Comparison of Premixed Turbulent Burning Velocity Models Taking Account of Turbulence and Flame Spatial Scales 930218

Conventionally, turbulent burning velocity models are compared by showing the model-predicted S_T/S_L0 ratios in an S_T/S_L0 - u′/S_L0 plane, where S_T and S_L0 are the turbulent and laminar burning velocities, respectively, with u′ being the turbulence intensity. Such a method applies to only those models which take u′ or u′/S_L0 as the only variable of S_T or of S_T/S_L0.

In order to analyze and compare most recent models in which turbulence and flame spatial scales (or length scales) are also taken into account because of their importance in combustion, this paper showed the model-predicted S_T/S_L0 ratios as contours in three planes (Re-Da, η_κ/η₀ - u′/S_L0 and L/η₀ - u′/S_L0, where Re, Da, L, η_κ and η₀ are the Reynolds number, Damköhler number, turbulence integral scale, Kolmogorov scale and laminar flame preheat zone thickness, respectively); these planes are usually used in discussing the flame structure. The obtained planes showing contours of the model-predicted S_T/S_L0 ratios were referred to as burning velocity diagrams of the models. As a burning velocity diagram shows not only detailed S_T/S_L0 ratios under different u′/S_L0 ratios but also those under different ratios of L/η₀, as well as the overall characteristics of the model (such as the flame quenching limit, etc.) at the same time, it gives a thorough representation of the model. Therefore, comparison of different models on the basis of their respective burning velocity diagrams can take account of the influences of turbulence and flame spatial scales in addition to the influences of the u′/S_L0 ratios. Five models proposed by different authors were shown as diagrams respectively. Based on the diagrams obtained and with an emphasis put on a model proposed by the authors previously, these models were discussed and compared with recent experimental results on (1) S_T/S_L0 ratios under the same turbulence characteristics and the same mixture properties; (2) flame quenching limit and; (3) relation between turbulent burning velocity and flame structure.