Research Papers

Meanline Modeling of Inlet Recirculation in Automotive Turbocharger Centrifugal Compressors

[+] Author and Article Information
Peter Harley

Queen's University Belfast,
Belfast BT9 5AH, UK
e-mail: pharley01@qub.ac.uk

Stephen Spence

Queen's University Belfast,
Belfast BT9 5AH, UK
e-mail: s.w.spence@qub.ac.uk

Dietmar Filsinger

IHI Charging Systems International,
Heidelberg 69126, Germany
e-mail: d.filsinger@ihi-csi.de

Michael Dietrich

IHI Charging Systems International,
Heidelberg 69126, Germany
e-mail: m.dietrich@ihi-csi.de

Juliana Early

Queen's University Belfast,
Belfast BT9 5AH, UK
e-mail: j.early@qub.ac.uk

Contributed by the International Gas Turbine Institute (IGTI) Division of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 18, 2014; final manuscript received July 25, 2014; published online September 4, 2014. Editor: Ronald Bunker.

J. Turbomach 137(1), 011007 (Sep 04, 2014) (9 pages) Paper No: TURBO-14-1154; doi: 10.1115/1.4028247 History: Received July 18, 2014; Revised July 25, 2014

This study provides a novel meanline modeling approach for centrifugal compressors. All compressors analyzed are of the automotive turbocharger variety and have typical upstream geometry with no casing treatments or preswirl vanes. Past experience dictates that inducer recirculation is prevalent toward surge in designs with high inlet shroud to outlet radius ratios; such designs are found in turbocharger compressors due to the demand for operating range. The aim of the paper is to provide further understanding of impeller inducer flow paths when operating with significant inducer recirculation. Using three-dimensional (3D) computational fluid dynamics (CFD) and a single-passage model, the flow coefficient at which the recirculating flow begins to develop and the rate at which it grows are used to assess and correlate work and angular momentum delivered to the incoming flow. All numerical modeling has been fully validated using measurements taken from hot gas stand tests for all compressor stages. The new modeling approach links the inlet recirculating flow and the pressure ratio characteristic of the compressor. Typically for a fixed rotational speed, between choke and the onset of impeller inlet recirculation the pressure ratio rises gradually at a rate dominated by the aerodynamic losses. However, in modern automotive turbocharger compressors where operating range is paramount, the pressure ratio no longer changes significantly between the onset of recirculation and surge. Instead the pressure ratio remains relatively constant for reducing mass flow rates until surge occurs. Existing meanline modeling techniques predict that the pressure ratio continues to gradually rise toward surge, which when compared to test data is not accurate. A new meanline method is presented here which tackles this issue by modeling the direct effects of the recirculation. The result is a meanline model that better represents the actual fluid flow seen in the CFD results and more accurately predicts the pressure ratio and efficiency characteristics in the region of the compressor map affected by inlet recirculation.

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Fig. 1

Recirculation power loss correlations

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Fig. 2

Meridional shape modification with meanline radius reduction

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Fig. 3

Velocity triangle variations within the active flow zone with impeller inlet recirculation

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Fig. 4

Effects of impeller inlet recirculation derived from CFD results

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Fig. 5

Impeller inlet flow conditions at a low mass flow rate and tip speed

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Fig. 6

CFD single-passage domain

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Fig. 7

Active flow zone total temperature rise trend

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Fig. 8

C-3 meridional velocity calculation comparison

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Fig. 9

Active flow zone preswirl increase

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Fig. 10

C-1 comparison of simulations with test data

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Fig. 11

C-2 comparison of simulations with test data

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Fig. 12

C-3 comparison of simulations with test data




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