Simulation of Inlet Fogging and Wet-compression in a Single Stage Compressor Including Erosion Analysis

Gas turbine inlet fog / overspray cooling is considered as a simple and effective method to increase power output. To help understand the water mist transport in the compressor flow passage, this study conducts a computational simulation of wet compression in a single rotor-stator compressor stage using the commercial code, Fluent. A sliding mesh scheme is used to simulate the stator-rotor interaction in a rotating frame. The effect of different heat transfer models and forces (e.g. drags, thermophoretic, Brownian, Saffman's lift force etc.) are investigated. Models to simulate droplet breakup and coalescence are incorporated to take into consideration the effect of local acceleration and deceleration on water droplet dynamics. Analysis on droplet history (trajectory and size) with stochastic tracking is employed to interpret the mechanism of droplet dynamics under influence of local turbulence, acceleration, diffusion, and body forces. An erosion model is also included. The results show that droplet local slip velocity is noticeably affected by local acceleration and deceleration of the compressor blade, and in turn, the heat transfer and water evaporation rate are affected. Due to the short droplet residence time in the compressor stage, local thermal equilibrium is not always achieved, and the air may not always reach saturation even sufficient amount of liquid mass is in the air. The results also show erosion occurs near the rotor fore-body on the suction side with the present erosion model, which is subject to continuous improvement and further verification. The transient results of different rotor/stator relative positions show low airflow blockage produces more effective compression and higher temperature rise. Different types of droplet boundary conditions show the effect is negligible.