making, in turn, each cylinder of the engine inoperative and noting the reduction in brake power developed. In a petrol engine (gasoline engine), each cylinder is rendered inoperative by “shorting” the spark plug of the cylinder to be made inoperative. In a
Diesel engine, a particular cylinder is made inoperative by cutting off the supply of fuel. It is assumed that pumping and friction are the same when the cylinder is inoperative as well as during firing.
In this test, the engine is first run at the required speed and the brake power is measured. Next, one cylinder is cut off by short circuiting the spark plug if it is a petrol engine or by cutting of the fuel supply if it is a diesel engine. Since one of the cylinders is cut of from producing power, the speed of the engine will change. The engine speed is brought to its original value by reducing the load on the engine. This will ensure that the frictional power is the same.
If there are k cylinders, cylinders, then
Total indicated power
when all the cylinders are working = ip 1 + ip2 + ip3 + …………...+ ipk = ip j j = 1
We can write ip j = Bt + Ft ………………………………………..(1)
j = 1
where ip j is the indicated power produced by j th cylinder, k is the number of cylinders,
Bt is the total brake power when all the cylinders are producing power and Ft is the total frictional power for the entire engine.
If the first cylinder is cut – off, then it will not produce any power, but it will have frictional losses. Then
we can write ip j = B1 - Ft………………………………………..(2)
j = 2
where B1 = total brake power when cylinder 1 is cut - off and
Ft = Total frictional power.
Subtracting Eq. (2) from Eq. (1) ( 1) we have the indicated power of the cut off cylinder. Thus
ip1 = Bt – B1 ………………………………………..(3).
Similarly we can find the indicated power of all the cylinders, viz., ip2, ip3, …..ipk. Then the total indicated power is calculated as
(ip)total = ip j ……………………………………….(4)
j = 1
The frictional power of the engine is therefore given by
Ft = (ip)total – Bt ……………………………………(5)
The procedure is illustrated by some examples worked out at the end of the chapter.
NEED OF MORSE TEST
The i.p. and the mechanical efficiency of a multi-cylinder auto engine is found out in a very short time by this test. During the test the engine is run at a constant speed and at same throttle opening. First the b.p. of the engine with all cylinders operative is measured by means of dynamometer. Next, the b.p. of the engine is measured with each cylinder rendered inoperative one by one by shorting the spark plug in case of petrol engine or by cutting off the fuel supply in case of diesel engine. hen any cylinder is rendered inoperative, the speed abruptly goes down. !efore taking any reading, the initial speed must be restored by ad"usting the load. #t is assumed that the f.p. of the inoperative cylinder remains the same as it were when the cylinder was operative. $onsidering the case of a %-cylinder engine,
hen cylinder No.l is rendered inoperative, it does not develop any power& on the contrary contrary
some power is lost due to movement of piston inside the cylinder. Then,
When the Morse test is carried out:
'i( The b.p. should be measured as soon as possible after making cylinder inoperative. 'ii( The dynamometer load should be ad"usted soon to bring the speed to its constant value for the test& otherwise the engine may race. #n order to plot i.p., b.p. and r) m a series of tests should be conducted at predetermined engine speeds because b.p. varies with load and speed.
6 MEASUREMENT OF I.P OF MULTI-CYLINDER ENGINE (MORSE TEST)
This method is used in multi-cylinder engines to measure I.P with out the use of indicator. The BP of the engine is measured by cutting off each cylinder in turn. If the engine consists of 4-cylinders, then the BP of the engine should be measured four times cutting each cylinder turn by turn. This is applicable to petrol as well as for diesel engines. The cylinder of a petrol engine is made inoperative by “shorting” the spark plug whereas in case of diesel engine, fuel supply is cut-off to the required cylinder.
If there are ‘ n’ cylinders in an engine and all are working, then (B.P) n = (I.P)n – (F.P)n
Where F.P is the frictional power per cylinder.
If one cylinder is inoperative then the power developed by that cylinder (IP) is lost and the speed of the engine will fall as the load on the engine remains the same. The engine speed can be resorted to its original value by reducing the load on the engine by keeping throttle position same. This is necessary to maintain the FP constant, because it is assumed that the FP is independent of load and depends only on speed of the engine.
When cylinder “1” is cut off; then (B.P)n – 1 = (I.P)n – 1 – (F.P)n …..(12) By subtracting Eq. (23.7) from Eq.(23.6), we obtain the IP of the cylinder which is not firing i.e., (B.P) n – (B.P)n-1 = (IP)n – (IP)n-1 = I.P1
Similarly IP of all other cylinders can be measured one by one then the sum of IPs of all cylinders will be the total IP of the engine.
This method of obtaining IP of the multicylinder engine is known as ‘Morse Test’.
Illustrative examples:
develo ps a brake power of 20.9 kW. Example:- A gasoline engine working on four- stroke develops A Morse test was conducted on o n this engine and the brake br ake power (kW) obtained when wh en each cylinder was made inoperative by short circuiting the spark plug are 14.9, 14.3, 14.8 and 14.5 respectively. The test was conducted at constant speed. Find the indicated power, mechanical efficiency and brake mean effective pressure when all the cylinders are firing. The bore of the engine is 75mm and the stroke is 90 mm. The engine is running at 3000 rpm.
