mechanical engineering MCQs – Page 110

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 Review each marked answer and report any item that may be outdated or unclear.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

2181. 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

2182. 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

2183. 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

2184. 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

2185. 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

2186. 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

2187. 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

2188. The criterion of the thermodynamic efficiency for rotary compressor is_________________?
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A. polytropic compression

B. isentropic compression

C. isothermal compression

D. any one of the above

E. none of the above

2189. The following is true for an open cycle gas turbine having exhaust heat exchanger. Atmospheric air before entering the compressor is____________________?
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A. bled gas from turbine is heated and readmitted for complete expansion

B. compressed air before entering the combustion chamber is heated

C. exhaust gases drive the compressor

D. heated

E. part of exhaust gases are heated and mixed up with atmospheric air to utilise exhaust heat

2190. The fuel consumption in gas turbines is accounted for by___________________?
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A. higher heating value

B. heating value

C. highest calorific value

D. low.er heating value

E. higher calorific value

2191. What will be the volume of air at 327C if its volume at 27C is 1.5 m3/mt ?
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A. 3 m3/mt

B. 18 m3/mt

C. 0.75 m3/mt

D. 1.5 m3/mt

E. 6 m3/mt

2192. Which is false statement about advantages of multistage compressor in comparison to single stage compressor_________________?
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A. less power requirement

B. less loss of air due to leakage past the cylinder

C. better mechanical balance

D. more effective lubrication

E. lower volumetric efficiency

2193. For minimum work in multistage compression, assuming same index of compression in all stages_________________?
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A. work done in first stage should be more

B. work done in subsequent stages should decrease

C. work done in any stage is no criterion for minimum work but depends on other factors

D. work done in all stages should be equal

E. work done in subsequent stages should increase

2194. A rocket works with maximum overall efficiency when air craft velocity is equal to the_________________?
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A. no such co-relationship with jet velocity exists

B. jet velocity

C. average of the jet velocity

D. twice the jet velocity

E. half the jet velocity

2195. Isothermal compression though most efficient, but is not -practicable because_________________?
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A. it does not increase pressure much

B. it requires cylinder to be placed in water

C. it is impossible in practice

D. ityrequires very big cylinder

E. compressor has to run at very slow speed to achieve it

2196. Pick up the wrong statement ?
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A. ramjet-engine has no turbine

B. bypass turbo-jet engine increases the thrust without adversely affecting, the propulsive efficiency and fuel economy

C. pulsojet requires no ambient air for propulsion

D. propeller is an indirect reaction device

E. turbine drives compressor in a burbojet

2197. Intercooling in gas turbine results in ____________________ ?
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A. increase in net output but decrease in thermal efficiency

B. increase in thermal efficiency but decrease in net output

C. increase in both thermal efficiency and net output

D. decrease in both thermal efficiency and net output

E. none of the above

2198. Volumetric efficiency is_____________________?
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A. the ratio of stroke volume to clearance volume

B. reciprocal of compression ratio

C. proportional to compression ratio

D. the ratio of the air actually delivered to the amount of piston displacement

E. index of compressor performance

2199. Choose the correct statement ________________?
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A. gas turbine requires lot of cooling water

B. gas turbines can be used to generate power only

C. gas turbines have high standby losses and require lot of maintenance

D. gas turbines have flat efficiency at part loads

E. gas turbine is capable of rapid start up and loading

2200. Standard air is the air at_____________________?
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A. 25C, 1 kg/cm2 and RH of 60%.

B. 15C and 1 kg/cm2

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

D. 0C and standard atmospheric conditions

E. atmospheric conditions at any specific location

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