mechanical engineering MCQs – Page 108

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 Review each marked answer and report any item that may be outdated or unclear.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

2141. 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

2142. 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

2143. There is a certain pressure ratio (optimum) for a gas turbine at which its thermal efficiency is maximum. With increase in turbine temperature, the value of pressure ratio for the peak efficiency would__________________?
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A. remain same

B. decrease

C. unpredictable

D. none of the above

E. increase

2144. 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

2145. 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

2146. 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

2147. 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

2148. 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

2149. 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

2150. 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

2151. 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

2152. 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

2153. 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

2154. 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

2155. 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

2156. 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

2157. 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

2158. 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.

2159. The air-fuel ratio in gas turbines is of the order of ______________________?
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A. 30:01:00

B. 15:01

C. 7:01

D. 40:01:00

E. 50: 1

2160. 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

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