Role of Hub-Corner-Separation on Rotating Stall in an Axial Compressor

Abstract

A 3D computation was conducted to investigate the role of hub-corner-separation on the rotating stall in a low-speed axial compressor. It is generally known that tip leakage flow plays an important role in stall inception. However, not much attention has been paid to the role of hub-corner-separation on the rotating stall although it is a common flow feature in an axial compressor operating near the stall point. During our time-accurate unsteady simulation, we suspected that hub-corner-separation might be a trigger for the rotating stall. After an asymmetric disturbance is initiated at hub-corner-separation, this disturbance is transferred to the tip leakage flows and grows to become an attached stall cell, which adheres to the blade passage and rotates at the same speed as the rotor. When the attached stall cell reaches a critical size, it moves along the blade row and becomes the rotating stall. The rotating speed of the stall cell decreases to 79% of the rotor so the stall cell rotates in the opposite direction to the rotor in the rotating frame.

Large-eddy simulation of 3-D corner separation in a linear compressor cascade

“…However, the compressor blade loading is extremely limited by many 3-D flow losses in compressors, such as boundary layers, flow separations, leakages, and shocks. 1,2 During the last decades, the impact of corner separation in reducing the blade loading has been emphasized by many researchers, such as Dong et al, 3 Schulz et al, 4 Yocum and O'Brien, 5 Hah and Loellbach, 6 Gbadebo et al, 7 Lei, 8 Choi et al, 9 and Lewin et al 10 A corner separation forms at the junction between an end-wall (hub or casing) and a blade suction surface. It is closed off by limiting streamlines on walls, and a separation vortex is formed on the end-wall near the trailing edge, as sketched in Fig.…”

Effects of Low Reynolds Number on Loss Characteristics in Transonic Axial Compressor

“…16) This flow solver has been pre-validated by a series of calculations in a transonic axial compressor, a subsonic axial compressor and a subsonic axial turbine, and has also been used to simulate rotating stall in a subsonic rotor. 13,[17][18][19] TFlow uses compressible RANS (Reynolds Averaged Navier-Stokes) equations as the governing equations, discretized in space by the finite volume method. An upwind TVD (Total Variational Diminishing) scheme based on Roe's flux difference splitting method was used to discretize inviscid flux terms and the MUSCL (Monotone Upstream Centered Scheme for Conservation Law) technique was used to discretize viscous flux terms.…”

Effects of Inlet Boundary Layer Thickness on Characteristics of Rotating Stall in Subsonic Axial Compressor

“…Second, the attached stall is observed in stall inception regardless of the inlet boundary layer thickness. This stall inception via an attached stall cell has been already reported by Choi et al 19) using the rotating stall simulation with four passages in the same test case.…”