McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
| 51. |
In a reheating gas turbine cycle, reheating is done |
| A. | by gases from turbine exhaust |
| B. | by gases from intercooler |
| C. | in separate combustion chamber |
| D. | any of the above |
| Answer» C. in separate combustion chamber | |
| 52. |
The ratio of outlet whirl velocity to blade velocity in case of centrifugal compressor is called |
| A. | Blade efficiency |
| B. | Diagram efficiency |
| C. | slip factor |
| D. | Velocity ratio |
| Answer» C. slip factor | |
| 53. |
Thermal efficiency of a gas turbine is in the range |
| A. | 20 to 30 percent |
| B. | 40 to 50 percent |
| C. | 50 to 60 percent |
| D. | 30 to 40 percent |
| Answer» D. 30 to 40 percent | |
| 54. |
A roots blower compresses 0.06 cubic metres of air from 1.0 bar to 1.45 bar per revolution. The compressor efficiency is nearly |
| A. | 75% |
| B. | 63% |
| C. | 87% |
| D. | 99% |
| Answer» C. 87% | |
| 55. |
Basic closed cycle for gas turbine is |
| A. | Carnot cycle |
| B. | Rankine cycle |
| C. | Brayton cycle |
| D. | none of the above |
| Answer» C. Brayton cycle | |
| 56. |
The advantage of a gas turbine over a reciprocating engine is |
| A. | perfect balancing of rotor |
| B. | continuous and uniform power |
| C. | usually small working pressures |
| D. | all of the above |
| Answer» D. all of the above | |
| 57. |
A diffuser is used to |
| A. | increase velocity and decrease pressure |
| B. | increase velocity as well as pressure |
| C. | decrease velocity as well as pressure |
| D. | decrease velocity and increase pressure |
| Answer» D. decrease velocity and increase pressure | |
| 58. |
Air fuel ratio for a gas turbine is closer to |
| A. | 60 ; 1 |
| B. | 10 ; 1 |
| C. | 15 ; 1 |
| D. | 20 ; 1 |
| Answer» A. 60 ; 1 | |
| 59. |
Which of the following steam turbine has identical fixed and moving blades? |
| A. | Curtis turbine |
| B. | Rateau turbine |
| C. | Parson's turbine |
| D. | none of the above |
| Answer» C. Parson's turbine | |
| 60. |
Bleeding in steam turbine refers to |
| A. | purposely withdrawn steam for process application |
| B. | leakage of steam through bearings |
| C. | purposely withdrawn for feed water heating |
| D. | leakage of steam through packings |
| Answer» C. purposely withdrawn for feed water heating | |
| 61. |
As a result of blade friction, the outlet relative velocity of impulse turbine compared to inlet relative velocity is |
| A. | Nearly same |
| B. | 2% less |
| C. | 10% - 15% less |
| D. | 30% less |
| Answer» C. 10% - 15% less | |
| 62. |
As there is plenty of time for heat transfer across the walls, the flow in long pipes at low velocities attains |
| A. | adiabatic conditions |
| B. | isothermal conditions |
| C. | polytropic conditions |
| D. | isentropic conditions |
| Answer» B. isothermal conditions | |
| 63. |
The normal shock wave in compressible flow is analogous to |
| A. | hydraulic bore in tidal rivers |
| B. | vortex formation in centrifugal pump |
| C. | hydraulic jump in channel flow |
| D. | surges in open channel |
| Answer» C. hydraulic jump in channel flow | |
| 64. |
Greater the difference between jet velocity and aeroplane velocity |
| A. | greater the propulsive efficiency |
| B. | Lesser the propulsive efficiency |
| C. | unaffected is the propulsive efficiency |
| D. | None of the above |
| Answer» B. Lesser the propulsive efficiency | |
| 65. |
If stage efficiency is S, blade efficiency is B and nozzle efficiency in N, then |
| A. | BSN = 1 |
| B. | N = B.S |
| C. | S = B.N |
| D. | B = SN |
| Answer» C. S = B.N | |
| 66. |
Choking is |
| A. | Variation of mass flow rate in proportion to pressure ratio |
| B. | variation of mass flow rate in inverse proportion to pressure ratio |
| C. | fixed mass flow rate regardless of pressure ratio |
| D. | none of the above |
| Answer» C. fixed mass flow rate regardless of pressure ratio | |
| 67. |
The advantage of closed cycle gas turbine over open cycle gas turbine is |
| A. | no contamination of working substance with combustion gases |
| B. | inferior quality fuel can be used |
| C. | low maintenance costs |
| D. | All of the above |
| Answer» D. All of the above | |
| 68. |
Brayton cycle cannot be used in reciprocating engines even for same compression ratio and work output because |
| A. | Large volume of low pressure gas cannot be efficiently handled in reciprocating engines |
| B. | Brayton cycle is less efficient |
| C. | Otto cycle is more efficient |
| D. | Brayton cycle is for slow speed engines only |
| Answer» A. Large volume of low pressure gas cannot be efficiently handled in reciprocating engines | |
| 69. |
Working medium for closed cycle gas turbine should have |
| A. | high molecular weight |
| B. | low specific volume |
| C. | higher adiabatic index |
| D. | lower specific speed |
| Answer» C. higher adiabatic index | |
| 70. |
Thermal efficiency of a gas turbine cycle can be improved by |
