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MCQOPTIONS
This section includes 327 Mcqs, each offering curated multiple-choice questions to sharpen your GATE (Mechanical Engineering) knowledge and support exam preparation. Choose a topic below to get started.
| 251. |
In gas turbines^ high thermal efficiency is obtained in |
| A. | closed cycle |
| B. | open cycle |
| C. | both of the above |
| D. | closed/open depending on other con-siderations |
| Answer» B. open cycle | |
| 252. |
A closed gas turbine in which fuel is burnt directly in the air is not possible because of |
| A. | high pressure ratio |
| B. | increasing gas temperature |
| C. | high specific volume |
| D. | paucity of 02. |
| Answer» E. | |
| 253. |
The power available for take off and climb in case of turbojet engine as compared to reciprocating engine is |
| A. | less |
| B. | more |
| C. | same |
| D. | may be less or more depending on ambient conditons |
| Answer» B. more | |
| 254. |
Intercooling in gas turbine results in |
| 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 |
| Answer» B. increase in thermal efficiency but decrease in net output | |
| 255. |
Pick up the correct statement |
| A. | gas turbine uses low air-fuel ratio to economise on fuel |
| B. | gas turhine uses high air-fuel ratio to reduce outgoing temperature |
| C. | gas turbine uses low air-fuel ratio to develop the high thrust required |
| D. | all of the above |
| Answer» C. gas turbine uses low air-fuel ratio to develop the high thrust required | |
| 256. |
If infinite number of heaters be used in a gas turbine, then expansion process in turbine approaches |
| A. | isothermal |
| B. | isentropic |
| C. | adiabatic |
| D. | isochoric |
| Answer» B. isentropic | |
| 257. |
The closed cycle in gas turbines |
| A. | provides greater flexibility |
| B. | provides lesser flexibility |
| C. | in never used |
| D. | is used when gas is to be burnt |
| Answer» B. provides lesser flexibility | |
| 258. |
A gas turbine used in air craft should have |
| A. | high h.p. and low weight |
| B. | low weight and small frontal area |
| C. | small frontal area and high h.p. |
| D. | high speed and high h.p. |
| Answer» C. small frontal area and high h.p. | |
| 259. |
Water is injected in gas turbine cycle to |
| A. | control temperature |
| B. | control output of turbine |
| C. | control fire hazards |
| D. | increase efficiency |
| Answer» C. control fire hazards | |
| 260. |
For an irreversible gas turbine cycle, the efficiency and work ratio both depend on |
| A. | pressure ratio alone |
| B. | maximum cycle temperature alone |
| C. | minimum cycle temperature alone |
| D. | both pressure ratio and maximum cycle temperature |
| Answer» E. | |
| 261. |
The jnaximum combustion pressure in gas turbine as compared to I.C. engine is |
| A. | more |
| B. | less |
| C. | same |
| D. | depends on other factors |
| Answer» C. same | |
| 262. |
The combustion efficiency of a gas turbine using perfect combustion chamber is of the order of |
| A. | 50% |
| B. | 75% |
| C. | 85% |
| D. | 99%. |
| Answer» E. | |
| 263. |
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 |
| A. | remain same |
| B. | decreases |
| C. | increase |
| D. | none of the above |
| Answer» D. none of the above | |
| 264. |
As the turbine inlet temperature increases, the thermal efficiency of gas turbine for the optimum pressure ratio |
| A. | increases |
| B. | decreases |
| C. | remains same |
| D. | first increases and then decreases |
| Answer» B. decreases | |
| 265. |
Gas turbines use following type of air compressor |
| A. | centrifugal type |
| B. | reciprocating type |
| C. | lobe type |
| D. | axial flow type |
| Answer» E. | |
| 266. |
Temperature of gases at end of compression as compared to exhaust gases in a gas turbine is |
| A. | higher |
| B. | lower |
| C. | equal |
| D. | cant be compared |
| Answer» C. equal | |
| 267. |
Efficiency of gas turbine is increased by |
| A. | reheating |
