mechanical engineering MCQs – Page 109

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 Review each marked answer and report any item that may be outdated or unclear.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

2161. 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

2162. 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

2163. The volumetric efficiency of a compressor falls roughly as follows for every 5C increase in atmospheric temperature__________________?
0

A. 10%.

B. 0.50%

C. 5%

D. 1%

E. 0.10%

2164. The blades of gas turbine are made of_________________?
0

A. high alloy seel

B. mild steel

C. carbon steel

D. high nicket alloy (neimonic)

E. stainless steel

2165. The maximum compression ratio in an actual single stage axial flow comperssor is of the order of________________?
0

A. 1 : 1.2

B. 1:01

C. 1:05

D. 1:10

E. 1:02

2166. 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

2167. 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

2168. 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

2169. Maximum delivery pressure is a rotary air compressor is of the order of__________________?
0

A. 16 kg/cm2

B. 25 kg/cm2

C. 10 kg/cm2

D. 40 kg/cm2

E. 6 kg/cm2

2170. 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

2171. 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

2172. The capacity of compressor will be highest when its intake temperature is___________________?
0

A. highest

B. none of the above

C. anything.

D. atmospheric

E. lowest

2173. Gas turbine blades are given a rake___________________?
0

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

2174. Adiabatic compression is one in which___________________?
0

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

2175. The- most efficient method of compressing air is to compress it_________________?
0

A. isochronically

B. adiabatically

C. as per law pV

D. isothermally

E. isentropically

2176. 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.

2177. 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

2178. 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

2179. The ratio of isentropic work to Euler work is known as_____________________?
0

A. work coefficient

B. compressor efficiency

C. pressure coefficient

D. polytropic reaction

E. slip factor

2180. The compressor performance at higher altitude compared to sea level will be _______________?
0

A. same

B. none of the above

C. dependent on other factors

D. lower

E. higher

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