Experimental Study on the Effect of Blade Exit Angle on Centrifugal Pump Efficiency

Rotodynamic type pumps, particularly centrifugal pumps, enable lifting of liquid from a lower to higher level by developing dynamic pressure. The effect of the blade exit angle on centrifugal pump efficiency is a crucial aspect of pump design and operation as it has significant effects on flow dynamics, energy transfer, and pressure performance. So careful design and optimization of this parameter is important for substantial improvements in pump efficiency and operational effectiveness. The study focuses on adjusting the blade exit angles and analyzing their effects on the pump's hydraulic performance. Using pumps with varying blade exit angles, a number of tests were carried out under close observation of important performance metrics like head, flow rate, and overall efficiency. Impellers were designed using SolidWorks 2020, and fabricated using additive manufacturing of poly lactic acid to measure the performance of a centrifugal pump with different blade exit angles ranging from 40o to 90o. The experiments were carried out with a motor running at around 2990 rpm. The results showed that the efficiency of the centrifugal pump was significantly affected by the blade exit angle, with a maximum efficiency obtained at a blade exit angle of 40 degrees. As the blade exit angle decreases, the efficiency of the centrifugal pump increases. As the fluid flowed through the impeller, it gained kinetic energy and was directed towards the pump volume where the kinetic energy was converted into pressure energy. By decreasing the impeller blade exit angle, the fluid was directed more effectively towards the volume and there was less recirculation, resulting in an increased pump efficiency. However, decreasing the blade exit angle too much could also have negative effects on pump performance. It is also concluded that the metallic impeller has a better discharge rate and flow velocity than non-metallic impellers but is very close in terms of efficiency with the impeller of a similar angle. However, the cost of the impeller made by additive manufacturing of poly lactic acid is far lower than metallic impellers of the same parameters. The experimental study sheds light on how changing the blade exit angle of the impeller affects the efficiency of a centrifugal pump. Impellers with various exit angles were fabricated using additive manufacturing, their efficiencies were determined, and different parameters were analyzed to successfully conduct this experimental work.