| A. | reheating between expansion stage |
| B. | intercooling between compression stges |
| C. | regeneration |
| D. | any of the above |
| Answer» D. any of the above | |
| 71. |
Thermal efficiency of closed cycle gas turbine plant increases by |
| A. | reheating |
| B. | intercooling |
| C. | regenerator |
| D. | All of the above |
| Answer» D. All of the above | |
| 72. |
For gas turbine, compressors used are |
| A. | Centrifugal type |
| B. | Lobe type |
| C. | Axial flow type |
| D. | Reciprocating type |
| Answer» C. Axial flow type | |
| 73. |
Which of the following is the least efficient method of governing steam turbines? |
| A. | Combined throttle and nozzle governing |
| B. | Throttle governing |
| C. | Nozzle control governing |
| D. | Bypass governing |
| Answer» B. Throttle governing | |
| 74. |
The effect of blade friction in a steam turbine is to |
| A. | increase the specific output |
| B. | reduce work done |
| C. | reheat the steam |
| D. | reduce exhaust pressure |
| Answer» B. reduce work done | |
| 75. |
In rotory compressors, the ratio of isentropic work to Eulers work is known as |
| A. | degree of reaction |
| B. | slip factor |
| C. | work factor |
| D. | pressure coefficient |
| Answer» D. pressure coefficient | |
| 76. |
Ljungstrom steam turbine is a |
| A. | radial flow turbine |
| B. | axial flow turbine |
| C. | mixed flow turbine |
| D. | any of the above |
| Answer» A. radial flow turbine | |
| 77. |
A constant volume combustion gas turbine operates on |
| A. | Joule cycle |
| B. | Ericsson cycle |
| C. | Brayton cycle |
| D. | Atkinson cycle |
| Answer» D. Atkinson cycle | |
| 78. |
All of the following are positive displacement compressors EXCEPT |
| A. | Vane blower |
| B. | Roots blower |
| C. | Screw compressor |
| D. | Axial flow compressor |
| Answer» D. Axial flow compressor | |
| 79. |
De Laval turbine is used for applications requiring |
| A. | High power, low speed |
| B. | Low power, high speed |
| C. | High power, high speed |
| D. | Low power, low speed |
| Answer» B. Low power, high speed | |
| 80. |
Which type of rotary compressor is used in oil fired furnaces? |
| A. | Sliding vane type blower |
| B. | Axial flow compressor |
| C. | Screw compressor |
| D. | Centrifugal blower |
| Answer» D. Centrifugal blower | |
| 81. |
In a two stage gas turbine plant, reheating after first stage |
| A. | increases work ratio |
| B. | decreases work ratio |
| C. | does not affect work ratio |
| D. | none of the above |
| Answer» A. increases work ratio | |
| 82. |
The efficiency of a simple open cycle gas turbine depends upon |
| A. | pressure ratio |
| B. | compressor efficiency |
| C. | turbine inlet temperature |
| D. | All of the above |
| Answer» D. All of the above | |
| 83. |
In a nozzle under choked flow conditions pressure waves travel, in the divergent portion, at |
| A. | subsonic to supersonic speed |
| B. | supersonic speed |
| C. | sonic speed |
| D. | subsonic speed |
| Answer» C. sonic speed | |
| 84. |
Which of the following is a displacement compressors? |
| A. | Reciprocating air compressor |
| B. | Centrifugal blower |
| C. | Axial flow compressors |
| D. | Vane blower |
| Answer» D. Vane blower | |
| 85. |
With ideal regencrative heat exchanger, the thermal efficiency of gas turbine cycle is |
| A. | equal to work ratio |
| B. | is less than work ratio |
| C. | is more than work ratio |
| D. | none of the above |
| Answer» A. equal to work ratio | |
| 86. |
In a modern steam turbine, the steam rte is nearly |
| A. | 1 kg/kWhr |
| B. | 8 kg/kWhr |
| C. | 4 kg/kWhr |
| D. | 2 kg/kWhr |
| Answer» C. 4 kg/kWhr | |
| 87. |
In air compressor performance curve a surge line represents |
| A. | limits of compressor discharge |
| B. | limit of compressor efficiency |
| C. | lower critical speed of shaft |
| D. | limit of stable operation |
| Answer» D. limit of stable operation | |
| 88. |
In rotary compressors, slip factor is the ratio of |
| A. | stagnation pressure to static pressure |
| B. | isentropic work done to actual work |
| C. | outlet whirl velocity to the blade velocity |
| D. | none of the above |
| Answer» C. outlet whirl velocity to the blade velocity | |
| 89. |
In a gas turbine combined cycle plant, a waste heat boiler is used to |
| A. | heat air from intercooler |
| B. | gases from regenerator |
| C. | recover heat form exhaust gases |
| D. | none of the above |
| Answer» C. recover heat form exhaust gases | |
| 90. |
The flow on two sides of a normal shock wave is |
| A. | supersonic on one side and subsonic on the other side |
| B. | subsonic |
| C. | supersonic |
| D. | sonic |
| Answer» A. supersonic on one side and subsonic on the other side | |
| 91. |
Which of the following rotary compressor has two shafts? |
| A. | Sliding vane compressor |
| B. | Centrifugal compressor |
| C. | Lobe type compressor |
| D. | Axial flow compressor |
| Answer» C. Lobe type compressor | |
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