MCQOPTIONS
Saved Bookmarks
MCQOPTIONS
This section includes 88 Mcqs, each offering curated multiple-choice questions to sharpen your Turbo Machines knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
A control volume has an inlet area of 0.1 m2 and exit area of 0.05 m2. The density is 3.89 kg/m2 and constant. If the inlet velocity is 30 m/s, the force on the control volume will be |
| A. | 350 N |
| B. | 150 N |
| C. | 50 N |
| D. | 250 N |
| Answer» B. 150 N | |
| 2. |
When working substance is released through nozzles, the direction of reaction will be |
| A. | clockwise |
| B. | counter clockwise |
| C. | either of (A) and (B) above |
| D. | direction depends on other design features |
| Answer» C. either of (A) and (B) above | |
| 3. |
In a hot wire anemometer the rate of heat loss from sensing element is a function of |
| A. | pressure |
| B. | mass rate of flow |
| C. | velocity of flow |
| D. | none of the above |
| Answer» D. none of the above | |
| 4. |
Surging is |
| A. | an unsteady, periodic and reversal of flow in the compressor |
| B. | the fixed mass flow rate regardless of pressure ratio |
| C. | the reduction in lift force at higher angles of incidence |
| D. | none of the above |
| Answer» B. the fixed mass flow rate regardless of pressure ratio | |
| 5. |
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» C. unaffected is the propulsive efficiency | |
| 6. |
Maximum delivery pressure in case of rotary compressors is usually restricted to |
| A. | 5 atmospheres |
| B. | 10 atmospheres |
| C. | 2 atmospheres |
| D. | 20 atmospheres |
| Answer» C. 2 atmospheres | |
| 7. |
Though there are no cyclic variations even then rotary compressors need precise balancing because |
| A. | It is bulky in size |
| B. | it is driven by an electric motor |
| C. | cooling arrangement does not exist |
| D. | operating speeds are too high |
| Answer» E. | |
| 8. |
Overall efficiency of a gas turbine is |
| A. | less than Diesel cycle efficiency |
| B. | more than Otto or Diesel cycle efficiency |
| C. | equal to Rankine cycle efficiency |
| D. | equal to Carnot cycle efficiency |
| Answer» B. more than Otto or Diesel cycle efficiency | |
| 9. |
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» D. B = SN | |
| 10. |
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» E. | |
| 11. |
The range of compression ratio in a gas turbine is |
| A. | 3 to 6 |
| B. | 5 to 8 |
| C. | 12 to 22 |
| D. | 8 to 12 |
| Answer» C. 12 to 22 | |
| 12. |
A diffuser |
| A. | converts thermal energy into kinetic energy |
| B. | converts pressure energy into kinetic energy |
| C. | converts kinetic energy into thermal energy |
| D. | converts potential energy into kinetic energy |
| Answer» D. converts potential energy into kinetic energy | |
| 13. |
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» E. | |
| 14. |
Under standard atmospheric condition, the velocity of air is |
| A. | 236 m/s |
| B. | 436 m/s |
| C. | 336 m/s |
| D. | 536 m/s |
| Answer» D. 536 m/s | |
| 15. |
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» D. surges in open channel | |
| 16. |
For gas turbine, compressors used are |
| A. | Centrifugal type |
| B. | Lobe type |
| C. | Axial flow type |
| D. | Reciprocating type |
| Answer» D. Reciprocating type | |
| 17. |
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» C. polytropic conditions | |
| 18. |
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» D. 99% | |
| 19. |
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» E. | |
| 20. |
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» E. | |
| 21. |
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» D. none of the above | |
| 22. |
In an axial flow compressor, the pressure rise occurs in |
| A. | fixed blades only |
| B. | Moving blades only |
| C. | Both fixed and moving blades |
| D. | none of the above |
| Answer» D. none of the above | |
| 23. |
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» D. 30% less | |
| 24. |
Which of the following is a displacement compressors? |
| A. | Reciprocating air compressor |
| B. | Centrifugal blower |
| C. | Axial flow compressors |
| D. | Vane blower |
| Answer» E. | |
| 25. |
An axial flow compressor has |
| A. | smaller blades at gas entry and larger blades at exit |
| B. | identical dlades at exit as well as entry |
| C. | larger blades at gas entry and smaller blades at exit |
| D. | size of blades remains same only angles changes |
| Answer» D. size of blades remains same only angles changes | |
| 26. |
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» D. Axial flow compressor | |
| 27. |
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» E. | |
| 28. |
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» D. subsonic speed | |
| 29. |
For efficient operation of axial flow compressors the blades are made |
| A. | aerofoil section |
| B. | forward curved |
| C. | straight |
| D. | slightly curved |
| Answer» B. forward curved | |
| 30. |
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» E. | |
| 31. |
Maximum delivery pressure in a rotary air compressor is of the order of |
| A. | 10 KSC |
| B. | 16 KSC |
| C. | 6 KSC |
| D. | 25 KSC |
| Answer» C. 6 KSC | |
| 32. |
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» B. subsonic | |
| 33. |
In a nozzle, once the critical conditions are achieved at the throat, than which of the following remains constant |
| A. | Density of fluid |
| B. | Velocity of fluid |
| C. | Flow rate |
| D. | All of the above |
| Answer» E. | |
| 34. |
A constant volume combustion gas turbine operates on |
| A. | Joule cycle |
| B. | Ericsson cycle |
| C. | Brayton cycle |
| D. | Atkinson cycle |
| Answer» E. | |
| 35. |
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» E. | |
| 36. |
All of the following are positive displacement compressors EXCEPT |
| A. | Vane blower |
| B. | Roots blower |
| C. | Screw compressor |
| D. | Axial flow compressor |
| Answer» E. | |
| 37. |
Ljungstrom steam turbine is a |
| A. | radial flow turbine |
| B. | axial flow turbine |
| C. | mixed flow turbine |
| D. | any of the above |
| Answer» B. axial flow turbine | |
| 38. |
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» D. none of the above | |
| 39. |
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» C. High power, high speed | |
| 40. |
In which of the following heat exchanger, heat is extracted from air? |
| A. | Regenerator |
| B. | Reheater |
| C. | Intercooler |
| D. | All of the above |
| Answer» D. All of the above | |
| 41. |
Which of the following is a positive displacement rotory compressor? |
| A. | Roots blower |
| B. | Centrifugal compressor |
| C. | Axial flow compressor |
| D. | All of the above |
| Answer» B. Centrifugal compressor | |
| 42. |
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» B. Brayton cycle is less efficient | |
| 43. |
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» E. | |
| 44. |
An ideal fluid for vapour turbine cycle should have |
| A. | low critical temperature with high pressure |
| B. | high critical temperature with low pressure |
| C. | high critical temperature with high pressure |
| D. | low critical temperature with low presure |
| Answer» C. high critical temperature with high pressure | |
| 45. |
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» D. lower specific speed | |
| 46. |
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» B. is less than work ratio | |
| 47. |
Basic closed cycle for gas turbine is |
| A. | Carnot cycle |
| B. | Rankine cycle |
| C. | Brayton cycle |
| D. | none of the above |
| Answer» D. none of the above | |
| 48. |
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» E. | |
| 49. |
In a gas turbine cycle regenerator is used to |
| A. | heat fuel supplied to combustion chamber |
| B. | heat air supplied to combustion chamber |
| C. | heat the gases coming out of combustion chamber |
| D. | heat exhaust gases released from low pressure turbine |
| Answer» C. heat the gases coming out of combustion chamber | |
| 50. |
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» D. any of the above | |