Two-Regime Surge Mechanism in Centrifugal Compressors

Instability inception and evolution leading to surge have been key limiting factors to the stable operation of centrifugal compressors. The compressor generally experiences flow oscillation, which results from a deep surge, either or not preceded by a mild surge, depending on the operating condition. Research works over the years have identified a so-called two-regime surge phenomenon, which features a nonsurge region between the mild and deep surges. In this work, the flow mechanisms responsible for this phenomenon were investigated both experimentally and analytically using a dynamic compression system model. Results show that the slope alternation in the pressure ratio characteristic from positive to negative was the necessary condition for triggering this phenomenon. Correlation between the impeller inlet recirculation and the slope alternation has been established to elucidate the flow mechanisms responsible for this phenomenon. The growth rates of the work input and the flow loss were altered through the interloping of the impeller inlet recirculation such that a subtle balance between the two was achieved to formulate the slope alternation. Finally, both computational fluid dynamics and experiments were conducted to justify the correlation.