Session: 34-03 Endwall, Seal & Leakage Flows

Paper Number: 82868

82868 - Leakage Flow Impact on Shrouded Stator Cavity Flow Topology and Associated High Speed Axial Compressor Stage Performance 

In axial compressors shrouded stator blades are used to clear the rotor assembly axially and radially. The cavity volumes that are created under the stator platform experience a downstream-to-upstream flow recirculation triggered by the static pressure increase in the main channel. The leakage flow is then reinjected in the power stream, altering the stage performance. The present paper characterizes, experimentally and numerically, the effect of realistic cavity leakage flows on the performance of a high speed axial compressor stage. 

The Von Karman Institute H25 stage (with cavity of average Re_r = 2.2*10⁶ and average aspect ratio G = 0.06) is investigated. On top of overall performance measurements, time averaged data from unprecedented experimental dataset are used to characterize the stator hub shroud cavity flow field and its interaction with the power stream. The sensitivity of the stage performance and stability as well as the cavity flow topology is evaluated against injection conditions, compressor throttling and compressor speed. Parametric steady RANS simulations of the stage under injection are used to support the findings and state on the relevance of such approach in the preliminary design phase of axial compressors components.

A stage efficiency reduction of 0.97% for a leakage fraction of 0.56% at design point is retrieved. The performance drop is attributed to the change in blockage ratio, boundary layer skewness, and total temperature increase at stator row inlet. It is also presented that there is a mutual interaction between the cavity geometry and the cavity flow field organization. The injection homogenizes the cavity flow field and the associated pressure gradient. The various operating conditions presented also demonstrate that the cavity flow studied is, on average (time), more sensitive to changes in compressor rotation speed than changes in stage loading.

Presenting Author: Cedric Babin von Karman Institute

Presenting Author Biography: - Engineering degree in mechanical and aeronautical engineering at ISAE ENSMA in France<br/> - PhD in Fluid Mechanics at Ecole Centrale de Lyon in collaboration between Von Karman Institute, LMFA , and Safran Aircraft Engines

Authors:

Cedric Babin von Karman Institute
Xavier Ottavy Laboratoire de Mécanique des Fluides et d'Acoustique
Fabrizio Fontaneto von Karman Institute