Erosion prediction of gas turbine compressor blades subjected to water washing process

Blade fouling is a very relevant problem in turbomachin-ery applications. It affects both compressors and turbines. In the first case, fouling can be generated by the presence of dust, ashes or brackish air (in offshore applications). In turbines, fouling is mainly generated by residual of combustion process. Blade fouling generally leads to a reduction of the performance due to an increase on profile losses. Here we focus on the foul-ing due to salt deposition on naval/off-shore applications refer-ring to machines that are part of the fleet of gas turbines man-ufacturers. In such applications, it is common to introduce on-line washing devices aiming at removing fouling from the early stages of the compressors. The water is sprayed upstream of the first rotor, it impacts on the rotor blades and thus dissolving the deposited salt. However, this procedure possibly leads to blade erosion and/or corrosion. A clear comprehension of the erosion mechanism is the main objective of the present work. To this end, we propose an integrated multi-phase CFD tool. The multi-phase flow is analyzed by adopting a one-way cou-pling, thus assuming water droplets to be drag by the carrier flow without influencing the main flow. The droplets are dis-persed and tracked singularly by adopting a Lagrangian ap-proach. As for the erosion, well-known and widely accepted models are used. Firstly, a CFD study will be carried out to investigate the fluid-dynamic field by using ANSYS CFX 16.2 for the turbulent flow simulation. CFX is also used for carrying out a compara-tive analysis of the blade erosion mechanism. However, due to limits of the available models, sand particle (and not water droplets) erosion was modeled. Then, the capability of a La-grangian code, P-Track, developed and validated at the De-partment of Mechanical & Aerospace Engineering, Sapienza University in Rome, is presented. The code is able to predict the droplets trajectories, as well as to simulate the impact on the solid walls and the erosion mechanism.