premixed combustion is widely used for reducing pollutant emission from combustion chambers. however, these systems may be sensitive to complex phenomena such as flashback. in the present study flame, flashback and structure of premixed laminar flames are investigated theoretically. the mathematical model includes the axi-symmetric continuity, navier stocks, energy, and species equations. combu...

Minimum ignition energies and flame radii as a function of time were measured for near-limit, limit, and sublimit fuel-lean methane-air mixtures burning at one-g and zero-g. Minimum ignition energy values were the same at one-g and zero-g except for mixtures very near the zero-g flammability limit and leaner, where the zero-g values were much higher than the one-g values. For sublimit mixtures ...

The effect of gravity and thermal expansion on the propagation of a triple flame in a horizontal channel. Combustion and Flame Submitted (2013). [3] Al-Malki, F and Daou, J. Triple-flame propagation against a Poiseuille flow in a channel with porous walls. Submitted (2013). [4] Daou, J. Strained premixed flames: effect of heat-loss, preferential diffusion, and the reversibility of the chemical ...

To reveal the inner mechanism of gas explosion dynamic behavior affected by gas equivalent concentration, a high speed Schlieren image system and flow field measurement technology was applied to record the gas explosion flame propagation and flame structure transition. The results show that a flame front structure transition occurs, followed by a flame accelerating propagation process. The lami...

Turbulent-flame speeds in methane–air mixtures were measured in a Taylor–Couette apparatus with counter-rotating cylinders, used to generate turbulence that is nearly homogeneous and isotropic over many integral length and time scales. While laminar-flame propagation is found to be influenced by the Darrieus– Landau instability and heat loss to the walls of the apparatus, turbulent-flame propag...

Premixed methane-air mixture is introduced at the center of two parallel circular quartz plates separated by a millimeter scale distance (<or= 5mm). Two plates are heated with an external heater to create a positive temperature gradient condition along the flow direction. The combustion characteristics of lean methane-air mixtures are investigated at phi=0.67 and phi=0.85 in the laminar flow re...

A counterflow diffusion flame model is studied revealing that, at least as a part of the quenching boundary is approached in parameter space at low enough Lewis numbers, an edge of a diffusion flame, or triple flame, has a propagation speed that still advances the burning solution into regions that are not burning. In crossing the quenching boundary, the advancing flame edge remains a robust pa...

Abstract In this study, the optical diagnostics techniques of infrared (IR) absorption and chemiluminescence were applied to a racing engine. A small M5 IR sensor and Cassegrain optics sensors were developed to measure in-cylinder fuel concentrations and local chemiluminescence intensities. The small IR sensor was able to withstand racing engine operating conditions up to 16,000 rpm and exhibit...

An investigation is carried out into the ranges of Damköhler number and Lewis number, less than unity, in which different forms of combustion phenomena arise within a non-premixed counterflow; cases that are symmetrical across the counterflow are chosen for study. These link oscillatory and steady propagation of flame edges, zero propagation speeds, isolated flame tubes, quenching and marginal ...

A dominant factor in determining the burning rate of a premixed turbulent flame is the degree to which the flame front is wrinkled by turbulence. Higher turbulent intensities lead to greater wrinkling of the flame front and an increase in the turbulent burning rate. This picture of turbulent flame dynamics must be modified, however, to accommodate the affects of variations in the local propagat...