Numerical Investigation of Circumferential Coupled Deterioration Effects of a Jet Engine Compressor Front Stage Compared to BLISK Geometry

The performance of a compressor decreases during a flight operation interval due to deterioration effects. This results in an increase of specific fuel consumption (SFC) and exhaust gas temperature (EGT), both having an influence on the On-Wing-Time of a jet engine and hence the maintenance intervals. A significant type of deterioration is erosion leading to misshaped airfoils such as thinner or thicker leading- and trailing edges, thinner airfoils as well as a reduction in chord length and an increase in tip clearance. Another deterioration effect are changes in stagger angles. The parameters mentioned above vary between each airfoil in a compressor stage. For a BLISK (BLade-Integrated-diSK) the arrangement of blades in each stage cannot be changed during maintenance, so these effects will grow stronger until the part reaches its life limit. Therefore, the objective of this study is to analyze the effect of circumferential different types of misshaped airfoils on the performance of a compressor stage. A conventional high pressure compressor stage is to be simulated with maximum leading edge thickness in combination with maximum and minimum stagger angle using realistic boundary conditions. In general, the coupled effects due to detoration lead to mistuned throttle lines and a different operation range. Further the geometry of a BLISK being at its life limit is digitalized by a structured light 3D scanner in conjunction with a photogrammetry system to examine the state of detoration and evaluate if the results of a conventional compressor stage can be applied to the new BLISK design. Thus, this study gives a preview on the changes of the expected BLISK performance caused by coupled deterioration effects.