Category: Steam and Gas Turbines Objective Questions

Steam and Gas Turbines Interview Questions and Answers for experienced on “Blade Angle, Gauging and Pitch, Width and Height”.

1. Ram Air turbine generates ________ from air stream.
a) losses
b) power
c) work
d) none
Answer: b
Clarification: Ram Air turbine generates power from air stream.

2. Ram Air turbine can be connected to hydraulic pump.
a) True
b) False
Answer: a
Clarification: Ram air turbine can be connected to generator or hydraulic pump.

3. In steam and gas turbines Casing contains controls for working fluids.
a) True
b) False
Answer: a
Clarification: In steam and gas turbines casing over turbine blades contains controls for working fluids.

4. When pressure drop is in stages then that turbine is called as ________
a) velocity compounded impulse turbine
b) pressure compounded impulse turbine
c) velocity compounded reaction turbine
d) none of the mentioned
Answer: b
Clarification: In pressure compounded impulse turbine pressure drop is in several stages and pressure loss is reduced.

5. Steam velocities in pressure compounding is ______
a) low
b) high
c) velocity has nothing to do with pressure compounding
d) none of the mentioned
Answer: a
Clarification: In pressure compounding the Conversion of kinetic energy in work is in several small stages and hence velocity of steam is low.

6. In parsons turbine to increase area between blades its height is to be ________
a) height has nothing to do with area between blades
b) decreased
c) increased
d) none of the mentioned
Answer: c
Clarification: In parsons turbine velocity is increased and as a result area between the blades is to be increased and it was increased by tapering the blade height.

7. If specific volume of steam increases its blade height _______
a) increases
b) decreases
c) not related with each other
d) none of the mentioned
Answer: a
Clarification: If the specific volume of steam increases its area need to be increased and hence its blade height is increased.

8. Blade entrance angle is measure for __________
a) stationary blades
b) moving blades
c) stationary & moving blades
d) none of the mentioned
Answer: b
Clarification: Steam initially enters moving blades and hence blade entrance angle is measured for moving blades.

9. Blade exit angle is a measure for _________
a) moving & fixed blade
b) moving blade
c) fixed blade
d) none of the mentioned
Answer: c
Clarification: Steam exits the moving blade and then it enters fixed blade and hence blade exit angle is measured at fixed blades.

10. Nozzle exit angle is the measure of angle with which steam is leaving the nozzle.
a) True
b) False
Answer: a
Clarification: Nozzle exit angle is the angle with which steam exits the nozzle.

Steam and Gas Turbines for interviews,

Steam and Gas Turbines Multiple Choice Questions on “Mixed Pressure Turbine Perfomance”.

1. Mixed pressure steam turbines are driven by _________ kinds of steam.
a) 1
b) 2 or more
c) 3
d) 5
Answer: b
Clarification: Mixed pressure turbines are driven by two or more kinds of steam.

2. In mixed pressure turbine existing boiler can be combined with new boiler.
a) True
b) False
Answer: a
Clarification: Both the steams are fed into turbine independently and in this type of turbine existing boiler can be combined with new boiler.

3. In dual heat sources optimum heat for each condition cannot be selected in mixed pressure turbine.
a) True
b) False
Answer: b
Clarification: In dual heat sources optimum heat for each condition can be selected in mixed pressure turbine.

4. Radial turbines gain their high efficiencies at the speed ratio of ___________
a) 0.5
b) 0.7
c) 1
d) 2.6
Answer: c
Clarification: Radial turbines get their peak efficiencies at the speed ratio of 0.7

5. Radial turbine has _______ degree of freedom when compared to mixed flow turbine.
a) more
b) less
c) equal
d) none of the mentioned
Answer: b
Clarification: Radial turbine has less degree of freedom when compared to mixed flow turbine.

6. The blade inlet angle at radial blade section is ________ in mixed flow turbine.
a) non zero
b) zero
c) depends on the mass flow rate
d) none of the mentioned
Answer: a
Clarification: The blade inlet angle at radial blade section is non zero in mixed flow turbine.

7. Stress levels in mixed flow turbine are ________
a) high
b) less
c) medium
d) none of the mentioned
Answer: b
Clarification: Stress levels in mixed flow turbines are less.

8. Mixed flow turbines are designed at ________ inertia.
a) high
b) medium
c) low
d) none of the mentioned
Answer: c
Clarification: Mixed flow turbines are designed at low inertia.

9. Radial turbines are characterized by ____________
a) radial fibers
b) centrifugal compressors
c) radial compressors
d) none of the mentioned
Answer: a
Clarification: Radial turbines are characterized by radial fibers.

10. Turbochargers in automobiles works under _______ pulsation inlet flows.
a) low
b) high
c) medium
d) none of the mentioned
Answer: b
Clarification: Turbochargers in automobiles works under high pulsation inlet flows.

