21 Questions
What type of energy is converted by hydraulic machines into pressure energy?
Mechanical energy
In which direction does the flow occur in centrifugal pumps?
Radial outward
What principle does a centrifugal pump operate on?
Forced vortex flow
What part of a centrifugal pump is responsible for raising the pressure head of the liquid?
Impeller
Which part of a centrifugal pump consists of a series of backward curved vanes?
Impeller
To what is the impeller of a centrifugal pump connected?
The shaft of an electric motor
What is the main effect of cavitation on metallic surfaces?
Cavities are formed on the surfaces
What is one precaution that should be taken against cavitation?
Using materials like aluminium-bronze and stainless steel
How does cavitation affect the efficiency of a turbine?
The efficiency decreases
What does NPSH stand for in the context of pump industry?
Net Positive Suction Head
How is the Net Positive Suction Head (NPSH) calculated?
$\text{NPSH} = \text{Inlet pressure} - \text{Vapour pressure} + \text{Velocity head}$
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
What is the purpose of the casing in a centrifugal pump?
To convert kinetic energy into pressure energy
What type of valve is typically fitted at the lower end of a suction pipe in a centrifugal pump system?
Foot valve
In a multistage centrifugal pump, what is the purpose of connecting impellers in series?
To produce a high head
What happens when the pressure of a flowing liquid falls below its vapour pressure?
Formation of vapour bubbles
How do cavitation bubbles affect metallic surfaces in pumps?
They cause pitting on the surfaces
What defines cavitation in pumps?
Formation and collapsing of vapour bubbles
What differentiates a multistage centrifugal pump for high heads from one for high discharge?
Connection of impellers (series vs parallel)
Why is a foot valve used in a suction pipe of a centrifugal pump system?
To prevent backflow of water from the pump
What occurs when more impellers are mounted on the same shaft in a centrifugal pump?
The pressure at the outlet increases
This quiz covers the introduction to centrifugal pumps, which are hydraulic machines that convert mechanical energy into pressure energy by means of centrifugal force acting on the fluid. Learn about the working principles and comparison with radial flow reaction turbines.
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