Stall Inception Behavior in a Centrifugal Compressor

Abstract

In studying the stall inception process, while most results were reported for axial compressors, the present paper investigates the stall inception behavior typified in a centrifugal compressor. The test was conducted with a radially-bladed impeller and in a speed range of 8000–14000 rpm. Extensive pressure transducers were used to study the frequency characteristics of emerging stall waves. As a result, stall precursors were detected, all with clear mode seen from frequency analysis, but very much different by the behavior of their onset, existence and development. The first type, called the stable-amplitude precursor, exists in a time range of about 20–90 impeller revolutions, with unpredictable and different frequencies from the fully developed stall. Such perturbation, once appeared, may grow to the full stall straightly, or may appear for several times intermittently before finally reaching the full stall, thus acting as a pre-precursor in the whole stall inception process. The second type is the progressive-amplitude precursor when the perturbation emerges as long as 270 impeller revolutions prior to and progressively develops into the full amplitude stall with no change of frequency during this process. The third type, which has been detected for the rotating stall with evident reverse flow symptom, is the precursive pressure increase accompanied with the stable- or progressive-amplitude perturbation, before the full stall establishes. The inception process is also examined for surge during the test of the same compressor, in which the existence of rotating stall in front of every surge cycle and the low frequency precursive wave before surge cycles is demonstrated. Finally, the blade passage frequencies for precursor pressure signals are further analysed to address the monitoring strategy during stall inception process.

Time-Frequency Analysis of Compressor Rotating Stall by Means of Wavelet Transform

“…In this figure, several prevailing 51111111511611M Fig. ? Wavelet transform of a signal an axial compressor frequencies of those segments are detected, which comform with the results by wavelet transform and by Chen et al (1994). The conclusion that the frequency of rotating stall is lower than those of the precursors, is also valid.…”

“…In order • to verify the effectiveness of wavelet transform in analyzing rotating stall signals, the experimental signals are adopted from a previous study written by one of the authors and his co-authors( Fig.7 in Chen et al, 1994). The experiments were conducted in a high speed centrifugal compressor at 12000 rpm in University of Hannover, Germany.…”

Dämpfung von Rotating Stall in Radialverdichterstufen

“…B. [1], [2], [3], [4], [5] und [6]. Es gibt jedoch bisher keine Untersuchungen daru Èber, Rotating Stall durch aktive Bauelemente zu beeinflussen, die nach einem anderen Prinzip arbeiten, wie z.…”

Dämpfung von Rotating Stall in Radialverdichterstufen

“…The enforced turbulent eddy flow with unsteady gas pressure oscillation in side channel stages diminishes unsteady gas pressure oscillation in the centrifugal compressor stage and limits pressure gradient as well as the maximum reachable value of gas pressure oscillation at rotating stall. [2], [3], [4], [5] und [6]. Es [14], [15], [16].…”