90+ Turbo Machines Solved MCQs

1.

Normal standard of compression for rotary compressor is

A. polytropic compression
B. constant pressure compression
C. isentropic compression
D. adiabatic compression
Answer» C. isentropic compression
2.

The continuity equation in compressible fluids is derived on the basis of

A. conservation of velocity head
B. conservation of mass
C. conservation of energy
D. conservation of momentum
Answer» B. conservation of mass
3.

Gas turbine used in aircraft is of

A. closed cycle type with reheating and regeneration and intercooling
B. closed cycle type with reheating
C. open cycle type with reheating, regeneration and intercooling
D. open cycle type
Answer» D. open cycle type
4.

With increase in pressure ratio, thermal efficiency of a simple gas turbine plant with fixed turbine inlet temperature

A. increases
B. decreases
C. first increases and then decreases
D. none of the above
Answer» C. first increases and then decreases
5.

The ratio of actual velocity to the local velocity of sound is called

A. Velocity factor
B. Speed ratio
C. Mach number
D. Velicity ratio
Answer» C. Mach number
6.

Actual gas turbine cycle is different from ideal cycle because

A. of internal irreversibility of the process due to friction, turbulence, etc.
B. of variation of specific heats with temperature
C. of losses due to incomplete combustion
D. all of the above
Answer» D. all of the above
7.

Gas turbines are taken to

A. the gasoline and diesel engines in its working medium
B. the petrol and diesel engines in its internal combustion
C. the steam turbine in its aspect of steady flow of the working medium
D. All of the above
Answer» D. All of the above
8.

Which component of a gas turbine consumes maximum power?

A. Combustion chamber
B. Regenerator
C. Starter
D. Compressor
Answer» D. Compressor
9.

Critical pressure for steam is

A. 185.85 kg/cm2
B. 245.55 kg/cm2
C. 225.65 kg/cm2
D. 212.55 kg/cm2
Answer» C. 225.65 kg/cm2
10.

Which of the following preferred for supercharging of internal combustion engines?

A. Roots blower
B. Reciprocating compressor
C. Sliding vane type compressor
D. Axial flow compressor
Answer» A. Roots blower
11.

Which gas turbine has lest weight per bhp developed?

A. Simple open cycle gas turbine
B. Open cycle gas turbine with intercooling, reheating and regeneration
C. Closed cycle gas turbine
D. Open cycle gas turbine with intercooling and reheating
Answer» A. Simple open cycle gas turbine
12.

In which of the following plant inferior quality fuel can be used?

A. Open cycle gas turbine with regeneration
B. Open cycle gas turbine with intercooling
C. Closed cycle gas turbine
D. Open cycle gas turbine with reheating and regeneration
Answer» C. Closed cycle gas turbine
13.

Which of the following loss in steam turbines is negligible?

A. Residual velocity loss
B. Radiation loss
C. Leakage loss
D. Mechanical friction loss
Answer» B. Radiation loss
14.

Most serious energy loss in reaction steam turbine

A. Steam leakage between diaphragm and shaft
B. Impact loss as steam enters moving blades
C. Frictional resistance between steam and nozzle side
D. Leakage over blade ends through radia clearance passages
Answer» D. Leakage over blade ends through radia clearance passages
15.

An axial flow compressor is suitable for

A. low volume flow rates with high pressure rise
B. high volume flow rates with a small pressure rise
C. low volume flow rates with low pressure rise
D. high volume flow rates with high pressure rise
Answer» B. high volume flow rates with a small pressure rise
16.

For a jet prepulsion unit, ideally the compressor work and turbine work are

A. unequal
B. equal
C. not related to each other
D. none of the above
Answer» B. equal
17.

Stalling of the blades of axial flow compressor is

A. an unsteady periodic and reversal of flow
B. the fixed mass flow rate regardless of pressure ratio
C. the reduction in lift force at higher angle of incidence
D. none of the above
Answer» C. the reduction in lift force at higher angle of incidence
18.

In a two stage gas turbine plant reheating after first stage

A. increases thermal efficiency
B. decreases thermal efficiency
C. doesoes not affect thermal efficiency
D. none of the above
Answer» B. decreases thermal efficiency
19.

