Effect of tip gap size on the performance of an axial compressor stage with and without active flow control.

Authors

Clémence Rannou  - DAAA, ONERA, Université Paris Saclay, F-92190 Meudon - France; Univ. Lille, CNRS, ONERA, Arts et Metiers Institute of Technology, Centrale Lille Institut, UMR 9014-LMFL, Laboratoire de Mécanique des Fluides de Lille, Kampé de Fériet F-59000, Lille, France
Julien Marty - DAAA, ONERA, Université Paris Saclay, F-92190 Meudon - France
Geoffrey Tanguy - Univ. Lille, CNRS, ONERA, Arts et Metiers Institute of Technology, Centrale Lille Institut, UMR 9014-LMFL, Laboratoire de Mécanique des Fluides de Lille, Kampé de Fériet F-59000, Lille, France
Antoine Dazin - Univ. Lille, CNRS, ONERA, Arts et Metiers Institute of Technology, Centrale Lille Institut, UMR 9014-LMFL, Laboratoire de Mécanique des Fluides de Lille, Kampé de Fériet F-59000, Lille, France

Abstract

The tip gap region of an axial compressor rotor is the source of complex flows, which induces losses and can lead to a reduction of the stable operating range of the machine. Several recent works have proven the ability of blowing high-speed jets in the tip region to act on these flows and improve the surge margin of an axial compressor stage, on a configuration with a narrow tip gap. Nevertheless, the tip gap size of an axial compressor can evolve during the lifetime of the machine. This can lead to a modification of the leakage flow and affect noticeably its performance and operability. The objective of this paper is to evaluate the performance of an active flow control system on a compressor with different tip gap sizes. The machine support of the present work is the single stage compressor CME2, located at the Lille Laboratory of Fluid Mechanics (LMFL) equipped with 40 actuators blowing at the leading edge of the rotor tip. Two configurations with different values of the tip gap to chord ratio (0.6 % and 2.4%) have been experimentally tested. RANS and URANS simulations have been carried out as well as experiments involving global performance measurements and unsteady measurements at the casing. An intermediary tip gap size (1.2%) is also evaluated with RANS and URANS computations. The effects of the tip gap size and of the tip-blowing on the flow topology at blade tip are reported. Their impact on the machine performance and especially on the surge margin are analyzed.