compressors gas turbines and jet engines MCQs – Page 4

Practise focused compressors gas turbines and jet engines questions with marked answers for exam preparation and subject revision.

compressors gas turbines and jet engines Mcqs
151. The compressor capacity with decrease in suction temperature_________________?
comments icon0

A. remains unaffected

B. increases

C. increases upto certain limit and then decreases

D. decreases

E. may increase or decrease depending on compressor capacity

152. For supplying intermittent small quantity of air at high pressure, following compressor is best suited__________________?
comments icon0
A. reciprocating

B. axial

C. screw

D. centrifugal

E. turbo jet

153. The volumetirc efficiency of a compressor is calculated on the basis of __________________?
comments icon0
A. volume of air inhaled at N.T.P. conditions

B. volume of air inhaled at working conditions

C. none of the above

D. volume at 0C and 1 kg/cm2

E. volume at 20C and 1 kg/cm2

154. The compression ratio in a gas turbine is of the roder of____________________?
comments icon0

A. 5:01

B. 3.5 : 1

C. 12:01

D. 8 : 1

E. 20:01

155. In the aircraft propellers __________________?
comments icon0
A. all of the above

B. its functioning does not depend on presence of air

C. none of the above

D. propulsive matter is ejected from within the propelled body

E. the propulsive matter is caused to flow around the propelled body

156. For a compressor, least work will be done if the compression is________________ ?
comments icon0

A. none of the above

B. somewhere in between isentropic and isothermal

C. isentropic

D. polytropic

E. isothermal
157. Fighter bombers use following type of engine __________________?
comments icon0

A. ram-jet ,

B. turbo-propeller

C. pulsojet

D. turbo-jet

E. rocket

158. The advantage of multistage compression over single stage compression is ________________?
comments icon0
A. all of the above

B. moisture free air

C. lower power consumption per unit of air delivered

D. decreased discharge temperature

E. higher volumetric efficiency

159. Volumetric efficiency of air compressors is of the order of________________?
comments icon0

A. 20-30%

B. 70-90%

C. 40-50%

D. 90-100%

E. 60-70%

160. During base load operation, the best method of controlling compressor is ___________________?
comments icon0

A. variable speed

B. relief valve

C. none of the above

D. start-stop motor

E. constant speed unloader

161. It is not possible to use closed gas turbine cycle in aeronautical engines because_________________ ?
comments icon0

A. non of theses

B. it is inefficient

C. it is bulky

D. it requires cooling water for its operation
162. The air entry velocity m a rocket as compared to aircraft is_________________?
comments icon0

A. more

B. zero

C. same

D. dependent on power and speed

E. less

163. Water is injected in gas turbine cycle to___________________?
comments icon0

A. it is never done

B. control fire hazards

C. control temperature

D. increase efficiency

E. control output of turbine
164. Atmospheric pressure is 1.03 kg/cm and vapour pressure is 0.03 kg/cm . The air pressure will be_____________________ ?
comments icon0

A. 0.5 kg/cm2

B. 1.06 kg/cm2

C. 1.03 kg/cm2

D. 0.53 kg/cm2

E. 1.00 kg/cm2
165. Mechanical efficiency of gas turbines as compared to I.C engines is____________________?
comments icon0

A. depends on on odier considerations

B. same

C. higher

D. lower

E. unpredictable

166. Inter cooling in compressors__________________?
comments icon0

A. enables compression in two stages

B. prevents compressor jacket running very hot

C. results in saving of power in compressing a given volume to given pressure

D. cools the delivered air

E. is the standard practice for big compressors

167. Propulsion efficiency of the following order-is obtained in practice _______________?
comments icon0
A. 60%

B. 72%

C. 85%.

D. 34%

E. 50%

168. The combustion efficiency of a gas turbine using perfect combustion chamber is of the order of________________?
comments icon0

A. 75%

B. 99%

C. 85%

D. 50%

E. 90%

169. Efficiency of gas turbine is increased by________________ ?
comments icon0

A. reheating

B. all of the above

C. inter cooling

D. none of the above

E. adding a regenerator
170. The work ratio of simple gas turbine cycle depends on_________________?
comments icon0

A. maximum cycle temperature

B. minimum cycle temperature

C. pressure ratio

D. all of the above

E. none of die above

171. Surging phenomenon in centrifugal com-pressor depends on ___________________?
comments icon0

A. k up wrong statement ?

B. stagnation pressure at the outlet

C. pressure ratio

D. change in load

E. all of the above

F. mass flow rate

172. Open cycle gas turbine works on___________________?
comments icon0
A. Brayton or Atkinson cycle

B. ankine cycle

C. Carnot cycle

D. Joule cycle

E. Erricsson cycle

173. An ideal air compressor cycle with clearance on p-v diagram can be represented by following processes_______________?
comments icon0

A. two adiabatic, one isobaric and one constant volume,

B. two adiabatic and two isobaric

C. two isobaric, two adiabatic and one constant volume

D. one adiabatic, one isobaric and two constant volume

E. one adiabatic, two isobaric, and one constant volume

174. The thermodynamic efficiency of rotary compressor is based on_______________?
comments icon0

A. none of the above

B. polytropic compression

C. isentropic compression

D. adiabatic compression

E. isothermal compression

175. Maximum temprature in a gas turbine is of the order of COMPRESSORS, GAS TURBINES AND JET ENGINES______________________?
comments icon0

A. 1500C

B. 700C

C. 2000C

D. 1000C

E. 2500C

176. Ratio of indicated h.p. to shaft h.p. in known as__________________?
comments icon0

A. adiabatic efficiency

B. mechanical efficiency

C. volumetric efficiency

D. compressor efficiency

E. isothermal efficiency

177. Phenomenon of choking in compressor means __________________?
comments icon0

A. no flow of air

B. does not occur

C. reducing mass flow rate with increase in pressure ratio

D. fixed mass flow rate regardless of pressure ratio

E. increased inclination of chord with air steam

178. Isothermal compression efficiency, even when running at high speed, can be approached by using A. multi-stage compression B. cold water spray C. both A. and B. above D. fully insulating the cylinder E. high stroke_________________?
comments icon0

A. thermal compression efficiency, even when running at high speed, can be approached by using

B. multi-stage compression

C. cold water spray

D. both A. and B. above

E. fully insulating the cylinder

F. high stroke

179. Pick up the wrong statement ?
comments icon0

A. axial flow compressors apt to be longer as compared to centrifugal type

B. Axial flow compressors have a sub-stantially constant delivery at variable pressures

C. centrifugal compressors have a wider stable operating range than axial flow compressors

D. centrifugal compressors deliver prac-tically constant pressure over a considerable range of capacities

E. axial flow compressors are bigger in diameter compared to centrifugal type
180. In jet engines, paraffin is usually used as the fuel because of its _________________?
comments icon0
A. A. and C. above

B. low freezing point

C. ease of atomisation

D. high calorific value

E. none of the above

181. The ratio of isentropic work to eulers work is known as _____________________?
comments icon0

A. pressure ratio

B. Eulers efficiency

C. isentropic efficiency

D. compressor efficiency

E. pressure coefficient
182. The maximum propulsion efficiency of a turbojet is attained at around following speed __________________?
comments icon0

A. 4000 km/hr

B. 1050km/hr

C. 550 km/hr

D. 1700 km/hr

E. 2400km /hr