Diesel Electric Power Plants

Q. What is the basic difference between a diesel engine and a steam turbine?
Ans. The main difference between a diesel engine and a steam turbine is that in the diesel engine the chemical energy of combustion is released inside the cylinder whereas in case of steam turbine the energy developed during combustion of fuel is first transformed into steam outside the turbine and then supplied to the turbine which in turn develops mechanical power in the turbine.
Q. Why are superchargers provided in the air intake system of a diesel engine?
Ans. The supercharger is usually provided in the air intake system of a diesel engine so as to increase the pressure of intake air above atmospheric one and so develop an increased power output.
Q. Why are strainers provided in the fuel supply system of a diesel engine?
Ans. Strainers are provided in the fuel supply of a diesel engine in order to remove suspended impurities and thus ensure clean fuel supply to the engine.
Q. What is supercharging?
Ans. Supercharging, also known as boosting, can be defined as the admittance of an air charge into the cylinder larger than that obtainable as a result of the regular suction stroke. It is accomplished by external means as compared to regular suction, called the natural aspiration. The main object of supercharging is to increase the power output of the diesel engine without increasing its rotational speed or the cylinder dimensions. This is achieved by increasing the charge of air causing burning of more fuel and resulting in the increase in mean effective pressure.
Q. What are the advantages of supercharging?
Ans. Supercharging offers advantages of an increased power output (30-50%) at the given speed, fuel economy due to better combustion, higher mechanical efficiency, better scavenging action (in the case of two-stroke engines), increased volumetric efficiency and reduced possibility of knocking in diesel engines.

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