A compressor at high altitudes will require ________ power.
1.Same
2.Less
3.More
4. None of these
A turboprop is preferred to turbojet because
1. It has high propulsive efficiency at high speeds
2.It can fly at supersonic speeds
3. It can fly at high elevations
4.It has high power for take off
An after-cooler is used to
1.Remove impurities from air
2.Reduce volume of air
3.Cause moisture and oil vapour to drop out
4. Cool the air
Atmospheric pressure is 1.03 kg/cm and vapour pressure is 0.03 kg/cm. The air pressure will be
1.1.03 kg/cm²
2.1.06 kg/cm²
3.1.00 kg/cm²
4.0.53 kg/cm²
For an irreversible gas turbine cycle, the efficiency and work ratio both depend on
1.Pressure ratio alone
2.Maximum cycle temperature alone
3.Minimum cycle temperature alone
4. Both pressure ratio and maximum cycle temperature
For maximum work, the reheating should be done to an intermediate pressure of
(Where p₁ = Maximum pressure, and p₂ = Minimum pressure)1. (p₁ - p₂)/2
2.(p₁ + p₂)/2
3. p₁/p₂
4.p₁ p₂
In a centrifugal compressor, an increase in speed at a given pressure ratio causes
1.Increase in flow
2.Decrease in flow
3. Increase in efficiency
4.Increase in flow and decrease in efficiency
In a single stage, single acting reciprocating air compressor without clearance volume, the work-done is maximum during
1.Isothermal compression
2.Isentropic compression
3.Polytropic compression
4.None of these
Inter-cooling in multistage compressors is done
1.To cool the air during compression
2.To cool the air at delivery
3.To enable compression in two stages
4.To minimize the work of compression
Open cycle gas turbine works on (A)
1.Brayton or Atkinson cycle
2.Rankine cycle
3.Carnot cycle
4.Ericsson cycle
Pick up the wrong statement
1.Centrifugal compressors deliver practically constant pressure over a considerable range of capacities
2.Axial flow compressors have a substantially constant delivery at variable pressures
3.Centrifugal compressors have a wider stable operating range than axial flow compressors
4.Axial flow compressors are bigger in diameter compared to centrifugal type
Temperature of gases at end of compression as compared to exhaust gases in a gas turbine is
1.Higher
2.Lower
3.Equal
4.Can’t be compared
The degree of reaction in an axial flow compressor is defined as the ratio of static enthalpy rise in the
1.Rotor to static enthalpy rise in the stator
2.Stator to static enthalpy rise in the rotor
3.Rotor to static enthalpy rise in the stage
4.Stator to static enthalpy rise in the stage
The material commonly used for air craft gas turbine is
1.Stainless steel
2.High alloy steel
3.Duralumin
4.Timken, Haste alloys
The material commonly used for air craft gas turbine is
1.Stainless steel
2.High alloy steel
3.Duralumin
4.Timken, Haste alloys
The work ratio of simple gas turbine cycle depends on
1.Pressure ratio
2.Maximum cycle temperature
3.Minimum cycle temperature
4.All of the above
A closed gas turbine in which fuel is burnt directly in the air is not possible because of
1.Paucity of O2
2.Increasing gas temperature
3. High specific volume
4.High friction losses
A gas turbine used in air craft should have
1.High h.p. and low weight
2.Low weight and small frontal area
3.Small frontal area and high h.p.
4.High speed and high h.p.
