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This set of Turbo Machines Multiple Choice Questions & Answers (MCQs) focuses on Turbo Machines Set 3
Q1 | In a reheating gas turbine cycle, reheating is done
- by gases from turbine exhaust
- by gases from intercooler
- in separate combustion chamber
- any of the above
Q2 | The ratio of outlet whirl velocity to blade velocity in case of centrifugal compressor is called
- Blade efficiency
- Diagram efficiency
- slip factor
- Velocity ratio
Q3 | Thermal efficiency of a gas turbine is in the range
- 20 to 30 percent
- 40 to 50 percent
- 50 to 60 percent
- 30 to 40 percent
Q4 | 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
- 75%
- 63%
- 87%
- 99%
Q5 | Basic closed cycle for gas turbine is
- Carnot cycle
- Rankine cycle
- Brayton cycle
- none of the above
Q6 | The advantage of a gas turbine over a reciprocating engine is
- perfect balancing of rotor
- continuous and uniform power
- usually small working pressures
- all of the above
Q7 | A diffuser is used to
- increase velocity and decrease pressure
- increase velocity as well as pressure
- decrease velocity as well as pressure
- decrease velocity and increase pressure
Q8 | Air fuel ratio for a gas turbine is closer to
- 60 ; 1
- 10 ; 1
- 15 ; 1
- 20 ; 1
Q9 | Which of the following steam turbine has identical fixed and moving blades?
- Curtis turbine
- Rateau turbine
- Parson's turbine
- none of the above
Q10 | Bleeding in steam turbine refers to
- purposely withdrawn steam for process application
- leakage of steam through bearings
- purposely withdrawn for feed water heating
- leakage of steam through packings
Q11 | As a result of blade friction, the outlet relative velocity of impulse turbine compared to inlet relative velocity is
- Nearly same
- 2% less
- 10% - 15% less
- 30% less
Q12 | As there is plenty of time for heat transfer across the walls, the flow in long pipes at low velocities attains
- adiabatic conditions
- isothermal conditions
- polytropic conditions
- isentropic conditions
Q13 | The normal shock wave in compressible flow is analogous to
- hydraulic bore in tidal rivers
- vortex formation in centrifugal pump
- hydraulic jump in channel flow
- surges in open channel
Q14 | Greater the difference between jet velocity and aeroplane velocity
- greater the propulsive efficiency
- Lesser the propulsive efficiency
- unaffected is the propulsive efficiency
- None of the above
Q15 | If stage efficiency is S, blade efficiency is B and nozzle efficiency in N, then
- BSN = 1
- N = B.S
- S = B.N
- B = SN
Q16 | Choking is
- Variation of mass flow rate in proportion to pressure ratio
- variation of mass flow rate in inverse proportion to pressure ratio
- fixed mass flow rate regardless of pressure ratio
- none of the above
Q17 | The advantage of closed cycle gas turbine over open cycle gas turbine is
- no contamination of working substance with combustion gases
- inferior quality fuel can be used
- low maintenance costs
- All of the above
Q18 | Brayton cycle cannot be used in reciprocating engines even for same compression ratio and work output because
- Large volume of low pressure gas cannot be efficiently handled in reciprocating engines
- Brayton cycle is less efficient
- Otto cycle is more efficient
- Brayton cycle is for slow speed engines only
Q19 | Working medium for closed cycle gas turbine should have
- high molecular weight
- low specific volume
- higher adiabatic index
- lower specific speed
Q20 | Thermal efficiency of a gas turbine cycle can be improved by
- reheating between expansion stage
- intercooling between compression stges
- regeneration
- any of the above
Q21 | Thermal efficiency of closed cycle gas turbine plant increases by
- reheating
- intercooling
- regenerator
- All of the above
Q22 | For gas turbine, compressors used are
- Centrifugal type
- Lobe type
- Axial flow type
- Reciprocating type
Q23 | Which of the following is the least efficient method of governing steam turbines?
- Combined throttle and nozzle governing
- Throttle governing
- Nozzle control governing
- Bypass governing
Q24 | The effect of blade friction in a steam turbine is to
- increase the specific output
- reduce work done
- reheat the steam
- reduce exhaust pressure
Q25 | In rotory compressors, the ratio of isentropic work to Eulers work is known as
- degree of reaction
- slip factor
- work factor
- pressure coefficient