EXPERIMENTAL STUDY OF ACOUSTIC RESONANCES IN THE SIDE CAVITIES OF A HIGH-PRESSURE CENTRIFUGAL COMPRESSOR EXCITED BY ROTOR/STATOR INTERACTION

摘要

Under unfavorable conditions aerodynamic and aeroacoustic excitation mechanisms may lead to fatigue failures of centrifugal compressor impellers. The mechanisms for consideration me, for example, the arising pressure patterns due to rotor/stator interactions, the so-called Tyler/Sofrin modes, or acoustic resonances in the compressor housing. In a research program, a high-pressure radial compressor has been equipped with a multiplicity of sensors to investigate the excitation and interaction mechanisms in a complete centrifugal compressor stage. The current paper deals with the experimental detection of acoustic resonances in the compressor side cavities and the excitation of these acoustic eigenmodes due to Tyler/Sofrin modes. In this context the test rig and the installed instrumentation are briefly described. The methods of measuring as well as the analyzing techniques for detecting acoustic resonances and evaluating the measurements are presented. In addition, acoustic eigenmodes have been calculated by the finite-element method for the representative numerical test rig parameters. Results are presented and compared to the experimental findings. The accomplished experiments are the first available in open literature showing that the fluid core rotation in the compressor side cavities plays a crucial role for the prediction of the acoustic eigenfrequencies with respect to the rotor frame of reference. Without taking into account the effect of fluid rotation, large deviations between predicted (simulated) and measured acoustic eigenfrequencies would be the result.