Given:- brake power when all cylinders are working = B t = 20.9 kW ; Brake power when cylinder 1 is inoperative = B 1 = 14.9 kW ; Brake power when cylinder 2 is inoperative = B 2 = 14.3 kW ; Brake power when cylinder 3 is inoperative = B 3 = 14.8 kW ; Brake power when cylinder 4 is inoperative = B 4 = 14.5 kW ;
N = 3000 rpm ; d = 0.075 m ; L = 0.09 m ;
To find:- (i) (ip)total ; (ii)
mech ; (iii) bmep ;
Solution:
(ip)total = ip1 + ip2 + ip3 + ip4 = (Bt – B1) + (Bt – B2) + (Bt – B3) + (Bt – B4)
4Bt – (B1 + B2 + B3 + B4) = 4 x 20.9 – (14.9 + 14.3 + 14.8 + 14.5)
25.1 Kw
Bt
20.9 (ii)
mech = -------------
= ---------=0.833=83.3 %
(ip)total 25.1
60,000 B t 60,000 x 20.9 (iii) bmep = ---------------
=--------------------------------------------------
LAnK 2
0.09x(/4)x 0.075 x (3000 / 2) x 4
5
2
= 5.25 x 10 N / m = 5.25 bar.
MORSE TEST T EST ON MUL MU LTI CYLINDER CYL INDER PETROL ENGINE
Ex.No. :
Date:
Aim :
To conduct morse test on given multi cylinder petrol engine in order to determine the indicated power developed in the each cylinder of the engine and to determine the mechanical efficiency.
Apparatus Required :
*ulti cylinder petrol engine with ignition cut off arrangement
+oading arrangements
Tachometer
Theory and Description :
For slow speed engine the indicated power is directly calculated from the indicator diagram. !ut in modern high speed engines , it is difficult to obtain accurate indicator diagram due to inertia forces , and therefore , this method cannot be applied . #n such cases the morse test can be used to measure the indicated power and mechanical efficiency of multi cylinder engines . The engines test is carried out as follows . The engine is run at maximum load at certain speed . The !. is then measured when all cylinders are working .
Then one cylinder is made in operative by cutting off the ignition to that cylinder . s a result of this the speed of the engine will decrease . Therefore , the load on the engine is reduced so that the engine speed is restored to its initial value . The assumption made on the test is that frictional power is depends on the speed and not upon the load on the engine .
Definitions :
Break poer : !B"#
The useful power available at the crank shaft of the engine is called brake power of the engine . The brake power of the engine are determined by
.
/ope brake dynamometer.
T 0 /e
0 net load
/e 0 effective radius of the brake drum 1.
rony brake dynamometer
T 0 +
0 +oad
+ 0 Distance at which the load is applied
$%ser&ation and Ta%u'ation :
'( !rake power !. 0........... 2
'1( /ated 3peed N 0.........../pm 0.........../pm
'4( Type Type of loading 5 0...........
'%( /adius of brake drum 5 / 0........... 6m7
'8( /adius of /ope r 0 0........... 6m7
'9( Number of cylinders 0 %
( No
)onditions *oadin+
(peed B" ,-W
W/ k+ W0
W/ 1 W0 Net 'oad Rpm
k+
k+
W in ,N
/
A'' cy'inders are
orkin+
0
2irst cy'inder
as cut off and
remainin+ are in
orkin+
3
(econd cy'inder
as cut off and
remainin+ are in
orkin+
4
Third cy'inder
as cut off and
remainin+ are in
orkin+
5
2ourth cy'inder
as cut off and
remainin+ are in
orkin+
Note 5 The speed should be same same for all readings
4. :ydraulic dynamometer !. 0 N
$ 0 +oad
N 0 3peed in /* $ 0 Dynamometer constant
%. ;lectrical dynamometer
6ndicated poer : ! 6 " #
The power actually developed inside the engine cylinder due to the combustion of the fuel are called indicated power . # 0 F < ! & F 0 Frictional power
2rictiona' poer !2"# :
The power loss due to friction between the moving parts are called as frictional power .
Mechanica' efficiency : ! ηmech #
#t is defined as the ratio of !rake power to indicated power .
ηmech0!.,x == #.
"rocedure :
From the name plate details , determine the maximum load that can be given to the
engine For example 5 !. 0 1.8 kw , N 0 1=== rpm
!. 0 >>1?NT>>
9= x ===
T
0 9= x === x 1.8 0
[email protected] N-m
1 ? x 1===
T 0 ./e 3ay /e 0 =.%m
.
.. 0 T>> 0
[email protected] 0 %@.1N
/e
=.%
B 8= N
max 5 load that can be given to the engine was
C8 w 0 C8 x 8= 0 1.8N
==
max 0 net load 0 1.8 0 .18kg
=
$heck the engine for fuel availability, lubricant and cooling water connections .
/elease the load completely on the engine and start the engine in no load conditions and allow the engine to run for few minutes to attain the rated speed.
pply the load and increase the load upto maximum load. 'll ' ll four cylinders should be in working ( . Now note the load on the engine and speed of the engine say the speed is
6N7 rpm
$ut-off the ignition of first cylinder, Now the speed of engine decreased . /educe the load on the engine and bring the speed of the engine to 6N7 rpm. Now note the load on on the engine.
!ring the all four cylinders are in working conditions and cut off the 1 nd , 4rd and %th cylinder in turn and ad"ust the load to maintain same 6N7 rpm and note the load .
Resu't:
*orse test was conducted on given petrol engine and indicated power developed in each cylinder are determined and mechanical efficiency are also determined .