Flow phenomena leading to surge in a centrifugal compressor

Semlitsch, Bernhard; Mihăescu, Mihai

doi:10.1016/j.energy.2016.03.032

Cited by 89 publications

(62 citation statements)

References 31 publications

(38 reference statements)

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“…Semlitsch et al [15, 16] could confirm by studying the same ported shroud compressor numerically that this reversed flow originates from the tip leakage and back flow jets generated via the ported shroud. Semlitsch and Mihăescu [17] suggested that the increased tip leakage swirling the inflow toward off design operating conditions degenerates the incidence flow angles such that the rotor blades might be incapable to maintain a constant back pressure and cause surging.…”

Section: Introductionmentioning

confidence: 99%

Generation Mechanisms of Rotating Stall and Surge in Centrifugal Compressors

Sundström

Semlitsch

Mihăescu

2017

Flow Turbulence Combust

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Flow instabilities such as Rotating Stall and Surge limit the operating range of centrifugal compressors at low mass-flow rates. Employing compressible Large Eddy Simulations (LES), their generation mechanisms are exposed. Toward low mass-flow rate operating conditions, flow reversal over the blade tips (generated by the back pressure) causes an inflection point of the inlet flow profile. There, a shear-layer induces vortical structures circulating at the compressor inlet. Traces of these flow structures are observed until far downstream in the radial diffuser. The tip leakage flow exhibits angular momentum imparted by the impeller, which deteriorates the incidence angles at the blade tips through an over imposed swirling component to the incoming flow. We show that the impeller is incapable to maintain constant efficiency at surge operating conditions due to the extreme alteration of the incidence angle. This induces unsteady flow momentum transfer downstream, which is reflected as compression wave at the compressor outlet traveling toward the impeller. There, the pressure oscillations govern the tip leakage flow and hence, the incidence angles at the impeller. When these individual self-exited processes occurs in-phase, a surge limit-cycle establishes.

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Section: Introductionmentioning

confidence: 99%

Generation Mechanisms of Rotating Stall and Surge in Centrifugal Compressors

Sundström

Semlitsch

Mihăescu

2017

Flow Turbulence Combust

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“…Therefore, code validation is assessed alternatively by means of a grid dependency study, which is presented further below. Nevertheless, the solver has been used previously for calculating flow scenarios associated with centrifugal compressors at low mass flow rates and validations against experimental data were carried out, see [19][20][21].…”

Section: Numerical Methodologymentioning

confidence: 99%

Analysis of Vaneless Diffuser Stall Instability in a Centrifugal Compressor

Sundström

Mihăescu

Giachi³

et al. 2017

IJTPP

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Abstract:Numerical simulations based on the large eddy simulation approach were conducted with the aim to explore vaneless diffuser rotating stall instability in a centrifugal compressor. The effect of the impeller blade passage was included as an inlet boundary condition with sufficiently low flow angle relative to the tangent to provoke the instability and cause circulation in the diffuser core flow. Flow quantities, velocity and pressure, were extracted to accumulate statistics for calculating mean velocity and mean Reynolds stresses in the wall-to-wall direction. The paper focuses on the assessment of the complex response of the system to the velocity perturbations imposed, the resulting pressure gradient and flow curvature effects.

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“…Recent numerical work presented by the researchers of KTH [15,16,17] investigated the performance and acoustic characteristics of the ported shroud compressor operating near surge. Although authors [16] attempted to predict the value of surge frequency, relatively lower surge frequencies are seen in literature as the upstream and downstream duct volumes were not considered by the authors in the numerical model.…”

Section: Introductionmentioning

confidence: 99%

Acoustic and pressure characteristics of a ported shroud turbocompressor operating at near surge conditions

et al. 2019

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The operation of compressor at lower mass flow rates is limited by surge which is marked by large fluctuations in operational variables and accompanied by significant increase in noise. Ported shroud casing treatment is a widely used method to control the flow near unstable conditions in order to obtain a stable operation and enhance deep surge margin. The research on the acoustic effects of the ported shroud design is limited. Therefore, this paper numerically characterises the acoustic features of a turbocharger compressor with ported shroud design operating at marginal or soft surge conditions and investigates the correlation between acoustic characteristics and the spatial flow structures. The acoustic and the flow field features are analysed using spectral signatures obtained from an experimentally validated numerical model using both performance and acoustic measurements. Propagation of the frequency content through the ducts has been estimated with the aid of the beamforming and method of characteristics to enhance the content coming from the compressor. Expected acoustic phenomena such as rotating order tones and blade passing peaks are correctly identified in the modelled spectrum with the limitation to capture the specific broadband features. Hence, the numerical model can be used to further the research encompassing the impact these flow enhancement solutions have on the noise emission of the turbocharger. Inspection of the flow field shows radially exiting fluid at the ported shroud slot leading to the formation of the high-speed jets exiting the ported shroud cavity. Circumferential propagation of the stall cells is also identified in the impeller. Further inspection of the pressure field through modal decomposition implies the localisation of the energetic noise sources in the impeller downstream components. The influence of the ported shroud cavity on the acoustic characteristic of the compressor is not significant and is limited to the propagation of the tonal noise in the direction of impeller upstream.

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Flow phenomena leading to surge in a centrifugal compressor

Cited by 89 publications

References 31 publications

Generation Mechanisms of Rotating Stall and Surge in Centrifugal Compressors

Generation Mechanisms of Rotating Stall and Surge in Centrifugal Compressors

Analysis of Vaneless Diffuser Stall Instability in a Centrifugal Compressor

Acoustic and pressure characteristics of a ported shroud turbocompressor operating at near surge conditions

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