Which loss/es is/are considered in the actual cycle?

Which loss/es is/are considered in the actual cycle?

1. Time loss
2. Heat loss
3. Friction loss
4. Pumping loss

Options:

a. only (2)
b. only (3)
c. (1), (2) and (3)
d. all (1), (2), (3) and (4)

Correct Answer: d. all (1), (2), (3) and (4)

Explanation:

Actual cycle is different from air-standard cycle because of losses occurred in the actual cycle. All the four above mentioned losses are considered in the actual cycle. Time loss occurs due to time required for mixing of air and fuel and time required for complete combustion of the mixture.

Time loss depends upon type of fuel used, air-fuel ratio and flame velocity in the combustion chamber. Heat loss occurs due to transfer of heat through water jackets and cooling fins. Some heat is also transferred during compression and expansion stroke. Due to this heat loss, temperature gets reduced and specific heat also gets reduced. Hence decreases efficiency.

Friction loss occurs due to friction between piston and cylinder walls as well as friction between engine bearings and various other engine moving parts. Friction losses increases with increase in the speed of the engine. Some work has to be done in including fresh charge during suction stroke and expelling the exhaust gases. The difference between work done in including fresh charge and work done in expelling exhaust gases is called as pumping work. The pumping loss occurs due to the pumping gases from low inlet pressure to high exhaust pressure.