The surge limit of compressors is one key parameter in the design process of modern turbocharger compressors for automotive applications. Since the compressor is operated close to the surge limit, the determination of the surge limit is of high importance. Unfortunately, the determination of the surge limit with any numerical method with high accuracy is still an unsolved challenge. The numerical surge limit is often determined bv the operating point with the minimum converged mass flow rate. But, as this investigation will clearly show, this cannot be used as a surge limit of the investigated compressor configuration. In this paper it will be shown that a more differentiated approach is required when it comes to operating limits. Especially, two different operating limits can be determined. A methodology for the determination of each limit will be presented. One is based on the system approach defined by Greitzer and the other one is based on the analysis of the low momentum fluid in the shroud region of the compressor wheel. Finally, experimental data will be used as benchmark data for both limits. The determination of the experimental surge limit is based on the analysis of transient experimental pressure signals. This is achieved through a fourier analysis of the unsteady compressor outlet pressure signal for transient surge runs.
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