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Research Papers: Internal Combustion Engines

The Effect of Iso-Octane Addition on Combustion and Emission Characteristics of a HCCI Engine Fueled With n-Heptane

[+] Author and Article Information
Cosmin E. Dumitrescu1

Institute for Chemical Process and Environmental Technology, National Research Council of Canada, 1200 Montreal Road, Ottawa, ON, K1A 0R6, Canadacosmin.dumitrescu@nrc-cnrc.gc.ca

Hongsheng Guo, Vahid Hosseini, W. Stuart Neill, Wallace L. Chippior

Institute for Chemical Process and Environmental Technology, National Research Council of Canada, 1200 Montreal Road, Ottawa, ON, K1A 0R6, Canada

Trevor Connolly

 Environment Canada, Ottawa, ON, K1A 0H3, Canada

Lisa Graham

 University of Canterbury, Christchurch 8140, New Zealand

Hailin Li

 West Virginia University, Morgantown, WV 26506-6106

1

Corresponding author.

J. Eng. Gas Turbines Power 133(11), 112801 (May 13, 2011) (7 pages) doi:10.1115/1.4003640 History: Received April 14, 2010; Revised November 16, 2010; Published May 13, 2011; Online May 13, 2011

This paper investigates the effects of iso-octane addition on the combustion and emission characteristics of a single-cylinder, variable compression ratio, homogeneous charge compression ignition (HCCI) engine fueled with n-heptane. The engine was operated with four fuel blends containing up to 50% iso-octane by liquid volume at 900 rpm, 50:1 air-to-fuel ratio, no exhaust gas recirculation, and an intake mixture temperature of 30°C. A detailed analysis of the regulated and unregulated emissions was performed including validation of the experimental results using a multizone model with detailed fuel chemistry. The results show that iso-octane addition reduced HCCI combustion efficiency and retarded the combustion phasing. The range of engine compression ratios where satisfactory HCCI combustion occurred was found to narrow with increasing iso-octane percentage in the fuel. NOx emissions increased with iso-octane addition at advanced combustion phasing, but the influence of iso-octane addition was negligible once CA50 (crank angle position at which 50% heat is released) was close to or after top dead center. The total unburned hydrocarbons (THC) in the exhaust consisted primarily of alkanes, alkenes, and oxygenated hydrocarbons. The percentage of alkanes, the dominant class of THC emissions, was found to be relatively constant. The alkanes were composed primarily of unburned fuel compounds, and iso-octane addition monotonically increased and decreased the iso-octane and n-heptane percentages in the THC emissions, respectively. The percentage of alkenes in the THC was not significantly affected by iso-octane addition. Iso-octane addition increased the percentage of oxygenated hydrocarbons. Small quantities of cycloalkanes and aromatics were detected when the iso-octane percentage was increased beyond 30%.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Combustion phasing (CA50) versus CR for four PRF blends

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Figure 2

Combustion efficiency versus combustion phasing for four PRF blends

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Figure 3

Measured (EXP) and calculated (NS) cylinder pressure traces at CA50≈−5 deg CA ATDC for four PRF blends

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Figure 4

CO, THC, and NOx emissions versus combustion phasing (CA50) for four PRF blends

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Figure 5

Selected hydrocarbon percentages in THC emissions at CA50≈−5 deg CA ATDC for four PRF blends

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