A rocket engine uses __________ for the combustion of its fuel.
1.Surrounding air
2.Compressed atmospheric air
3.Its own oxygen
4.None of these
A simple turbojet engine is basically
1. propeller system
2.Gas turbine engine equipped with a propulsive nozzle and diffuse
3.Chemical rocket engine
4.Ramjet engine
During base load operation, the best method of controlling compressor is
1. Start-stop motor
2.Constant speed unloader
3.Relief valve
4.Variable speed
For speed above 3000 km/hour, it is more advantageous to use
1.Turbojet engine
2.Ramjet engine
3. Propellers
4.Rockets
Gas turbine cycle with regenerator
1.Increases thermal efficiency
2.Allows high compression ratio
3.Decreases heat loss is exhaust
4. Allows operation at very high altitudes
In a centrifugal compressor, the flow of air is ________ to the axis of compressor.
1.Parallel
2.Perpendicular
3.Inclined
4.None of these
In a four stage compressor, if the pressure at the first and third stage is 1 bar and 16 bar, then the delivery pressure at the fourth stage will be
1.1 bar
2.16 bar
3. 64 bar
4.256 bar
In a high pressure compressor, the delivery pressure is
1. 1 to 5 bar
2.5 to 8 bar
3.8 to 10 bar
4. 10 to 15 bar
In a jet propulsion
1.The propulsive matter is ejected from within the propelled body
2. The propulsive matter is caused to flow around the propelled body
3. Its functioning does not depend upon presence of air
4.None of these
In jet engines the products of combustion after passing through the gas turbine are discharged into
1.Atmosphere
2.Back to the compressor
3.Discharge nozzle
4.Vacuum
In turbo fan engine, the jet velocity as compared to turbojet engine is
1. Less
2.More
3.Same
4.May be less or more depending upon speed
Isothermal compression efficiency, even when running at high speed, can be approached by using
1. Multistage compression
2.Cold water spray
3.Both (A) and (B) above
4.Fully insulating the cylinder
Maximum temperature in a gas turbine is of the order of
1. 700°C
2.2000°C
3. 1500°C
4.1000°C
Reheating in multistage expansion gas turbine results in
1.High thermal efficiency
2.Reduction in compressor work
3.Decrease of heat loss in exhaust
4.Maximum work output
Standard air is the air at
1.Atmospheric conditions at any specific location
2.20°C and 1 kg/cm² and relative humidity 36
3. 0°C and standard atmospheric conditions
4. 15°C and 1 kg/cm²
The compression ratio in a gas turbine is of the order of
1. 3.5 : 1
2. 5 : 1
3. 8 : 1
4. 12 : 1
The effective power of gas turbines is increased by adding the following in compressor
1. Ammonia and water vapour
2.Carbon dioxide
3.Nitrogen
4.Hydrogen
Which is false statement about advantages of multistage compressor in comparison to single stage compressor?
1. Less power requirement
2.Better mechanical balance
3.Less loss of air due to leakage past the cylinder
4.Lower volumetric efficiency
Which is false statement about air receivers?
1. These are used to dampen pulsations
2.These act as reservoir to take care of sudden demands
3.These increase compressor efficiency
4.These knock out some oil and moisture
Work ratio of a gas turbine plant is ratio of
1. Net work output and work done by turbine (B) (D)
2. Net work output and heat supplied
3.Work done by turbine and heat supplied
4.Work done by turbine and net work output
A 3 m³/min compressor means that it
1.Compresses 3 m³/min of standard air
2.Compresses 3 m³/ min of free air
3. Delivers 3 m³/ min of compressed air
4. Delivers 3 m³/ min of compressed air at delivery pressure
Aeroplanes employ following type of compressor
1.Radial flow
2.Axial flow
3.Centrifugal
4.None of these
Air-fuel ratio in a jet engine will be of the order of
1. 10: 1
2.15: 1
3. 20: 1
4.60: 1
An air compressor may be controlled by
1.Throttle control
2.Clearance control
3.Blow off control
4.Any one of the above
Euler's equation is applicable for
1. Centrifugal compressor
2. Axial compressor
3.Pumps
4.All of the above
Fighter bombers use following type of engine
1. Turbojet
2.Turbo-propeller
3.Rocket
4.Ramjet
For a two stage reciprocating compressor, compression from p₠to p₃ is with perfect intercooling and no pressure losses. If compression in both the cylinders follows the same polytropic process and the atmospheric pressure is pa, then the intermediate pressure p₂ is given by
1.p₂ = (p₠+ p₃)/2
2. pâ‚‚ = pâ‚. p₃
3. Pâ‚‚ = Pa × p₃/pâ‚
4.pâ‚‚ = Pa p₃/pâ‚
For slow speed large capacity compressor, following type of valve will be best suited
1.Poppet valve
2.Mechanical valve of the Corliss, sleeve, rotary or semi rotary type
3.Disc or feather type
4.Any of the above
Free air is the air at
1.Atmospheric conditions at any specific location
2.0°C and standard atmospheric conditions
3.15°C and 1 kg/cm²
4.20°C and 1 kg/cm² and relative humidity of 36%
High air-fuel ratio is used in gas turbines
1. To increase the output
2.To increase the efficiency
3.To save fuel
4.To reduce the exit temperature
If V, U and Vr represent the absolute velocity of fluid, velocity of blade, and relative velocity of fluid, and suffix ‘I’ and ‘o’ stand for entry and exit conditions, then in a rotary machine whose degree of reaction is unity
1.Vi = Vo
2. Vt > Vo
3.U < Vo
4.V = Uo
In a reciprocating air compressor, the compression work per kg of air
1.Increases as clearance volume increases
2. Decreases as clearance volume increases
3. Is independent of clearance volume
4.Increases as clearance volume decreases
In a single stage, single acting reciprocating air compressor, without clearance, the work-done on the air during isentropic compression is ________ the heat required to raise the temperature of air from Tâ‚ to Tâ‚‚ at a constant pressure.
