Category: Steam and Gas Turbines Objective Questions

Steam and Gas Turbines Multiple Choice Questions on “Efficiencies”.

1. What does thermodynamic efficiency of steam turbine mean?
a) Ratio of power developed to the power that can be developed by ideal turbine
b) Ratio of power that can be developed by ideal turbine to the power developed by the actual turbine
c) Ratio of inlet temperature to outlet temperature
d) None of the mentioned

Answer: a
Clarification: Thermodynamic efficiency is the ratio of power developed by actual turbine to the power that can be developed by ideal turbine.

2. What does aerodynamic efficiency mean?
a) Energy that can be extracted from a given volume of steam at given temperature and pressure
b) Amount of steam turbine blade can allow to flow inside
c) Amount of energy contained in steam
d) None of the mentioned

Answer: a
Clarification: Aerodynamic efficiency means energy that can be extracted from given volume of steam at given pressure and temperature.

3. If efficiency of boiler increases then efficiency of steam turbine ______
a) decreases
b) increases
c) cannot be determined
d) none of the mentioned

Answer: b
Clarification: If the efficiency of steam boiler increases temperature also increases which indirectly increases its efficiency.

4. If condenser efficiency increases then overall efficiency of steam turbine _______
a) decreases
b) increases
c) remains constant
d) none of the mentioned

Answer: b
Clarification: If condenser efficiency increases it raises the steam temperature and hereby increasing overall efficiency.

5. What does combustion efficiency mean?
a) Boiler ability to burn the fuel to fuel that is not burned and amount of air present at exit
b) Calorific value that can be obtained by burning a fuel
c) Energy that is released when fuel is burned
d) None of the mentioned

Answer: a
Clarification: Combustion efficiency is used to denote the amount of fuel burned by using the air.

6. What does fluid to fuel efficiency mean?
a) It indicates the overall efficiency of the boiler
b) Indicates fuel efficiency
c) Overall efficiency excluding boiler efficiency
d) None of the mentioned

Answer: a
Clarification: Fluid to fuel efficiency indicates overall efficiency including Boiler efficiency, conduction, convection and radiation, etc.

7. The total energy in the fuel is called as _____________
a) boiler efficiency
b) boiler energy
c) gross calorific value
d) none of the mentioned

Answer: c
Clarification: Gross calorific value indicates the total energy a fuel can release when burned.

8. Flue gases _______ efficiency.
a) decreases
b) increases
c) does not effect
d) none of the mentioned

Answer: b
Clarification: Flue gases effect combustion of the fuels and due to that it affects the overall efficiency.

9. Nozzle efficiency can be defined by __________
a) ratio of kinetic energy of the steam leaving the nozzle to the potential energy available with the steam while entering
b) pressure of the steam leaving the nozzle to pressure of the steam entering the nozzle
c) temperature of the steam leaving the nozzle to the temperature of the steam entering the nozzle
d) none of the mentioned

Answer: a
Clarification: Nozzle is used to convert the potential energy of the steam available into kinetic energy to run the turbine.

10. What is the typical efficiency of the nozzle?
a) 0.45-0.56
b) 0.9-0.99
c) 0.5-0.7
d) 0.67-0.86

Answer: b
Clarification: The typical efficiency of the nozzle is between 0.9 and 0.99.

Steam and Gas Turbines Test on “Elements of Airfoil, Single Airfoil Principle and Limitations”.

1. Shape of a wing or blade as seen from top view is called as airfoil.
a) True
b) False
Answer: b
Clarification: Shape of a wing or blade as seen from cross section is called as airfoil.

2. Airfoil can also be called as ________
a) aerofoil
b) propeller
c) sail
d) none of the mentioned
Answer: a
Clarification: Airfoil can also be called as Aerofoil.

3. When airfoil shape moves through fluid it produces __________
a) Thrust force
b) Drag force
c) Aerodynamic force
d) None of the mentioned
Answer: c
Clarification: When an airfoil shape is moved through a fluid it produces aerodynamic forces. The rest thrust and drag forces are the components of the aerodynamic force.

