Diesel Electric Power Plants Interview Questions and Answers:

1. What is the basic difference between a diesel engine and steam turbine ?

Ans. The basic difference between a diesel engine and a steam turbine is that in the first case the chemical energy of combustion is released inside the cylinder whereas in the second case the energy developed during combustion of fuel is first transformed into steam which in turn develops mechanical power in the turbine.

2. Inspite of various advantages of diesel power plants over other power plants their use is limited. Why ?

Ans. The size limitations and the escalating fuel cost have made the operation of diesel power plants very uneconomical and thereby their use limited. The other drawbacks of diesel power plants are high maintenance and lubrication costs, limited useful life, noise from exhaust and incapability of supplying overloads.

3. Why cannot diesel power stations be employed to generate bulk power ?

Ans. Because of limited capacity, escalating fuel cost, high maintenance and lubrication costs, limited useful life, noise from exhaust and incapability of supplying overloads, diesel power stations cannot be employed to generate bulk power.

4. Why is supercharger used in the air intake system of a diesel engine ?

Ans. The supercharger is usually employed to increase the pressure of intake air above atmospheric one in order to develop an increase power output.

5. Why are strainers provided in the fuel supply system of a diesel engine ?

Ans. Strainers are provided to remove suspended impurities and thus ensure clean fuel supply to the engine.

6. Why is exhaust system provided in the diesel power plant ?

Ans. The exhaust system is provided to discharge the engine exhaust to the atmosphere outside the building.

7. Why is cooling essential for a diesel engine ?

Ans. It is known that the heat generated by the burning of fuel in the engine cylinder is partially converted into useful work. The remainder is wasted as heat in the outgoing exhaust gases and in heating the engine, and if not removed may disintegrate the lubricating oil film on the cylinder walls and damage the cylinder liners, heads, walls, piston and rings. That is why cooling is essential for a diesel engine.

8. Why it is necessary to maintain the exit temperature of cooling water at about 70°C ?

Ans. It is necessary to maintain the exit temperature of cooling water at about 70°C because in case it is too low, the lubricating oil film will not spread properly and will result in wear of cylinder and piston and if it is too high, the lubricating oil will burn.

9. Why is lubrication of a diesel engine necessary ?

Ans. The engine lubricating oil system is of great importance and is provided for lubricating the moving parts, removing the heat from the cylinders and the bearings, helping the piston rings to seal the gases in the cylinders and for carrying away the solid dirt particles from the rubbing parts. The life of the engine and its efficiency depend largely on its lubrication system. The parts of the engine requiring lubrication are piston and cylinders, gears, crankshaft and connecting rod, bearings etc. Piston and cylinder require special lubricating oil.

10. Why are the generating units usually placed parallel to each other ?

Ans. The generating units are usually placed parallel to each other in order to keep the length of electrical connections for generator to control board and air ducts and exhaust pipes minimum.