Analysis of the effects of simulated fouling on an axial compressor stage through CFD modeling

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 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 compressor ratio was also noticed. Reductions of the flow coefficient and of the pressure coefficient were found to be of the same order of magnitude of the experimental results found in literature. Different non-uniform combinations of surface roughness levels on rotor and stator blades were also imposed. Simulations showed that the greatest effect on performance is attributable to the rotor, and, by analyzing the effect of roughening pressure surface and suction surface separately, to its suction surface.