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Research Papers

Physics Based Control Oriented Model for HCCI Combustion Timing

[+] Author and Article Information
Mahdi Shahbakhti

Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta T6G 2G8, Canadam.shahbakhti@ualberta.ca

Charles Robert Koch1

Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta T6G 2G8, Canadabob.koch@ualberta.ca

In Ref. 48, the need for instantaneous parameters is removed by modifying the Arrhenius rate threshold model.

This heat capacity effect also delays HCCI auto-ignition timing and prolongs the combustion duration when EGR is increased (52).

TKM simulations in which the second stage of HCCI combustion occurs at the crank angle higher than 15 deg after Top Dead Center (TDC).

1

Corresponding author.

J. Dyn. Sys., Meas., Control 132(2), 021010 (Feb 04, 2010) (12 pages) doi:10.1115/1.4000036 History: Received April 02, 2008; Revised May 29, 2009; Published February 04, 2010; Online February 04, 2010

Incorporating homogeneous charge compression ignition (HCCI) into combustion engines for better fuel economy and lower emission requires understanding the dynamics influencing the combustion timing in HCCI engines. A control oriented model to dynamically predict cycle-to-cycle combustion timing of a HCCI engine is developed. The model is designed to work with parameters that are easy to measure and to have low computation time with sufficient accuracy for control applications. The model is a full-cycle model and consists of a residual gas model, a modified knock integral model, fuel burn rate model, and thermodynamic models. In addition, semi-empirical correlations are used to predict the gas exchange process, generated work and completeness of combustion. The developed model incorporates the thermal coupling dynamics caused by the residual gases from one cycle to the next cycle. The model is parameterized by over 5700 simulations from a detailed thermokinetic model and experimental data obtained from a single-cylinder engine. Cross-validation of the model with both steady-state and transient HCCI experiments for four different primary reference fuel blends is detailed. With seven model inputs, the combustion timing of over 150 different HCCI points is predicted to within an average error of less than 1.5 deg of crank angle. A narrow window of combustion timing is found to provide stable and efficient HCCI operation.

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Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Main modeling approaches to predict HCCI combustion timing for control applications

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Figure 2

MKIM predicted SOC versus TKM simulations at various engine conditions at 800 rpm using PRF0 as the fuel: the line represents where SOC from MKIM and that of TKM are the same

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Figure 3

Measured lift profile for the valves used in this study. (The solid horizontal line shows the defined threshold (≃0.15 mm) for opening/closing point of valves.)

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Figure 4

Schematic of the developed model

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Figure 5

Simulation conversion rate for the Teoc for a sample operating point (ON=0, N=810 rpm, Φ=0.44, Pm=101 kPa, Tm=102°C)

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Figure 6

Conversion rate of the simulated residual gas mass fraction for a sample operating point (ON=0, N=810 rpm, Φ=0.44, Pm=101 kPa, Tm=102°C)

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Figure 7

Ricardo single-cylinder testbench schematic

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Figure 8

Comparison between predicted and experimental CA50 for four PRF blends at different steady-state engine conditions

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Figure 9

Equivalence ratio step: comparison between predicted and experimental cycle-by-cycle CA50 (ON=0; Pm=100 kPa, Tm=67°C, EGR=0%, Pexh=97.3 kPa)

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Figure 10

Octane number step: comparison between predicted and experimental cycle-by-cycle CA50 (Pm=110 kPa, Tm=91°C, Φ≅0.42, EGR=0%, Pexh=99 kPa)

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Figure 11

Octane number and equivalence ratio (Φ) step: comparison between predicted and experimental cycle- by-cycle CA50 (Pm=110 kPa, Tm=91°C, EGR=0%, Pexh=99 kPa)

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