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Multiple choice question for engineering

Set 1

1. The hydraulic efficiency of Pelton turbine will be maximum when blade velocity is equal to _______
a) V/2
b) V/3
c) V/4
d) V/5

View Answer

Answer: a [Reason:] Hydraulic efficiency is defined as ratio between power given by water to runner of turbine and to the power supplied by water at inlet of the turbine. This efficiency will be maximum when differentiating it with “u” and it is obtained as u=v/2.

2. In Pelton turbine ___________ is defined as ratio between power delivered to runner and power supplied at inlet of turbine
a) Mechanical efficiency
b) Volumetric efficiency
c) Hydraulic efficiency
d) Overall efficiency

View Answer

Answer: c [Reason:] Hydraulic efficiency is defined as ratio between power given by water to runner of turbine and to the power supplied by water at inlet of the turbine.

3. The maximum efficiency of Pelton turbine is _________
a) 80%
b) 70%
c) 50%
d) 88%

View Answer

Answer: c [Reason:] We know that efficiency will be Maximumwhen blade velocity is equal to half of its jet velocity upon substitution we get efficiency as 50%.

4. In Pelton turbine product of mechanical efficiency and hydraulic efficiency is known as _____________
a) Mechanical efficiency
b) Volumetric efficiency
c) Hydraulic efficiency
d) Overall efficiency

View Answer

Answer: d [Reason:] Overall efficiency is defined as ratio of power available at shaft of turbine to power supplied at the inlet of turbine which is also product of mechanical and hydraulic efficiency.

5. Among the following which turbine has least efficiency?
a) Pelton turbine
b) Kaplan turbine
c) Francis turbine
d) Propeller turbine

View Answer

Answer: a [Reason:] Pelton is impulse turbine and remaining are reaction turbine, efficiency of reaction turbine is more compared to impulse turbine.

6. In Pelton ____________ is ratio of volume of water actually striking the runner and volume of water supplied to turbine?
a) Mechanical efficiency
b) Volumetric efficiency
c) Hydraulic efficiency
d) Overall efficiency

View Answer

Answer: b [Reason:] Volumetric efficiency is ratio between volume of water actually striking the runner of turbine and volume of water supplied to the turbine.

7. In Pelton turbine the ratio of volume available at shaft of turbine and power supplied at the inlet of the turbine is _______
a) Mechanical efficiency
b) Volumetric efficiency
c) Hydraulic efficiency
d) Overall efficiency

View Answer

Answer: d [Reason:] Overall efficiency is defined as ratio of power available at shaft of turbine to power supplied at the inlet of turbine which is also product of mechanical and hydraulic efficiency.

8. The expression for maximum hydraulic efficiency of Pelto turbine is given by ______________
a) (1+cos k)/2 where k is outlet blade angle
b) (2+cos k)/2 where k is outlet blade angle
c) (3+cos k)/2 where k is outlet blade angle
d) (4+cos k)/2 where k is outlet blade angle

View Answer

Answer: a [Reason:] Hydraulic efficiency is defined as ratio between power given by water to runner of turbine and to the power supplied by water at inlet of the turbine. Its maximum value is obtained by replacing u=v/2 and it is (1+cos k)/2 where k is outlet blade angle.

9. In the expression for overall efficiency of turbine, which is p/ (k*g*q*h), where “k” is known as _______
a) Specific density of liquid
b) Density of liquid
c) Specific gravity of liquid
d) Volume of liquid

View Answer

Answer: b [Reason:] Overall efficiency is defined as ratio of power available at shaft of turbine to power supplied at the inlet of turbine which is also product of mechanical and hydraulic efficiency. Its expression is given by p/ (k*g*q*h) where k is density of liquid.

10. In Pelton turbine hydraulic efficiency is product of mechanical efficiency and overall efficiency.
a) True
b) False

View Answer

Answer: b [Reason:] The above statement is false generally overall efficiency is product of mechanical and hydraulic efficiency.

11. The expression for hydraulic efficiency is given by
a) 2(V1-u)[1+cos k]u/V1*V1
b) 2(V1+u)[1+cos k]u/V1*V1
c) 2(V1-u)[1-cos k]u/V1*V1
d) 2(V1+u)[1+cos k]u/V1*V1
Where, V1=inlet jet velocity, u=blade velocity, k=outlet blade angle

View Answer

Answer: a [Reason:] Hydraulic efficiency is ratio of power delivered to runner to power supplied at inlet of turbine upon substituting the mathematical terms we get expression as follows.

