Identification of combustion mode under MILD conditions using Chemical Explosive Mode Analysis

Doan, Nguyen Anh Khoa; Bansude, S.; Osawa, K.; Minamoto, Yuki; Lu, T.; Chen, J. H.; Swaminathan, Nedunchezhian

Identification of combustion mode under MILD conditions using Chemical Explosive Mode Analysis

Journal article (2021)

Authors

Nguyen Anh Khoa Doan Technische Universität München

S. Bansude University of Connecticut

K. Osawa Tokyo Institute of Technology

Yuki Minamoto Tokyo Institute of Technology

T. Lu University of Connecticut

J. H. Chen Sandia National Laboratories, California

Nedunchezhian Swaminathan University of Cambridge

Affiliation

External organisation

MILD combustion Turbulent combustion CEMA Deflagration Ignition

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Published Date

2021

Language

English

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Abstract

Direct Numerical Simulations (DNS) data of Moderate or Intense Low-oxygen Dilution (MILD) combustion are analysed to identify the contributions of the autoignition and flame modes. This is performed using an extended Chemical Explosive Mode Analysis (CEMA) which accounts for diffusion effects allowing it to discriminate between deflagration and autoignition. This analysis indicates that in premixed MILD combustion conditions, the main combustion mode is ignition for all dilution and turbulence levels and for the two reactant temperature conditions considered. In non-premixed conditions, the preponderance of the ignition mode was observed to depend on the axial location and mixture fraction stratification. With a large mixture fraction lengthscale, ignition is more preponderant in the early part of the domain while the deflagrative mode increases further downstream. On the other hand, when the mixture fraction lengthscale is small, sequential autoignition is observed. Finally, the various combustion modes are observed to correlate strongly with mixture fraction where lean mixtures are more likely to autoignite while stoichiometric and rich mixtures are more likely to react as deflagrative structures.