Aerodynamics of compressor casing treatment Part II: A Quasi-steady model for casing treatment flows

In order to predict more efficiently the flow in compressor with casing treatment in a integrated manner as well as to facilitate an integrated tool for the design optimization of casing treatment, a mathematical-physical quasi-steady model for the slot-type casing treatment flows were developed based on the understanding of the unsteady flow physics of the rotor-casing treatment combination. The new model has been coded up and validated against a slot-type casing treatment which is examined by experiment and unsteady RANS calculations in the companion paper Part I. The calculations using this model show an encouraging agreement with those obtained from measurements and unsteady RANS calculations, indicating the essence of the flow physics has been captured by the model. Although the model is based on the slot type casing treatment, the principle behind it is rather wide-catching and extensions to other types of casing/hub treatment can also be realized. Since the model equations for the casing treatment flow are solved in the same way as that for conventional steady flows, considerable amount of computer resources can be saved. This enables the model applicable in the current steady RANS-based design system, and overall assessments of a compressor with an applied casing treatment are readily achievable.