Modeling of complex premixed burner systems by using flamelet-generated manifolds

The numerical modeling of realistic burner systems puts a very high demand on computational resources. The computational cost of combustion simulations can be reduced by techniques that simplify the chemical kinetics. In this paper, the recently introduced flamelet-generated manifold method for premixed combustion systems is applied to laminar flames. In this method, the reduced mechanism is created by using solutions of one-dimensional flamelet equations as steady-state relations. For a methane/air mixture a manifold is constructed with two controlling variables: one progress variable and the enthalpy to account for energy losses. This manifold is used for the computation of a two-dimensional burner-stabilized flame and the results are compared with results of detailed computations. The results show that these two controlling variables are sufficient to reproduce the results of detailed computations. The influence of flame stretch on the accuracy of the method is investigated by simulating strained flames in stagnation-point flows. The computation time can be reduced by a factor of 20 when a flamelet-generated manifold is applied. The reduction in computation time enables us to perform simulations of combustion in more complex combustion systems. To show that the method can be used to give accurate predictions, a semi-practical furnace is modeled and the results are compared with temperature measurements. The experimental setup consists of a cylindrical radiating furnace with a ceramic-foam surface burner in the top disc. Radial profiles of temperature have been measured at two different heights in the furnace. The measurements agree quite well with the results of the numerical simulation using a flamelet-generated manifold. (C) 2001 by The Combustion Institute.