OPTIMIZATION OF ROBUST TRANSONIC COMPRESSOR BLADES

Surface degradation in an axial compressor during its lifetime can have a considerable adverse effect on its performance. The present study investigates how the optimized design of compressor blades in a single compressor stage is affected by considering a high level of surface roughness on a level representative of a long period of in-service use. It is shown that including surface roughness in the optimization process is of relatively little importance, however, matching of compressor stages is shown to require consideration as the rotational speed must be increased to reach the design point as surface quality decrease. An increased surface roughness in itself is shown to have a large effect on performance. Two optimization approaches are compared. The first approach considers the compressor blades to be hydraulically smooth. The designs obtained from this approach are subsequently degraded by increasing the level of surface roughness. The compressor blades from the first approach are compared to designs obtained from a second optimization approach, which considers a high level of surface roughness from the outset. The degraded compressor stages from the first approach are shown to be among the best performing designs in terms of poly tropic efficiency and stability when compared to designs obtained with the second approach.