Centrifugal Pumps Overview

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What type of energy is converted by hydraulic machines into pressure energy?

Thermal energy
Mechanical energy (correct)
Electrical energy
Chemical energy

In which direction does the flow occur in centrifugal pumps?

Axial
Radial inward
Radial outward (correct)
Tangential

What principle does a centrifugal pump operate on?

Steady-state flow
Turbulent flow
Laminar flow
Forced vortex flow (correct)

What part of a centrifugal pump is responsible for raising the pressure head of the liquid?

Impeller (A) Signup and view all the answers

Which part of a centrifugal pump consists of a series of backward curved vanes?

Impeller (B) Signup and view all the answers

To what is the impeller of a centrifugal pump connected?

The shaft of an electric motor (C) Signup and view all the answers

What is the main effect of cavitation on metallic surfaces?

Cavities are formed on the surfaces (D) Signup and view all the answers

What is one precaution that should be taken against cavitation?

Using materials like aluminium-bronze and stainless steel (D) Signup and view all the answers

How does cavitation affect the efficiency of a turbine?

The efficiency decreases (B) Signup and view all the answers

What does NPSH stand for in the context of pump industry?

Net Positive Suction Head (D) Signup and view all the answers

How is the Net Positive Suction Head (NPSH) calculated?

$\text{NPSH} = \text{Inlet pressure} - \text{Vapour pressure} + \text{Velocity head}$ (A) Signup and view all the answers

Why is it important for the available NPSH to be greater than the required NPSH in pump installations?

To prevent cavitation and have smooth pump operation (D) Signup and view all the answers

What is the purpose of the casing in a centrifugal pump?

To convert kinetic energy into pressure energy (D) Signup and view all the answers

What type of valve is typically fitted at the lower end of a suction pipe in a centrifugal pump system?

Foot valve (A) Signup and view all the answers

In a multistage centrifugal pump, what is the purpose of connecting impellers in series?

To produce a high head (D) Signup and view all the answers

What happens when the pressure of a flowing liquid falls below its vapour pressure?

Formation of vapour bubbles (B) Signup and view all the answers

How do cavitation bubbles affect metallic surfaces in pumps?

They cause pitting on the surfaces (C) Signup and view all the answers

What defines cavitation in pumps?

Formation and collapsing of vapour bubbles (A) Signup and view all the answers

What differentiates a multistage centrifugal pump for high heads from one for high discharge?

Connection of impellers (series vs parallel) (B) Signup and view all the answers

Why is a foot valve used in a suction pipe of a centrifugal pump system?

To prevent backflow of water from the pump (B) Signup and view all the answers

What occurs when more impellers are mounted on the same shaft in a centrifugal pump?

The pressure at the outlet increases (C) Signup and view all the answers

Energy conversion in hydraulic machines

Mechanical energy is converted into pressure energy by hydraulic machines.

Flow direction in centrifugal pumps

The flow in centrifugal pumps moves radially outwards from the center of the impeller.

Operating principle of centrifugal pumps

Centrifugal pumps work based on the principle of forced vortex flow, where the fluid is forced to rotate with the impeller.

Role of the impeller in a centrifugal pump

The impeller is the heart of a centrifugal pump, responsible for increasing the pressure head of the liquid.