Fluid Machines MCQ

These 25 MCQs cover a range of topics within Fluid Machines, including types of pumps and turbines, their operating principles, characteristics, and applications. They are designed to test knowledge in both theoretical and practical contexts in the field of Mechanical Engineering.

1. What is a centrifugal pump?

a) A pump that increases pressure by using a rotating impeller to add energy to the fluid
b) A pump that uses reciprocating motion to move fluid
c) A pump that relies solely on gravitational force
d) A pump used exclusively for compressing gases

Answer:

a) A pump that increases pressure by using a rotating impeller to add energy to the fluid

Explanation:

A centrifugal pump is a type of pump that uses a rotating impeller to impart kinetic energy to the fluid, which is then converted into pressure energy, thus increasing the fluid's pressure.

2. What is the primary function of a hydraulic turbine?

a) To increase the pressure of a fluid
b) To convert hydraulic energy into mechanical energy
c) To compress a fluid
d) To transfer fluid from one location to another

Answer:

b) To convert hydraulic energy into mechanical energy

Explanation:

A hydraulic turbine is a fluid machine that converts hydraulic energy (from water or other fluids) into mechanical energy, which is often used to drive an electric generator.

3. What characterizes a positive displacement pump?

a) The flow rate depends on the pump speed
b) The flow rate is independent of the pressure
c) The pump imparts kinetic energy to the fluid
d) The pump uses centrifugal force to move fluid

Answer:

b) The flow rate is independent of the pressure

Explanation:

In positive displacement pumps, a fixed amount of fluid is trapped and forced through the pump, making the flow rate largely independent of the discharge pressure. These pumps are characterized by their ability to provide a consistent flow rate.

4. What is cavitation in fluid machines?

a) The formation and collapse of vapor bubbles in a fluid
b) The increase in fluid velocity
c) The decrease in fluid pressure
d) The creation of a vacuum within a pump

Answer:

a) The formation and collapse of vapor bubbles in a fluid

Explanation:

Cavitation is a phenomenon where vapor bubbles form in a fluid due to local drops in pressure and subsequently collapse. It can cause damage to fluid machinery, such as pumps and turbines.

5. What is the principle of operation of a Pelton wheel?

a) Reaction force from fluid jet
b) Centrifugal force
c) Fluid pressure on blades
d) Impulse force from fluid jet

Answer:

d) Impulse force from fluid jet

Explanation:

A Pelton wheel operates on the impulse principle. High-velocity jets of water strike the buckets on the wheel's perimeter, and the impulse force of the jet transfers energy to the wheel, causing it to rotate.

6. What is the primary difference between axial and radial flow pumps?

a) The direction of fluid flow relative to the impeller
b) The type of fluid they can pump
c) The speed at which they operate
d) The pressure head they produce

Answer:

a) The direction of fluid flow relative to the impeller

Explanation:

The key difference between axial and radial flow pumps is the direction of fluid flow in relation to the impeller. In axial flow pumps, the fluid flows parallel to the impeller axis, while in radial flow pumps, the fluid flows perpendicular to the axis.

7. What is a Francis turbine?

a) An impulse turbine
b) A reaction turbine
c) A turbine used only in wind power generation
d) A turbine used only for pumping water

Answer:

b) A reaction turbine

Explanation:

The Francis turbine is a type of reaction turbine, commonly used in hydroelectric power plants. It combines radial and axial flow concepts and operates under a wide range of flow conditions.

8. In fluid machines, what is meant by 'head'?

a) The top part of a machine
b) The energy per unit weight of fluid
c) The pressure of the fluid
d) The velocity of the fluid

Answer:

b) The energy per unit weight of fluid

Explanation:

In fluid mechanics, 'head' refers to the energy per unit weight of fluid. It can be represented in terms of potential, kinetic, and pressure energy and is a useful concept in analyzing fluid flow and machine performance.

9. What is the main purpose of a gear pump?

a) To increase the pressure of gases
b) To pump high-viscosity fluids
c) To generate electrical power
d) To measure fluid flow

Answer:

b) To pump high-viscosity fluids

Explanation:

Gear pumps are a type of positive displacement pump ideal for pumping high-viscosity fluids. They operate by meshing gears to pump fluid by displacement.

10. What type of pump is commonly used for water supply in buildings?

a) Centrifugal pump
b) Gear pump
c) Piston pump
d) Diaphragm pump

Answer:

a) Centrifugal pump

Explanation:

Centrifugal pumps are commonly used for water supply in buildings due to their suitability for pumping low-viscosity fluids like water and their ability to provide a steady flow at variable pressures.

11. What is the primary advantage of a screw pump?

a) High flow rate
b) Ability to pump high-viscosity fluids
c) Low maintenance
d) High pressure generation

Answer:

b) Ability to pump high-viscosity fluids

Explanation:

Screw pumps are particularly advantageous for pumping high-viscosity fluids. Their design allows for efficient transport of thicker fluids, which might pose a challenge for other pump types.

12. In a Kaplan turbine, what feature allows it to operate efficiently at various flow rates?

a) Variable speed operation
b) Adjustable blades
c) High-speed rotation
d) Fixed geometry

Answer:

b) Adjustable blades

Explanation:

The Kaplan turbine features adjustable blades, allowing it to operate efficiently across a range of flow rates. The ability to adjust the blade angle helps optimize performance under varying operating conditions.

13. What is the primary function of a draft tube in a turbine?

a) To control the flow rate
b) To convert kinetic energy of water into pressure energy
c) To supply water to the turbine
d) To cool the turbine

Answer:

b) To convert kinetic energy of water into pressure energy

Explanation:

A draft tube in a turbine is used to convert the kinetic energy of water leaving the turbine into pressure energy. This improves the efficiency of the turbine by recovering energy from the fluid leaving the turbine.

