Session: 14-02 Compressor Cavities 2

Paper Number: 124027

124027 - Numerical Investigation of Flow Structure and Pressure Drop Prediction for Radial Inflow Between Co-Rotating Discs With Negative Effective Inlet Swirl Ratio 

This paper presents a numerical simulation of the flow structure of radial inflow between co-rotating discs with negative c_eff (inlet effective swirl ratio) which may occur in a vortex reducer equipped with deswirl nozzles. Based on the knowledge gained from the flow structure, flow partitioning was conducted, and the turbulent boundary layer integral equations were employed to predict the radial distributions of swirl ratio and pressure throughout the cavity.

The two-dimensional axisymmetric computational domain was chosen, and the CFD model was thoroughly tested against experimental results in the open literature. CFD results indicate that the flow structure of radial inflow between co-rotating discs with negative c_eff can be divided into a source region, a sink layer, Ekman layers on each disc, and an internal core region between Ekman layers. This is similar to the phenomenon of radial inflow between co-rotating discs with 0<c_eff<1. In a stationary coordinate system, the absolute tangential velocity of the fluid entering the cavity with negative c_eff is greater than that of the blended fluid in the source region. Hence, it will exert a radial outward motion owing to centrifugal force, resulting in a stagnation point on the periphery. This is distinct from the cavity with 0<c_eff<1, wherein the flow passing through the source region, whose swirl ratio is approximately unity, is entrained into the Ekman layers, resulting in a stagnation point on the disc. It is noteworthy to mention that, when the turbulence parameter λ_T is fixed, the cavity exhibits an asymmetric flow structure as the negative c_eff approaches zero, probably due to the Coanda effect.

Based on flow structure partitioning, in the source region and core region, inviscid equations are employed, while in the Ekman layers, boundary layer equations are employed. Furthermore, velocity profiles and wall shear stress assumptions based on the von Karman model for free discs are employed. By solving the boundary layer equations in integral form, it is possible to obtain the radial distribution of swirl ratio and pressure in the cavity. The results are in good agreement with CFD and experimental data published in the open literature. The above flow structure partitioning and integral method neglects the asymmetric flow structure when the negative c_eff approaches zero, as the pressure drop inside the disc cavity tends to zero at the same time the deviation of the calculation results will not affect practical applications.

Presenting Author: Xv Yang School of Energy and Power Engineering, Beihang University

Presenting Author Biography: Yang Xv, graduate student from School of Energy and Power Engineering, Beihang University, Beijing, China, since 2019. He is from the group of Aeroengine Complex Systems Safety and Airworthiness. His research interests include flow in vortex reducer and transient performance of air system.

Authors:

Xu Yang School of Energy and Power Engineering, Beihang University
Shuiting Ding Research Institute of Aero-Engine, Beihang University
Peng Liu Research Institute of Aero-Engine, Beihang University
Yu Zhao Research Institute of Aero-Engine, Beihang University
Tian Qiu Research Institute of Aero-Engine, Beihang University