A jet engine has
1. No propeller
2.Propeller in front
3.Propeller at back
4.Propeller on the top
A jet engine works on the principle of conservation of
1.Mass
2.Energy
3.Flow
4.Linear momentum
A large clearance volume in a reciprocating compressor results in
1.Increased volume flow rate
2.Reduced volume flow rate
3. Lower suction pressure
4. Lower delivery pressure
Actual compression curve is
1.Same as isothermal
2.Same as adiabatic
3.Better than isothermal and adiabatic
4. In between isothermal and adiabatic
Axial flow compressor has the following advantage over centrifugal compressor
1.Larger air handling ability per unit frontal area
2.Higher pressure ratio per stage
3.Aerofoil blades are used
4.Higher average velocities
Axial flow compressor resembles
1. Centrifugal pump
2. Reciprocating pump
3.Turbine
4.Sliding vane compressor
Choose the correct statement
1.Gas turbine requires lot of cooling water
2.Gas turbine is capable of rapid start up and loading
3.Gas turbines has flat efficiency at part loads
4.Gas turbines have high standby losses and require lot of maintenance
Euler's equation can be used for
1.Radial flow compressors
2.Axial flow compressors
3.Pumps
4.All of the above
Gas turbine blades are given a rake
1.Equal to zero
2.In the direction of motion of blades
3.Opposite to the direction of motion of blades
4.Depending on the velocity
Gas turbine blades are given a rake
1.Equal to zero
2.In the direction of motion of blades
3.Opposite to the direction of motion of blades
4.Depending on the velocity
If the flow of air through the compressor is parallel to its axis, then the compressor is
1. Reciprocating compressor
2.Centrifugal compressor
3.Axial flow compressor
4. Turbo compressor
In a single acting reciprocating compressor, the suction, compression and delivery of air takes place in ________ of the piston. (A) One stroke (B) Two strokes (C) (D)
1.One stroke
2.Two strokes
3. Three strokes
4. Four strokes
In air compressors, free air delivery means the
1.Actual volume of the air delivered by the compressor when reduced to normal temperature and pressure conditions
2.Volume of air delivered by the compressor
3.Volume of air sucked by the compressor during its suction stroke
4.None of the above
In open cycle turbojet engines used in military aircraft, reheating the exhaust gas from the turbine by burning, more fuel is used to increase the
1.Thrust and range of aircraft
2.Efficiency of the engine
3. Both (A) and (B)
4.None of these
In the axial flow gas turbine, the work ratio is the ratio of
1. Compressor work and turbine work
2.Output and input
3.Actual total head temperature drop to the isentropic total head drop from total head inlet to static head outlet
4.Actual compressor work and theoretical compressor work
In the cross compounding of the gas turbine plant
1.H.P. compressor is connected to H.P. turbine and L.P. compressor to L.P. turbine
2.H.P. compressor is connected to L.P. turbine and L.P. compressor is connected to H.P. turbine
3. Both the arrangements can be employed
4.All are connected in series
It is not possible to use closed gas turbine cycle in aeronautical engines because
1.It is inefficient
2.It is bulky
3.It requires cooling water for its operation
4.None of the above
Pick up the wrong statement
1. Large gas turbines employ axial flow compressors
2.Axial flow compressors are more stable than centrifugal type compressors but not as efficient
3.Axial flow compressors have high capacity and efficiency
4.Axial flow compressors have instability region of operation
Pick up wrong statement. Surging phenomenon in centrifugal compressor depends on
1.Mass flow rate
2.Pressure ratio
3. Change in load
4.Stagnation pressure at the outlet
Producer gas is produced by
1.Carbonisation of coal
2.Passing steam over incandescent coke
3.Passing air and a large amount of steam over waste coal at about 65°C
4.Partial combustion of coal, coke, anthracite coal or charcoal in a mixed air steam blast
Separators are generally used in air compressor installations
1.Before the inter-cooler
2.After the inter-cooler
3.Between the after-cooler and receiver
4.Before first stage suction
The air-fuel ratio in gas turbines is of the order of
1.7: 1
2. 15: 1
3. 30: 1
4.50: 1.
The combustion efficiency of a gas turbine using perfect combustion chamber is of the order of
1.75%
2.85%
3.90%
4.99%
The compression ratio for the compressor is always _________ unity.
1. Equal to
2. Less than
3.More than
4.None of these
The degree of reaction of an axial flow turbine is the ratio of isentropic temperature drop in a blade row to the
1.Adiabatic temperature drop in the stage
2. Total temperature drop
3.Total temperature drop in the stage
4.Total adiabatic temperature drop
The efficiency of a jet engine is higher at
1.Low speeds
2.High speeds
3.Low altitudes
4.High altitudes
The efficiency of roots blower ________ with the increase in pressure ratio.
1.Decreases
2.Increases
3.Does not change
4.None of these
The following is true for an open cycle gas turbine having exhaust heat exchanger. Atmospheric air before entering the compressor is
1.Heated
2.Compressed air before entering the combustion chamber is heated
3.Bled gas from turbine is heated and readmitted for complete expansion
4.Exhaust gases drive the compressor
The following is true for an open cycle gas turbine having exhaust heat exchanger. Atmospheric air before entering the compressor is
1.Heated
2.Compressed air before entering the combustion chamber is heated
3.Bled gas from turbine is heated and readmitted for complete expansion
4.Exhaust gases drive the compressor
The following is true for an open cycle gas turbine having exhaust heat exchanger. Atmospheric air before entering the compressor is
1.Heated
2.Compressed air before entering the combustion chamber is heated
3.Bled gas from turbine is heated and readmitted for complete expansion
4.Exhaust gases drive the compressor
The fuel consumption in gas turbines is accounted for by
1. Lower heating value
2.Higher heating value
3.Heating value
4. Higher calorific value
The inlet pressure is always ________ the discharge pressure.
