Alexandria Engineering Journal (Dec 2022)
Modelling of turbulent hydrogen-blended premixed flames using algebraic flame surface wrinkling closure for the Lewis numbers and mean local burning velocity
Abstract
Hydrogen-blended fuel is of fundamental interest due to difficulties in modelling and its practical significance for the development of high-performance hydrogen combustion devices and safety technologies for the prediction and prevention of fire or explosion. In this analytical study, we validate an algebraic premixed turbulent model [13] for molecular transport effects in both spherical expanding methane flames enriched with hydrogen and Bunsen burner flames. Experiment comparisons are supported with theoretical ideas. Bunsen flames are measured at varied turbulence, equivalence ratios, temperatures, and pressures. We also consider other, very recent, experimental data [32] of similar fuel mixtures to support the trends.In the study of outwardly evolving spherical expanding flames, we present three variants of this model, with two functions based on the Lewis number Le, and one based on the experimentally measured mean local flame burning velocity SFm. The Lewis number is significant in understanding the role of the diffusion of deficient reactants, which is particularly noticeable in blended fuels. The utilitarian part of this work is to demonstrate that the Le-based premixed turbulent models take into account the preferential diffusion effect, and to embed a term that quantifies turbulent flame speed explicitly for mixtures, for example, having the same unstretched burning velocity as the model input. We show that in the modelling of turbulent burning velocity, the use of SFm avoids the use of input parameters the unstretched laminar flame speed and the Lewis number. Moreover, we validate high-pressure experiments by Bagdanavicius [12] to show that the pressure has less significant impact on the Bunsen flames and, therefore, we model without the pressure term. The model correlates well with most of the data.