12. In Pelton turbine inlet velocity of jet is 85.83m/s, inlet and outlet whirl velocities be 85.83 and 0.143 and blade velocity be 38.62 then its hydraulic efficiency is ___________
a) 90.14%
b) 80%
c) 70%
d) 85%

View Answer

Answer: a [Reason:] Substitute the above given values in expression for hydraulic efficiency which is given by expression 2[Vw1+Vw2] u/V1*V1 and we get it as 90.14%.

Set 2

1. How many number of valves are required for the rotary pump?
a) 0
b) 1
c) 2
d) 3

View Answer

Answer: a [Reason:] There are no valves required for a rotary pump. A rotary pump is the one in which the flow is continuous. Since, the flow is continuous, we do not require any valves.

2. Reciprocating pump is divided into how many types, based on its cylinders?
a) 0
b) 5
c) 2
d) 3

View Answer

Answer: b [Reason:] Based on the number of cylinders, the reciprocating pump is divided into five types. It is divided on the basis of cylinders as single, double, triple , duplex and quintuplex.

3. At each stage the fluid is directed ________
a) Towards the centre
b) Away the centre
c) Towards the surface
d) Away from the centre

View Answer

Answer: a [Reason:] At each stage in the centrifugal pump, the fluid is directed to towards the centre. A multistage centrifugal pump has more than two impellers. The multistage centrifugal is similar to the centrifugal pumps working.

4. The maximum efficiency of the reciprocating pump is _________
a) 20
b) 50
c) 70
d) 85

View Answer

Answer: d [Reason:] Reciprocating pump is more favourable for small liquid quantities. As the chamber in the liquid is trapped, it has a stationary cylinder which contains a piston and a plunger. The maximum efficiency of the reciprocating pump is 85 percent.

5. The two opposite motion that comprise a single reciprocation is called _________
a) Turbocharger
b) Stokes
c) Fluid motion
d) Auto motion

View Answer

Answer: a [Reason:] Degree of reaction is most commonly used in turbomachinery. Degree of reaction is defined as the ratio of the static pressure drop in the rotor to the static pressure drop in the stage. It can also be defined in the same way for enthalpy in different stages. It is denoted by the letter ‘R’.

6. Reciprocating pumps has ____ efficiency compared to centrifugal pumps
a) Higher
b) Lower
c) Equal
d) Exponential

View Answer

Answer: b [Reason:] Reciprocating pumps has lower efficiency compared to centrifugal pumps. They are generally just used for discharges at higher heads. Their main purpose is to pump water in hilly areas.

7. Reciprocating pumps works on the principle of __________
a) Drag force
b) Liquid flow push
c) Shock waves
d) Flow speed

View Answer

Answer: b [Reason:] Reciprocating pumps works on the principle of liquid flow push by a piston that reciprocates in a closed fitting cylinder.

8. Reciprocating pump is a type of ___________
a) Positive displacement pump
b) Bicycle pump
c) Multistage pumps
d) Centrifugal pumps

View Answer

Answer: a [Reason:] Reciprocating pump is a type of positive displacement pump. The positive displacement pump includes piston pump, diaphragm and plunger pump.

9. During the suction stroke the _______ moves left thus creating vacuum in the Cylinder.
a) Piston
b) Cylinder
c) Valve
d) Pump

View Answer

Answer: a [Reason:] During the suction stroke the piston moves left. Thus, a vacuum is created in the cylinder. This vacuum causes the suction valve to open and water enters the Cylinder.

10. In reciprocating pumps, the chamber in which the liquid is trapped is a stationary cylinder that contains piston or cylinder
a) True
b) False

View Answer

Answer: a [Reason:] In reciprocating pumps, the chamber in which the liquid is trapped is a stationary cylinder that contains piston or cylinder.

11. Reciprocating pump works like a positive displacement pump.
a) True
b) False

View Answer

Answer: a [Reason:] Reciprocating pump works like a positive displacement pump. In reciprocating pumps, the chamber in which the liquid is trapped is a stationary cylinder that contains piston or cylinder.

12. When both the sources are effective it is called as __________
a) Double acting pump
b) Single acting pump
c) Triple acting pump
d) Normal pump

View Answer

Answer: a [Reason:] When both the sources are effective it is called as double acting centrifugal pump. The pumping unit consists of piston and cylinder.

13. A repetitive variation about the central value of equilibrium is called ________
a) Reciprocation
b) Oscillation
c) Filtration
d) Excavation

View Answer

Answer: b [Reason:] A repetitive variation about the central value of equilibrium is called as oscillation. It need not be linear.