In a nozzle if back pressure is equal to inlet pressure

A. maximum flow occurs
B. no flow occurs
C. flow is subsonic in diverging section
D. flow is supersonic in converging as well as supersonic sections
Answer» B. no flow occurs
20.

The source of power for driving a turbocharger is

A. chemical energy of exhaust gases
B. air motor
C. kinetic energy of exhaust gases from the engine
D. electric motor
Answer» C. kinetic energy of exhaust gases from the engine
21.

The diverging portion of the nozzle acts as a diffuser for

A. the subsonic flow
B. the supersonic flow
C. both the subsonic as well as supersonic flow
D. none of the above
Answer» A. the subsonic flow
22.

Efficiency of gas turbine is increased by

A. Reheating
B. Intercooling
C. Adding a regenerator
D. All of the above
Answer» D. All of the above
23.

Curtis turbine is

A. a velocity pressure compounded turbine
B. a velocity compounded turbine
C. in impulse turbine
D. a pressure compounded turbine
Answer» A. a velocity pressure compounded turbine
24.

Which of the following is a pressure compounded turbine?

A. Parson's turbine
B. Curtis turbine
C. Rateau turbine
D. All of the above
Answer» C. Rateau turbine
25.

The work ratio of closed cycle gas turbine plant with fixed top temperature of the cycle and fixed pressure ratio rp

A. increases with increase in an inlet temperature to compressor
B. increases with decrease in an inlet temperature to compresor
C. remain same irrespective of inlet temperature to compressor
D. none of the above
Answer» B. increases with decrease in an inlet temperature to compresor
26.

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» C. Both fixed and moving blades
27.

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» A. an unsteady, periodic and reversal of flow in the compressor
28.

A regenerator can be used on

A. open cycle gas turbines only
B. closed cycle gas turbines only
C. both open as well as closed cycle gas turbines
D. none of the above
Answer» C. both open as well as closed cycle gas turbines
29.

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» B. 16 KSC
30.

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» C. larger blades at gas entry and smaller blades at exit
31.

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» B. heat air supplied to combustion chamber
32.

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» D. All of the above
33.

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» B. 5 to 8
34.

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» C. velocity of flow
35.

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» B. counter clockwise
36.

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» D. operating speeds are too high
37.

In a velocity compounded steam turbine, as steam moves along moving and guide blades

A. both pressure and velocity gradually decrease
B. Both pressure and velocity gradually increase.
C. pressure gradually increases and velocity is low
D. pressure is low and velocity gradually decreases
Answer» D. pressure is low and velocity gradually decreases
38.

Generally, steam turbines in power stations operate at

A. 3000 rpm
B. 375 rpm
C. 1000 rpm
D. 1500 rpm
Answer» A. 3000 rpm
39.

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» B. high critical temperature with low pressure
40.

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» A. less than Diesel cycle efficiency
41.

In gas turbines, intercooling results in

A. decrease in net output and increase in thermal efficiency
B. decrease in net output as well as thermal efficiency
C. increase in net output as well as thermal efficiency
D. increase in net output but decrease in thermal efficiency
Answer» C. increase in net output as well as thermal efficiency
42.

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» B. 10 atmospheres
43.

For efficient operation of axial flow compressors the blades are made

A. aerofoil section
B. forward curved
C. straight
D. slightly curved
Answer» A. aerofoil section
44.

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» C. 336 m/s
45.

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» C. converts kinetic energy into thermal energy
46.

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» A. Roots blower
47.

In which of the following heat exchanger, heat is extracted from air?

A. Regenerator
B. Reheater
C. Intercooler
D. All of the above
Answer» C. Intercooler
48.

The following property is the most important for material used for gas turbine blades

A. Fatigue
B. Strength against bending
C. Strength against direct force
D. Group
Answer» D. Group
49.

Which of the following fluid can be used in binary vapour cycle?

A. Mercury
B. Diphenyl oxide
C. Aluminium bromide
D. any of the above
Answer» D. any of the above
50.

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» A. 350 N
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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