An experimental study of the effect of the projection ratio and throat-aspect ratio on the efficiency and loss coefficient of a water jet pump

Abstract

This study focuses on the influence of dimensionless geometry parameters on the performance and loss coefficient of the throat and diffuser of the water jet pump apparatus. A water jet pump system was designed for a total of nine experimental cases with three different projection ratios and three throat-aspect ratios . The volumetric and pressure ratios - performance parameters are measured at a constant motive pressure and under varying backpressure. The efficiencies of the water jet pump in each configuration were assessed and compared. It was found that increasing 2 or 3 times of projection ratio degrades efficiency about 2% to 5.5%, respectively. Higher projection ratio (   > 1) expands the water jet diameter, which clogs the secondary flow. Hence, the changes in  > 3 may have a significant impact on efficiency degradation. Shorter may cause the loss of kinetic energy in the diffuser, while longer  reduces momentum transfer on the secondary flow. Moreover, the changes in  and  influence friction loss coefficient in the throat and diffuser section, and it reduces with increasing of volumetric ratio. It can be concluded that the appropriate value of projection ratio and throat-aspect ratio plays a role in the kinetic energy dissipation. It is also responsible for the location friction process, at a different volumetric ratio. However, the experimental results denoted the best efficiency and loss coefficient was achieved at a low projection ratio ( = 1) and small throat-aspect ratios (  = 5). The best efficiency of the study was about 23.37%.