1. Equal to
2.Less than
3.More than
4. None of these
The inlet pressure is always ________ the discharge pressure.
1. Equal to
2.Less than
3.More than
4. None of these
The inlet pressure is always ________ the discharge pressure.
1. Equal to
2.Less than
3.More than
4. None of these
The inlet pressure is always ________ the discharge pressure.
1. Equal to
2.Less than
3.More than
4. None of these
The inlet pressure is always ________ the discharge pressure.
1. Equal to
2.Less than
3.More than
4. None of these
The inlet pressure is always ________ the discharge pressure.
1. Equal to
2.Less than
3.More than
4. None of these
The maximum temperature in a gas turbine is
1.200°C
2. 500°C
3.700°C
4.1000°C
The power available for takeoff and climb in case of turbojet engine as compared to reciprocating engine is
1.Less
2.More
3.Same
4.May be less or more depending on ambient conditions
The pressure ratio for an open cycle gas turbine compared to closed cycle gas turbine of same h.p. is
1. Low
2.High
3.Same
4.Low/high depending on make and type
The pressure ratio in gas turbines is of the order of
1. 2: 1
2.4:1
3.61: 1
4. 9: 1
The pressure ratio of an ideal vaned compressor with increase in mass flow rate
1.Increases
2.Decreases
3.Remain constant
4.First decreases and then increases
The ratio of the increase in pressure in rotor blades to total increase in pressure in the stage is called
1.Pressure ratio
2.Pressure coefficient
3.Degree of reaction
4.Slip factor
The ratio of the indicated power to the shaft power or brake power of the motor or engine required to drive the compressor, is called
1.Compressor efficiency
2.Volumetric efficiency
3. Isothermal efficiency
4.Mechanical efficiency
The thermal efficiency of a gas turbine as compared to a diesel plant is
1.Same
2.More
3.Less
4.Depends on other factors
The volume of air delivered by the compressor is called
1.Free air delivery
2.Compressor capacity
3.Swept volume
4.None of these
The volumetric efficiency for reciprocating air compressors is about
1. 10 to 40%
2.40 to 60%
3.60 to 70%
4.70 to 90%
The work ratio of a gas turbine plant is defined as the ratio of
1.Net work output and heat supplied
2.Net work output and work done by turbine
3.Actual heat drop and isentropic heat drop
4.Net work output and isentropic heat drop
The work ratio of simple gas turbine cycle depends on
1.Pressure ratio
2.Maximum cycle temperature
3.Minimum cycle temperature
4. All of the above
Water gas is produced by
1.Carbonisation of coal
2. Passing steam over incandescent coke
3.Passing air and a large amount of steam over waste coal at about 65°C
4.Partial combustion of coal, eke, anthracite coal or charcoal in a mixed air steam blast
Water is injected in gas turbine cycle to
1.Control temperature
2.Control output of turbine
3.Control fire hazards
4.Increase efficiency
When the outlet angle from the rotor of a centrifugal compressor is more than 90°, then the blades are said to be
1.Forward curved
2.Backward curved
3.Radial
4.None of these
Which of the following fuels can be used in turbojet engines?
1.Liquid hydrogen
2.High speed diesel oil
3.Kerosene
4.Methyl alcohol
Which of the following statement is correct relating to rocket engines?
1.The combustion chamber in a rocket engine is directly analogous to the reservoir of a supersonic wind tunnel
2. The stagnation conditions exist at the combustion chamber
3.The exit velocities of exhaust gases are much higher than those in jet engine
4. All of the above
Which of the following statement is wrong?
1.In a two stage reciprocating air compressor with complete intercooling, maximum work is saved
2.The minimum work required for a two stage reciprocating air compressor is double the work required for each stage
3. The ratio of the volume of free air delivery per stroke to the swept volume of the piston is called volumetric efficiency
4.None of the above
Which of the following statement is wrong?
1. In a two stage reciprocating air compressor with complete intercooling, maximum work is saved
2. The minimum work required for a two stage reciprocating air compressor is double the work required for each stage
3.The ratio of the volume of free air delivery per stroke to the swept volume of the piston is called volumetric efficiency
4.None of these
With the decrease in compression ratio, the volumetric efficiency
1.Does not change
2.Increases
3.Decreases
4.First decrease and then increase