Steam and Gas Turbines MCQs on “The Combustor”.

1. Combustor is also called as _________
a) combustion
b) ramjet
c) inlet manifold
d) none of the mentioned
Answer: a
Clarification: Combustor is also called as a ramjet. Inlet manifold is the inlet pipe provided for adding materials.

2. Combustor can also be called as __________
a) burner
b) ramjet
c) inlet manifold
d) none of the mentioned
Answer: b
Clarification: Combustor can be called as ramjet or burner.

3. Pressure inside the combustor is ________
a) Constant
b) Increases
c) Decreases
d) None of the mentioned
Answer: a
Clarification: Pressure inside the combustor is constant.

4. In _________ air is directly fed to the nozzle.
a) burner & ramjet
b) burner
c) ramjet
d) none of the mentioned
Answer: c
Clarification: In ramjet air is directly fed to the nozzle. Ramjet or burner both mean the same.

5. Flow rates are ________ in combustor.
a) high
b) low
c) medium
d) none of the mentioned
Answer: a
Clarification: Flow rates are high in the combustors. As pressure is high flow rate is also high in the combustor.

6. When 1 kg of jet fuel is produced _______ amount of co₂ is released.
a) 3kg
b) 3.2kg
c) 3.4kg
d) 3.8kg
Answer: b
Clarification: When 1 kg of jet fuel is burned 3.2 kgs of co₂ is released.

7. Fuel that was not completely burnt is called as _______
a) Ramjets
b) UHC
c) Emissions
d) None of the mentioned
Answer: b
Clarification: Incompletely combusted fuels are called as UHC.

8. UHC’s are produced at _________ power levels.
a) high
b) medium
c) low
d) none of the mentioned
Answer: c
Clarification: UHC’s are generally produced at low power levels.

9. Combustors which doesn’t produce more CO doesn’t emit much UHC.
a) True
b) False
Answer: a
Clarification: Combustors that have highly optimized UHC are the combustors which produce low CO emissions.

10. CO produced in combustion is eliminated by __________
a) reduction
b) oxidation
c) reduction & oxidation
d) none of the mentioned
Answer: b
Clarification: CO produced in combustion is eliminated by oxidation.

Advanced Gas Turbines Questions & Answers on “Micro Gas Turbines”.

1. _________ jets produce micro gas turbines.
a) Bladon
b) Turbo
c) Bladon & Turbo
d) None of the mentioned
Answer: a
Clarification: Bladon jets produce micro gas turbines. Due to the weight to size constraint these are used.

2. Hybrid electric vehicles are powered by _________
a) turbo shafts
b) micro gas turbines
c) turbo jets
d) none of the mentioned
Answer: b
Clarification: Hybrid electric vehicles are powered by micro gas turbines. Micro gas turbines are used by considering weight to size ratio.

3. Micro turbines are based on _________
a) weight
b) size
c) micro combustion
d) none of the mentioned
Answer: c
Clarification: Micro combustion is the basic principle micro turbines are based upon.

4. In micro turbines generator is integrated with _________
a) turbine shaft
b) combustor
c) turbine shaft & combustor
d) none of the mentioned
Answer: a
Clarification: In micro turbines generator is integrated with turbine shaft.

5. Micro turbines have ________ power to weight ratio.
a) constant
b) low
c) high
d) none of the mentioned
Answer: c
Clarification: Micro turbines have high power to weight ratio. As the weight of the micro gas turbines is less it automatically increases the ratio.

6. Micro turbines have ________ emissions.
a) high
b) low
c) medium
d) none of the mentioned
Answer: b
Clarification: Micro turbines have low emissions. As power to weight ratio is less for micro turbines emissions are also reduced in micro gas turbines.

7. Micro turbines are more efficient at ________ power level when compared to reciprocating engines.
a) high
b) low
c) medium
d) none of the mentioned
Answer: b
Clarification: Micro turbines are more efficient at low power levels when compared to reciprocating engines. As the size of micro gas turbines is less the total power produced is also less when compared to reciprocating engines.

8. Micro turbines use _______ bearings.
a) air & journal
b) journal
c) air
d) none of the mentioned
Answer:c
Clarification: Micro turbines use air bearings. As journal bearings are huge in size when compared to air bearings and weight of air bearings is also less.

9. Micro turbines can also use magnetic bearings.
a) True
b) False
Answer: a
Clarification: High temperatures and high speed of micro turbines make usage of ball bearings impractical and so micro turbines can be used with air bearings or magnetic bearings.

10. Throttling of the fuel in gas turbines is impractical.
a) True
b) False
Answer: a
Clarification: Battery is used as a buffer in micro turbines for storing electricity and hence throttling is not required in micro turbines.