14. A linear wheel turning motion is called as a ________
a) Reciprocation
b) Rotation
c) Oscillation
d) Bicycle pump

View Answer

Answer: b [Reason:] A linear wheel turning motion is called as a rotational motion. It is linear motion that takes place along a circular section.

15. A reciprocating pump that has 1200 crank is _________
a) Froth pump
b) Single acting
c) Double acting
d) Triple acting

View Answer

Answer: d [Reason:] A reciprocating pump that has 1200 crank is triple acting or triple cylinder pump. Each cylinder in a reciprocating pump has it suction and delivery pipes. Thus, has a crank of 1200.

Set 3

1. In nozzle governing, the flow rate of steam is regulated by _________
a) Nozzles
b) Pumping
c) Drafting
d) Intercooling

View Answer

Answer: a [Reason:] The process of controlling the flow rate of a substance is called as governing. It is done by maintaining the speed of rotation at a constant rate. In nozzle governing, the flow rate of steam is regulated by nozzles.

2. The flow rate of steam is controlled by regulating the_________
a) Steam
b) Pressure
c) Temperature
d) Speed

View Answer

Answer: b [Reason:] The process of controlling the flow rate is called as governing. It is done to maintain its speed at a constant rate during rotation of the turbine rotor. The flow rate of steam is controlled by regulating the pressure.

3. The main function of nozzle is to __________
a) Varying temperatures
b) Pressure variations
c) Load variations
d) Heat variations

View Answer

Answer: b [Reason:] The main function of nozzle is to vary the pressure of fluid passing through the nozzle. It is done by opening and shutting the sets of nozzles. Thus, its main function is to regulate pressure of the fluid.

4. What is primary objective of steam turbine governing?
a) Maintain constant speed
b) Maintain constant pressure
c) Maintain constant temperature
d) Maintain constant expansion

View Answer

Answer: a [Reason:] The primary objective of steam turbine governing is to maintain a constant speed at varying loads. That means, irrespective of the load that is developed in the turbine, the speed remains a constant.

5. Which among the following is not a parameter to determine the efficiency of the turbine?
a) Unit speed
b) Unit power
c) Unit volume
d) Unit discharge

View Answer

Answer: c [Reason:] Unit volume is not a parameter to determine the efficiency of the turbine. Power of a turbine is measured mechanically by adjusting the flow of fluid using the percentage variations in a sluice gate. It helps in determining the overall efficiency of the turbine.

6. Which among the following control the flow rate?
a) Valve
b) Pump
c) Head
d) Tank pipe

View Answer

Answer: a [Reason:] Flow rate of the tank is controlled by the valve. The actuation of individual valve closes. This corresponds to the set of nozzle thereby controlling the actual flow rate of the fluid passing through the valve.

7. The advantage of nozzle governing is that no regulating pressure is applied.
a) True
b) False

View Answer

Answer: a [Reason:] The advantage of nozzle governing is that no regulating pressure is applied. The actuation of individual valve closes the corresponding set of nozzle. Thus, controlling the flow rate.

8. The inlet passage of water entry is controlled by ________
a) Head race
b) Gate
c) Tail race
d) Pump

View Answer

Answer: b [Reason:] The inlet passage of water entry is controlled by the gate opening. The gate opening is an opening that sends only a percentage of fluid through the inlet passages for water to enter to the turbine.

9. When do we apply by pass governing?
a) When turbine is overloaded
b) When Unit speed decreases
c) When Unit power increases
d) When Unit pressure decreases

View Answer

Answer: a [Reason:] The main purpose of by pass governing is taken into full action when the turbine is overloaded for short durations. This happens occasionally in the working of the turbine. During this, a bypass valve is used.

10. When bypass valve is opened to _______
a) Increase Pressure
b) Increase Unit speed
c) Increase Unit power
d) Increase the amount of fresh steam

View Answer

Answer: d [Reason:] When a by pass valve is opened, a fresh steam is introduced into the turbine, thereby increasing the amount of fresh steam. The main purpose of by pass governing is taken into full action when the turbine is overloaded for short durations.

11. What is the unit of steam rate?
a) kg
b) kg/m
c) kg/kWh
d) N/m

View Answer

Answer: c [Reason:] The unit of stream is equal to kg/kWh. In the process of throttle governing, it is denoted by the symbol ‘a’. The variation of the steam consumption rate with the turbine load during governing is linear.

