Investigation of an inhomogeneous turbulent mixing model for conditional moment closure applied to autoignition

Journal Article · Sun Aug 15 00:00:00 EDT 2010 · Combustion and Flame

DOI:https://doi.org/10.1016/J.COMBUSTFLAME.2010.05.001· OSTI ID:21331451

Milford, A; Devaud, C B ^[1]

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1. Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON (Canada)

The present paper examines the case of autoignition of high pressure methane jets in a shock tube over a range of pre-heated air temperatures in engine-relevant conditions. The two objectives of the present paper are: (i) to examine the effect of the inhomogeneous mixing model on the autoignition predictions relative to the results obtained using homogeneous mixing models and (ii) to see if the magnitude of the change can explain the discrepancy between the predictions of ignition delay previously obtained with homogeneous mixing models and the experimental data. The governing equation of the scalar dissipation rate is solved for transient conditions and two different formulations of the same model are tested and compared: one using the linear model for the conditional velocity and one including the gradient diffusion model. The predicted ignition kernel location and time delay over a range of pre-combustion air temperatures are compared with results obtained using two homogeneous turbulent mixing models and available experimental data. The profiles of conditional velocity and the conditional scalar dissipation rate are examined. Issues related to the conditional velocity model are discussed. It is found that the differences in the predictions are due to the mixing model only. The inhomogeneous model using the gradient conditional velocity model produces much larger ignition delays compared to the other models, whereas the inhomogeneous form including the linear model does not produce any significant differences. The effect of the turbulent inhomogeneous model is larger at high air temperatures and decreases with decreasing air temperatures. In comparison with the measured ignition delays, the inhomogeneous-Gradient model brings a small improvement at high air temperatures over the results from the turbulent homogeneous models. At low air temperatures, other parameters need to be investigated in order to bring the predicted ignition delays and locations within the experimental data scatter. (author)

• OSTI ID: 21331451
• Journal Information: Combustion and Flame, Vol. 157, Issue 8; Other Information: Elsevier Ltd. All rights reserved; ISSN 0010-2180
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
AIR
AUTOIGNITION
MIXING
PRESSURE RANGE MEGA PA 10-100
METHANE
VELOCITY
MATHEMATICAL MODELS
SCALARS
COMPARATIVE EVALUATIONS
SHOCK TUBES
TIME DELAY
DIFFUSION
INTERNAL COMBUSTION ENGINES
JETS
KERNELS
TRANSIENTS
TURBULENCE
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 1000-4000 K
Scalar dissipation rate
Conditional moment closure