Instability detection of centrifugal compressors by means of acoustic measurements

Section: -Introductionmentioning

confidence: 99%

A comprehensive investigation of acoustic power level in a moderate or intense low oxygen dilution in a jet-in-hot-coflow under various working conditions

Mousavi

Kamali

Sotoudeh

et al. 2019

“…It is apparently the initiation of the compressor surge, which can be solidly confirmed by the natural frequency of the compressing system. As studied by previous research [23,24], the flow oscillates at the natural frequency of the compressing system when the surge happens. Therefore, the surge frequency can be estimated by the value of Helmholtz frequency, as in Eq.…”

Section: Surge Characteristicmentioning

confidence: 88%

Experimental study on performance of centrifugal compressor exposed to pulsating backpressure

Shu

Yang

Zhang

et al. 2019

Pressure fluctuations in intake manifold of Internal Combustion Engine introduce a pulsating boundary condition to the centrifugal compressor. In this study, the performance of centrifugal compressor exposed to pulsating backpressure is experimentally investigated. Unsteady performance and surge characteristic of the compressor at different pulsating conditions are analyzed. Results show that instantaneous performance of the compressor forms a hysteresis loop encapsulating steady performance. A correlation of compressor unsteadiness with pulse frequency, magnitude, and local slope of the characteristic curve is obtained based on measurements. Cycle-average performance of the compressor is notably lower than that at constant conditions. Specifically, the averaged peak efficiency at pulsating condition drops 3%~7%. Fast Fourier Transformation method is applied to study surge characteristics at pulsating conditions. Results manifest that compressor surge is postponed remarkably by pulsating backpressure at all conditions. As the compressor approaches to small mass flow rate, flow fluctuations decay quickly and then increase dramatically when the surge happens, forming the variation with 'V-shape' for frequency domains. This phenomenon is resulted from the influence of the slope of characteristic curve on the filling-empty and compressor stability. Smaller slope produces less filling-empty and hence smaller size of the loop, but reduces the stability of compressing system and initiates surge.

“…In turn, these unstable flow phenomena related to the geometric characteristics are linked to the spectral signature of the compressor noise [12]. This opens the door to geometry improvements that optimize both flow stability and acoustics, such as the use of hub [13] or shroud [14,15] cavities.…”

Section: Introductionmentioning

confidence: 99%

Dynamic mode decomposition of the acoustic field in radial compressors

Broatch

García-Tíscar

Roig

et al. 2019

Widely recognized since the beginning of air travel as a major issue, noise reduction remains nowadays a pressing concern for all stakeholders in the aviation industry. While aeroengine compressors, specially at the approach phase, have been historically identified as a leading source of noise, most of the research has been conducted on compressors of the axial type. However, radial compressors are found in a wide array of applications: smaller business jets, helicopters, unmanned aerial vehicles (UAVs), auxiliary power units (APUs), turbochargers for reciprocating engines, etc. Owing to their geometrical particularities, radial compressors feature flow patterns that differ from their axial counterparts, leading to different acoustic performance but also opening the door for different optimization approaches. Yet, classical modal decomposition techniques focused on duct propagation may fail to reveal the complex interactions between geometry and flow features that act as noise sources. In this paper we apply, in addition to the classical approach, a data-driven Dynamic Mode Decomposition (DMD) to pressure data coming from a Detached Eddy Simulation (DES), in which we have experimentally validated the correct reproduction of the modal behaviour of the compressor, thus obtaining in-depth details of the link between flow phenomena and noise generation and transmission across the inlet and outlet ducts.