A modelling approach for hydrogen doped lean premixed turbulent combustion

Muppala, Siva Prasad Reddy [UCL] Papalexandris, Miltiadis [UCL]

In this study, we investigate some preliminary reaction model predictions analytically in comparison with experimental premixed turbulent combustion data from four different flame configurations, which include i) high-jet enveloped, ii) expanding spherical, iii) Bunsen-like, and iv) wide-angled diffuser flames. The special intent of the present work is to evaluate the workability range of the model to hydrogen and hydrogen-doped hydrocarbon mixtures, emphasizing on the significance of preferential diffusion, PD, and Le effects in premixed turbulent flames. This is carried out in two phases: first, involving pure hydrocarbon and pure hydrogen mixtures from two independent measured data, and second, with the blended mixtures from two other data sets. For this purpose, a novel reaction closure embedded with explicit high-pressure and exponential Lewis number terms developed in the context of hydrocarbon mixtures is used. These comparative studies based on the global quantity, turbulent flame speed, indicate that the model predictions are encouraging yielding proper quantification along with reasonable characterization of all the four different flames, over a broad range of turbulence, fuel-types and for varied equivalence ratios. However, with each flame involved the model demands tuning of the (empirical) constant to allow for either or both of these effects, or for the influence of the burner geometry. This provisional stand remains largely insufficient. Therefore, a submodel for chemical time scale from the leading point analysis based on the critically curved laminar flames employed in earlier studies for expanding spherical flames is introduced here. By combining the submodel and the reaction closure, the dependence of turbulent flame speed on physicochemical properties of the burning mixtures including the strong dependence of preferential diffusion and/or Le effects can be determined.