Numerical Analysis of the Effects of Surface Roughness Localization on the Performance of an Axial Compressor Stage

In this paper, the most common and experienced source of loss for a gas turbine, i.e. compressor fouling, is modeled and analyzed by means of a three-dimensional numerical approach. In particular, CFD simulations of fouling affecting an axial compressor stage are carried out. To do this, the NASA Stage 37 is considered as compressor model for numerical investigation. The numerical model, validated against experimental data available from literature, is used to simulate the occurrence of fouling by imposing different combinations of added thickness and surface roughness. The results highlighted that the main effect of fouling is the decrease in the flow rate, even if a decrease in the stage compression ratio was also noticed. Therefore, different non-uniform combinations of surface roughness levels on rotor and stator blades were imposed. Simulations showed that the greatest effect on performance is attributable to the rotor, and in particular, by analyzing the effect of roughening pressure surface and suction surface separately, to its suction surface. Moreover, a rotor roughness non-uniformity is considered also in spanwise direction, which causes a significant work redistribution.