Detection of vaneless diffuser rotating stall by means of dynamic pressure sensors and acoustic measurements

Abstract

An accurate estimation of rotating stall is one of the key technologies for high-pressure centrifugal compressors. Several techniques have been proposed to detect the stall onset; inter alia, few dynamic pressure probes have been shown to not only properly detect the phenomenon, but also reconstruct the stall characteristics after an ensemble averaging approach. The massive use of this technique in the field is, however, not a common practice yet. In the present study, the use of dynamic pressure probes has been combined with that of an environmental microphone to evaluate the prospects of this latter for a possible stall onset detection. To this end, experimental tests have been carried out in the experimental test rig of the Department of Industrial Engineering (DIEF) of Università degli Studi di Firenze. Results show that the microphone was able to distinguish the onset of rotating stall accurately and promptly, even though – differently from dynamic pressure sensors - it does not provide sufficient information to determine the characteristics of the stall pattern. On this basis, the use of acoustic measurements could find room for automatic detection of rotating stall onset.

Instability Phenomena in Centrifugal Compressors and Strategies to Extend the Operating Range: A Review

“…In Guillou et al's work [70], an experimental investigation of flow instability phenomena with reference to rotating stalls and surges was presented with reference to a turbocharger compressor with a ported shroud. The good capabilities of an ambient microphone to detect the onset of a vaneless diffuser rotating stall were presented by Romani et al [71]; in particular, using a power spectrum analysis, they revealed that the relationship between the amplitude of the sub-synchronous region and that of the blade passing frequency, theorized in the case of dynamic pressure sensors through one dimensionless stall onset parameter, was still valid. The same techniques can be adopted for surge precursors; in fact, a rotating stall creates a rotating force that acts as a destabilizing external load on the rotor dynamics of the compressor [72,73].…”

An experimental and numerical investigation on the impact of tip gap on the performance of vaned diffuser for industrial centrifugal compressors

“…The upper limit of the flow path is limited by an annular spacer (14) that acts like the junction between the intake duct and the compressor stage. The suitability of this model geometry for detailed flow analyses has been discussed in [9]. To modify the blade's tip gap, an innovative methodology was developed in this research.…”