To practice advanced questions on all areas of Gas Turbines,

Basic Automobile Engineering Questions and Answers on “Universal Joints and Differential”.

1. Which types of joints are used when the shafts are inclined?
a) Universal joint
b) Hinge joint
c) Ball and socket joint
d) Pivot joint
Answer: a
Clarification: Universal joint is used when the shafts are inclined and intersecting. It is very compact in design and simple in construction. It is very effective at small angles of propeller shaft movement.

2. The axes of the two shafts are intersecting and are at 25° to each other. These two shafts are connected by Hook’s joint. At which position of the drives shaft velocity ratio will be maximum?
a) 90°, 270°
b) 0°, 180°
c) 180°, 270°
d) 90°, 180°
Answer: b
Clarification: (ω_B / ω_A) = (cos α) / (1 – cos²θ sin²α) where A = driving shaft and B = driven shaft and α is the angle between shaft A and shaft B. θ is the angle through which the shaft A rotates. Velocity ratio is maximum when θ = nπ where n = 1, 2, 3, …… i.e. θ = θ° or 180°.

3. Which of the following is the disadvantage of the open differential?
a) High in cost
b) Not reliable
c) Complex design
d) Sends most of the power to the wheel having less traction
Answer: d
Clarification: The major disadvantage of the open differential in that it transfers the power to the wheel even if it is on a slippery road. That’s why it is not used in off driving cars.

4. Why do the hypoid gears require special lubricant?
a) Teeth are soft
b) Teeth are hard
c) Gears run faster
d) There is relative motion between teeth
Answer: d
Clarification: Hypoid gears require special lubricant because of the extreme pressure between the teeth. The sliding motion of the teeth is effective due to the use of special lubricant.

5. The axes of the two shafts are intersecting and are at 30° to each other. These two shafts are connected by Hook’s joint. At which position of the drives shaft velocity ratio will be minimum?
a) 90°, 270°
b) 0°, 180°
c) 180°, 270°
d) 90°, 180°
Answer: a
Clarification: (ω_B / ω_A) = (cos α) / (1 – cos²θ sin²α) where A = driving shaft and B = driven shaft and α is the angle between shaft A and shaft B. θ is the angle through which the shaft A rotates. Velocity ratio is minimum when θ = m&pi/2 where m = 1, 3, 5, …… i.e. θ = 90° or 270°.

6. Where is the differential located?
a) Between transmission and rear axle
b) Between engine and transmission
c) Between two propeller shaft
d) Between steering wheel and steering column
Answer: a
Clarification: The differential used to incorporate the speed of the rear wheels and front wheels during turning. It is located between the transmission and rear axle.

7. The axes of the two shafts are intersecting and are at 35° to each other. These two shafts are connected by Hook’s joint. At which position of the drives shaft velocity ratio will not be unity?
a) 42.145°
b) 222.145°
c) 317.85°
d) 141.52°
Answer: d
Clarification: (ω_B / ω_A) = (cos α) / (1 – cos²θ sin²α) where A = driving shaft and B = driven shaft and α is the angle between shaft A and shaft B. θ is the angle through which the shaft A rotates. Velocity ratio is unity when tanθ = ± (sqrt{cosalpha} = ± sqrt{cos35}) = ± 0.90 i.e. θ = 42.145°, 222.145°, 317.85°, and 137.85°.

8. What is the need of the universal joint?
a) To change inclination
b) To bend sideways
c) To transfer torque at an angle
d) To change length
Answer: c
Clarification: The universal joint transfers the torque to two intersecting shafts. One or two universal joints are used depending upon the type of rear-drive used.

9. The axes of the two shafts are intersecting and are at 35° to each other. These two shafts are connected by Hook’s joint. At which position of the drives shaft acceleration will be maximum?
a) 68.4°
b) 96.1°
c) 225.5°
d) 330.7°
Answer: c
Clarification: (ω_B / ω_A) = (cos α) / (1 – cos²θ sin²α) where A = driving shaft and B = driven shaft and α is the angle between shaft A and shaft B. θ is the angle through which the shaft A rotates. Acceleration will be maximum when cos2θ = (2 sin²α) / (2 – sin²α) =(2 sin²40°) / (2 – sin²40°) = 0.5207 i.e. 2θ = 58.62 i.e. θ = 29.31°, 180° – 29.31° = 150.69°, 180° + 29.31° = 209.31°, 360° – 29.31° = 330.69°

10. A two-piece propeller shaft requires one universal joint.
a) True
b) False
Answer: b
Clarification: A two-piece propeller shaft requires a center support bearing. If there is a large wheelbase, the long propeller shaft is needed. So a two-piece propeller shaft is used in such case with a center support bearing. By incorporating this there is no sag or whirl.

Steam and Gas Turbines Multiple Choice Questions on ” Carnot, Rankine and Reheat Cycle-2″.