| B. | inter cooling |
| C. | adding a regenerator |
| D. | all of the above |
| Answer» D. all of the above | |
| 268. |
Gas turbine blades are given a rake |
| 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 |
| Answer» C. opposite to the direction of motion of blades | |
| 269. |
The pressure ratio in gas turbines is of the order of |
| A. | 2:1 |
| B. | 4:1 |
| C. | 61: 1 |
| D. | 9:1 |
| Answer» D. 9:1 | |
| 270. |
The air-fuel ratio in gas turbines is of the order of |
| A. | 7 : 1 |
| B. | 15 : 1 |
| C. | 30 : 1 |
| D. | 50: 1 |
| Answer» E. | |
| 271. |
The thermal efficiency of a gas turbine as compared to a diesel plant is |
| A. | same |
| B. | more |
| C. | less |
| D. | depends on other factors |
| Answer» D. depends on other factors | |
| 272. |
The ratio of specific weighf/h.p. of gas turbin and I.C engines may be typically of the order of |
| A. | 1 : 1 |
| B. | 2 : 1 |
| C. | 4 : 1 |
| D. | 1 : 6 |
| Answer» E. | |
| 273. |
The fuel consumption in gas turbines is accounted for by |
| A. | low.er heating value |
| B. | higher heating value |
| C. | heating value |
| D. | higher calorific value |
| Answer» B. higher heating value | |
| 274. |
Open cycle gas turbine works on |
| A. | Brayton or Atkinson cycle |
| B. | Rankine cycle |
| C. | Carnot cycle |
| D. | Erricsson cycle |
| Answer» B. Rankine cycle | |
| 275. |
The pressure ratio for an open cycle gas turbine compared to closed cycle gas turbine of same h.p. is |
| A. | low |
| B. | high |
| C. | same |
| D. | low/high depending on make and type |
| Answer» B. high | |
| 276. |
The work ratio of a gas turbine plant is defined as the ratio of |
| A. | net work output and heat supplied (6) net work output and work done by tur¬bine |
| B. | actual heat drop and isentropic heat drop |
| C. | net work output and isentropic heat drop |
| D. | isentropic increase/drop in tempera¬ture and actual increase/ drop in temperature. |
| Answer» C. net work output and isentropic heat drop | |
| 277. |
Stalling of blades in axial flow compressor is the phenomenon of |
| A. | air stream blocking the passage |
| B. | motion of air at sonic velocity |
| C. | unsteady periodic and reversed flow |
| D. | air stream not able to follow the blade contour |
| Answer» E. | |
| 278. |
The pressure ratio of an ideal vaned compressor with increase in mass flow rate |
| A. | increases |
| B. | decreases |
| C. | remains constant |
| D. | first decreases and then increases |
| Answer» D. first decreases and then increases | |
| 279. |
Atmospheric pressure is 1.03 kg/cm and vapour pressure is 0.03 kg/cm . The air pressure will be |
| A. | 1.03 kg/cm2 |
| B. | 1.06 kg/cm2 |
| C. | 1.00 kg/cm2 |
| D. | 0.53 kg/cm2 |
| Answer» D. 0.53 kg/cm2 | |
| 280. |
Actual compression curve is |
| A. | same as isothermal |
| B. | same as adiabatic |
| C. | better than isothermal and adiabatic |
| D. | in between isothermal and adiabatic |
| Answer» E. | |
| 281. |
The ratio of the increase in pressure in rotor blades to total increase in pressure in the stage is called |
| A. | pressure ratio |
| B. | pressure coefficient |
| C. | degree of reaction |
| D. | slip factor |
| Answer» D. slip factor | |
| 282. |
Pick up wrong statement. Surging phenomenon in centrifugal com-pressor depends on |
| A. | mass flow rate |
| B. | pressure ratio |
| C. | change in load |
| D. | stagnation pressure at the outlet |
| Answer» E. | |
| 283. |
Surging is the phenomenon of |
| A. | air stream blocking the passage |
| B. | motion of air at sonic velocity |
| C. | unsteady, periodic and reversed flow |
| D. | air stream not able to follow the blade contour |
| Answer» D. air stream not able to follow the blade contour | |
| 284. |
Phenomenon of choking in compressor means |
| A. | no flow of air |
| B. | fixed mass flow rate regardless of pressure ratio |
| C. | reducing mass flow rate with increase in pressure ratio |
| D. | increased inclination of chord with air steam |
