Pick up the false statement
Gas turbine is a self starting unit
Gas turbine does not require huge quantity of water like steam plant
Exhaust losses in gas turbine are high due to large mass flow rate
Overall efficiency of gas turbine plant is lower than that of a reciprocating engine
Correct Answer :
A. Gas turbine is a self starting unit
Related Questions
Intercooling in gas turbines
Decreases net output but increases thermal efficiency
Increases net output but decreases thermal efficiency
Decreases net output and thermal efficiency both
Increases net output and thermal efficiency both
Which of the following statement is correct?
The ratio of the discharge pressure to the inlet pressure of air is called compressor efficiency
The compression ratio for the compressor is always greater than unity
The compressor capacity is the ratio of workdone per cycle to the stroke volume
During isothermal compression of air, the workdone in a compressor is maximum
Rotary compressors are suitable for
Large discharge at high pressure
Low discharge at high pressure
Large discharge at low pressure
Low discharge at low pressure
The fuel consumption in gas turbines is accounted for by
Lower heating value
Higher heating value
Heating value
Higher calorific value
Open cycle gas turbine works on
Brayton or Atkinson cycle
Rankine cycle
Carnot cycle
Erricson cycle
Gas turbine cycle with regenerator
Increases thermal efficiency
Allows high compression ratio
Decreases heat loss is exhaust
Allows operation at very high altitudes
In a centrifugal compressor, the flow of air is ________ to the axis of compressor.
Parallel
Perpendicular
Inclined
None of these
The absolute pressure of air at the outlet of a compressor is called
Back pressure
Critical pressure
Discharge pressure
None of these
The following property is most important for material used for gas turbine blade
Toughness
Fatigue
Creep
Corrosion resistance
The pressure and temperature conditions of air at the suction of compressor are
Atmospheric
Slightly more than atmospheric
Slightly less than atmospheric
Pressure slightly less than atmospheric and temperature slightly more than atmospheric
The volume of air delivered by the compressor is called
Free air delivery
Compressor capacity
Swept volume
None of these
Stalling of blades in axial flow compressor is the phenomenon of
Air stream blocking the passage
Motion of air at sonic velocity
Unsteady periodic and reversed flow
Air stream not able to follow the blade contour
Pick up wrong statement. Surging phenomenon in centrifugal compressor depends on
Mass flow rate
Pressure ratio
Change in load
Stagnation pressure at the outlet
The air entry velocity m a rocket as compared to aircraft is
Same
More
Less
Zero
The overall efficiency of the compressed air system is the
Ratio of shaft output of the air motor to the shaft input to the compressor
Ratio of shaft input to the compressor to the shaft output of air motor
Product of shaft output of air motor and shaft input to the compressor
None of the above
Axial flow compressor has the following advantage over centrifugal compressor
Larger air handling ability per unit frontal area
Higher pressure ratio per stage
Aerofoil blades are used
Higher average velocities
The degree of reaction in an axial flow compressor is defined as the ratio of static enthalpy rise in the
Rotor to static enthalpy rise in the stator
Stator to static enthalpy rise in the rotor
Rotor to static enthalpy rise in the stage
Stator to static enthalpy rise in the stage
Separators in compressor installations are located
Before intercooler
After intercooler
After receiver
Between after-cooler and air receiver
To avoid moisture troubles, the branch connections from compressed air lines should be taken from
Top side of main
Bottom side of main
Left side of main
Right side of main
The efficiency of roots blower ________ with the increase in pressure ratio.
Decreases
Increases
Does not change
None of these
The following is true for an open cycle gas turbine having exhaust heat exchanger. Atmospheric air before entering the compressor is
Heated
Compressed air before entering the combustion chamber is heated
Bled gas from turbine is heated and readmitted for complete expansion
Exhaust gases drive the compressor
Ram compression in turbojet involves
Reduction of speed of incoming air and conversion of part of it into pressure energy
Compression of inlet air
Increasing speed of incoming air
Lost work
Isothermal compression efficiency, even when running at high speed, can be approached by using
Multistage compression
Cold water spray
Both (A) and (B) above
Fully insulating the cylinder
Water gas is produced by
Carbonisation of coal
Passing steam over incandescent coke
Passing air and a large amount of steam over waste coal at about 65°C
Partial combustion of coal, eke, anthracite coal or charcoal in a mixed air steam blast
In a centrifugal compressor, the ratio of the ________ to the blade velocity is called slip factor.
Inlet whirl velocity
Outlet whirl velocity
Inlet velocity of flow
Outlet velocity of flow
For slow speed large capacity compressor, following type of valve will be best suited
Poppet valve
Mechanical valve of the Corliss, sleeve, rotary or semi rotary type
Disc or feather type
Any of the above
The efficiency of jet engine is
Lower at low speed
Higher at high altitudes
Same at all altitudes
Higher at high speed
The combustion efficiency of a gas turbine using perfect combustion chamber is of the order of
75 %
85 %
90 %
99 %
The ratio of the volume of free air delivery per stroke to the swept volume of the piston, is known as
Compressor efficiency
Volumetric efficiency
Isothermal efficiency
Mechanical efficiency
The material commonly used for air craft gas turbine is
Stainless steel
High alloy steel
Duralumin
Timken, Haste alloys