compressors gas turbines and jet engines Mcqs
1. Compression efficiency is compared against_____________________?
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A. isothermal compression

B. adiabatic compression

C. isentropic compression

D. botii isothermal and adiabatic compression

E. ideal compression

2. During peak load periods, the best method of controlling compressors is___________________?
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A. constant speed unloader

B. relief valve

C. start-stop motor

D. variable speed

E. none of the above

3. Out of the following, from where you will prefer to take intake for air compressor_________________?
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A. from any one of the above locations

B. from coal yard side

C. from outside atmosphere at 1C

D. from an air conditioned room maintained at 20C

E. from a side where cooling tower is located nearby
4. The vloumetric efficiency of compressor with increase in compression ratio will ___________________?
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A. may increase/decrease depending on clearance volume

B. increase

C. remain same

D. decrease

E. none of the above

5. Clearance volume in actual reciprocating compressors is essential __________________?
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A. to attain high volumetric efficiency

B. to provide cushioning effect and also to avoid mechanical bang of piston with cylinder head

C. to avoid mechanical bang of piston with cylinder head

D. to provide cushioning effect

E. to accommedate Valves in the cylinder head

7. Surging is the phenomenon of___________________?
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A. air stream blocking the passage

B. unsteady, periodic and reversed flow

C. air stream not able to follow the blade contour

D. production of no air pressure

E. motion of air at sonic velocity

8. In turbo fan engine, the jet velocity as compared to turbo-jet engine is_________________?
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A. may be less or more depening upon speed

B. less

C. same

D. none of the above

E. more

9. A closed gas turbine in which fuel is burnt directly in the air is not possible because of__________________?
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A. high friction losses

B. paucity of 02

C. high pressure ratio

D. high specific volume

E. increasing gas temperature

10. The ideal efficiency of simple gas turbine cycle depends on________________?
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A. minimum cycle temperature

B. maximum cycle temperature

C. none of the above

D. all of the above

E. pressure ratio
11. The thrust on the rotor in a centrifugal compressor is produced by________________?
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A. resultant component

B. tangential component

C. axial component

D. radial component

12. Axial flow compressor resembles____________________ ?
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A. none of the above

B. turbine

C. centrifugal pump

D. reciprocating pump

E. sliding vane compressor

13. Producer gas is produced by_____________________?
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A. passing steam over incandescent coke

B. passing air and a large amount of steam over waste coal at about 65C

C. carbonisation of coal

D. same way as the natural gas

E. partial combustion of coal, coke, anthracite coal or charcoal in a mixed air steam blast
14. A gas turbine used in air craft should have______________________?
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A. high h.p. and low weight

B. high speed and high h.p.

C. small frontal area and high h.p.

D. all of the above

E. low weight and small frontal area
15. Reheating in multistage expansion gas turbine results in____________________?
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A. decrease of heat loss in exhaust

B. none of the above

C. maximum work output

D. high thermal efficiency

E. reduction in compressor work

16. High air-fuel ratio is used in gas turbines______________________?
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A. to save fuel

B. to reduce the exit temperature

C. to increase the efficiency

D. to increase the output

E. none of the above

17. The efficiency and work ratio of a gas turbine plant can be increased by _____________________?
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A. all of the above

B. using mulit-stage compressor with mfercooler

C. adding heat exchanger

D. reheating the air after partial expansion in the turbine

E. injecting water in/around combustion chamber

18. Ram compression in turbojet involves____________________?
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A. lost work

B. increasing speed of incoming air

C. compression of inlet air

D. leakage losses

E. reduction of speed of incoming air and conversion of part of it into pressure energy
19. A compressor at high altitude will draw________________?
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A. less power

B. none of the above

C. more/less power depending on other factors

D. same power

E. more power

20. For slow-speed large capacity compressor, following type of valve will be best suited________________?
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A. none of the above

B. disc or feather type

C. poppet valve

D. mechanical valve of the corliss, sleeve, rotary or semirotary type

E. any of the above

21. Pick up the correct statement ?
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A. large gas turbines use radial inflow turbines

B. gas turbines have their blades similar to steam turbine

C. gas .turbines blade will appear as impulse section at the hub and as a reaction section at tip

D. gas turbines use both air and liquid cooling

E. all of the above are correct.

23. Free air is the air at________________?
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A. 25C, 1 kg/cm2 and relative humidity of 50%.

