Research Papers: Internal Combustion Engines

Premixed-Diffusive Multizone Model for Combustion Diagnostics in Conventional and PCCI Diesel Engines

[+] Author and Article Information
Mirko Baratta, Alessandro Ferrari, Roberto Finesso, Ezio Spessa

IC Engines Advanced Laboratory, Politecnico di Torino, c.so Duca degli Abruzzi 24, 10129 Torino, Italy

Andrea E. Catania1

IC Engines Advanced Laboratory, Politecnico di Torino, c.so Duca degli Abruzzi 24, 10129 Torino, Italyandrea.catania@polito.it


Corresponding author.

J. Eng. Gas Turbines Power 133(10), 102801 (Apr 25, 2011) (13 pages) doi:10.1115/1.4003048 History: Received March 16, 2010; Revised November 12, 2010; Published April 25, 2011; Online April 25, 2011

A new multizone premixed-diffusive combustion model has been developed, assessed, and applied to diagnose the burning process and emission formation in a conventional and in a premixed charge compression ignition (PCCI) diesel engine. The model is based on the Dec conceptual scheme, which considers combustion as a two-stage quasi-steady process: All fuel particles undergo a first rich premixed combustion phase, and the products complete their oxidation in close-to-stoichiometric conditions at the jet periphery through a diffusion flame. The combustion chamber contents have been divided into several homogeneous zones to which the energy and mass conservation principles were applied. The computed thermodynamic and thermochemical properties in the burned gas zones allowed a post-processing analysis to be made of the nitric oxides (NO), particulate matter (PM), and carbon monoxide (CO) formation. The model requires the in-cylinder pressure trace and other experimental engine quantities as input data and calculates the premixed and diffusive heat release rates along with the temperature and mass evolutions of the different zones. Thus, the model is not predictive but diagnostic: The objective is to interpret measured engine data in order to obtain insight into the in-chamber combustion and pollutant formation processes. The model has been tested on EGR-sweeps and under full-load conditions on the conventional engine and under a high EGR operating condition on the PCCI engine. With reference to NO emissions, the model results showed an excellent agreement with the experimental data for all the tests even when the main model parameters were kept constant for different test conditions. Good results were also obtained for the prediction of the CO and PM emission levels. Finally, for the premixed combustion zone, it was ascertained that higher local A/F ratios were required in the PCCI combustion mode than in the conventional mode as a consequence of the increase in the degree of premixing.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 1

Pressure and injection rate data (EGR=19.4%)

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Figure 2

(a) Mixture zone mass and injection rate, (b) heat release rate, and (c) premixed burned gas zone mass

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Figure 3

(a) Time-histories of heat release and injection rate, (b) mass and (c) temperature of the zones, mass of the mixture, premixed burned gas, and (d) liquid fuel zones, (e) temperature of the various diffusive burned gas zones, (f) NO, (g) CO, and (h) PM concentrations of the burned gas zones and whole in-cylinder charge

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Figure 4

(a), (c), and (e) Calculated and experimental exhaust levels of NO, CO, and PM for different EGR levels and (b), (d), and (f) at full-load conditions for different engine speeds

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Figure 5

(a) Time-histories of in-cylinder pressure and (b) its derivative with respect to CA, (c) average temperature, (d) fuel burned mass fraction, (e) heat release rate, (f) NO, (g) CO, and (h) PM emissions at the indicated EGR levels

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Figure 6

(a) and (b) Time-histories of heat release, (c) and (d) temperature, and (e) and (f) CO concentration, (a), (c), and (e) with the conventional and (b), (d), and (f) PCCI combustion calibration sets



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