Numerical study on effect of seal leakage on performance of centrifugal impeller with low flow coefficient

The analysis with the three-dimensional viscous computational fluid dynamics (CFD) was carried out for a carbon dioxide centrifugal impeller with a low flow coefficient. The results show that the impeller isentropic efficiency decreases by 8.1 percent at the design mass flow rate with the consideration of the seal leakage compared with that without the consideration of the seal leakage. It is suggested that the seal leakage should be considered in the numerical simulation to predict accurately the performance and the flow in impellers with a low flow coefficient. In order to explore the effect of the seal leakage on the performance of the impeller, the seal clearance was changed and the numerical simulation was performed on the centrifugal impeller with different seal configurations at the low and high mass flow rates as well as the design mass flow rate, respectively. Our results indicate that, at a given mass flow rate, the seal leakage loss coefficient increases and the impeller isentropic efficiency decreases almost linearly with the increase in the seal clearance.