4. The lift to the airfoil is mainly the result of ______________
a) angle of attack
b) shape
c) angle of attack & shape
d) none of the mentioned
Answer: c
Clarification: The lift caused by the airfoil is primarily the result of angle of attack and shape.

5. Cambered airfoil generates lift at _________ angle of attack.
a) high
b) low
c) zero
d) none of the mentioned
Answer: c
Clarification: Cambered airfoil can generate lift at zero angle of attack whereas other airfoils require positive angle of attack.

6. For an airfoil fluid velocity will be ______ on upper surface when compared to lower surface.
a) higher
b) lower
c) equal
d) none of the mentioned
Answer: a
Clarification: As pressure is high on the upper surface than lower surface, through Bernoulli’s principle velocity is also high on the upper surface when compared to lower surface.

7. The lift force is directly proportional to _________
a) difference in the pressure between upper and lower surfaces
b) difference in the velocity between upper and lower surfaces
c) difference in the pressure & velocity between upper and lower surfaces
d) none of the mentioned
Answer: c
Clarification: The lift force is directly proportional to the pressure difference between the upper and lower surfaces and from Bernoulli’s principle it is also directly proportional to difference in the velocities between upper and lower surfaces.

8. Elements of airfoil are _________
a) Slats
b) Flaps
c) Slats & Flaps
d) None of the mentioned
Answer: c
Clarification: Basic elements of airfoil consists of slats and flaps.

9. To increase the lift at given angle of attack _______ are used.
a) Slats
b) Flaps
c) Cannot be increased
d) None of the mentioned
Answer: b
Clarification: Flaps are used to increase the lift at given angle of attack.

10. Increase in angle of attack can be done by ________
a) Slats
b) Governor mechanism
c) Flaps
d) None of the mentioned
Answer: c
Clarification: Angle of attack can be increased by slats.

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Steam and Gas Turbines Multiple Choice Questions on “Free and Forced Vortex”.

1. In vortex region flow rotates perpendicular to the axis line.
a) True
b) False
Answer: b
Clarification: In vortex region fluid rotates on an axis line.

2. Viscous friction in the fluid causes the flow to become vortex.
a) True
b) False
Answer: a
Clarification: In the absence of forces viscous friction causes the flow to become vortex.

3. In vortex fluid flow velocity is ______________ to the distance from the axis line.
a) directly proportional
b) inversely proportional
c) not related
d) none of the mentioned
Answer: b
Clarification: In vortex fluid velocity is more near to the axis and decreases as the distance from the axis line increases. Hence Fluid flow velocity is inversely proportional to the distance from the axis line.

4. Vorticity is _______ in the core region.
a) very high
b) very low
c) zero
d) none of the mentioned
Answer: a
Clarification: In the core region fluid rotates with high velocity and hence vorticity is high in the core region.

5. Steam lines and Path lines are _______ in stationary vortex.
a) high
b) less
c) closed
d) none of the mentioned
Answer: c
Clarification: Steam lines and Path lines are closed in stationary vortex where as in moving vortex it carries momentum and energy.

6. In a fluid with constant density Vortex flow pressure is proportional to ________
a) square of the distance from axis
b) distance from the axis
c) cube of the distance from the axis
d) none of the mentioned
Answer: a
Clarification: In a vortex flow with constant fluid density its fluid pressure is inversely proportional to the square of the distance from the axis line.

7. In forced vortex all fluid particles rotate with the ________________
a) constant velocity
b) constant angular velocity
c) variable angular velocity
d) none of the mentioned
Answer: b
Clarification: In forced vortex all fluid vortex rotates with constant angular velocity.

8. Solid body rotation is another name for ________
a) free vortex
b) forced vortex
c) free & forced vortex
d) none of the mentioned
Answer: b
Clarification: Solid body rotation is another name for forced vortex as all fluid particles in forced vortex rotate with same angular velocity like a solid rotation.

