Active Stabilization of Surge in an Axicentrifugal Turboshaft Engine

Nelson, E.; Paduano, James D.; Epstein, A. H.

doi:10.1115/1.1304915

Cited by 26 publications

(4 citation statements)

References 14 publications

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“…The identification of stall pre-cursors has been a significant element of research into active control of compressors to extend operating range. For example, Skoch [11], Nelson et al [12] and Spakovszky and Roduner [10] consider the use of air injection within the vaned diffusers of a centrifugal compressor upon early detection of stall or surge behavior, and report an extension in operating range (with some performance penalty).…”

Section: Introductionmentioning

confidence: 99%

An Investigation of Stall Inception in Centrifugal Compressor Vaned Diffusers

Everitt¹,

Spakovszky²

2011

Volume 7: Turbomachinery, Parts A, B, and C

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In compression systems the stable operating range is limited by rotating stall and/or surge. Two distinct types of stall precursors can be observed prior to full scale instability: the development of long-wavelength modal waves or a short-wavelength, three-dimensional flow breakdown (so-called “spike” stall inception). The cause of the latter is not well understood; in axial machines it has been suggested that rotor blade-tip leakage flow plays an important role, but spikes have recently been observed in shrouded vaned diffusers of centrifugal compressors where these leakage flows are not present, suggesting an alternative mechanism may be at play. This paper investigates the onset of instability in a shrouded vaned diffuser from a highly loaded turbocharger centrifugal compressor and discusses the mechanisms thought to be responsible for the development of short-wavelength stall precursors. The approach combines unsteady 3D RANS simulations of an isolated vaned diffuser with previously obtained experimental results. The unsteady flow field simulation begins at the impeller exit radius, where flow is specified by a spanwise profile of flow angle and stagnation properties, derived from single-passage stage calculations but with flow pitchwise mixed. Through comparison with performance data from previous experiments and unsteady full-wheel simulations, it is shown that the diffuser is accurately matched to the impeller and the relevant flow features are well captured. Numerical forced response experiments are carried out to determine the diffuser dynamic behavior and point of instability onset. The unsteady simulations demonstrate the growth of short-wavelength precursors; the flow coefficient at which these occur, the rotation rate and circumferential extent agree with experimental measurements. Although the computational setup and domain limitations do not allow simulation of the fully developed spike nor full-scale instability, the model is sufficient to capture the onset of instability and allows the postulation of the following necessary conditions: (i) flow separation at the diffuser vane leading edge near the shroud endwall; (ii) radially reversed flow allowing vorticity shed from the leading edge to convect back into the vaneless space; and (iii) recirculation and accumulation of low stagnation pressure fluid in the vaneless space, increasing diffuser inlet blockage and leading to instability. Similarity exists with axial machines, where blade-tip leakage sets up endwall flow in the circumferential direction leading to flow breakdown and the inception of rotating stall. Rather than the tip leakage flows, the cause for circumferential endwall flow in the vaned diffuser is the combination of high swirl and the highly non-uniform spanwise flow profile at the impeller exit.

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Section: Introductionmentioning

confidence: 99%

An Investigation of Stall Inception in Centrifugal Compressor Vaned Diffusers

Everitt¹,

Spakovszky²

2011

Volume 7: Turbomachinery, Parts A, B, and C

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“…Later, Nelson et al [23] managed to experimentally reduce the surge mass flow rate of an axicentrifugal stage by 1% using air injection into the throats of the diffuser passages.…”

Section: Previous Control Strategiesmentioning

confidence: 99%

Active Flow Control in a Radial Vaned Diffuser for Surge Margin Improvement: A Multislot Suction Strategy

Marsan

Trébinjac

Moreau

et al. 2017

International Journal of Rotating Machinery

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This work is the final step of a research project that aims at evaluating the possibility of delaying the surge of a centrifugal compressor stage using a boundary-layer suction technique. It is based on Reynolds-Averaged Navier-Stokes numerical simulations. Boundary-layer suction is applied within the radial vaned diffuser. Previous work has shown the necessity to take into account the unsteady behavior of the flow when designing the active flow control technique. In this paper, a multislot strategy is designed according to the characteristics of the unsteady pressure field. Its implementation results in a significant increase of the stable operating range predicted by the unsteady RANS numerical model. A hub-corner separation still exists further downstream in the diffuser passage but does not compromise the stability of the compressor stage.

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“…This control system succeeded in increasing the stall margin by suppressing the first spatial mode. Nelson et al [2] were able to reduce surging mass flow by 1 percent and increase operating range by 11 percent on an axicentrifugal turboshaft engine by using air injection actuators near the diffuser throat. Stein et al [3] numerically investigated a high-speed centrifugal compressor numerically.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Suction Flow Control on Centrifugal Compressor with Vaned Diffuser

Çadırcı

2022

Energies

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In this study, the effect of suction flow control on a centrifugal compressor at operation and stall flow rates was investigated using computational fluid dynamics (CFD). The compressor geometry was reconstructed from available open source profile data and the CFD analyses have been performed on this geometry using the appropriate mesh. To validate the CFD results, the compressor performance line was acquired and compared with the experimental results obtained at the design rotational speed. Then, suction flow control was employed at various suction slot positions with different suction flow rates to improve the performance of the compressor at operation and stall flow rates. As a result of the suction flow control trials, 0.85% increase in pressure ratio and 0.8% increase in adiabatic efficiency were achieved while the compressor was running at operation flow rate. The performance improvements corresponding to the stall flow rate of the compressor were 2.5% increase in pressure ratio and 2% increase in adiabatic efficiency.

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Active Stabilization of Surge in an Axicentrifugal Turboshaft Engine

Cited by 26 publications

References 14 publications

An Investigation of Stall Inception in Centrifugal Compressor Vaned Diffusers

An Investigation of Stall Inception in Centrifugal Compressor Vaned Diffusers

Active Flow Control in a Radial Vaned Diffuser for Surge Margin Improvement: A Multislot Suction Strategy

Investigation of Suction Flow Control on Centrifugal Compressor with Vaned Diffuser

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