Category: Steam and Gas Turbines Objective Questions

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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Steam and Gas Turbines Multiple Choice Questions on “Energy Distribution and Effect of Carry Over Velocity”.

1. Most of the energy produced by gas turbine is utilized by _______
a) compressor
b) condenser
c) to drive turbine blade
d) none of the mentioned
Answer: a
Clarification: Two third of the energy produced by gas turbine is utilized by the compressor to compress the air.

2. In gas turbines during expansion rotor’s blades rotate, which is an __________ transformation.
a) reversible
b) irreversible
c) no energy transformation occurs by rotation of rotor blades
d) none of the mentioned
Answer: b
Clarification: Rotation of rotor blades is an irreversible transformation.

3. Energy losses in gas turbines are __________
a) flue gasses energy loss
b) rotational loss
c) flue gasses energy & rotational loss
d) none of the mentioned
Answer: c
Clarification: Flue gases loss and rotational loss are some of the energy losses in gas turbine.

4. In steam turbines carry over losses are due to _____________
a) formation of eddies in annular spaces
b) decrease in pressure
c) increase in temperature
d) none of the mentioned
Answer: a
Clarification: Carry over losses are due to formation of eddies in steam turbines.

5. Corrosion and Erosion takes place if dryness factor of steam is __________ in last stage.
a) less than 0.68
b) more than 0.60
c) less than 0.88
d) none of the mentioned
Answer: c
Clarification: Liquid particles have lesser velocity than steam particles and hence if dryness fraction is less than 0.88 even erosion and corrosion can takes place.

6. Radiation losses can be covered by _______
a) decreasing the temperature of steam
b) proper insulation
c) decreasing the temperature of steam and proper insulation
d) none of the mentioned
Answer: b
Clarification: Radiation and convention losses can be reduced by proper insulation.

7. Enthalpy __________ takes place when steam enters from turbine to condenser.
a) decrease
b) increase
c) depends on the situation
d) none of the mentioned
Answer: a
Clarification: When steam leaving turbine has kinetic energy and when it enters condenser enthalpy loss takes place.

8. Energy balance states that total energy input is equal to arithmetic sum of Energy losses, output work, flue gasses loss and rotational loss.
a) True
b) False
Answer: a
Clarification: Energy balance equation states that
Total energy input = Energy output + energy losses + flue gasses loss + rotational loss.

9. ______________ is commonly called as carry over velocity.
a) Compressor velocity
b) Inlet velocity
c) Exit velocity
d) None of the mentioned
Answer: c
Clarification: Velocity at exit is called carryover velocity.

10. Carryover loss is also called a leaving loss.
a) True
b) False
Answer: a
Clarification: Loss in exit velocity is called carryover loss or leaving loss.

Steam and Gas Turbines Multiple Choice Questions on “Losses in Reaction Blade Passages”.

1. Passages in steam turbines are _______
a) convergent
b) divergent
c) convergent & divergent
d) none of the mentioned
Answer: a
Clarification: Passages in steam turbines are convergent so that steam expands.

2. The flow of steam through the nozzle is isoentropic.
a) True
b) False
Answer: b
Clarification: The flow of steam is not isoentropic.

3. In reaction turbines a pressure drop occurs between rotors and stator.
a) True
b) False
Answer: a
Clarification: Steam when leaving the stator changes its speed relative to the blade speed and pressure drop occurs.

4. Steam is directed towards rotor by _________
a) rotor vanes
b) moving blades
c) fixed blades
d) none of the mentioned
Answer: c
Clarification: Steam is directed by fixed vanes in steam turbine.

5. Losses that occur when steam is supplied from boiler to turbine is called as ___________
a) regulating loss
b) friction loss
c) gland loss
d) none of the mentioned
Answer: a
Clarification: When steam is supplied from boiler to turbine it passes through regulating valve and some energy loss is occurred while passing through regulating valve which is called as regulating loss.

