Flame ignition by short-duration (≈ 50 ns) transient plasma, or corona, discharges was investigated for methane-air, propane-air and butane-air mixtures at atmospheric and elevated pressures. Such discharges produce a larger fraction of high-energy electrons, yield more spatially distributed energy and deposit energy in the gas more efficiently than conventional arc discharges do. We show that ...

In this paper we study turbulent premixed methane flames with swirl using three-dimensional numerical simulation. The simulations are performed using an adaptive time-dependent low Mach number combustion algorithm based on a second-order projection formulation that conserves both species mass and total enthalpy. The species and enthalpy equations are treated using an operator-split approach tha...

1 Introduction A balance between the flame propagation speed and the fluid velocity must be maintained to maintain the flame in a chemically reacting flow. Since the fluid velocity exceeds the flame speed in supersonic combustion applications, the flameholding issue is solved by generation of some sort of recirculation region which ensures sufficient residence time so that the processes involve...

We explore the detailed structure of heat release and the energy budget for a freely-propagating lean, premixed hydrogen flame. At lean conditions, the flame is thermodiffusively unstable and spontaneously develops the cellular burning structures, characteristic of this type of flame. The instabilities in the system saturate quickly, resulting in robust, slowly evolving cellular burning feature...

A combination of microgravity experiments and computational simulations were used to study effects of diluents on the near-limit properties of laminar, premixed hydrogen/air flames. The experiments were conducted in a short-drop free-fall laboratory facility that provided at least 450 ms of 10−2g conditions. Outwardly propagating spherical flames were used to measure near-limit laminar burning ...

The relative importance of formation pathways for benzene, an important precursor to soot formation, was determined from the simulation of 22 premixed flames for a wide range of equivalence ratios (1.0– 3.06), fuels (C1–C12), and pressures (20–760 torr). The maximum benzene concentrations in 15 out of these flames were well reproduced within 30% of the experimental data. Fuel structural propert...

Laminar burning velocities and flammability limits of premixed methane/air flames in the presence of various inert gases including helium, argon, nitrogen and carbon dioxide were investigated by combined use of microgravity experiments and computations. The experiments used a short-drop free-fall laboratory facility that can eliminate the effect of buoyancy on flames and therefore enable accura...

the premixed counterflow flames propagation in combustion of mixture which is a uniform mixture of fuel particles and air is analytically studied. this analysis framework is based on thermal-diffusion model with assumption that the lewis number is unit and the strain rate is constant. velocity profile is assumed as a function of one variable like x. the structure of the flame is presumed to con...

A computational study has been conducted to determine the critical conditions for the transition from localized flame ignition and propagation to the establishment of a flame ball. Lean H2/air mixtures are investigated using a time-dependent, spherically symmetric code with detailed chemistry, transport, and radiation submodels. Results show that outwardly propagating spherical flames can be ig...