A methodology for solving unsteady premixed turbulent flame propagation problems in high Reynolds number (Re), high Damkohler number (Da) spatially evolving flows is developed. The method is based on Large-Eddy Simulation (LES) with a subgrid combustion model based on the Linear-Eddy Model (Kerstein, 1991). An inter-LES cell burning mechanism has been added to the present formulation to account...

An idealized model for turbulent premixed flames is introduced. It consists of a scalar advection-reaction-diffusion equation that describes the interaction of a thin flame with a turbulentlike flow field acting on two separate scales. Rigorous asymptotic results as well as affordable and reliable direct numerical simulations are available to predict the effective large scale behavior of the id...

An experimental study of the intrinsic instabilities of H2/CO lean (φ = 0.4 to φ = 1.0) premixed flames at different hydrogen fractions ranging from 0% to 100% at elevated pressure and room temperature was performed in a constant volume vessel using a Schlieren system. The unstretched laminar burning velocities were compared with data from the previous literature and simulated results. The resu...

Experimental measurements of laser-induced ionization were performed for ethene-air premixed flames operated near the soot inception point. Soot was ionized with a pulsed laser operated at 532 nm. The ionization signal was collected with a tungsten electrode located in the postflame region. Ionization signals were collected by use of both single-electrode and dual-electrode configurations. Earl...

New combustion systems based on ultra-lean premixed combustion have the potential for dramatically reducing pollutant emissions in transportation systems, heat, and stationary power generation. However, lean premixed flames are highly susceptible to fluiddynamical combustion instabilities, making robust and reliable systems difficult to design. Lowswirl burners are emerging as an important tech...

Combustion instability is a process which involves unsteady chemical kinetic, fluid mechanic, and acoustic processes. It can lead to unstable behavior and be detrimental in ways ranging from faster part fatigue to catastrophic system failure. In terms of combustion methodology, combustion instability has been a key issue for lean premixed combustion. The primary objective of this work is to imp...

Nonlinear model equation for weakly turbulent premixed flames with realistic fuel expansion is proposed. The equation describes both the hydrodynamic flame instability and flame response to external turbulence in the regime of flamelets. On the basis of the proposed equation the velocity of turbulent flames is investigated for the cases of both weak and relatively strong turbulence. Comparison ...

The nonlinear nonlocal Michelson-Sivashinsky equation for isolated crests of unstable flames is studied, using pole-decompositions as starting point. Polynomials encoding the numerically computed 2N flame-slope poles, and auxiliary ones, are found to closely follow a MeixnerPollaczek recurrence; accurate steady crest shapes ensue for N3. Squeezed crests ruled by a discretized Burgers equation ...

A key outstanding issue with turbulent premixed flames lies in modeling the burning rate which may be related to the flame surface density if the laminar flamelet assumption applies. Although it is generally accepted that, in the flamelet regimes, higher turbulence levels increases flame wrinkling and hence its surface density, recent imaging experiments are not consistent making this a controv...

Nonlinear non-stationary equation describing evolution of weakly curved premixed flames with arbitrary gas expansion, subject to the Landau-Darrieus instability, is derived. The new equation respects all the conservation laws to be satisfied across the flame front, as well as correctly takes into account influence of vorticity, generated in the flame, on the flame front structure and flame velo...