12. With the increase in load, Energy in the turbine ________
a) Decreases
b) Increases
c) Remains same
d) Independent

View Answer

Answer: a [Reason:] When there is an increase in the load, the energy in the turbine is drained off. Thus, to increase the energy, the by pass valve is opened to increase the amount of fresh steam entry. This increases the energy in the turbine.

13. Combination governing involves usage of two or more governing.
a) True
b) False

View Answer

Answer: a [Reason:] Yes, Combination governing involves usage of two or more governing. Most usage is the by pass and the nozzle governing as they tend to match the load on the turbine. Thus, increasing its efficiency.

14. When the mechanical speed of the shaft increases beyond 110 percent, we use _________
a) Throttle governing
b) Steam governing
c) Nozzle governing
d) Emergency governing

View Answer

Answer: d [Reason:] When the mechanical speed of the shaft increases beyond 110 percent, we use emergency governing. These governors come into action only when there are emergencies in the turbine.

15. When the balancing of the turbine is disturbed, we use ________
a) Throttle governing
b) Steam governing
c) Nozzle governing
d) Emergency governing

View Answer

Answer: d [Reason:] When the balancing of the turbine is disturbed, we use emergency governing. These governors come into action only when there are emergencies in the turbine.

Set 4

1. What is the water flow direction in the runner in a Francis turbine?
a) Axial and then tangential
b) Tangential and then axial
c) Radial and then axial
d) Axial and then radial

View Answer

Answer: c [Reason:] Francis turbine is radial flow reaction turbine. Though the water enters the turbine tangentially, it enters the runner radially inward and flows outward along the axis of the runner.

2. Which of the following is true in case of flow of water before it enters the runner of a Francis Turbine?
a) Available head is entirely converted to velocity head
b) Available head is entire converted to pressure head
c) Available head is neither converted to pressure head nor velocity head
d) Available head is partly converted to pressure head and partly to velocity head

View Answer

Answer: d [Reason:] Since Francis Turbine is a reaction turbine, part of the available head is converted to velocity head. It is not entirely converted to velocity head. The rest of the available head is converted into pressure head.

3. Why does the cross sectional area of the Spiral casing gradually decrease along the circumference of the Francis turbine from the entrance to the tip?
a) To ensure constant velocity of water during runner entry
b) To prevent loss of efficiency of the turbine due to impulsive forces caused by extra area
c) To prevent leakage from the turbine
d) To reduce material costs in order to make the turbine more economical

View Answer

Answer: a [Reason:] The primary purpose of the gradual decrease in area is so that the runner sees constant velocity of water at each point of entry. Absence of this may lead to inefficiency. The spiral casing is used to prevent leakage from the turbine but the gradual decrease in area is not for that reason.

4. Which of the following profiles are used for guide vanes to ensure smooth flow without separation?
a) Rectangular
b) Bent Rectangular
c) Elliptical
d) Aerofoil

View Answer

Answer: d [Reason:] Smooth flow and flow without separation (eddiless flow) can be ensured when the cross sectional profile of the guide vanes are aerofoil in nature. Aerofoil shape is used in airplane wings to ensure smooth flow too. Rectangular profiles are not effective in guiding the water into the runner. Elliptical profiles will cause more drag, finally ending up with turbine inefficiency.

5. In which of the following type of runners the velocity of whirl at inlet is greater than the blade velocity?
a) Such a case is practically impossible
b) Slow Runner
c) Medium Runner
d) Fast Runner

View Answer

Answer: b [Reason:] Considering the velocity diagram of Francis turbine at the inlet for a slow runner, we notice that the whirl velocity exceeds the blade velocity along the same direction. They are equal in case of a medium runner.

6. Which of the following runner types will have the highest vane angle at inlet (β1 value)?
a) Slow Runner
b) Medium Runner
c) Fast Runner
d) Vane angle is defined only for Kaplan Turbines and not Francis turbines

View Answer

Answer: c [Reason:] Considering the velocity diagram of Francis turbine at the inlet for a fast runner, vane angle is an obtuse angle. Whereas, it is right angle for medium runner and an acute angle for a slow runner.

7. In case of a Medium runner, tan (α1) CANNOT be given by (α1 = Guide vane angle at inlet)?
a) Vf1 / Vw1
b) Vr1 / Vw1
c) Vr1 / u1
d) Vw1 / u1

View Answer

Answer: d [Reason:] In medium runner, Vf1 = Vr1 & Vw1 = u1. Vw1 and u1 are along the same direction, hence that cannot be written as tan (α1).