1. Equal to
2.Less tha
3.Greater than
4.None of these
In air breathing jet engine, the jet is formed by expanding
1.Highly heated atmospheric air
2.Solids
3.Liquid
4.Plasma
In which case the air-fuel ratio is likely to be maximum?
1.Gas turbine
2. 4-stroke petrol engine
3. 4-stroke diesel engine
4.Multi cylinder engine
Inter cooling in compressors
1.Cools the delivered air
2. Results in saving of power in compressing a given volume to given pressure
3.Is the standard practice for big compressors
4. Enables compression in two stages
Inter-cooling in gas turbine results in
1. Increase in net output but decrease in thermal efficiency
2.Increase in thermal efficiency but decrease in net output
3. Increase in both thermal efficiency and net output
4. Decrease in both thermal efficiency and net output
Pick up the correct statement
1.Closed cycle gas turbine is an I.C engine
2.Gas turbine uses same working fluid over and over again
3. Ideal efficiency of closed cycle gas turbine plant is more than Carnot cycle efficiency
4.Thrust in turbojet is produced by nozzle exit gases
Ramjet engine
1. Is self operating at zero flight speed
2.Is not self operating at zero flight speed
3.Requires no air for its operation
4.Produces a jet consisting of plasma
Reheating in gas turbine results in
1.Increase of work ratio
2.Decrease of thermal efficiency
3.Decrease of work ratio
4. Both (A) and (B) above
The air entry velocity m a rocket as compared to aircraft is
1.Same
2.More
3.Less
4.Zero
The air power of the compressor is also known as
1.Indicated power
2.Brake powe
3.Frictional power
4.None of these
The clearance volume of the air compressor is kept minimum because
1. It allows maximum compression to be achieved
2.It greatly affects volumetric efficiency
3.It results in minimum work
4.It permits isothermal compression
The compressor capacity with decrease in suction temperature
1.Increases
2.Decreases
3.Remain unaffected
4.May increase or decrease depending on compressor capacity
The compressor performance at higher altitude compared to sea level will be
1.Same
2.Higher
3.Lower
4. Dependent on other factors
The main purpose of reheating in gas turbine is to
1.Increase temperature
2.Reduce turbine size
3.Increase power output
4. Increase speed
The maximum propulsion efficiency of a turbojet is attained at around following speed
1. 550 km/hr
2.1050 km/hr
3.1700 km/hr
4.2400 km/hr
The minimum work required for a three stage reciprocating air compressor is ________ the work required for each stage.
1.Equal to
2.Double
3.Three times
4.Six times
The ratio of isentropic work to Euler work is known as
1.Pressure coefficient
2.Work coefficient
3.Polytropic reaction
4.Slip factor
The ratio of the discharge pressure to the inlet pressure of air is called
1.Compression ratio
2. Expansion ratio
3.Compressor efficiency
4.Volumetric efficiency
The specific output per kg mass flow rate of a gas turbine (having fixed efficiencies of compressor and turbine and fixed higher and lower temperature) with increase in pressure ratio will
1.Increase first at fast rate and then slow
2. Increase first at slow rate and then fast
3.Decrease continuously
4.First increase, reach maximum and then decrease
The stagnation pressure rise in a centrifugal compressor takes place
1. In the diffuser only
2.In the impeller only
3.In the diffuser and impeller
4. In the inlet guide vanes only
The type of rotary compressor used in gas turbines, is of
1. Centrifugal type
2.Axial flow type
3.Radial flow type
4. None of these
The volumetric efficiency of a compressor falls roughly as follows for every 100 m increase in elevation
1. 0.1%
2.0.5%
3.1.0%
4. 5%
The weight per horse power ratio for gas in Turbine as compared to I.C. engine and steam turbine is
1. Same (
2.Higher
3.Lower
4.None of these
The working fluid in a turbine is
1.In two phases
2.In three phases
3.In a single phase
4.In the form of air and water mixture
What will be the volume of air at 327°C if its volume at 27°C is 1.5 m³/ mt?
1.3 m³/ mt.
2. 1.5 m³/ mt.
3.18 m³/ mt.
4.6 m³/ mt.
Which of the following plants is smallest and lightest for generating a given amount of power?
1.Gas turbine plant
2.Petrol engine
3.Diesel engine
4.Solar plant
Which of the following plants is smallest and lightest for generating a given amount of power?
1.Gas turbine plant
2.Petrol engine
3.Diesel engine
4.Solar plant
Work ratio of a gas turbine may be improved by
1.Decreasing the compression work
2.Increasing the compression work
3.Increasing the turbine work
4.Both (A) and (C) above