Investigation of Flame Stretch in Turbulent Lifted Jet Flame
Combustion Science and Technology
Taylor & Francis
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Ruan, S., Swaminathan, S., & Mizobuchi, Y. (2014). Investigation of Flame Stretch in Turbulent Lifted Jet Flame. Combustion Science and Technology, 186 243-272. https://doi.org/10.1080/00102202.2013.877335
DNS data of a laboratory-scale turbulent lifted hydrogen jet flame has been analysed to show that this flame has mixed mode combustion not only at the flame base but also in downstream locations. The mixed mode combustion is observed in instantaneous structures as in earlier studies and in averaged structure, in which the predominant mode is found to be premixed combustion with varying equivalence ratio. The nonpremixed combustion in the averaged structure is observed only in a narrow region at the edge of the jet shear layer. The analyses of flame stretch show large probability for negative flame stretch leading to negative surface averaged flame stretch. The displacement speed-curvature correlation is observed to be negative contributing to the negative flame stretch and partial premixing resulting from jet entrainment acts to reduce the negative correlation. The contribution of turbulent straining to the flame stretch is observed to be negative when the scalar gradient aligns with the most extensive principal strain rate. The physics behind the negative flame stretch resulting from turbulent straining is discussed and elucidated through a simple analysis of the flame surface density transport equation.
Partially Premixed Flame, Flame Surface Density, Displacement Speed, Turbulent flame stretch, Lifted jet flame, Mixed mode combustion
The authors are grateful for the inspiring discussion with Prof. K.N.C. Bray, and financial support from Mitsubishi Heavy Industries (MHI) is gratefully acknowledged. A part of this work is performed under the collaborative research between Cambridge University and JAXA.
External DOI: https://doi.org/10.1080/00102202.2013.877335
This record's URL: https://www.repository.cam.ac.uk/handle/1810/246763