Consideration on the Flow Velocity in the Experimental Analysis of the Flame Displacement Speed Using DNS Data of Turbulent Premixed Flames with Different Lewis Numbers

Kazuya Tsuboi,Eiji Tomita,Shingo Morishita

doi:10.4236/ojfd.2014.43021

Abstract

The flame displacement speed is one of the major characteristics in turbulent premixed flames. The flame displacement speed is experimentally obtained from the displacement normal to the flame surface, while it is numerically evaluated by the transport equation of the flame surface. The flame displacement speeds obtained both experimentally and numerically cannot be compared directly because their definitions are different. In this study, two kinds of experimental flame displacement speeds—involving the mean inflow velocity and the local flow velocity—were simulated using the DNS data with the different Lewis numbers, and were compared with the numerical flame displacement speed. The simulated experimental flame displacement speed involving the mean inflow velocity had no correlation with the numerical flame displacement speed, while the simulated displacement speed involving the local flow velocity had a clear correlation with the numerical displacement speed in the cases of higher Lewis number than unity. The correlation coefficient of the simulated displacement speed involving the local flow velocity with the numerical displacement speed had a maximum value on the isosurface of the reaction progress variable with the maximum temperature gradient where the dilation effect of the flame is strongest.

Highlights

Turbulent flames are the configuration to have been widely used for actual combustors for automobiles, ships, aircraft, power generations, and industrial furnaces
The flame displacement speed is experimentally obtained from the displacement normal to the flame surface, while it is numerically evaluated by the transport equation of the flame surface which is defined as the isosurface of the reaction progress variable
The correlation coefficients were low values in all cases, even the largest coefficient on the isosurface of cT = 0.690 in case Mh did not reach 0.3. This implies that the mean inflow velocity is not appropriate to the flow velocity involved in the flame displacement speed

Summary

Introduction

Turbulent flames are the configuration to have been widely used for actual combustors for automobiles, ships, aircraft, power generations, and industrial furnaces. The flame displacement speed is experimentally obtained from the displacement normal to the flame surface, while it is numerically evaluated by the transport equation of the flame surface which is defined as the isosurface of the reaction progress variable. In the simulated analysis on the experimental flame displacement speed, the treatment of the local flow on the flame surface was discussed, and it was found that the correlation between the experimental and numerical flame displacement speeds was affected by the density ratio and the isosurface of the reaction progress variable due to the dilation effect of the flame. The two-dimensional flame displacement speed obtained with simulating the experimental measurement and analysis was compared with the two-dimensional flame displacement speed numerically evaluated by the transport equation, and subsequently the correlation between the both flame displacement speeds was shown. The experimental measurement and analysis on the flame displacement speed were assessed on the basis of the results simulated them using the DNS data

DNS Database

Numerical Analysis Simulating Experimental Measurement

Flame Displacement Speed Involving the Mean Inflow Velocity

Flame Displacement Speed Involving the Local Flow Velocity

Conclusion