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Research Papers

# Mean Value Modeling and Analysis of HCCI Diesel Engines With External Mixture Formation

[+] Author and Article Information
Marcello Canova1

Center for Automotive Research, Ohio State University, 930 Kinnear Road, Columbus, OH 43212canova.1@osu.edu

Shawn Midlam-Mohler, Yann Guezennec, Giorgio Rizzoni

Center for Automotive Research, Ohio State University, 930 Kinnear Road, Columbus, OH 43212

1

Corresponding author.

J. Dyn. Sys., Meas., Control 131(1), 011002 (Dec 04, 2008) (14 pages) doi:10.1115/1.2977465 History: Received February 24, 2006; Revised November 14, 2007; Published December 04, 2008

## Abstract

Homogeneous charge compression ignition (HCCI) is a promising concept for internal combustion engines that can considerably decrease $NOx$ and soot emissions in part-load operations without penalizing fuel consumption. The HCCI combustion can be implemented in direct injection diesel engines without major modifications by introducing a specialized fuel injector in the intake port. This decouples the homogeneous mixture formation from the traditional in-cylinder injection, thus providing two fueling systems that can be used to optimize exhaust emissions and fuel consumption over the engine operating range. However, understanding and controlling the complex mechanisms and interactions driving the HCCI combustion process is still a difficult task. For this reason, it is essential to identify the most important control parameters and understand their influence on the auto-ignition process. The current work analyzes HCCI combustion with external mixture formation through experimental investigation and the definition of a control-oriented model. An extensive testing activity was performed on a passenger car diesel engine equipped with an external fuel atomizer to operate in HCCI mode. This provided an understanding of the process as well as experimental data to identify a mean value model of the system and its parameters. The model includes a thermodynamic combustion calculation that estimates the heat release, cylinder pressure, and the relevant variables for combustion control. The tool developed was then validated and used for analyzing the system behavior in steady state conditions. Finally, a description of the HCCI system behavior in transient operations is presented.

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## Figures

Figure 4

Block diagram of the HCCI engine model

Figure 5

Results of the compressor flow mapping

Figure 6

Example of fuel burn rate model calibration: (a) ṁfuel=0.9 g/s, EGR=0%; (b) ṁfuel=0.9 g/s, EGR=20%; and (c) ṁfuel=0.9 g/s, EGR=40%

Figure 3

Comparison of the cylinder pressure and heat release rate in CIDI and HCCI mode (test condition: 2000 rpm, 25 Nm)

Figure 1

Schematic of the test engine setup

Figure 2

Comparison of NOx emissions and engine fuel efficiency (test condition: 2000 rpm, 25 Nm)

Figure 7

Mean-value model validation results: (a) intake manifold pressure (bar), (b) intake manifold temperature (°C), (c) exhaust manifold pressure (bar), (d) exhaust manifold temperature (°C), (e) air/fuel ratio (−), and (f) EGR ratio (%)

Figure 8

Validation of the combustion model at 1800 rpm: (a) ṁfuel=0.79 g/s, EGR=0%; (b) ṁfuel=0.79 g/s, EGR=20%; and (c) ṁfuel=0.79 g/s, EGR=40%

Figure 9

Validation of the combustion model at 2000 rpm: (a) ṁfuel=0.67 g/s, EGR=0%; (b) ṁfuel=0.72 g/s, EGR=0%; and (c) ṁfuel=0.99 g/s, EGR=0%

Figure 10

Results of steady state simulations for engine mapping: (a) intake manifold states and (b) mass air flow rate and engine IMEP

Figure 11

Manifold state mapping at 1500 rpm: (a) intake manifold pressure (bar), (b) intake manifold temperature (°C), (c) exhaust manifold pressure (bar), and (d) exhaust manifold temperature (°C)

Figure 12

Combustion output mapping at 1500 rpm: (a) CA50 (CAD), (b) maximum pressure gradient (bar/CAD), (c) BMEP (bar), and (d) BSFC (g/kWh)

Figure 13

Mapping of BSFC and BMEP for static optimization: (a) engine speed: 1000 rpm, (b) engine speed: 1500 rpm, and (c) engine speed: 2000 rpm

Figure 14

System dynamic response to a load transient: (a) intake and exhaust manifold states and (b) EGR ratio and air/fuel ratio

Figure 15

System dynamic response to a load transient: combustion submodel outputs

Figure 16

System dynamic response to a load transient: in-cylinder variables: (a) in-cylinder pressure and (b) normalized fuel burn rate (FBR) function

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