NUMERICAL STUDY OF LOW AREA RATIO JET PUMPS

Jet pumps with low area ratio are used to achieve a higher flow amplification in specific applications; however, numerical analyses of these type of jet pumps are scarcely reported in the literature. In this study, three different low area ratio jet pumps were selected to compare numerical predictions with experimental results. Performance curve obtained using standard k-ω turbulent model significantly underpredicts the performance at all flow ratio, while that obtained using standard k-ε turbulent model significantly overpredicts the performance at flow ratios higher than 3. When the performance curves obtained using the shear stress transport k-ω turbulence model were compared with the experimental results, it was found that the model agrees well at low to moderate flow ratios and shows marginal deviation at higher flow ratios. By altering the standard model coefficient σ<sub>ω1</sub> to 0.4 from its standard value of 0.5, the numerical model predictions were found to improve at higher flow ratios. It was observed that changing the model coefficient σ<sub>ω1</sub> affects the turbulent viscosity profile in the pressure recovery region, thereby improving the pressure profile prediction. For the specific application of miniature size low area ratio jet pump designed for flow ratio of 4, effficiency is found to increase to 20% from 18% with increase in operating temperature from room temperature to 340°C. Effect of the diffuser angle was also analyzed and the design was optimized to improve pressure recovery and increase efficiency to 22% by using diffuser angle of 3.7°.