Stall Warning Indicator

Performance data of newly developed compressors are so far measured on a test bench and then transferred to a characteristic diagram. An essential component of such a characteristic field is the so-called surge limit, since this is essential for ensuring safe operation. Exceeding the surge limit will result in instabilities, causing extremely high aerodynamic loads to the compressor that may result in considerable structural damages. However, since the surge line on the test bench can only be identified if it has already been exceeded, so far costly complete failures of the tested compressors are accepted. It is thus an object of the invention to provide a method for determining an indicator for a prediction of instabilities in a compressor, which reliably allows an early warning of the possible occurrence such instabilities, especially the achievement of the surge limit.

The method developed by scientists from the institute of Aerospace Engineering is an early warning system for compressor instabilities. According to this method the compressor on a test bench is gradually been moved to its surge limit. During this process high-resolution pressure measurement is performed and the collected data can be used to calculate a specific integral parameter. If this parameter is afterwards subsequently plotted over all measured operating points, one can obtain a secure possibility of predicting the operating limit and thus the surge limit, enabling a due detection of burner instabilities. Functionality and potential of the novel method where successfully investigated using a newly built miniature single-stage low speed axial compressor at an test stand of the respective field of the TU Berlin.