Numerical study of droplet erosion in the first-stage rotor of an axial flow compressor

In the present paper, a procedure for the study of the water washing in axial flow compressors is presented. The study is part of an ongoing partnership between Baker Hughes and Sapienza University of Rome aiming at maximizing the washing of the compressor blades while maintaining the erosion under specific thresholds. A computational analysis in the first part of an axial flow compressor (i.e. up to the first rotor) was carried out by using Ansys Fluent for the solution of multi-phase flow, while the water droplet erosion mechanism was modeled by the authors by using a properly developed methodology implemented in Fluent though the use of User Defined Functions. The washing process efficiency as well as the erosion rate are evaluated by introducing appropriate indexes. A parametric analysis was carried out by varying the mass flow rate of injected water. Two different computational grids were considered aiming at simulating two different configurations. In the first one the rotor blades leading edge (LE) is placed in the wake released by IGVs trailing edge (TE). In the second configuration, the rotor blades LE is located in a circumferential position corresponding to the mid-pitch between two successive IGVs. These two configurations simulate the situations of minimum and maximum water impact on the rotor blade surfaces. For all the injection conditions here considered, the configuration where IGVs trailing edges were aligned with the rotor blades LEs resulted in higher impacts and erosion on the blade pressure sides. When rotating rotor blades LEs in the middle of the IGVs vanes, rotor LEs were found to be the mostly washed regions but also the most subject to erosion phenomena. The computed indexes show the not optimal distribution of the injectors from the washing efficiency point of view