Effects of Dilution and Flammability Changes on Mixture Reactivity in a Natural Gas Internal Combustion Engine

Changes in the flammability characteristics of a combusting mixture and its 'dilution' levels - characterized, respectively, by the mixture's equivalence ratio and residual gas fraction - can have significant impacts on the nature of combustion in internal combustion engines. These co...

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Bibliographic Details
Published in:Combustion science and technology 2023-07, Vol.195 (10), p.2381-2399
Main Authors: Bajwa, A. U., Linker, T., Patterson, M. A., Beshouri, G., Jacobs, T. J.
Format: Article
Language:English
Subjects:
Carbon dioxide
Carbon dioxide concentration
Chemical kinetics
Combustion
cyclic variability
Diluted combustion
Dilution
Engine cylinders
engine stability
Equivalence ratio
Flame speed
Flames
Flammability
Internal combustion engines
Mixtures
Natural gas
Pressure effects
Reaction kinetics
Residual gas
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Summary:Changes in the flammability characteristics of a combusting mixture and its 'dilution' levels - characterized, respectively, by the mixture's equivalence ratio and residual gas fraction - can have significant impacts on the nature of combustion in internal combustion engines. These combustion changes can manifest as variations in combustion phasing and repeatability, and affect engine efficiency, emissions, and performance. The current work uses experimental, high-speed, in-cylinder CO 2 concentration data from a single-cylinder, natural gas-fueled engine to track compositional variations in the combusting mixture; and then uses a chemical kinetics solver to isolate the effects of flammability and dilution changes on the mixture's 'reactivity,' which is characterized by its laminar flame speed (LFS) and ignition delay (ID). It is found that LFS changes are driven strongly by the trapped equivalence ratio, while ID changes are driven primarily by dilution and pressure changes. Additionally, the effects of LFS changes on the overall combustion phasing are found to be more pronounced than those from ID changes, as the former influences both the combustion initiation and propagation processes.
ISSN:0010-2202
1563-521X
DOI:10.1080/00102202.2021.2019242