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Research Papers

Modeling and Control of an Exhaust Recompression HCCI Engine Using Split Injection

[+] Author and Article Information
Nikhil Ravi1 n2

Department of Mechanical Engineering,  Stanford University, Stanford, CA 94305nikhil.ravi@us.bosch.com

Hsien-Hsin Liao

Department of Mechanical Engineering,  Stanford University, Stanford, CA 94305hhliao@stanford.edu

Adam F. Jungkunz

Department of Mechanical Engineering,  Stanford University, Stanford, CA 94305ajungkun@stanford.edu

Chen-Fang Chang

 Propulsion Systems Research Lab, General Motors R&D Center, Warren, MI 48090chen-fang.chang@gm.com

Han Ho Song3

 Bosch Research and Technology Center, 4009 Miranda Avenue, Palo Alto, CA 94304hhsong@snu.ac.kr

J. Christian Gerdes

Department of Mechanical Engineering,  Stanford University, Stanford, CA 94305gerdes@stanford.edu

1

Corresponding author.

2

Current address: Bosch Research and Technology Center, 4005 Miranda Avenue, Palo Alto, CA 94304.

3

Current address: Department of Mechanical Engineering, Seoul National University, Seoul, South Korea.

J. Dyn. Sys., Meas., Control 134(1), 011016 (Dec 05, 2011) (12 pages) doi:10.1115/1.4004787 History: Received February 16, 2010; Revised June 09, 2011; Published December 05, 2011; Online December 05, 2011

Homogeneous charge compression ignition (HCCI) is currently being pursued as a cleaner and more efficient alternative to conventional engine strategies. Control of the load and phasing of combustion is critical in the effort to ensure reliable operation of an HCCI engine over a wide operating range. This paper presents an approach for modeling the effect of a small pilot injection during the recompression process of an HCCI engine, and a controller that uses the timing of this pilot injection to control the phasing of combustion. The model is a nonlinear physical model that captures the effect of fuel quantity and intake and exhaust valve timings on work output and combustion phasing. It is seen that around the operating points considered, the effect of a pilot injection can be modeled as a change in the Arrhenius threshold, an analytical construct used to model the phasing of combustion as a function of the thermodynamic state of the reactant mixture. The relationship between injection timing and combustion phasing can be separated into a linear, analytical component and a nonlinear, empirical component. Two different control strategies based on this model are presented, both of which enabled steady operation at low load conditions and effectively track desired load-phasing trajectories. These strategies demonstrate the potential of split injection as a practical cycle-by-cycle control knob requiring only minimal valve motion that would be easily achievable on current production engines equipped with cam phasers.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

HCCI with exhaust recompression––in-cylinder pressure

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Figure 2

Comparison of in-cylinder pressure between main and early injection of fuel (five engine cycles each)

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Figure 3

Comparison of in-cylinder pressure between 6 mg and 10 mg early injected fuel (five engine cycles each)

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Figure 4

Comparison of in-cylinder pressure with different pilot injection timings (five engine cycles each)

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Figure 5

Variation of combustion phasing (CA50 ) with pilot injection timing

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Figure 6

Relationship between combustion threshold and combustion phasing

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Figure 7

Relationship between combustion threshold and fuel residence time

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Figure 8

Midranging controller––block diagram

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Figure 9

Phasing controller without midranging action––simulation results

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Figure 10

Phasing controller with midranging action––simulation results

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Figure 11

Experimental control results––feedback + feedforward + integral controller (dotted line––desired trajectory, solid line––actual trajectory)

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Figure 12

Experimental control results––controller range (dotted line––desired trajectory, solid line––actual trajectory)

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Figure 13

Experimental control results––controller limits (dotted line––desired trajectory, solid line––actual trajectory)

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Figure 14

Midranging control––experimental results

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Figure 15

Cycle-by-cycle action of controller––cylinder 2

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