1. The cycle of evaporation and rain in nature can be assumed to be a kind of Carnot cycle. If ocean water instead of evaporation are boiled by the heat of Sun at a constant temperature of 100 deg C and the condensation of steam into water droplets within the clouds occur at constant temperature of -20 deg C. Find the thermal efficiency of Carnot cycle of nature?
a) 0.2777
b) 0.3030
c) 0.3333
d) 0.50

Answer: b
Clarification: Carnot thermal efficiency = 1-(Mean temperature of heat addition)/( Mean temperature of heat rejection).

2. How is it advantageous to expand steam at 250 deg C in a turbine as compared to expanding saturated steam in similar turbine?
a) Enhances the thermal efficiency of the cycle
b) Reduces the mechanical damage caused to turbine blades due to wet steam
c) Increases the mean temperature of heat addition
d) All of the mentioned

Answer: d
Clarification: Superheating steam makes expansion within turbine to take place in dry region to a greater extent.

3. In a steam turbine power plant, the boiler feedwater temperature is marked as 30 deg C, ocean as sink with temperature 20 deg C and desired thermal efficiency of the plant is 0.46. Find the temperature of steam entering the turbine?
a) 500degC
b) 505.55degC
c) 507.62degC
d) 509.18degC

Answer: d
Clarification: Mean temperature of heat addition = (Temperature of feedwater + Temperature of steam entering turbine)/2.

4. In a newly developed innovative idea brought up by CSIR in India, gas turbine exhaust gas are being utilized to convert feedwater into steam. Certain data of the experiment are as follows: mass flow rate of exhaust gas = 40 kg/hr, enthalpy of exhaust gas at the time of their exit from gas turbine is 600 kJ/kg, steam turbine output as measured by brake dynamometer = 60 hp-sec, thermal efficiency of steam power plant is 0.25, efficiency of exhaust gas in converting feedwater into steam is taken as 50%. Find the enthalpy of exhaust gas remaining after they generate steam from feedwater?
a) 350.0KJ/Kg
b) 241.2KJ/Kg
c) 112.45KJ/Kg
d) 512.56KJ/Kg

Answer: b
Clarification: Heat added = difference of enthalpies * efficiency of exhaust gas in converting feedwater into steam and then apply thermal efficiency formula for Carnot efficiency.

5. Why does Carnot cycle has maximum efficiency?
a) Since all the processes in Carnot cycle are completely reversible
b) Since only process of expansion and compression are reversible
c) Since only the process of heat addition and heat rejection are reversible
d) Since all processes involved are irreversible

Answer: a
Clarification: All the processes in Carnot cycle are completely reversible.

6. A researcher during an experiment found that mean temperature of heat addition and heat rejection for a steam power plant operating on a Carnot cycle is 127 deg C and 27 deg C respectively. Later, he calculated the thermal efficiency of the steam cycle. Can you predict what was it?
a) 0.20
b) 0.25
c) 0.30
d) 0.35

Answer: b
Clarification: Thermal efficiency of a Carnot cycle is given by (Mean temperature of heat addition-Mean temperature of heat rejection)/(Mean temperature of heat addition).

7. If Carnot cycle has maximum possible thermal efficiency, then why don’t the steam turbine power plants run on Carnot cycle?
a) Because the process of heat addition is at constant temperature
b) As mean temperature of heat addition is quite low in case of Carnot cycle
c) Since work consumed by compressor is approximately equal to work produced by turbine
d) Because boiler can’t be maintained at constant pressure in Carnot cycle

Answer: c
Clarification: As compressor and turbine both work on wet steam, therefore they don’t have significant difference in their work.

8. The mass of coal(lignite) used in boiler of a steam power plant is 20 ton per hour and calorific value of lignite is 13600 KJ/kg. Also, if the entropy of steam entering turbine is 750 J/K and that of feedwater entering the boiler is 550J/K. Find the mean temperature of heat addition?
a) 100 deg C
b) 115 deg C
c) 110 deg C
d) 105 deg C

Answer: d
Clarification: Tmean = Q/(change in entropy).

9. In a solar operated steam power plant, water is converted into steam via solar heat. If the effective area of solar plate is 200m², value of solar constant is 1.362KW per m², efficiency of solar components is 17% and overall thermal efficiency of steam cycle desired is 12%. Find the turbine power output?
a) 45KW
b) 22.46KW
c) 5.55KW
d) 16.54KW

Answer: c
Clarification: Efficiency of steam cycle = (Turbine power output/(solar constant*area*solar efficiency)).

10. A boiler feed pump is used to raise ___________
a) Static pressure of feedwater
b) Dynamic pressure of feedwater
c) Static & Dynamic pressure of feedwater
d) None of the mentioned

Answer: a
Clarification: Since water needs to be brought to boiler pressure and is not in motion.

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