Spatial correlation of heat release rate and sound emission from turbulent premixed flames

作者：Liu Yu^*; Dowling Ann P; Swaminathan Nedunchezhian; Dunstan Thomas D

来源：Combustion and Flame, 2012, 159(7): 2430-2440.

DOI：10.1016/j.combustflame.2012.03.003

• Combustion noise from open flames
• Two-point correlation
• Heat release rate fluctuation
• Correlation volume and length scale
• DNS V-flames

The two-point spatial correlation of the rate of change of fluctuating heat release rate is central to the sound emission from open turbulent flames, and a few attempts have been made to address this correlation in recent studies. In this paper, the two-point correlation and its role in combustion noise are studied by analysing direct numerical simulation (DNS) data of statistically multi-dimensional turbulent premixed flames. The results suggest that this correlation function depends on the separation distance and direction but, not on the positions inside the flame brush. This correlation can be modelled using a combination of Hermite-Gaussian functions of zero and second order, i.e. functions of the form (1 - Ax(2))e-(Bx2) for constants A and B, to include its possible negative values. The integral correlation volume obtained using this model is about 0.2 delta(3)(L) with the length scale obtained from its cube root being about 0.6 delta(L), where delta(L), is the laminar flame thermal thickness. Both of the values are slightly larger than the values reported in an earlier study because of the anisotropy observed for the correlation. This model together with the turbulence-dependent parameter kappa, the ratio of the root-mean-square (RMS) value of the rate of change of reaction rate to the mean reaction rate, derived from the DNS data is applied to predict the far-field sound emitted from open flames. The calculated noise levels agree well with recently reported measurements and show a sensitivity to kappa values.

• 出版日期2012-7