9. In forced vortex the total head _______ with radius.
a) radius is not related to head in forced vortex
b) decreases
c) increases
d) none of the mentioned
Answer: c
Clarification: In forced vortex total head increases with radius from the head equation.

10. For forced vortex external torque is to be supplied continuously.
a) True
b) False
Answer: a
Clarification: To maintain forced vortex external energy is to be supplied constantly and hence external torque is to be supplied constantly.

Steam and Gas Turbines Multiple Choice Questions on “Energy Transfer Relation and Losses”.

1. Temperature of the steam leaving the boiler is ____________
a) low
b) high
c) medium
d) none of the mentioned
Answer: b
Clarification: Steam leaves the boiler at super heated stage with high temperature.

2. Pressure of the steam leaving the boiler is ______
a) low
b) medium
c) high
d) none of the mentioned
Answer: c
Clarification: Steam leaves the boiler at super heated stage with high pressure.

3. Steam when passes through the nozzle _______ its kinetic energy.
a) Increases
b) Decreases
c) Nozzle has nothing to do with kinetic energy
d) None of the mentioned
Answer: a
Clarification: When steam is passed through the nozzle its velocity increases as a result its kinetic energy increases.

4. In a reaction turbine fixed nozzle is replaced by __________
a) guide blades
b) fixed blades
c) moving vanes
d) none of the mentioned
Answer: b
Clarification: In a reaction turbine the work of increasing kinetic energy is done by fixed blades.

5. Work done by the condenser is product of mass flow and _______
a) final enthalpy
b) initial enthalpy
c) change in enthalpy
d) none of the mentioned
Answer: c
Clarification: Work done by the condenser is product of mass flow and change in enthalpy.

6. Turbine performance is ____________ proportional to isoentropic efficiency.
a) directly
b) inversly
c) not proportional
d) none of the mentioned
Answer: a
Clarification: Turbine performance is directly proportional to isoentropic efficiency.

7. While calculating isoentropic efficiency heat loss to the surroundings is assumed to be _______
a) high
b) low
c) medium
d) none of the mentioned
Answer: b
Clarification: While calculating isoentropic efficiency heat loss to the surrounding is assumed to be zero.

8. The starting temperature of actual turbine is ________ the ideal turbine.
a) less than
b) greater than
c) equal to
d) none of the mentioned
Answer: c
Clarification: The starting temperature of the both actual and ideal turbine is equal.

9. The starting pressure of actual turbine is __________ that of ideal turbine.
a) equal to
b) more than
c) less than
d) none of the mentioned
Answer:a
Clarification: The starting pressure of both actual and ideal turbine is equal.

10. Isoentropic efficiency is the _________ of actual work and ideal work.
a) product
b) ratio
c) sum
d) none of the mentioned
Answer: b
Clarification: Isoentropic efficiency is the ratio of actual work to ideal work.

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Steam and Gas Turbines Multiple Choice Questions & Answers on “Regenerator Types and Mean Temperature Difference”.

1. In rotary regenerators matrix is __________
a) constant
b) varying
c) zero
d) none of the mentioned
Answer: b
Clarification: In rotary regenerators matrix rotates continuously.

2. In rotary regenerators matrix is ________
a) isothermal
b) isochoric
c) constant pressure process
d) none of the mentioned
Answer: a
Clarification: In rotary regenerators matrix is isothermal.

3. In rotary regenerators rotation is _________ to the flow direction.
a) parallel
b) perpendicular
c) concurrent
d) none of the mentioned
Answer: b
Clarification: In rotary regenerator rotation is always perpendicular to the flow direction.

4. In rotary regenerator rotation is __________ to the temperature gradient.
a) parallel
b) congruent
c) perpendicular
d) none of the mentioned
Answer:c
Clarification: In rotary regenerator rotation is always perpendicular to both temperature gradient and flow direction.