| Answer» C. reducing mass flow rate with increase in pressure ratio | |
| 285. |
The thermodynamic efficiency of rotary compressor is based on |
| A. | isothermal compression |
| B. | adiabatic compression |
| C. | isentropic compression |
| D. | polytropic compression |
| Answer» C. isentropic compression | |
| 286. |
The ratio of isentropic work to euler's work is known as |
| A. | compressor efficiency |
| B. | isentropic efficiency |
| C. | Eulers efficiency |
| D. | pressure coefficient |
| Answer» E. | |
| 287. |
For minimum work in multistage compression, assuming same index of compression in all stages |
| A. | work done in first stage should be more |
| B. | work done in subsequent stages should increase |
| C. | work done in subsequent stages should decrease |
| D. | work done in all stages should be equal |
| Answer» E. | |
| 288. |
For supplying intermittent small quantity of air at high pressure, following compressor is best suited |
| A. | centrifugal |
| B. | reciprocating |
| C. | axial |
| D. | screw |
| Answer» C. axial | |
| 289. |
The criterion of the thermodynamic efficiency for rotary compressor is |
| A. | isentropic compression |
| B. | isothermal compression |
| C. | polytropic compression |
| D. | any one of the above |
| Answer» B. isothermal compression | |
| 290. |
The indicated work per unit mass of air delivered is |
| A. | directly proportional to clearance volume |
| B. | greatly affected by clearance volume |
| C. | not affected by clearance volume |
| D. | inversely proportional to clearance volume |
| Answer» D. inversely proportional to clearance volume | |
| 291. |
The volumetric efficiency of a compressor falls roughly as follows for every 5°C increase in atmospheric temperature |
| A. | 0.1% |
| B. | 0.5% |
| C. | 1% |
| D. | 5% |
| Answer» D. 5% | |
| 292. |
Losses in a centrifugal compressor are due to |
| A. | inlet losses |
| B. | impeller channel losses |
| C. | diffuser losses |
| D. | all of the above |
| Answer» E. | |
| 293. |
Pick up the wrong statement about advantages of multistage compression |
| A. | better lubrication is possible advantages of multistage |
| B. | mechanical balance is better |
| C. | air can be cooled perfectly in between |
| D. | more uniform torque, light cylinder and saving in work. |
| Answer» C. air can be cooled perfectly in between | |
| 294. |
The advantage of multistage compression over single stage compression is |
| A. | lower power consumption per unit of air delivered |
| B. | higher volumetric efficiency |
| C. | decreased discharge temperature |
| D. | all of the above. |
| Answer» E. | |
| 295. |
More than one stage will be preferred for reciprocating compressor if the delivery pressure is more than |
| A. | 2 kg/cm2 |
| B. | 6 kg/cm2 |
| C. | 10 kg/cm2 |
| D. | 14.7 kg/cm2 |
| Answer» B. 6 kg/cm2 | |
| 296. |
The volumetric efficiency of a compressor falls roughly as follows for every 100 m increase in elevation |
| A. | 0.1% |
| B. | 0.5% |
| C. | 1.0% |
| D. | 5% |
| Answer» D. 5% | |
| 297. |
The volumetirc efficiency of a compressor is calculated on the basis of |
| A. | volume of air inhaled at working conditions |
| B. | volume of air inhaled at N.T.P. conditions |
| C. | volume at 0°C and 1 kg/cm2 |
| D. | volume at 20°C and 1 kg/cm2 |
| Answer» C. volume at 0°C and 1 kg/cm2 | |
| 298. |
In a compressor, free air delivered is the actual volume delivered at the stated pressure reduced to |
| A. | N.T.P. conditions |
| B. | intake temperature and pressure conditions |
| C. | 0°C and 1 kg/cm2 |
| D. | 20°C and 1 kg/cm2 |
| Answer» C. 0°C and 1 kg/cm2 | |
| 299. |
During peak load periods, the best method of controlling compressors is |
| A. | start-stop motor |
| B. | constant speed unloader |
| C. | relief valve |
| D. | variable speed |
| Answer» C. relief valve | |
| 300. |
A compressor at high altitude will draw |
| A. | more power |
| B. | less power |
| C. | same power |
| D. | more/less power depending on other factors |
| Answer» C. same power | |