Effects of Inlet Flow Field Conditions on the Performance of Centrifugal Compressor Diffusers: Part 1 — Discrete-Passage Diffuser

Filipenco, Victor G.; Deniz, Sabri; Johnston, James M.; Greitzer, E. M.; Cumpsty, N. A.

doi:10.1115/98-gt-473

Cited by 14 publications

(16 citation statements)

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“…Hence, we can expect the diffuser static pressure recovery to be affected by the flow non-uniformity at impeller exit. Filipenco et al [2000] and Deniz et al [2000] showed that mass-averaged stagnation pressure at diffuser inlet is satisfactory in correlating the diffuser pressure recovery. Based on the above considerations, it is appropriate to express the results on a mass average basis.…”

Section: Conceptual Choices For Averaged Resultsmentioning

confidence: 99%

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Aerospace Turbomachinery Flow Physics

Tan¹

2003

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Public reporting burden for this collection of information is estimated to average 1 hour per response, inclt turces, gathering and maintaining the data needed, and completing and reviewing the collection of information. S of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Ser% fferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Pa

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Section: Conceptual Choices For Averaged Resultsmentioning

confidence: 99%

“…Philips [1997], Filipenco et al [2000] and Deniz et al [2000] showed that vaned diffuser channel performance is weakly dependent on inlet blockage, but strongly affected by momentum-averaged flow angle. The three authors used the following definition for the momentum-averaged flow angle:…”

Section: Conceptual Choices For Averaged Resultsmentioning

confidence: 99%

Aerospace Turbomachinery Flow Physics

Tan¹

2003

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“…The CFD data further support the correlation, with the same exception as observed earlier for the cases with low average diffuser inflow angles. As observed by Filipenco and Deniz [3,4], the emphasis placed on blockage in typical approaches to the analysis of vaned diffusers appears misplaced. Mixing occurs through the vaneless space between impeller and diffuser; CFD data shows that, for the peak efficiency point at the design corrected speed, the non-uniformity in mass flux reduces by 7% from impeller trailing edge to the diffuser trailing edge.…”

Section: Effect Of Time-average Mach Number and Flow Anglementioning

confidence: 99%

“…This total temperature ( ) probe comprises a 0.81 mm tube with two aligned holes drilled radially through the tube. The first hole, 0.46 mm in diameter, is rotated to face 3 The work done by the swirl rig rotor is low, resulting in total temperature ratios below 1.15. The assumption of uniform total temperature is fair.…”

Section: Thementioning

confidence: 99%

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The Role of Impeller Outflow Conditions on the Performance of Vaned Diffusers

Everitt

Spakovszky

Rusch

et al. 2016

Volume 2D: Turbomachinery

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Highly-loaded impellers, typically used in turbocharger and gas turbine applications, exhaust an unsteady, transonic flow that is non-uniform across the span and pitch and swirling at angles approaching tangential. With the exception of the flow angle, conflicting data exist regarding whether these attributes have substantial influence on the performance of the downstream diffuser. This paper quantifies the relative importance of the flow angle, Mach number, non-uniformity and unsteadiness on diffuser performance, through diffuser experiments in a compressor stage and in a rotating swirling flow test rig. This is combined with steady and unsteady Reynolds-Averaged Navier Stokes computations. The test article is a pressure ratio 5 turbocharger compressor with an airfoil vaned diffuser. The swirling flow rig is able to generate rotor outflow conditions representative of the compressor except for the periodic pitchwise unsteadiness, and fits a 0.86 scale diffuser and volute. In both rigs, the time-mean impeller outflow is mapped across a diffuser pitch using miniaturized traversing probes developed for the purpose.Across approximately two-thirds of the stage operating range, diffuser performance is well correlated to the average impeller outflow angle when the metric used is effectiveness, which describes the pressure recovery obtained relative to the maximum possible given the average inflow angle, Mach number and the vane exit metal angle. Utilizing effectiveness captures density changes through the diffuser at higher Mach numbers; a 10% increase in pressure recovery is observed as the inlet Mach number is increased from 0.5 to 1. Further, effectiveness is shown to be largely independent of the timeaveraged spanwise and unsteady pitchwise non-uniformity from the rotor; this independence is reflective of the strong mixing processes that occur in the diffuser inlet region. The observed exception is for operating points with high timeaveraged vane incidence. Here, it is hypothesized that temporary excursions into high-loss flow regimes cause a nonlinear increase in loss as large unsteady angle variations pass by from the rotor.Given that straight-channel diffuser design charts typically used in preliminary radial vaned diffuser design capture neither streamtube area changes from impeller exit to the diffuser throat nor vane incidence effects, their utility is limited. An alternative approach, utilizing effectiveness and vane leading edge incidence, is proposed. INTRODUCTIONModern high pressure ratio centrifugal compressors typically utilize a high speed impeller with backswept blades and a vaned diffuser. As part of ongoing efforts for a systemwide reduction in weight, increase in efficiency and/or reduction of emissions, designers seek to improve the pressure ratio, operating range and efficiency of the centrifugal compressor, which is often limited by the diffuser. Despite the relative simplicity of its geometry, the flow in the diffuser is complex and there is no well-established, reliable approach to gui...

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Effect of high negative incidence on the performance of a centrifugal compressor stage with conventional vaned diffusers

et al. 2011

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Three vaned diffusers, designed to have high negative incidence (8°) at the design operating point, are studied experimentally. The overall performance (efficiency and pressure ratio) are measured at three rotational speeds, and flow angles before and after the diffuser are measured at the design rotational speed and with three mass flow rates. The results are compared to corresponding results of the original vaneless diffuser design. Attention is paid to the performance at lower mass flows than the design mass flow. The results show that it is possible to improve the performance at mass flows lower than the design mass flow with a vaned diffuser designed with high negative incidence. However, with the vaned diffusers, the compressor still stalls at higher mass flow rates than with the vaneless one. The flow angle distributions after the diffuser are more uniform with the vaned diffusers.

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Effects of Inlet Flow Field Conditions on the Performance of Centrifugal Compressor Diffusers: Part 1 — Discrete-Passage Diffuser

Cited by 14 publications

References 0 publications

Aerospace Turbomachinery Flow Physics

Aerospace Turbomachinery Flow Physics

The Role of Impeller Outflow Conditions on the Performance of Vaned Diffusers

Effect of high negative incidence on the performance of a centrifugal compressor stage with conventional vaned diffusers

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