A METHOD FOR EFFICIENT PERFORMANCE PREDICTION FOR FAN AND COMPRESSOR STAGES WITH DEGRADED BLADES

Over service time fan and compressor blades vary in their geometry. Due to the geometric irregularities it is difficult to reliably assess the fan or compressor performance. Therefore, in the present study, a method that allows an efficient and accurate estimation of the performance for fan and compressors with degraded blades is established. In a first step, the blade regions mainly exposed to geometry variations are identified. Then, a simple parameterization that enables to easily describe the blade geometry as well as to independently represent the variations of all relevant geometric parameters is defined. For each geometric parameter (e.g. leading edge shape, rotor clearance gap height), the shifts of the operating points in the performance map due to the geometric variations are calculated. This is done with an adjoint flow solver which simultaneously provides the shifts for all extents of geometric parameter variations. As the geometric parameters are assumed to be independent of each other, the combination of variations in several geometric parameters is estimated by simply adding the shift vectors determined for the individual parameters. The results for a subsonic compressor stage show a significant influence of the variations in the geometric parameters on the compressor performance. As validation with few nonlinear simulations demonstrates, this influence is well predicted by the method presented in this study. The relative deviation of the performance map parameters in the operating points around peak efficiency is less than 0.5 %. Compared to the nonlinear simulations, the numeric effort to determine the influence of seven geometric parameters on the performance map with the method based on adjoint simulations is considerably reduced by a factor of 35. In summary, the results demonstrate the feasibility of the method and encourage its application in an industrial context.