In experiments of hot surface ignition and subsequent flame propagation, a puffing flame instability is observed in mixtures that are stagnant and premixed prior to ignition. By varying the size of the hot surface, power input, and combustion vessel volume, it was determined that the instability is a function of the interaction of the flame, with the fluid flow induced by the combustion product...

The propagation of turbulent premixed flames influenced by the intrinsic hydrodynamic flame instability (the Darrieus-Landau instability) is considered in a two-dimensional case using the model nonlinear equation proposed recently by Bychkov [Phys. Rev. Lett. 84, 6122 (2000)]. The nonlinear equation takes into account both the influence of external turbulence and the intrinsic properties of a f...

This paper presents an application of fuzzy logics for controlling the combustion flame of a premixed gas burner. The control objective is to achieve a good characteristic of combustion flame by visualizing the colors of the flame while maintaining its size as desired. The fuzzy logic controller adjusts the flow rates of gas and air independently through two stepper-driven needle valves. A CCD ...

A one-dimensional, non-premixed flame stability analysis is undertaken. Oscillatory and cellular flame instabilities are identified by a careful study of the numerically calculated eigenvalues of the linearized system of equations. The numerical investigation details the critical locations for changes in flame behaviour, as well as the critical values of various parameters that affect flame sta...

The acoustic power of an oscillating flame is measured. A turbulent premixed propane/air flame is situated near a pressure antinode of a standing wave in a laboratory combustion chamber. This standing wave is generated by a piston. The fluctuating heat release of the flame will supply acoustic power to the standing wave as postulated by Rayleigh. This flame acoustic power is obtained by setting...

Three-dimensional direct numerical simulations are performed of turbulent combustion of initially spherical flame kernels. The chemistry is described by a progress variable which is attached to a flamelet library. The influence of flame stretch and curvature on the local mass burning rate is studied and compared to an analytical model. It is found that there is a good agreement between the simu...

This article reports nonlinear bifurcations observed in a laboratory scale, turbulent combustor operating under imperfectly premixed mode with global equivalence ratio as the control parameter. The results indicate that the dynamics of thermoacoustic instability correspond to quasi-periodic bifurcation to low-dimensional, deterministic chaos, a route that is common to a variety of dissipative n...

Picosecond four-wave mixing experiments have been used to study collisions in a Na-seeded, premixed, methane-air flame. Population gratings are used to measure Na excited-state quenching collision rates, while polarization gratings are used to measure Na ground-state hyperfine coherence randomizing collision rates and overall Na diffusion rates, even though these processes are slower than the e...

In this paper, a one dimensional premixed laminar methane flame is subjected to acoustic oscillations and studied. The purpose of this analysis is to investigate the effects of acoustic perturbations on the reaction rates of different species, with a view to their respective contribution to thermoacoustic instabilities. Acoustically transparent non reflecting boundary conditions are employed. T...

Unsteady simulations of stagnation point flames are conducted in order to study flame turbulence interactions in a relatively simple flow environment. Flame propagation is represented using a flamelet model called the G equation. Two subgrid models are used to close the filtered G equation. The effects of significant heat release on the turbulent flow and the effect of varying turbulence intens...