Pre-Chamber Ignition Mechanism: Simulations of Transient Autoignition in a Mixing Layer Between Reactants and Partially-Burnt Products

The structure of autoignition in a mixing layer between fully-burnt or partially-burnt combustion products from a methane-air flame at ϕ = 0.85 and a methane-air mixture of a leaner equivalence ratio has been studied with transient diffusion flamelet calculations. This configuration is relevant to s...

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Bibliographic Details
Published in:Flow, turbulence and combustion turbulence and combustion, 2018, Vol.101 (4), p.1093-1102
Main Authors: Sidey, Jennifer A. M., Mastorakos, Epaminondas
Format: Article
Language:English
Subjects:
Aerodynamics
Automotive Engineering
Combustion products
Ejection
Engineering
Engineering Fluid Dynamics
Engineering Thermodynamics
Engines
Equivalence ratio
Fluid dynamics
Fluid flow
Fluid- and Aerodynamics
Heat and Mass Transfer
Ignition
Methane
Natural gas
Organic chemistry
Spontaneous combustion
Turbulent jets
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Summary:The structure of autoignition in a mixing layer between fully-burnt or partially-burnt combustion products from a methane-air flame at ϕ = 0.85 and a methane-air mixture of a leaner equivalence ratio has been studied with transient diffusion flamelet calculations. This configuration is relevant to scavenged pre-chamber natural-gas engines, where the turbulent jet ejected from the pre-chamber may be quenched or may be composed of fully-burnt products. The degree of reaction in the jet fluid is described by a progress variable c ( c = taking values 0.5, 0.8, and 1.0) and the mixing by a mixture fraction ξ ( ξ = 1 in the jet fluid and 0 in the CH 4 -air mixture to be ignited). At high scalar dissipation rates, N 0 , ignition does not occur and a chemically-frozen steady-state condition emerges at long times. At scalar dissipation rates below a critical value, ignition occurs at a time that increases with N 0 . The flame reaches the ξ = 0 boundary at a finite time that decreases with N 0 . The results help identify overall timescales of the jet-ignition problem and suggest a methodology by which estimates of ignition times in real engines may be made.
ISSN:1386-6184
1573-1987
DOI:10.1007/s10494-018-9960-0