When impeller rotates it adds a rotating motion to the adjacent fluid and as a result K.E and Pressure in the fluid increases and a negative pressure is developed in the suction side of the impeller. So water-fluid flows continuously through the impeller. But when the pipe is filled with air, the impeller rotates but the pressure difference is negligible as a result no water flows through the pump. Thats why priming is done.
1. Why the Centrifugal Pump is called High Discharge pump?
Ans. Centrifugal pump is a kinetic device. The centrifugal pump uses the centrifugal force to push out the fluid. So the liquid entering the pump receives kinetic energy from the rotating impeller. The centrifugal action of the impeller accelerates the liquid to a high velocity, transferring mechanical (rotational) energy to the liquid. So it discharges the liquid in high rate. It is given in the following formulae:
Centrifugal force F= (M*V2)-R.
Hello friends, science lovers and fellow mechanical engineers, In todays article I will discuss about some important but most basic questions about mechanical engineering. After all this site is all about basic mechanical engineering, right?? 😉 Its actually a small endeavor for the newly graduated engineers. I know it is arduous to get a good job just after having your BSc. degree. I am intending to write a series of articles regarding the mechanical engineering interview questions. So lets move on. 🙂
Mechanical Engineering – Hydraulic Machines
In this section you can learn and practice Mechanical Engineering Questions based on "Hydraulic Machines" and improve your skills in order to face the interview, competitive examination and various entrance test (CAT, GATE, GRE, MAT, Bank Exam, Railway Exam etc.) with full confidence.
How do you calculate the power of a centrifugal pump?
Power is required by every machine, in order to move and work. Similarly, the centrifugal pump also requires power to move and increase the pressure of a fluid. This power depends on a number of factors, including the pump and motor efficiency, the differential pressure and the fluid density, as well as the viscosity and flow rate.
1. What is efficiency?
An important part of the volute is the tongue, or cutwater. Its purpose is to maintain flow into the throat while minimizing recirculation back into the case. The optimum clearance between the tongue and the impeller periphery is the smallest distance that does not give rise to pressure pulsations during vane tip passing. A well-designed pump will have a full-size impeller that meets these clearance criteria. When an impeller is trimmed, this distance increases and allows more fluid to recirculate back into the case. As recirculation increases, hydraulic efficiency decreases.
Explanation: The power consumption varies as the cube of the peripheral speed or propeller diameter for a given rotational speed. Hydraulic pump capacity could be calculated as. q = 0.26 A s – t where q = pump output capacity gpm. A = area of cylinder in square inches. s = piston stroke in inches. t = required time for full stroke.
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