Explain Morse test conducted to find the frictional power of a multi-cylinder petrol engine
Morse Test
Morse test is a method to measure the frictional power of a multicylinder SI engine.
Morse Test – This test carried out on multi cylinder I.C. engine. In this test, first engine is allowed to run at constant speed and brake power of engine is measured when all cylinders are working and developing indicated power. (Considering Four cylinders)
I1+I2+I3+I4 = (BP)engine +(F1+F2+F3+F4)
Where I1, I2, I3 and I4 – Indicated power of four cylinders
(BP)engine – Brake power of engine when all cylinders are working
F1, F2, F3, F4 – Frictional power of all four cylinders
Then the first cylinder is cut off by short circuiting spark plug in case S.I. engine (or cutting fuel supply in case C.I. engine). This causes the speed to drop due to non firing of first cylinder. It should be noted that although first cylinder is not producting power still it is moving up and down so its frictional power must be considered. This speed is once again maintained to its original value by reducing load on the engine
I2+I3+I4 = (BP)2,3,4 +(F1+F2+F3+F4)
Where (BP)2,3,4 – Brake power of 2,3 & 4 cylinders only.
Repeat the above procedure for remaining cylinders and calculate I.P. of the engine.
Cylinder 2 is cut off – I1+I3+I4 = (BP)1,3,4 +(F1+F2+F3+F4)
Cylinder 3 is cut off – I1+I2+I4 = (BP)1,2,4 +(F1+F2+F3+F4)
Cylinder 4 is cut off – I1+I2+I3 = (BP)1,2,3 +(F1+F2+F3+F4)
I.P. of cylinder 1 is calculated as ,
I1 = (BP)engine – (BP)2,3,4
Similarly I2,I3 and I4 is calculated as follows
I2 = (BP)engine – (BP)1,3,4
I3 = (BP)engine – (BP)1,2,4
I4 = (BP)engine – (BP)1,2,3
Total Indicated power of engine = I.P.
IP = I1+I2+I3+I4
Frictional power of engine
FP = IP – (BP)engine
and mechanical efficiency
Thus Morse test is used to calculate IP, FP and mech efficienc by assuming FP of each cylinder remains constant.
Numerical Problems on Morse test
A ) Problems On Morse Test
1. Following results are obtained doing morse test
Brake power when all cylinders firing 16.2kw
Brake power when cyl.1 cut off 11.5 kw .
Brake power when cyl. 2 cut off 11.6 kw.
Brake power when cyl.3 cut off 11.68 kw.
Brake power when cyl.4 cut off 11.57 kw.
Calculate mechanical efficiency.
(Ans: 87.80%)
2. Following observation were recorded on four stroke four cylinder engine .
Brake power with all cylinders working 14.7 kw.
Brake power with all 1 cut off 10.14 kw .
Brake power with all 2 cut off 10.3 kw.
Brake power with all 3 cut off 10.36 kw .
Brake power with all 4 cut off 10.21 kw. Calculate mechanical efficiency.
(Ans: 82.63% )
3. During a trial on 4 cylinders four stroke engine coupled to hydraulic dynamo-meter, the following readings were recorded.
Brake power with all cylinder working =14.7kw
Brake power with cylinder 1 cut off =10.14kw
Brake power with cylinder 2 cut off =10.3kw
Brake power with cylinder 3 cut off=10.36 kw
Brake power with cylinder 4 cut off= 10.21kw
Petrol consumption 5.5 kg/hr.
calorific value of CV petrol=42000 kJ/kg.
Dia of cylinder = 8 cm,stroke of piston =10 cm.
clearance volume =0.1 liter
Calculate 1] Mech efficiency 2] Air std efficiency 3] Indicated thermal efficiency 4] Brake thermal efficiency 5] relative efficiency (Ans: 82.63%, 52.15%,27.8%,23.02%,53.30%)
4.Following data relates to 4 cylinder ,4 stroke petrol engine.
Dia of piston =80mm
stroke length =120mm
clearance volume 0.1 litre
fuel supply =4.8 kg/hr
CV =44100 kJ/kg
Brake power all cylinder working 14.5 kw
Brake power 1 cut off 9.8kw
Brake power 2 cut off 10.3kw
Brake power 3 cut off 10.14kw
Brake power 4 cut off 10kw
Calculate 1] Mech efficiency 2)air std. Efficiency 3] Indicated thermal efficiency 4] Brake thermal efficiency 5] relative efficiency
( Ans=81.64%,54.18%,30.207%,24.65%,55.26%. )
Morse test kit Image
