الفهرس 
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Abstract
Centrifugal pumps can be considered the most used machinery in any industrial facility. Raising the efficiency of centrifugal pumps was the target for many developers through the last decades. The developing process took place by reducing impeller weight in order to reduce mechanical stresses and enable using centrifugal pumps at high operating revolutions. As a result, depending on semi-open impellers has become a good choice for high-speed applications as the weight is reduced. Also, extending the range of operating fluids that the pump can handle as semi open impeller is much more appropriate for viscous fluids. Because Semi-open impellers are usually used with liquids or products that have solids. Efficiency reduction is a common problem with semi-open impellers, but the ability to pass solids and high viscous fluid is an important trade-off. As a result, several studies were held to increase the performance and efficiency of centrifugal pumps by studying the effect of some design parameters one of these was side clearance of semi-open impeller and its effect on pump performance. The current thesis is dedicated to emphasizing more details about the effect of centrifugal pump side clearance on semi-open centrifugal pump efficiency at different flow rates by using water and liquid fuel oil (C19H30) as operating fluid and the 3-D flow throughout the centrifugal pump volute was simulated to study the flow pattern. Also, the effect of changing exit blade width of impeller on pump performance, blade load, slip factor was discussed by numerical results and flow simulation throughout the pump. Using Ansys Fluent, the finite volume method was used for solving the governing equations, and the high-resolution algorithm has been employed to solve the equations. In addition, the Realizable ’’ k _ ԑ ’’ model was used as a turbulence model in the simulation. In steady state, this simulation is defined by the technique of the multi-reference frame, in which the impeller is located in the rotating frame and volute is located in the fixed frame and are connected to each other by the ”frozen rotor”. Post processing study was held to reveal the behavior of flow through the pump by studying pressure distribution, velocity vector, and velocity streamlines. Through these studies the effect of changing the impeller side clearance was clearly emphasized and noticeable. The numerical solution was compared with experimental results to validate the solution. The results of CFD affirm a remarkable agreement with the acquired experimental data. The negative effect of changing the pump side clearance was emphasized. Also, the effect of changing the viscosity of operating fluid was explained.