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Research Papers: Gas Turbines: Turbomachinery

Modeling and Estimation of Unmeasured Variables in a Wastegate Operated Turbocharger

[+] Author and Article Information
Rasoul Salehi

e-mail: r_salehi@mech.sharif.ir

Gholamreza Vossoughi

Professor
e-mail: vossough@sharif.edu

Aria Alasty

Professor
e-mail: aalasti@sharif.edu

School of Mechanical Engineering,
Sharif University of Technology,
Azadi Avenue,
Tehran 1458889694, Iran

1Corresponding author.

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received June 17, 2013; final manuscript received September 17, 2013; published online January 2, 2014. Assoc. Editor: Song-Charng Kong.

J. Eng. Gas Turbines Power 136(5), 052601 (Jan 02, 2014) (9 pages) Paper No: GTP-13-1169; doi: 10.1115/1.4025498 History: Received June 17, 2013; Revised September 17, 2013

Estimation of relevant turbocharger variables is crucial for proper operation and monitoring of turbocharged (TC) engines, which are important in improving fuel economy of vehicles. This paper presents mean-value models developed for estimating gas flow over the turbine and the wastegate (WG), the wastegate position, and the compressor speed in a TC gasoline engine. The turbine is modeled by an isentropic nozzle with a constant area and an effective pressure ratio calculated from the turbine upstream and downstream pressures. Another physically sensible model is developed for estimating either the WG flow or position. Provided the WG position is available, the WG flow is estimated using the orifice model for compressible fluids. The WG position is predicted considering forces from the WG passing flow and actuator. Moreover, a model for estimating the compressor speed in low and medium compressor pressure ratios is proposed, using the compressor head and efficiency modified by the turbine effective pressure ratio. The estimates of the turbocharger variables match well with the experimentally measured data. The three proposed models are simple in structure, accurate enough to be utilized for engine modeling, and suitable to be validated and calibrated on an internal combustion engine in a test cell.

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Figures

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Fig. 1

Schematic of the engine test bed and the GCU to adjust the WG position independent of the engine operation

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Fig. 2

Comparison between the turbine corrected flow and a conventional orifice corrected flow

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Fig. 3

The turbine schematic and 0D model

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Fig. 4

Modeled turbine flow compared to measured exhaust flow with closed WG

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Fig. 5

WG discharge factor at different WG positions

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Fig. 6

Wastegate schematic and its force diagram

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Fig. 7

(a) Schematic of the geometry used for the WG 3D numerical simulation; (b) normalized pressure difference across the WG flapper area at different radial positions

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Fig. 8

Results of the wastegate model: (a) wastegate flow; (b) wastegate displacement

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Fig. 9

Contribution factor of forces applied to the WG actuator

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Fig. 10

(a) The compressor characteristic map and its trajectory during the engine test points. (b) Transformation results from the compressor map and the engine test points.

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Fig. 11

(a), (b) The compressor corrected speed and ηc/Ψ at different compressor corrected flows. (c) Alignment of the test points to a single curve using the defined speed coefficient.

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Fig. 12

Sensitivity (∂/∂m·c,corr) of CFc and ηc/Ψ to the compressor corrected flow

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Fig. 13

Overall structure of the compressor speed model

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Fig. 14

Results of modeling the compressor downstream temperature

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Fig. 15

Estimation results for the compressor rotational speed, ωc

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