Meanline Modelling of Inlet Recirculation in Automotive Turbocharger Centrifugal Compressors

Peter Harley, Stephen Spence, Dietmar Filsinger, Michael Dietrich, Juliana Early

Research output: Contribution to conferencePaperpeer-review

6 Citations (Scopus)

Abstract

This study provides a novel meanline modelling approach for centrifugal compressors. All compressors analysed are of the automotive turbocharger variety and have typical upstream geometry with no casing treatments or pre-swirl 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 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 modelling has been fully validated using measurements taken from hot gas stand tests for all compressor stages.

The new modelling 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 modelling 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 modelling 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.
Original languageEnglish
Publication statusPublished - 16 Jun 2014
EventASME Turbo Expo 2014: Turbine Technical Conference and Exposition - Düsseldorf, Germany
Duration: 16 Jun 201420 Jun 2014

Conference

ConferenceASME Turbo Expo 2014: Turbine Technical Conference and Exposition
CountryGermany
CityDüsseldorf
Period16/06/201420/06/2014

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