14. How does a diaphragm pump operate?

a) Using a rotating impeller
b) Using a reciprocating diaphragm
c) Using centrifugal force
d) Using a meshing gear system

Answer:

b) Using a reciprocating diaphragm

Explanation:

A diaphragm pump operates using a reciprocating diaphragm which expands and contracts, creating a variable-volume chamber. As the diaphragm moves, it draws fluid in and then expels it, providing a pumping action.

15. What distinguishes a submersible pump from other types of pumps?

a) Its ability to operate underwater
b) Its use of centrifugal force
c) Its high-pressure output
d) Its low-speed operation

Answer:

a) Its ability to operate underwater

Explanation:

A submersible pump is designed to operate while submerged underwater. It is completely sealed and waterproof, making it suitable for pumping liquids from within wells, tanks, or other submerged locations.

16. What is a vortex pump?

a) A pump that creates a vortex to move fluid
b) A pump that uses centrifugal force to increase pressure
c) A pump designed for high-viscosity fluids
d) A pump used in hydraulic turbines

Answer:

a) A pump that creates a vortex to move fluid

Explanation:

A vortex pump operates by creating a vortex with its impeller, allowing solids and fibrous materials to pass through without clogging. It is ideal for applications requiring the handling of challenging fluids.

17. In fluid machinery, what is 'slip' in a positive displacement pump?

a) The backward flow of fluid due to pressure differences
b) The reduction in pump speed
c) The wear of mechanical parts over time
d) The leakage of fluid through the pump seals

Answer:

a) The backward flow of fluid due to pressure differences

Explanation:

'Slip' in a positive displacement pump refers to the backward flow of fluid that occurs when the discharge pressure is higher than the suction pressure, leading to a reduction in the actual flow rate compared to the theoretical flow rate.

18. What is the primary use of an axial flow pump?

a) Pumping high-viscosity fluids
b) Generating high pressures
c) Moving large volumes of fluid at low pressure
d) Pumping abrasive fluids

Answer:

c) Moving large volumes of fluid at low pressure

Explanation:

Axial flow pumps are used for moving large volumes of fluid at low pressure. They are characterized by their propeller-like impeller and are commonly used in applications such as flood control and irrigation.

19. What is the significance of the NPSH (Net Positive Suction Head) in pump operation?

a) It determines the maximum depth from which a pump can draw fluid
b) It indicates the efficiency of the pump
c) It is a measure to prevent cavitation
d) It represents the power consumption of the pump

Answer:

c) It is a measure to prevent cavitation

Explanation:

NPSH is a critical factor in preventing cavitation in pumps. It represents the minimum pressure required at the suction port of the pump to keep the fluid from boiling or forming vapor bubbles.

20. What is the function of a jet pump?

a) To compress gases
b) To increase the velocity of fluids
c) To mix two different fluids
d) To use a high-velocity jet to entrain and move another fluid

Answer:

d) To use a high-velocity jet to entrain and move another fluid

Explanation:

A jet pump uses a high-velocity jet (usually of the same fluid) to entrain and move another fluid. It operates on the principle of fluid dynamics, where a high-speed jet creates a low-pressure area that draws in and propels the surrounding fluid.

21. What is the primary characteristic of a mixed-flow pump?

a) It operates only in a horizontal position
b) The fluid flows radially and axially through the pump
c) It is used exclusively for low-viscosity fluids
d) It generates high pressures at low speeds

Answer:

b) The fluid flows radially and axially through the pump

Explanation:

A mixed-flow pump is characterized by the combined radial and axial flow of fluid through the pump. This design allows the pump to handle a wide range of flow rates and pressures.

22. In fluid machinery, what is meant by 'dynamic head'?

a) The height at which a pump can raise fluid
b) The velocity head plus the pressure head of a fluid
c) The maximum pressure a pump can generate
d) The rotational speed of a turbine

Answer:

b) The velocity head plus the pressure head of a fluid

Explanation:

Dynamic head in fluid machinery refers to the total head consisting of both velocity head (related to the fluid's velocity) and pressure head (related to the fluid's pressure). It is a measure of the energy content of the fluid.

23. What is an impeller in a centrifugal pump?

a) A valve that controls the flow rate
b) The rotating component that imparts energy to the fluid
c) A static component that reduces fluid velocity
d) A filter that cleans the fluid

Answer:

b) The rotating component that imparts energy to the fluid

Explanation:

The impeller is the rotating part of a centrifugal pump that transfers energy from the motor to the fluid. It accelerates the fluid outward from the center of rotation, thereby increasing the fluid's pressure and velocity.

24. What is the primary purpose of a sump pump?

a) To circulate fluid in a closed system
b) To increase the pressure of a fluid
c) To remove accumulated water from a sump pit or basement
d) To filter impurities from water

Answer:

c) To remove accumulated water from a sump pit or basement

Explanation:

A sump pump is used to remove water that has accumulated in a sump pit or basement, typically in homes or buildings where basement flooding is a concern. It pumps out the water to prevent damage and maintain a dry area.

25. What is the operating principle of a gear pump?

a) Centrifugal force
b) Reciprocating motion
c) Meshing of gears to trap and move fluid
d) High-velocity fluid jet

Answer:

c) Meshing of gears to trap and move fluid

Explanation:

A gear pump operates on the principle of using meshing gears to trap fluid between the teeth and the pump casing, and then transport it around the circumference of the gear to the pump outlet. This mechanism makes gear pumps suitable for handling viscous fluids.

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