Use of Pressure Spectral Maps for Analysis of Influence of the Plenum Volume on the Surge in Centrifugal Blower

Abstract

*The influence of plenum volume on surge phenomenon in a centrifugal blower was studied by means of quasidynamic analysis. In this procedure, signals were gathered at 5 pressure tappings at 146 different positions of the throttling valve controlling the mass flow rate. Frequency spectra obtained by means of Fourier analysis are combined together in the form of colour maps with frequency as the abscissa and valve position as the ordinate. Such a map provides high-resolution information about spectral structures of pressure signals attained at different mass flow rates. Analysis was conducted at two system configurations characterized by different volumes between the blower and the valve i.e. plenum volume. Research confirmed that in both cases the first disturbances appear in the vicinity of the impeller leading edge in the same position of a throttling valve before the surge. Arising flow structure is characterized by strong and random pressure jumps and does not have any dominating frequency. At further valve closure pressure disturbances propagate towards the volute and at deep surge the strongest peaks are observed at the outlet. The moment of deep surge onset is also independent of the plenum volume, however, a difference is observed in the frequency and amplitude of the main modes. With the higher outlet volume the observed oscillations fit well to the frequency of a Helmholtz resonator while, in the case of the smaller volume, the frequency is higher than the frequency of a corresponding Helmholtz resonator. † ASME member

Experimental analysis of the influence of outlet network volume and inlet guide vane positioning on surge behavior in a single-stage low-speed centrifugal compressor

“…Earlier studies performed on the current machine and described e.g. by Liskiewicz et al 6 or by Kabalyk et al 5 suggested referring the appearance of this spectral pattern to inlet recirculation, the phenomenon typical to semi-open unshrouded impellers. 12 .…”

“…On the other hand, it is also known that if B mod;DP1:12 is decreased to 0.96 (by cutting the outlet pipeline), the pattern as in Figure 9 will not appear and no 12.7 Hz peaks will be noticeable on FFT spectra. 5 The above theses erect the following suggestions:…”

“…Since 2009 the machine has been extensively utilized to study surge and other unstable flow phenomena occurring in centrifugal compressors. [5][6][7] The design modification of the rig implemented in this work consisted of the following basic elements:…”

“…Henceforth, the results of surge tests obtained at manufacturer's rig may occur to be not 100% valid at the consumer's site. From the studies by Pfleiderer, 1 Greitzer, 2,3 Koyama et al, 4 or Kabalyk et al 5 it is known that e.g. the location of actual surge margin, the amplitude, and frequency of pressure fluctuations in surge and even the probability of surge inception vary with the network volume.…”

Experimental Dynamic Analysis on a T100 Microturbine Connected With Different Volume Sizes

“…The recent development of high temperature energy storage systems could drive gas turbine cycles toward further layout modifications [9,10]. In all the mentioned cases, the gas turbine connection with such additional components generates a size increase for the volume located between the compressor outlet and the combustor inlet [11][12][13].…”