Quasi-steady and unsteady propagations of methane and propane–air premixed flames in a mesoscale divergent channel were investigated experimentally and theoretically. The emphasis was the impact of variable cross-section area and the flame-wall coupling on the flame transition between different regimes and the onset of flame instability. Experimentally, for the first time, spinning flames were ...

Dynamic models for large eddy simulation of the G-equation of turbulent premixed combustion are proposed and tested in forced homogeneous isotropic turbulence. The basic idea is to represent the ‘‘filtered propagation term’’ as ‘‘propagation of the filtered front at higher speed,’’ where the enhanced filtered-front speed is modeled. The validity of the linear relation between the turbulent flam...

Since most of the practical combustion devices operate in turbulent environments, study of turbulent combustion is fundamentally appealing and practically important. Turbulence enhances the flame propagation by wrinkling an otherwise laminar smooth flame, leading to an increase in the flame surface area and hence the total burning rate. There have been number of studies performed to achieve a s...

Hot surface ignition was examined using a variety of heat sources in a series of premixed hydrocarbon, hydrogen, and air mixtures. Building off previous work, hexane-air, heptane-air and hydrogen-air experiments were performed in addition to the eventual hexane-hydrogen-air mixtures. Using high-speed schlieren photography, thermocouples, and a fast-response pressure transducer, flame characteri...

Turbulent methane flames exhibit a change in Markstein number as the equivalence ratio changes. In this paper, we demonstrate how these changes in Markstein number are related to shifts in the chemistry and transport. We focus on the analysis of simulations of two-dimensional premixed turbulent methane flames at equivalence ratios φ=0.55 and φ=1.00 computed using the GRI-Mech 3.0 mechanism. The...

Carbon-oxygen white dwarfs contain 22Ne formed from α-captures onto 14N during core He burning in the progenitor star. In a white dwarf (type Ia) supernova, the 22Ne abundance determines, in part, the neutronto-proton ratio and hence the abundance of radioactive 56Ni that powers the lightcurve. The 22Ne abundance also changes the burning rate and hence the laminar flame speed. We tabulate the f...

We study a thermo-diffusive combustion model for premixed flames propagating in reactive gaseous mixtures which contain inert dust. As observed by Joulin, radiative transfer of heat may significantly enhance the flame temperature and its propagation speed. The Joulin effect is at its most pronounced in the parameter regime where the medium is very transparent while radiative flux dominates conv...

The main objective of the present study is to demonstrate accurate low frequency transient turbulent combustion modeling. For accurate flame dynamics some improvements were made to the standard TFC combustion model for lean premixed combustion. With use of a 1D laminar flamelet code, predictions have been made for the laminar flame speed and the critical strain rate to improve the TFC (Turbulen...

Direct numerical simulations of two-dimensional unsteady premixed methane/air flames are performed to determine the correlation of flame-speed with stretch over a wide range of curvatures and strain rates generated by intense two-dimensional turbulence. Lean and stoichiometric premixtures are considered with a detailed C1-mechanism for methane oxidation. The computed correlation shows the exist...

In gas explosions, the unsteady coupling of the propagating flame and the flow field induced by the presence of blockages along the flame path produces vortices of different scales ahead of the flame front. The resulting flame/vortex interaction intensifies the rate of flame propagation and the pressure rise. In this paper, a joint numerical and experimental study of unsteady premixed flame pro...