Evaluation of Higher-Order Terms in the Throughflow Approximation Using 3D Navier-Stokes Computations of a Transonic Compressor Rotor

Abstract

Two three-dimensional Reynolds-averaged Navier-Stokes solutions of the Nasa 67 transonic compressor rotor with tip clearance, computed at near-peak efficiency and near-stall flow conditions, have been circumferentially averaged in order to evaluate the circumferential spatial fluctuation terms such as u′u′, u′v′, u′w′, etc. The three-dimensional distribution of these fluctuations is presented and physically interpreted for the two flow conditions. Then, the meridional distributions of the tangential average of each of these fluctuation terms, the so-called perturbation stresses, are described and interpreted for the two flow conditions. A meridional throughflow computation for which all stresses were included has been performed for the near-peak efficiency flow condition using a time-marching finite-volume solver. The calculation proved to be in good agreement with the tangentially averaged 3D solution. Moreover, the relative importance of the perturbation and viscous stresses has been investigated. The influence of the viscous stresses on the meridional flow was not found important whereas the perturbation stresses were identified as significant contributors to the blade passage losses and to the spanwise mixing phenomenon. Furthermore, the relative effects of each perturbation term on the meridional flow prediction have been investigated for the near-peak efficiency case. The u′w′~, v′w′~, u′v′~ and u′u′~ stresses proved to exert a significant influence on the prediction of blade design key parameters such as flow angles and losses in the tip region, essentially.

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