Numerical investigation of the effect of geometry on the performance of a jet pump

Abstract

Jet pump plays a major role in transporting materials. The efficiency of jet pump is poor and it usually has a sharp peak in the efficiency–discharge ratio curve. These are undesirable. In the past, experiments were conducted to understand the functioning of each component of the jet pump. The experimental method is reliable but performing parametric studies through experiments is problematic as it is difficult to systematically vary one parameter while keeping other parameters unchanged. In this study, numerical simulations were carried out to determine the effects of area ratio, setback distance, mixing tube length, and shape of the driving nozzle on the performance of the jet pump. It was seen that major losses arise in the jet pump primarily due to an improper mixing of primary and secondary fluids and because of the formation of recirculation near the mixing tube entrance. Based on these studies, a normalized mixing tube length (L _m/D _m) of 7–9, area ratio of 0.28, setback ratio of 1.54–2.02, and a modified shape of the outer wall of driving nozzle are recommended. Such geometry offers maximum efficiency of 40 per cent, a relatively flat efficiency curve, and a lower total pressure drop. This last effect is important from the energy requirement to drive the centrifugal pump.