6. Losses occurred while passing through blades are called as ________
a) efficient losses
b) blade friction loss
c) efficient & blade friction losses
d) none of the mentioned
Answer: b
Clarification: Blade friction loss are caused due to friction between blade and steam and loss occurs due to that friction.

7. Disc friction loss is due to ___________
a) churning action of disc
b) friction between blade and steam
c) pressure drop
d) none of the mentioned
Answer: a
Clarification: Blades re connected to the disc and there will be some amount of energy loss due to churning action of the disc.

8. For fixing blades and rotating components together ___________ are used.
a) bolt and nut
b) valve
c) glands
d) none of the mentioned
Answer: c
Clarification: Glands are used to fix blades and rotating components together.

9. Losses occurred at gap between glands are called as _________
a) valve losses
b) gland losses
c) valve & gland losses
d) none
Answer: b
Clarification: Gland losses are the losses that are occurred at the gap between the glands.

10. Kinetic energy that steam has while coming out of turbines is called as ________
a) residual loss
b) friction loss
c) gland loss
d) none of the mentioned
Answer: a
Clarification: Residual losses are the energy that steam contains while exiting the turbine. This energy cannot be used and hence it is called as residual losses.

Steam and Gas Turbines Multiple Choice Questions on “AIEE-ASME Preferred Standard Turbine”.

1. AIEE ASME preferred turbines don’t have any side condensers.
a) True
b) False
Answer: b
Clarification: AIEE ASME preferred turbine have side condensers mounted.

2. Usage of condensers mounted on sides reduces the ___________
a) Power supply
b) Support structures
c) Temperature
d) None of the mentioned
Answer: b
Clarification: Usage of condensers mounted on sides reduces the height of the turbine and support structures can be reduced.

3. AIEE ASME preferred standard power plant is first operated in Greens Bayou electric power plant.
a) True
b) False
Answer: a
Clarification: AIEE ASME preferred standard power plant was first operated in greens bayou electric power plant.

4. The capacity of first AIEE ASME preferred standard turbine is _______
a) 105MW
b) 55MW
c) 66MW
d) 77MW
Answer: c
Clarification: The capacity of AIEE ASME preferred standard turbine generator which first came into use is 66MW.

5. AIEE-ASME preferred standard turbine was presented in _______ ratings when first came into outdoor use.
a) 2
b) 8
c) 3
d) 6
Answer: b
Clarification: AIEE-ASME preferred standard turbine was presented in 8 ratings when it first came into existence. They are 12.65 MW, 16.5 MW, 22 MW, 33 MW, 44 MW, 66 MW, 100 MW, 150 MW.

6. Gantry rolling over the turbine deck ________ on AIEE-ASME preferred standard turbine.
a) done
b) not done
c) depends on the use
d) none of the mentioned
Answer: a
Clarification: Gantry rolling over the turbine deck can be done on AIEE-ASME preferred standard turbine.

7. Outdoor lagging of the turbine generator _________ the effectiveness of the time.
a) reduces
b) increases
c) depends on the load
d) none of the mentioned
Answer: b
Clarification: Outdoor lagging of the turbine generator increases the effectiveness of the time.

8. The outdoor lagging for AIEE-ASME preferred standard turbine is designed for ________
a) 70 P/Sq.ft
b) 80 P/Sq.ft
c) 90 P/Sq.ft
d) 85 P/Sq.ft
Answer: a
Clarification: Outdoor lagging of AIEE-ASME preferred standard turbine is designed for 70 P/Sq.ft.

9. Green Bayou Turbine generator rotates at __________
a) 4000rpm
b) 3000 rpm
c) 3600 rpm
d) 3100 rpm
Answer: c
Clarification: Green Bayou turbine generator works at 3600 rpm.

10. Power factor of Green bayou turbine generator is ______
a) 85
b) 95
c) 60
d) 70
Answer: a
Clarification: Green bayou has a power factor of 85.