Modeling of the Hub Cavity Leakage Flows in Axial Compressors

Computational analyses are carried out to predict the effect of the hub leakage flow from the inner banded stator cavities on the overall performance of an axial high pressure compressor. The results of a full fidelity simulation model, which includes cavities, sealing and main flow, is compared with models without the hub leakage flow. The CFD prediction confirms a significant effect from the hub leakage on the performance of the multistage axial compressor. A simpler and faster CFD modeling technique is explored and discussed for the modeling of the effect of the hub cavity leakage. In this approach, costly details of the stator cavities are ignored. Transfer functions or correlations are derived from the 1.5 stage (IGV-Rotor1-Stator1) of a multistage compressor having inner banded stator cavity. These correlations are used as boundary conditions to the primary flow path of the compressor while carrying out the simplified CFD models for the complete 4 stage compressor model. A MINITAB study is conducted to understand the most influencing parameters and their interactions in deriving the correlations. Analyses are then carried out using the simplified model with the hub leakage boundary conditions derived from these correlations. The CFD results of the full fidelity simulation and the simplified models are compared in this paper.