8. In the velocity diagrams for Francis turbine, which of the following velocity directions is along the blade curvature?
a) Vr1
b) Vw1
c) V1
d) u1

View Answer

Answer: a [Reason:] Vr1 is the relative velocity of the water flow as seen from the blade. Thus, relative velocity is along the direction of the curvature of the blade.

9. In the figure shown below,which of the following angles replace the question mark?
hydraulic-machines-questions-answers-velocity-diagrams-q9
a) Guide vane angle at inlet
b) Blade angle at inlet
c) Vane angle at inlet
d) Blade angle at outlet

View Answer

Answer: a [Reason:] The angle between V1 and the blade velocity u1 is α1, which is the guide vane angle at the inlet.

10. In the figure shown below, which of the following type of runners has the blade curvature as shown in the above figure (The arrow denotes direction of blade motion)?
hydraulic-machines-questions-answers-velocity-diagram-q10
a) Information insufficient to determine
b) Slow Runner
c) Medium Runner
d) Fast Runner

View Answer

Answer: b [Reason:] Fast runners have forward curved blades, where slow runners have backward curved blades. The blades shown in the figure are backward curved blades of a runner, which are used for slow runners.

Set 5

1. Hydraulic turbines are classified based on ____________
a) Energy available at inlet of turbine
b) Direction of flow through vanes
c) Head at inlet of turbine
d) Energy available, Direction of flow, Head at inlet.

View Answer

Answer: d [Reason:] Hydraulic Turbines can be classified on any basis like energy supplied, direction of flow, and head at inlet.

2. Impulse turbine and reaction turbine are classified based on ?
a) Type of energy at inlet
b) Direction of flow through runner
c) Head at inlet of turbine
d) Specific speed of turbine

View Answer

Answer: a [Reason:] In impulse turbine, pressure energy firstly converts into kinetic energy but in reaction turbine pressure change of water is present only when it passes through the rotor of the turbine.

3. Tangential flow, axial flow, radial flow turbines are classified based on?
a) Type of energy at inlet
b) Direction of flow through runner
c) Head at inlet of turbine
d) Specific speed of turbine

View Answer

Answer: b [Reason:] Different types of flow of water classify turbines into tangential, axial, radial flow.

4. High head, low head and medium head turbines are classified based on
a) Type of energy at inlet
b) Direction of flow through runner
c) Head at inlet of turbine
d) Specific speed of turbine

View Answer

Answer: c [Reason:] Different heads of turbines classifies turbines based on their heads, namely Kaplan, Francis, Pelton.

5. Low specific speed, high specific speed and medium specific speed are classified based on
a) Type of energy at inlet
b) Direction of flow through runner
c) Head at inlet of turbine
d) Specific speed of turbine

View Answer

Answer: d [Reason:] Different specific speed of turbines classifies turbines based on their heads, namely Kaplan, Francis, Pelton.

6. If energy available at inlet of turbine is only kinetic energy then it is classified based on
a) Type of energy at inlet
b) Direction of flow through runner
c) Head at inlet of turbine
d) Specific speed of turbine

View Answer

Answer: a [Reason:] When there is energy such as kinetic energy at inlet, turbines is classified based on their energies at inlet. In this case, it is an impulse turbine.

7. If water flows in radial direction at inlet of runner and leaves axially at outlet then turbine is named as
a) Tangential flow turbine
b) Axial flow turbine
c) Radial flow turbine
d) Mixed flow turbine

View Answer

Answer: d [Reason:] In a mixed flow turbine, water enters in radial direction and exits axially.

8. Pelton turbine is operated under_________
a) Low head and high discharge
b) High head and low discharge
c) Medium head and high discharge
d) Medium head and medium discharge

View Answer

Answer: b [Reason:] Based on heads and discharges, turbines are classified into Pelton, Francis or Kaplan. Pelton has high head and low discharge.

9. Kaplan turbine is operated under __________
a) Low head and high discharge
b) High head and low discharge
c) Medium head and high discharge
d) Medium head and medium discharge

View Answer

Answer: a [Reason:] Based on heads and discharges, turbines are classified into Pelton, Francis or Kaplan. Kaplan has low head and high discharge.

10. Medium specific speed of turbine implies _____________
a) Pelton turbine
b) Kaplan turbine
c) Francis turbine
d) Propeller turbine

View Answer

Answer: c [Reason:] Francis turbine is a widely used turbine. It has a medium specific speed.

11. High specific speed of turbine implies that it is___________
a) Francis turbine
b) Propeller turbine
c) Pelton turbine
d) Kaplan turbine

View Answer

Answer: d [Reason:] Kaplan turbines have high specific speeds compared to Francis and Pelton turbines.