B. 20C and 1 kg/cm2 and relative humidity of 36%

C. 15C and 1 kg/cm2

D. atmospheric conditions at any specific location

E. 0C and standard atmospheric conditions

24. Pick up the false statement ?
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A. gas turbine can be easily started and stopped and thus is best suited for peaking demands

B. exhaust losses in gas turbine are high due to large mass flow rate

C. gas turbine is a self-starting unit

D. gas turbine does not require huge quantity of water like steam plant

E. overall efficiency of gas turbine plant is lower than that of a reciprocating engine

25. The clearance volume of the air compressor is kept minimum because____________________?
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A. none of the above

B. it permits isothermal compression

C. it greatly affects volumetric efficiency

D. it allows maximum compression to be achieved

E. it results in minimum work

27. The blades of gas turbine are made of_________________?
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A. high alloy seel

B. mild steel

C. carbon steel

D. high nicket alloy (neimonic)

E. stainless steel

29. Reheating in gas turbine results in___________________?
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A. increase of work ratio

B. decrease of thermal efficiency

C. decrease of work ratio

D. both A. and B. above

E. both B. and C. above

30. The material commonly used for air craft gas turbine is__________________?
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A. stainless steel

B. titanium

C. Timken, Haste and Inconel allpys

D. duralumin

E. high alloy steel

31. In jet engines the compression ratio__________________?
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A. varies as square root of the speed

B. Varies linearly to the speed

C. varies as square of the speed

D. varies as cube of the speed

E. is constant irrespective of variation in speed

33. The degree of reaction of an axial flow turbine is the ratio of isentropic temperature drop in a blade row to the_____________________?
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A. total temperature drop

B. total adiabaitc temperature drop

C. adiabatic temperature drop in the stage

D. difference of maximum and minimum temperature in the cycle

E. total temperature drop in the stage
34. Rotary compressor is best suited for_____________________?
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A. large quantity of air at high pressure

B. any one of the above

C. small quantity of air at low pressure

D. large quantity of air at low pressure

E. small quantity of air at high pressure
36. Gas turbine blades are given a rake___________________?
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A. equal to zero

B. in the direction of motion of blades

C. opposite to the direction of motion of blades

D. depending on the velocity

E. none of the above

37. Adiabatic compression is one in which___________________?
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A. work done is maximum

B. entropy decreases

C. no heat leaves or enters the compressor cylinder during cornpression

D. temperature rise follows a linear relationship

E. temperature during compression remains constant

38. The- most efficient method of compressing air is to compress it_________________?
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A. isochronically

B. adiabatically

C. as per law pV

D. isothermally

E. isentropically

39. The overall isothermal eiffciency of compressor is defined as the ratio of_______________?
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A. isothermal work to ideal work

B. work to compress air isothermally to work for actual compression

C. power to drive compressor to isothermal h.p.

D. isothermal h.p. to the BHP of motor

E. isothermal h.p. to adiabatic h.p.

40. Work ratio of a gas turbine plant is ratio of______________________?
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A. net work output and heat supplied

B. actual/heat drop and isentropic heat drop

C. work done by turbine and net work output

D. work done by turbine and heat supplied

E. net work output and work done by turbine
41. Pick up the correct statement?
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A. thrust in turbo-jet is produced by nozzle exit gases

B. gas turbine uses same working fluid over and over again

C. closed cycle gas turbine is an I.C engine

D. ideal efficiency of closed cycle gas turbine plant is more than carnot cycle efficiency

E. air-fuel ratio in a gas turbine is 100 : 1

42. The ratio of isentropic work to Euler work is known as_____________________?
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A. work coefficient

B. compressor efficiency

C. pressure coefficient

D. polytropic reaction

E. slip factor

43. The compressor performance at higher altitude compared to sea level will be _______________?
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A. same

B. none of the above

C. dependent on other factors

D. lower

E. higher

44. The thermal efficiency of a simple gas turbine for a given turbine inlet temperature with increase in pressure ratio_____________________?
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A. increases

B. decreases

C. remains same

D. first decreases and then increases

E. first increases and then decreases

45. In the axial flow gas turbine, the work ratio is the ratio of____________________?
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A. compressor work and turbine work

B. actual compressor work and theoretical comprssor work

C. actual total head tempeature drop to the isentrpic total head drop from total head inlet to static head outlet

D. output and input

E. none of the above

46. Reciprocating air compressor is best suited for___________________?
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A. large quantity of air at low pressure

B. small quantity of air at low pressure

C. small quantity of air at high pressure

D. any one of the above

E. large quantity of air at high pressure
47. Separators in compressor installations are located_____________________?
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A. after receiver

B. before suction

C. before intercooler

D. after intercooler

E. between after-cooler and air receiver
48. The indicated work per unit mass of air delivered is___________________?
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A. inversely proportional to clearance volume

B. directly proportional to clearance volume

C. not affected by clearance volume

D. greatly affected by clearance volume

49. The ratio of work doen per cycle to the swept volume in case of compressor is called ______________?
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A. mean effective pressure

B. compressor effectiveness

C. compression index

D. compressor efficiency

E. compression ratio

50. Maximum work is done in compressing air when the compression is_________________?
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A. adiabatic

B. any one of the above

C. isothermal

D. polytropic

E. none of the above