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Research Papers: Internal Combustion Engines

Model-Based Actuator Trajectories Optimization for a Diesel Engine Using a Direct Method

[+] Author and Article Information
Michael Benz

Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerlandmbenz@alumni.ethz.ch

Markus Hehn, Christopher H. Onder, Lino Guzzella

Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland

J. Eng. Gas Turbines Power 133(3), 032806 (Nov 10, 2010) (11 pages) doi:10.1115/1.4001807 History: Received September 09, 2009; Revised March 10, 2010; Published November 10, 2010; Online November 10, 2010

This paper proposes a novel optimization method that allows a reduction in the pollutant emission of diesel engines during transient operation. The key idea is to synthesize optimal actuator commands using reliable models of the engine system and powerful numerical optimization methods. The engine model includes a mean-value engine model for the dynamics of the gas paths, including the turbocharger of the fuel injection, and of the torque generation. The pollutant formation is modeled using an extended quasi-static modeling approach. The optimization substantially changes the input signals, such that the engine model is enabled to extrapolate all relevant outputs beyond the regular operating area. A feedforward controller for the injected fuel mass is used to eliminate the nonlinear path constraints during the optimization. The model is validated using experimental data obtained on a transient engine test bench. A direct single shooting method is found to be most effective for the numerical optimization. The results show a significant potential for reducing the pollutant emissions during transient operation of the engine. The optimized input trajectories derived assist the design of sophisticated engine control systems.

Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Illustration of a standard diesel engine system and its components

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Figure 2

Comparison between measurement data (black) and results of quasi-static simulations (gray) during a step from 20% to 80% load at 2000 rpm: (a) particulate matter emissions and (b) nitric oxide emissions

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Figure 3

Illustration of the pipe receiver model

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Figure 4

Comparison of simulation results and static measurement data: (a) engine torque and (b) engine exhaust temperature

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Figure 5

Comparison of simulation results (gray) and measurement data (black) during a load step and a load drop at constant engine speed: (a) exhaust manifold pressure and (b) turbocharger speed

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Figure 6

The used control-oriented emission and combustion model structure

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Figure 7

Comparison of simulation results and cylinder pressure analysis of (a) combustion center, (b) combustion end, and comparison of simulation results and measurement data, (c) PM, and (d) NOx emissions during a load step from 20% to 80% at 2250 rpm, measurement (black), model (gray)

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Figure 8

Comparison of simulation results and measurement data of the fuel rail pressure control system, measurement (black), simulation (gray) during a (a) pressure step and a (b) pressure drop

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Figure 9

Final model structure of the optimal control problem

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Figure 10

Comparison between measured (black) and smoothed (gray) load step at constant engine speed: (a) engine torque during the load step at 2250 rpm, and (b) engine torque during the load drop at 2750 rpm

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Figure 11

Comparison of reference (gray) and optimized (black) trajectories during a load step with an optimized start of injection at constant engine speed: (a) start of injection and (b) PM

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Figure 12

Comparison between reference (gray) and optimized (black) trajectories during a load step with an optimized fuel rail pressure at constant engine speed: (a) fuel rail pressure and (b) PM

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Figure 13

Comparison between reference (gray) and optimized (black) trajectories of the gas path actuators during a load step at constant engine speed: (a) VTG actuator position, (b) EGR valve position, (c) NOx emissions, (d) PM emissions, (e) boost pressure, and (f) EGR mass flow

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Figure 14

Comparison of reference (gray) and optimized (black) trajectories with optimized injection parameters during the load drop at constant engine speed: (a) start of injection, (b) fuel rail pressure, (c) NOx emissions, and (d) PM emissions

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Figure 15

Comparison between reference (gray) and optimized (black) trajectories of the start of injection, of the EGR valve, of the VTG actuator position, and of the throttle position during a load drop at constant engine speed: (a) start of injection, (b) EGR valve position, (c) VTG actuator position, (d) throttle position, (e) boost pressure, and (f) PM emissions

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