mechanical engineering MCQs – Page 112

Practise multiple-choice questions from mechanical engineering for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

mechanical engineering Mcqs

1. compressors gas turbines and jet engines 2. theory of machines 3. nuclear power plants 4. engineering materials 5. strength of materials mechanical engineering 6. thermodynamics 7. heat transfer 8. i c engines 9. steam boilers engines nozzles and turbines 10. engineering mechanics 11. fluid mechanics mechanical engineering 12. production technology 13. machine design 14. hydraulic machines 15. workshop technology 16. refrigeration and air conditioning

2221. In multistage compressor, the isothermal compression is achieved by_________________?
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A. by running compressor at very slow speed

B. employing intercooler

C. by constantly cooling the cylinder

D. none of the above

E. by insulating the cylinder

2222. Air-fuel ratio in a jet engine will be of the order of__________________?
0

A. 20:01

B. 100:00:00

C. 60 : 1

D. 15:01

E. 10:01

2223. The pressure ratio of an ideal vaned compressor with increase in mass flow rate_________________?
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A. remains constant

B. first decreases and then increases

C. unpredictable

D. decreases

E. increases

2224. Which is false statement about multistage compression ?
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A. Outlet temperature is reduced

B. It is best suited for compression ratios around 7:1

C. Power consumption per unit of air delivered is low

D. Volumetric efficiency is high

E. The moisture in air is condensed in the intercooler

2225. The power available for take off and climb in case of turbojet engine as compared to reciprocating engine is ___________________?
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A. more

B. less

C. same

D. unpredictable

E. may be less or more depending on ambient conditons

2226. Which of the following fuels can be used in turbojet engines _____________________?
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A. liquid hydrogne

B. high speed diesel oil

C. kerosene

D. demethylated spirit

E. methyl alcohol

2227. The ratio of the increase in pressure in rotor blades to total increase in pressure in the stage is called__________________?
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A. pressure coefficient

B. degree of reaction

C. slip factor

D. pressure ratio

E. stage factor

2228. The thermal efficiency of a gas turbine as compared to a diesel plant is__________________?
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A. less

B. depends on other factors

C. same

D. unpredictably

E. more

2229. The specific output per kg mass flow rate of a gas turbine (having fixed efficiencies of compressor and turine and fixed higher and lower temperature) with increase in pressure ratio will___________________?
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A. none of the above

B. first increase, reach maximum and then decrease

C. increase first at slow rate and then fast

D. increase first at fast rate and then slow

E. decrease continuously

2230. Turbofan engine employs ____________________ ?
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A. two or more air streams

B. rocket principle for its operation

C. one air stream

D. solid fuel firing

E. no air stream

2231. As the turbine inlet temperature increases, the thermal efficiency of gas turbine for the optimum pressure ratio_____________________?
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A. first increases and then decreases

B. remains same

C. decreases

D. first decreases and then increases

E. increases

2232. The effective power of gas turbines is increased by adding the following in compressor__________________?
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A. hydrogen

B. ammonia and water vapour

C. none of the above

D. nitrogen

E. carbon dioxide

2233. In gas turbines^ high thermal efficiency is obtained in_________________?
0

A. closed cycle

B. open cycle

C. both of the above

D. closed/open depending on other con-siderations

E. unpredictable

2234. The main purpose of reheating in gas turbine is to__________________?
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A. increase pressure ratio

B. increase power output

C. reduce turbine size

D. increase speed

E. increase temperature

2235. Mining industry usually employs following motive power___________________?
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A. diesel engine

B. D.C. electric motor

C. compressed air

D. A.C. electric motor

E. petrol engine

2236. The net work input required for compressor with increase in clearance volume_____________________?
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A. unpredictable

B. remains same

C. increases

D. increases/decreases depending on com-pressor capacity

E. decreases

2237. Ram-jet engine__________________?
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A. is self-operating at zero flight speed

B. is not self-operating at zero^flight speed

C. none of the above

D. requires no air for its operation

E. produces a jet consisting of plasma

2238. Gas turbine works on_______________?
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A. Erricsson cycle

B. Brayton or Atkinson cycle

C. Rankine cycle

D. Joule cycle

E. Carnot cycle

2239. Gas turbine works on______________?
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A. Brayton or Atkinson cycle

B. Joule cycle

C. Carnot cycle

D. Erricsson cycle

E. Rankine cycle

2240. Diffuser in a compressor is used to _____________________?
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A. increase degree of reaction

B. increase velocity

C. convert kinetic energy into pressure energy

D. make the flow stream-line

E. convert pressure energy into kinetic energy

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