Important Questions and Answers: Diesel,Gas Tubine and Combined Cycle Power Plants

1. Define heat engine?

Any type of engine or machine which derives heat energy from the combustion of fuel or any other source and converts this energy into mechanical work is termed as a heat engine.

2. What are the essential component of diesel power plants?

Essential components of a diesel power plant are:

(i) Engine

(ii)Air intake system (iii)Exhaust system (iv)Fuel system

(v) Cooling system

(vi)                Lubrication system

(vii)             Engine starting system

(viii)          Governing system.

3. What are the injection system’sareused in diesel power plants?

Commonly used fuel injection system in a diesel power station:

(i) Common-rail injection system (ii)Individual pump injection system

(iii)         Distribution system.

4. List the various Liquid Cooling System?

In liquid cooling following methods are used for circulating the water around the cylinder and cylinder head:

(i) Thermo-system cooling

Forced or pump cooling

(iii)         Cooling with thermostatic regulator

(iv)          Pressurized cooling

(v) Evaporative cooling.

5. What are the various Lubricating system’sare used in I.C Engines?

Various Lubrications systems use for I.C. engines are:

(i) Wet sump lubrication system

(ii)Dry sump lubrication system

(iii)         Mist lubrication system.

6. Mention three starting systems for Large and Medium size engines?

The following three are the commonly used starting systems in large and medium size engines:

(i) Starting by an auxiliary engine

(ii)Use of electric motors of self starters

(iii)         compressed air system.

7. What is the purpose of super charging?

The purpose of supercharging is to raise the volumetric efficiency above that value which can be obtained by normal aspiration.

8. What are the classifications of Heat Engine?

Heat engines are classified into two types:

1) External combustion engines,

2) Internal combustion engines.

9. Define connecting rod?

It connects the piston and the crankshaft, thereby transmitting the force exerted on the piston to the crankshaft.

10. Define crankshaft?

It converts the reciprocating motion of the piston into the rotary motion of the output shaft. It is enclosed in the crankcase.

11. Define Flywheel?

It is a heavy wheel mounted on the crankshaft. It stores the excess energy delivered by the engine during power stroke and supplies the energy needed during other strokes. Thus it keeps the fluctuations in the crankshaft speed within desired limits.

12. What are the 2 –cooling Medium in cooling system?

The cooling medium used in the cooling system can be air or water. There are two types of cooling systems:

1) Liquid or indirect cooling system,

2) Air or direct cooling system.

13. Write the three types of liquid cooling systems?

This system can be classified under three types:

i) Natural circulation type or thermo syphon system,

ii) forced circulation system,

iii)            Thermostatic cooling system.

14. Write the Disadvantages of over cooling of the Engine?

1) Engine starting is difficult,

2) Over-cooling reduces the overall efficiency of the system,

3)  At low temperatures, corrosion assumes considerable magnitude that it may reduce the life of various components.

15.            Write the advantages of Air cooling?

1.     It occupies less space,

2.     Air cooled engine are lighter than water-cooled engines. Hence used in two wheelers, agricultural sprayers, etc.

3.     Engine warms up faster than water cooled engines,

4.     Practically, there is no need for maintenance.

16.            Write the advantages of Water cooling?

1) Cooling is more efficient,

2) Uniformity in cooling,

3) Engines cooled by water can be placed anywhere in the vehicle.

17.            Write the function of Lubrication?

a.     To reduce the wear and tear between the moving parts and thereby increasing the life of the engine.

b.    The lubricating oil acts as a seal, i.e., it prevents the high pressure gases in the combustion chamber from entering the crankcase

c.      To cool the surfaces.

What are the classifications of Lubrication system?

Classification of Lubrication System: Some of the lubricating systems used for IC engines are:

i) Wet sump lubricating system,

ii) Mist lubricating system.

Wet sump lubricating system can be further classified as,

i) Splash type lubricating system,

ii) Pressure feed lubricating system.

19. What are the components of fuel injector?

The fuel injector or atomizer consists of:

1) Needle valve,

2) Compression spring,

3) Nozzle,

4) Injector body.

20. What are the duties of Air intake systems?

The duties of the air intake systems are as follows:

i) To clean the air intake supply,

ii) To silence the intake air,

iii)            To supply air for super charging.

21. Define –open cycle gas turbine?

In the open cycle gas turbine, air is drawn into the compressor from atmosphere and is compressed. The compressed air is heated by directly burning the fuel in the air at constant pressure in the combustion chamber. Then the high pressure hot gases expand in the turbine and mechanical power is developed.

22. Define –closed cycle gas turbine?

In this, the compressed air from the compressor is heated in a heat exchange (air heater) by some external source of heat (coal or oil) at constant pressure. Then the high pressure hot gases expand passing through the turbine and mechanical power is developed. The exhaust gas is then cooled to its original temperature in a cooler before passing into the compressor again.

23. Write the few fuels for Gas turbine and why these fuels are use for gas turbine?

Natural gas, last furnace gas, produce gas, coal gas and solid fuels distillate oils and residual oils paraffins used in gas turbine and methane, ethane, propane, octane. Important properties to be considered while selecting the fuel for gas turbine are as follows: 1) Volatility 2) Combustion products, 3) Energy contents, 4) Lubricating properties, 5) Availability.

24. Write the major field of application of gas turbines?

The major fields of application of gas turbines are:

i) Aviation

ii) Power generation

iii)            Oil and gas industry

iv)Marine propulsion.

25.            Define Gas turbine plant and write the working medium of this gas turbine?

A gas turbine plant may be defined as one ‚in which the principal prime-mover is of the turbine type and the working medium is a permanent gas‛.

26. What are the components of gas turbine plant?

A simple gas turbine plant consists of the following:

i) Turbine

ii)   Compressor

iii)   Combustor

iv)Auxiliaries.

A modified plant may have in addition and intercooler, a regenerator, a reheater etc.

27. What are the methods to improving the thermal efficiency in open cycle gas turbine plant?

Methods for improvement of thermal efficiency of open cycle gas turbine plant are :

i) Inter cooling

ii) Reheating

iii)            Regeneration

28.            What is the main difference between free piston engine plants and conventional gas turbine plant?

Free-piston engine plants are the conventional gas turbine plants with the difference that the air compressor and combustion chamber are replaced by a free piston engine.