Abstract
In the present paper, the steady RANS (Reynolds-Averaged Navier-Stokes) simulations based on our independently developed CFD (Computational Fluid Dynamics) solver NUAA-Turbo 2.0, are carried out to investigate the shock wave/tip leakage vortex (SW/TLV) interaction in two representative transonic axial fan rotors, NASA Rotor 67 and NASA Rotor 37. The intent of this study is mainly to verify if an identification method derived from relevant theories is suitable for shock-induced vortex stability in the real engineering environment. As the additional findings, a universal tip vortex model is established and the characteristics of vortex breakdown or not are also summarized under different load levels. To ensure the prediction accuracy of all numerical methods selected in this research, detailed comparisons are made between computational and experimental results before flow analysis. The excellent agreement between the both indicates that the current code is capable of capturing the dominant secondary flow structures and aerodynamic phenomenon, especially the vortex system in tip region and SW/TLV interaction. It is found that three vortical structures such as tip leakage vortex (TLV), shock-induced vortex (SIV), tip separation vortex (TSV) in addition the tip leakage vortex-induced vortex (TLV-IV, which only occurs when the TLV strength increases to a certain extent) frequently exist near the blade tip and then abstracted as a tip vortex model. A stable TLV after passing through the passage shock is commonly characterized by tight rolling-up, slow deceleration and slight expansion. Conversely, the vortex behaves in a breakdown state. The final verification results show that the above two vortex states can be satisfactorily detected by the theoretical discriminant introduced in this work.
Highlights
The secondary flow structures with their related aerodynamic phenomena distributed in the tip region, such as various vortices and their interactions with passage shock, have significant influences on further improvement in total pressure ratio, adiabatic efficiency and stable operating range [1, 2] for a highly-loaded transonic axial compressor
-called “numerical stall” operating point of the steady simulation is determined by two criteria: one is that the variation of inlet mass flow rate is greater than 0.3% of the average of the maximum and minimum value in 1000 iterative steps
The steady RANS simulations based on NUAATurbo 2.0 solver, are performed to investigate the application of an identification method proposed by Zhang Hanxin and Deng [22] to analyzing the shock-induced vortex stability in two well-known transonic axial fan rotors, NASA Rotor 67 and NASA Rotor 37
Summary
The secondary flow structures with their related aerodynamic phenomena distributed in the tip region, such as various vortices and their interactions with passage shock, have significant influences on further improvement in total pressure ratio, adiabatic efficiency and stable operating range [1, 2] for a highly-loaded transonic axial compressor. Based on the results of their detailed measurements, Inoue and Kuroumaru [3] firstly proposed a vortex model outlining the basic structure of vortex system in a axial-flow rotating blade row, which includes a leakage vortex, scraping vortex, horseshoe vortex, trailing vortex, etc. Yu et al [4] utilized a more sophisticated measurement technique called SPIV (stereoscopic particle image velocimetry) to construct the three-dimensional complex flow structures near the blade tip, they are clearly depicted with schematic model incorporating the tip leakage vortex accompanied by its induced vortex, corner vortex, etc. The unstable PTLV was further classified as two parts [7], oscillating PTLV-A and shedding PTLV-B. They can only provide a limited guidance on understanding of typical vortices in a transonic axial compressor rotor due to lack of shock effect. Few researchers has payed attention to studying its vortex model
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