https://hal.archives-ouvertes.fr/hal-00803230/document

Large Eddy Simulations of gaseous flames in gas turbine combustion chambers

Direct numerical simulation of a three-dimensional spatially developing turbulent slot-burner Bunsen flame has been performed with a new reduced methane–air mechanism. The mechanism, derived from sequential application of directed relation graph theory, sensitivity analysis and computational singular perturbation over the GRI-1.2 detailed mechanism is non-stiff and tailored to the lean conditions of the DNS. The simulation is performed for three flow through times, long enough to achieve statistical stationarity. The turbulence parameters have been chosen such that the combustion occurs in the thin reaction zones regime of premixed combustion. The data is analyzed to study possible influences of turbulence on the structure of the preheat and reaction zones. The results show that the mean thickness of the turbulent flame, based on progress variable gradient, is greater than the corresponding laminar flame. The effects of flow straining and flame front curvature on the mean flame thickness are quantified through conditional means of the thickness and by examining the balance equation for the evolution of the flame thickness. Finally, conditional mean reaction rate of key species compared to the laminar reaction rate profiles show that there is no significant perturbation of the heat release layer.

Structure of a spatially developing turbulent lean methane–air Bunsen flame

Molecular transport effects on turbulent flame propagation and structure

Large-eddy simulation of a lifted methane jet flame in a vitiated coflow

Premixed and nonpremixed generated manifolds in large-eddy simulation of Sandia flame D and F

Approximating the chemical structure of partially premixed and diffusion counterflow flames using FPI flamelet tabulation

Many models are now available to describe chemistry at a low CPU cost, but only a few of them can be used to describe correctly premixed, partially premixed and diffusion combustion. One of them is the FPI model that uses two coordinates: the mixture fraction Z and the progress variable c. In this paper, we introduce a new evolution of the FPI method that can now handle heat losses. After a short review of kinetic models used in turbulent combustion, the main features of the new three-dimensional FPI method, in which we introduce a third coordinate for enthalpy h, are presented. First, a one-dimensional radiative premixed flame validation case is presented for a large range of radiative heat losses. Second, we present the results of simulations of two laminar burners. Both the fully and the partially premixed burner simulations give a good estimation of all the flame features such as the flame stabilization (driven by heat losses), the flame structure and the profile of major and minor species.

Modelling non-adiabatic partially premixed flames using flame-prolongation of ILDM

Tabulated chemistry and presumed probability density function (PDF) approaches are combined to perform RANS modeling of premixed turbulent combustion. The chemistry is tabulated from premixed flamelets with three independent parameters: the equivalence ratio of the mixture, the progress of reaction, and the specific enthalpy, to account for heat losses at walls. Mean quantities are estimated from presumed PDFs. This approach is used to numerically predict a turbulent premixed flame diluted by hot burnt products at an equivalence ratio that differs from the main stream of reactants. The investigated flame, subjected to high velocity fluctuations, has a thickened-wrinkled structure. A recently proposed closure for scalar dissipation rate that includes an estimation of the coupling between flame wrinkling and micromixing is retained. Comparisons of simulations with experimental measurements of mean velocity, temperature, and reactants are performed.

Premixed turbulent combustion modeling using tabulated detailed chemistry and PDF

An experimental study of mild flameless combustion of methane/hydrogen mixtures

A method for improving the performance of a radiating burner designed to be supplied during operation by means of a flow (F) comprising a mixture of air and combustible gas. The burner includes a body defining a combustion chamber and provided with an inlet for the mixture; a porous wicking agent closes off the chamber in a non-sealing manner and is arranged downstream of the inlet in the direction of flow (F) of the mixture; and a distribution grid is arranged between the mixture inlet and the wicking agent. The method includes creating an electric field in the combustion chamber by applying an electric potential difference of at least 5 kV between the wicking agent and the distribution grid.

Stéphane Carpentier

Papers

Approximating the chemical structure of partially premixed and diffusion counterflow flames using FPI flamelet tabulation

Modelling non-adiabatic partially premixed flames using flame-prolongation of ILDM

Premixed turbulent combustion modeling using tabulated detailed chemistry and PDF

An experimental study of mild flameless combustion of methane/hydrogen mixtures

Radiating burner having enhanced performance and method for improving the performance of a radiating burner