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Research Papers: Gas Turbines: Cycle Innovations

Steady Modeling of a Turbocharger Turbine for Automotive Engines

[+] Author and Article Information
Fabio Bozza

e-mail: fabio.bozza@unina.it

Vincenzo De Bellis

e-mail: vincenzo.debellis@unina.it
University of Naples “Federico II”
Industrial Engineering Department (Mechanical and Energetic Section),
Via Claudio 21,
Napoli 80125, Italy

Contributed by the Cycle Innovations Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received January 30, 2013; final manuscript received July 9, 2013; published online October 21, 2013. Assoc. Editor: Song-Charng Kong.

J. Eng. Gas Turbines Power 136(1), 011701 (Oct 21, 2013) (13 pages) Paper No: GTP-13-1036; doi: 10.1115/1.4025263 History: Received January 30, 2013; Revised July 09, 2013

Nowadays the turbocharging technique is playing a fundamental role in improving automotive engine performance and reducing fuel consumption and the exhaust emissions, in spark-ignition and compression ignition engines, as well. To this end, one-dimensional (1D) modeling is usually employed to compute the engine-turbocharger matching, to select the boost level in different operating conditions, and to estimate the low-end torque level and the transient response. However, 1D modeling of a turbocharged engine requires the availability of the turbine and compressor characteristic maps. This leads to some typical drawbacks: (1)Performance maps of the turbocharger device are usually limited to a reduced number of rotational speeds, pressure ratios, and mass flow rates because of turbine/compressor matching limits; (2) as a consequence of previous issue, unphysical extrapolation of maps' data is commonly required; and (3) heat transfer conditions may strongly differ between test bench measurements and actual operation, where turbocharger is coupled to an internal combustion engine. To overcome the above problems, in the present paper a numerical procedure is introduced: It solves 1D steady flow equations inside the turbine components with the aim of accurately reproducing the experimentally derived characteristic maps. The steady procedure describes the main phenomena and losses arising within the stationary and rotating channels constituting the turbine. It is utilized to directly compute the related steady maps, starting from the specification of a reduced set of geometrical data. An optimization process is employed to identify a number of tuning constants included in the various loss correlations. The procedure is applied to the simulation of five different turbines: three waste-gated turbines, a twin-entry turbine, and a variable geometry turbine. The numerical results show good agreement with the experimentally derived maps for all the tested devices. The model is, hence, used to evaluate the turbine performance in the whole operating domain.

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References

Figures

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Fig. 1

Waste-gate turbine 1D model

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Fig. 2

Vaned nozzle turbine 1D model

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Fig. 4

(a) Diameters and (b) blade angles at wheel inlet and outlet

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Fig. 5

Rotation angles at wheel inlet and outlet

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Fig. 6

Date required for meridian profiles reconstruction, (a) elliptical and (b) Bezier curves

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Fig. 7

Infinitesimal wheel element schematization

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Fig. 8

Wheel simplified reconstruction (red) and “reverse engineering” geometry (gray) comparison

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Fig. 9

Wheel refined reconstruction (red) and “reverse engineering” geometry (gray) comparison

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Fig. 10

Schematization required to derive the geometry of the 1D blade to blade duct: (a) conical surface generating line, (b) cross section in the meridian plane, and (c) in the plane normal to the meanline

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Fig. 11

Vaned nozzle diameters

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Fig. 12

Vaned nozzle rotation angles

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Fig. 13

Vaned nozzle blade angles

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Fig. 14

Volute inlet and outlet velocity triangles

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Fig. 16

Velocity triangle at wheel outlet

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Fig. 15

Velocity triangle in off-design operation, for incidence losses calculation

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Fig. 24

Turbine E reduced mass flow rate versus expansion ratio map

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Fig. 27

Turbine C efficiency versus expansion ratio map

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Fig. 28

Turbine D efficiency versus expansion ratio map

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Fig. 29

Turbine E efficiency versus expansion ratio map

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Fig. 25

Turbine A efficiency versus expansion ratio map

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Fig. 26

Turbine B efficiency versus expansion ratio map

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Fig. 17

Power and heat flux in a turbocharger

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Fig. 18

Logic development of the optimization procedure (the scheme refers to turbine B)

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Fig. 19

Mass flow rate/efficiency plane identified by the optimization procedure, B turbine

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Fig. 20

Turbine A reduced mass flow rate versus expansion ratio map

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Fig. 21

Turbine B reduced mass flow rate versus expansion ratio map

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Fig. 22

Turbine C reduced mass flow rate versus expansion ratio map

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Fig. 23

Turbine D reduced mass flow rate versus expansion ratio map

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Fig. 30

Extended reduced mass flow rate versus expansion ratio map of turbine E

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Fig. 31

Extended efficiency versus expansion ratio map of turbine E

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