Effect of leading edge erosion on the performance of transonic compressor blades

Authors

Alexander Hergt  - German Aerospace Center (DLR), Germany
Joachim Klinner - German Aerospace Center (DLR), Germany
Sebastian Grund - German Aerospace Center (DLR), Germany
Manfred Beversdorff - German Aerospace Center (DLR), Germany
Christian Werner-Spatz - Lufthansa Technik AG

Abstract

Nowadays, fan and compressor blades for aircraft engines are designed using modern optimization procedures and CFD methods. These highly efficient components are subject to various types of wear and damage as soon as they are in use. Particularly in the case of transonic fan and compressor blades, erosion effects occur at the leading edges which may affects the performance over the operating cycle. In the context of engine maintenance, the question of the level of influence is essential, as a balance must be found between the loss of engine performance and the cost of replacing the eroded blading during maintenance. In order to develop a clear guidance for maintenance, the first step is to evaluate the influence of erosion on the aerodynamic performance of transonic blades. Therefore, an experimental investigation was performed on a transonic blade section of a high-pressure compressor front stage based on a presently operating engine. The measurements were carried out on a linear blade cascade in the transonic cascade wind tunnel of DLR in Cologne. In order to access the influence at different operating conditions the tests are carried out at Mach numbers of 1.05 and 1.12 as well as three inflow angles which represent near choke, design point and near stall condition. These are comparative measurements, which means that the aerodynamic performance of the reference cascade consisting of as-new blade profiles is compared with a cascade with eroded leading edges. The type and specifications of the erosions were derived from real engine blades and applied to the leading edges of the cascade blades using a waterjet process. Extensive wake measurements were carried out on the cascades to evaluate aerodynamic performance, which includes loss behavior, static pressure rise as well as flow deflection. The increase in losses was quantified to be 5 percent at the design point. In addition, an extensive evaluation was performed to describe the loss change based on Schlieren images and PIV measurements in the leading edge regions. Here, the influence of the eroded leading edge on the shock structure within the cascade could be shown. Furthermore, the increase in losses can be attributed to the changed shape of the leading edge due to erosion. Based on the results, a final assessment is made with regard to a maintenance process.