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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Analysis and Modeling of the Transient Thermal Behavior of Automotive Turbochargers

[+] Author and Article Information
Richard D. Burke

Department of Mechanical Engineering,
University of Bath,
Bath BA2 7AY, UK
e-mail: R.D.Burke@bath.ac.uk

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received February 18, 2014; final manuscript received February 25, 2014; published online May 2, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(10), 101511 (May 02, 2014) (10 pages) Paper No: GTP-14-1108; doi: 10.1115/1.4027290 History: Received February 18, 2014; Revised February 25, 2014

Turbochargers are a key technology to deliver fuel consumption reductions on future internal combustion engines. However, the current industry standard modeling approaches assume the turbine and compressor operate under adiabatic conditions. Although some state of the art modeling approaches have been presented for simulating the thermal behavior, these have focused on thermally stable conditions. In this work, an instrumented turbocharger was operated on a 2.2 liter diesel engine and in parallel a one-dimensional lumped capacity thermal model was developed. For the first time this paper presents analysis of experimental and modeling results under dynamic engine operating conditions. Engine speed and load conditions were varied to induce thermal transients with turbine inlet temperatures ranging from 200 to 800 °C; warm-up behavior from 25 °C ambient was also studied. Following a model tuning process based on steady operating conditions, the model was used to predict turbine and compressor gas outlet temperatures, doing so with an RMSE of 8.4 and 7.1 °C, respectively. On the turbine side, peak heat losses from the exhaust gases were observed to be up to double those observed under thermally stable conditions due to the heat accumulation in the structure. During warm-up, the model simplifications did not allow for accurate modeling of the compressor, however on the turbine side gas temperature prediction errors were reduced from 150 to around 40 °C. The main benefits from the present modeling approach appear to be in turbine outlet temperature prediction, however modeling improvements are identified for future work.

Copyright © 2014 by ASME
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References

Figures

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Fig. 1

Turbocharger thermal instrumentation

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Fig. 2

95% response time of 0.5, 1.5, and 3 mm diameter thermocouple in air flow at 200 °C as a function of Reynolds number

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Fig. 3

Engine speed, brake torque, and turbine inlet temperature (TIT) for dynamic experiments

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Fig. 4

Brake torque and engine coolant temperature for ambient start experiment

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Fig. 5

Diagram of mode structure

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Fig. 6

Convection model identification approach for each test point

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Fig. 7

Compressor and turbine gas outlet and wall temperature predictions for no heat transfer mode, physical model, and tuned physical model compared to measured values

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Fig. 8

Absolute turbine heat transfer and fraction of total enthalpy change

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Fig. 9

Turbine heat flow breakdown including convection before and after expansion (Qbefore and Qafter), conduction to bearing housing (QBH), and convection and radiation to ambient (Qconv and Qrad)

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Fig. 10

Heat flow in bearing housing from turbine housing (Qturb to BH), to oil (Qoil) and from bearing housing to compressor housing (QBH to comp); negative values signify reversal of heat flow

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Fig. 11

Compressor heat flow breakdown showing convection before and after compression (Qbefore and Qafter, positive means from working fluid), conduction to beaing housing (QBH, positive means to bearing housing) and to ambient (Qamb, positive to ambient)

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Fig. 12

Measured and predicted compressor and turbine wall temperatures during transient experiment (eng, amb, and neu correspond to locations in Fig. 1)

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Fig. 13

Measured and modeled compressor and turbine outlet temperatures over short period of dynamic step experiment

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Fig. 14

Predicted compressor and turbine outlet gas temperatures over dynamic step cycle with and without heat transfer model

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Fig. 15

Section of dynamic experiment showing turbine inlet temperature (top frame), shaft speed (second frame), and compressor and turbine heat flows (third and bottom frame). Heat flow show transfer from gas to wall (Qgas=>wall), accumulation in structure (Qint), and external transfer from wall to ambient (Qwall=>amb).

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Fig. 16

Ratio of dynamic to steady heat flow from exhaust gases to turbine housing as a function of step change in exhaust gas temperature

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Fig. 17

Measured and predicted turbine gas outlet and turbine wall temperatures during warm-up period; amb, eng, and neu correspond to temperature locations described in Fig. 1

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