5. In rotary regenerators fluid temperature is __________ across the flow area.
a) constant
b) varying
c) zero
d) none of the mentioned
Answer: b
Clarification: In rotary regenerators fluid temperature varies across the flow area.

6. In fixed matrix regenerator the fluid is ducted to the valves to flow through various matrices.
a) True
b) False
Answer: a
Clarification: In fixed matrix regenerator the fluid is ducted to the valves to flow through various matrices.

7. Outlet temperatures of fixed matrix regenerator is ______ with time.
a) constant
b) varying
c) zero
d) none of the mentioned
Answer: b
Clarification: Outlet temperatures of the fixed matrix regenerator varies with time.

8. Micro scale regenerator has multi grating structure.
a) True
b) False
Answer: a
Clarification: Micro scale regenerator has multi grating structure.

9. In micro scale regenerator each layer is _______ from the adjacent layer.
a) equal
b) subset
c) offset
d) none of the mentioned
Answer: c
Clarification: In micro scale regenerator each layer is offset from the adjacent layer.

10. Rothemuhle regenerator has a _______ matrix in a disk shape.
a) moving
b) fixing
c) no matrix
d) none of the mentioned
Answer: b
Clarification: Rothemuhle regenerator has a fixed matrix in a disk shape.

Steam and Gas Turbines Multiple Choice Questions on “Combustion System in Gas Turbines”.

1. After burners are used to ________ the thrust.
a) increase
b) decrease
c) afterburners are not related to thrust
d) none of the mentioned
Answer: a
Clarification: After burners are used to increase the thrust. After burners collect the exhaust gases from exhaust frame and reheat them and uses the remaining kinetic energy of the gases and increases the thrust produced.

2. Extra fuel is injected to afterburners to _________ the thrust.
a) decrease
b) increase
c) extra fuel is not injected
d) none of the mentioned
Answer: b
Clarification: Extra fuel is injected to afterburners to increase the thrust. All the exhaust gases from exhaust frame is brought into afterburners and burned again with the help of extra fuel added into afterburner.

3. Afterburners consume _______ fuel amounts.
a) medium
b) low
c) high
d) none of the mentioned
Answer: c
Clarification: Afterburners consume high fuel amounts. For exhaust gases left after combustion from combustion chamber extra amount of fuel is added to the afterburner to burn again so that the remaining traces of fuel in exhaust gases get burned.

4. By using afterburners efficiency is _________
a) increased
b) decreased
c) not effected
d) none of the mentioned
Answer: b
Clarification: By using afterburners efficiency is decreased. As more amount of fuel is required in after burners.

5. When jet engines use afterburners engines are ________
a) wet
b) dry
c) semi dry
d) none of the mentioned
Answer: a
Clarification: When jet engines use afterburners engines are wet. For working of afterburners a continuous supply of fuel need to be given and hence they are wet.

6. When afterburners are not used in jet engines they are ________
a) wet
b) dry
c) semi dry
d) none of the mentioned
Answer: b
Clarification: When afterburners are not used in jet engines they are dry. Exhaust gases are dry which makes jet engine dry.

7. Afterburners are not equipped with case and liners.
a) True
b) False
Answer: b
Clarification: After burners are equipped with both case and liners.

8. Afterburners have _______ rise in temperature than combustors.
a) low
b) equal
c) high
d) none of the mentioned
Answer: c
Clarification: Afterburners have high rise in temperature when compared to combustors. As already the exhaust gases are present in high temperatures and when again burned by adding some fuel the exhaust gases that are released from afterburners that have high temperatures.

9. Mixing of fuel takes place efficiently in afterburners.
a) True
b) False
Answer: b
Clarification: Mixing of fuel is not that efficient in afterburners.

10. Afterburners require _________
a) flame holder
b) nozzle
c) casing
d) none of the mentioned
Answer: a
Clarification: Flame holders are used to maintain a constant velocity of flame. If the flame in afterburners are produced with different velocities combustion of the flame may not be constant.