LES flamelet modeling of hydrogen combustion considering preferential diffusion effect

Abstract

A flamelet-generated manifold (FGM) method that explicitly considers the preferential diffusion effect, referred to as FGM-PD method, is employed for large-eddy simulations (LESs) of a lean-premixed H2/air low-swirl lifted flame, and the validity is examined by comparing with the experiment. First, the applicability of the FGM-PD method is investigated by one-dimensional numerical simulations of planar laminar premixed H2/air flames. Next, LESs of a lean-premixed H2/air low-swirl lifted flame are performed employing the FGM-PD and conventional FGM methods. Results of the one-dimensional numerical simulations show the importance of considering preferential diffusion to accurately predict species concentrations near the flame front. The FGM-PD method accurately predicts this, and therefore, reproduces the laminar burning velocity and spatial distributions of temperature and mixture fraction. Three-dimensional LES results confirm that the prediction accuracy of the velocities near the flame front is improved by employing this FGM-PD method. Additionally, the OH mass fraction distribution predicted by the FGM-PD method exhibits the inhomogeneous finger-like structure, which has been observed in previous experiments. This inhomogeneity of OH mass fraction distribution, which corresponds to that of the reaction rate, predicted by the FGM-PD method, strongly affects the flame front structure.