OBJECTIVE

1. To obtain and analyse the performance characteristics of a centrifugal pump operating at a given impeller speed.

INTRODUCTION

A centrifugal pump is a rotor dynamic pump that uses a rotating impeller to increase the velocity of a fluid. Centrifugal pumps are commonly used to move liquids through a piping system. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward into a diffuser or volute chamber, from where it exits into the downstream piping system. Centrifugal pumps are used for large discharge through smaller heads.

A centrifugal pump works by the conversion of the rotational kinetic energy, typically from an electric motor or turbine, to an increased static fluid pressure. This action is described by Bernoullis principle. The rotation of the pump impeller imparts kinetic energy to the fluid as it is drawn in from the impeller eye and is forced outward through the impeller vanes to the periphery. As the fluid exits the impeller, the fluid kinetic energy (velocity) is then converted to (static) pressure due to the change in area the fluid experiences in the volute section. Typically the volute shape of the pump casing (increasing in volume), or the diffuser vanes (which serve to slow the fluid, converting to kinetic energy in to flow work) are responsible for the energy conversion. The energy conversion results in an increased pressure on the downstream side ofthe pump, causing flow.

Cavitations is the problems in the pump. It is defined as the phenomenon of formation ofvapour bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapour pressure. Cavitation is usually divided into two classes of behaviour: inertial (or transient) cavitation and non-inertial cavitation. Inertial cavitation is the process where a void or bubble in a liquid rapidly collapses, producing a shock wave. Such cavitation often occurs in pumps, propellers, impellers, and in the vascular tissues of plants. Non-inertial cavitation is the processing which a bubble in a fluid is forced to oscillate in size or shape due to some form of energy input, such as an acoustic field. Such cavitation is often employed in ultrasonic cleaning baths and can also be observed in pumps, propellers etc.

Due to the general complexity of flow through a centrifugal pump, the actual performance of the pump cannot be predicted on a completely theoretical basis .Actual pump performance is determine experimentally through test on the pump and the result are presented as pump performance curve .Performance characteristics for a given pump geometry and operating speed are usually given in the form of plots of head rise, efficiency and power versus flow rate (commonly referred as capacity).This information is most helpful to the engineer responsible for incorporating pump into a given pipe flow system

THEORY

The centrifugal pump belongs to a family of turbo machines which is distinguished as an energy absorbing device. The performance characteristics of a typical centrifugal pump are governed mainly by the following parameters: pump head H, water horsepower, brake horsepower bhp, efficiency , and flow rate Q for a given impeller speed N.The pump head H is termed as the amount of energy measured in head added by the pump to the fluid. In this experiment, the observed data used to calculate this parameter is given asH= And are the delivery and intake pressure of the pump, respectively.The water horsepower is power received by the fluid from the pump and is given by the following relation:

The brake horsepower bhp to the pump can be regarded as the shaft power produced by the electric motor. An appropriate relation used for calculating this parameter using the observed data is given as:Bhp=T=T(2N)T=torque, =angular speed, N=pump rotational speed in revolution per second (rps).The pump overall efficiency for a given impeller size and speed is defined as : =

DISCUSSION(AMIRUL ASHRAF BIN HASSAN, 2013767009)

The experiment is conducted to obtain and analyse centrifugal pump performance characteristic operating at a given impeller speed. Efficiency is the benchmark of our experimental and theoretical result. From the result obtain we proceed to the graph section via calculation equation given. For a pump performance, we plot the graph of the Pump Head (H) versus flow rate Q (m3/s), the graph show that the head pump gradually decreased with the increased of flow rate. Next we plotted the graph for Brake Horse Power (BHP) versus Q (m3/s), here the line clearly show that with the increase of the flow rate, the brake horsepower also increased. Lastly, we plotted the graph for efficiency () versus flow rate Q (m3/s), the efficiency of the pump increase as the flow rate increase, with the max efficiency 62.76% at a 0.00133 m3/s. The average value for the pump head (H) and water horsepower are 16.37 m and 136.70 W. The average brake horsepower, (BHP) is 341.36 W and average efficiency () is 39.53%There are few functions of valve in a centrifugal pump, valve off and valve on. Valve off function are to avoid the back pressure and the valve on function are to let the water flow.There are slightly difference between the theoretical value and experiment value. The problem may come from the error during the experiment. One of the errors might come during the calculation proses, also known as calculation error. Other error that may occur are from cavitations where there isa non-uniform flow which cause the pressure gradient to shift, this is comment in pump.

CONCLUSION(AMIRUL ASHRAF BIN HASSAN, 2013767009)

As a conclusion, the objective of this experiment to obtain and analyse the performance characteristics of a centrifugal pump operating at a given impeller speed are achieve with the flying colour. The conclusion that we are made; the increasing of the flow rate Q will affect the pump head (H), Brake Horse Power (BHP) and efficiency () of the pump. The theoretical value and experimental value are slightly difference because of unavoidable factor such as the condition of the apparatus where the apparatus are not in a good workingcondition and the error that might come during and after the experiment.