Investigation of the Effect of Seal Clearance on the Performance Characteristics of a High Flow Coefficient Stage

Abstract During the design iterations for a centrifugal compressor, seal cavities are often omitted from computational fluid dynamics (CFD) simulations to streamline and expedite the design process, with parasitic loss models used to estimate the effects of seal clearances. However, for certain designs, the interaction between leakage flow and the primary flow can significantly influence stage performance, including the stall margin. This phenomenon is not well captured by conventional one-dimensional (1D) seal models. A high flow coefficient stage, consisting of an impeller with full and splitter blades, a vaneless diffuser, and a return channel, was tested with two distinct seal clearance sizes to assess their effect on the stage aerodynamic performance. The results showed a substantial impact of seal clearance on the stage's operating range. Complementary CFD simulations were conducted to further understand the interaction of the leakage flow from the seals with the primary flow. Additional effort was made to minimize the geometric and modeling fidelity of the simulations while still capturing the essential information with an aim to be able to use them during the design process. The discussion of the results presented in the study highlights the importance of considering seal clearance effects in the design phase and offers insights for incorporating such considerations to optimize stage performance and mitigate potential issues in future designs.