The local burning velocity, which is based on the consumption rate of the unburned mixture, is one of the dominant parameters in turbulent premixed flames. In this study, the evaluating method of the local burning vel...The local burning velocity, which is based on the consumption rate of the unburned mixture, is one of the dominant parameters in turbulent premixed flames. In this study, the evaluating method of the local burning velocity was investigated using DNS data of turbulent premixed flames with different Lewis numbers. The local burning velocity was evaluated by integrating the chemical reaction rates along normal to the flame surface within three kinds of integration ranges that were defined as follows: the range which is defined by the half length of normal to the flame surface between its certain point and the other point crossing the flame surface (Range 1);the range which is defined by the reaction progress variable that the chemical reaction rate along normal to a planer flame surface takes a half of the maximum value (Range 2);the range which is defined by the length of normal to the flame surface between its certain point and the point which has the extreme value of the reaction progress variable (Range 3). As a result, Range 1 and Range 2 were affected by the flame shapes greatly, since the quantities of the integration ranges fluctuated widely dependent on the variations of turbulent premixed flames. Under the conditions of the turbulent combustion in this study, Range 3, which is hardly affected by a flame shape, is considered to be appropriate to the evaluation of the local burning velocity.展开更多
The local burning velocity and the flame displacement speed are the dominant properties in the mechanism of turbulent premixed combustion. The flame displacement speed and the local burning velocity have been investig...The local burning velocity and the flame displacement speed are the dominant properties in the mechanism of turbulent premixed combustion. The flame displacement speed and the local burning velocity have been investigated separately, because the flame displacement speed can be used for the discussion of flame-turbulence interactions and the local burning velocity can be used for the discussion of the inner structure of turbulent premixed flames. In this study, to establish the basis for the discussion on the effects of turbulence on the inner structure of turbulent premixed flames, the indirect relationship between the flame displacement speed and the local burning velocity was investigated by the flame stretch, the flame curvature, and the tangential strain rate using DNS database with different density ratios. It was found that for the local tangential strain rate and the local flame curvature, the local burning velocity and the flame displacement speed had the opposite correlations in each density ratio case. Therefore, it is considered that the local burning velocity and the flame displacement speed have a negative correlation.展开更多
文摘The local burning velocity, which is based on the consumption rate of the unburned mixture, is one of the dominant parameters in turbulent premixed flames. In this study, the evaluating method of the local burning velocity was investigated using DNS data of turbulent premixed flames with different Lewis numbers. The local burning velocity was evaluated by integrating the chemical reaction rates along normal to the flame surface within three kinds of integration ranges that were defined as follows: the range which is defined by the half length of normal to the flame surface between its certain point and the other point crossing the flame surface (Range 1);the range which is defined by the reaction progress variable that the chemical reaction rate along normal to a planer flame surface takes a half of the maximum value (Range 2);the range which is defined by the length of normal to the flame surface between its certain point and the point which has the extreme value of the reaction progress variable (Range 3). As a result, Range 1 and Range 2 were affected by the flame shapes greatly, since the quantities of the integration ranges fluctuated widely dependent on the variations of turbulent premixed flames. Under the conditions of the turbulent combustion in this study, Range 3, which is hardly affected by a flame shape, is considered to be appropriate to the evaluation of the local burning velocity.
文摘The local burning velocity and the flame displacement speed are the dominant properties in the mechanism of turbulent premixed combustion. The flame displacement speed and the local burning velocity have been investigated separately, because the flame displacement speed can be used for the discussion of flame-turbulence interactions and the local burning velocity can be used for the discussion of the inner structure of turbulent premixed flames. In this study, to establish the basis for the discussion on the effects of turbulence on the inner structure of turbulent premixed flames, the indirect relationship between the flame displacement speed and the local burning velocity was investigated by the flame stretch, the flame curvature, and the tangential strain rate using DNS database with different density ratios. It was found that for the local tangential strain rate and the local flame curvature, the local burning velocity and the flame displacement speed had the opposite correlations in each density ratio case. Therefore, it is considered that the local burning velocity and the flame displacement speed have a negative correlation.
