Showing papers in "Combustion and Flame in 1990"

TL;DR: In this article, a four-step mechanism for the combustion of methane in air in non-premixed flames is obtained by making steady-state and partial equilibrium approximations for minor species.

TL;DR: In this paper, generalized staterelationship correlations giving the mass fractions of major gas species (N2, 02, fuel, CO2, H20, CO, and H2) and temperature as functions of local fuel-equivalence ratios were studied for hydrocarbon-air diffusion flames.

TL;DR: In this paper, the laminar flame speeds of methane-oxygen-nitrogen mixtures as functions of the flame temperature Tad and system pressure p have been experimentally determined by using the counterflow, twin-flame technique.

TL;DR: The characteristics of premixed gas flames in mixtures with low Lewis numbers near flammability limits were studied experimentally using a low-gravity environment to reduce buoyant convection.

TL;DR: In this article, the effects of periodic flow excitation on the performance of a two-dimensional dump combustor were investigated for lean premixed conditions, where the excitation was in the form of a sinusoidal cross-stream velocity perturbation applied just upstream of the flow separation.

TL;DR: In this paper, the effect of Damkohler number on OH superequilibrium was determined by performing measurements at selected locations in two argon-diluted hydrogen flames (Reynolds numbers 8,500 and 17,000).

TL;DR: In this paper, the blowout limits of a number of swirl-stabilized, non-premixed flames were measured, and the observed trends are successfully explained by applying certain concepts that previously have been applied only to nonswirling flames.

TL;DR: In this article, a fuel spray planar counterflow flame was modeled by means of a low-Mach-number boundary layer approach, and conditions for similarity in such a two-phase, particle-laden reacting boundary layer have been determined.

TL;DR: In this article, experimental measurements of the Markstein number (sensitivity to strain and curvature) of premixed diluted flames of hydrogen, methane, ethylene, and propane were made on weakly stretched, quasi-planar flames.

TL;DR: In this paper, the authors used simulations of turbulent premixed and diffusion flames in the flamelet regime to examine the straining on material surfaces, and the behavior of thin diffusive layers.

TL;DR: In this paper, the shape of an anchored premixed flame is analyzed as the result of the sum of wrinkles convected along the flame and of the wrinkles locally induced by the flow.

TL;DR: In this article, the authors construct stationary spherical premixed flames (flame balls) in which the only fluxes are diffusional, and examine the linear stability of these stationary solutions, and show that all small flames are unstable to one-dimensional (radial) perturbations.

TL;DR: In this paper, the effects of natural convection at high ambient pressure levels up to four times the fuel critical pressure were explored for a suspended fuel droplet under both normal and microgravity fields.

TL;DR: In this article, measured soot volume fraction profiles are combined with the modeled temperatures, velocities, and mixture fractions in an axisymmetric laminar diffusion flame to derive local soot formation rates.

TL;DR: In this article, the inner structure of a premixed flame is analyzed using a reduced four-step chemical kinetic mechanism, and an approximation for the burning velocity eigenvalue is obtained as a function of ω, which includes limiting expressions for ω → ∞.

TL;DR: In this paper, it was shown that in the case of wrinkled premixed flames with infinite Damkohler and Reynolds numbers, the reaction does not play any direct role on the time scale.

TL;DR: In this article, a simple model has been developed for the prediction of soot volume fractions in a laminar diffusion flame, which is used to evaluate the correlation between soot surface growth rates and the mixture fraction or fuel atom mass fraction.

TL;DR: In this paper, a laminar diffusion flame has been studied experimentally by examining the characteristics of soot particles using laser light scattering, and the kinetics mechanisms of oxidation by O2 and OH have been analyzed.

TL;DR: In this paper, the authors measured instantaneous soot volume fractions and temperatures in the fuel-rich (underfire) region of turbulent non-premixed acetylene, propylene, ethylene, and propane flames burning in still air.

TL;DR: In this paper, the integral length scale of flame wrinkling, evaluated along contours of reaction progress variable (c ), is found to be almost constant for all values of c. Its magnitude is measured to be very close to the integral lengths scale in the unreacted turbulent flow.

TL;DR: In this article, a study has been performed to elucidate the fundamental mechanisms controlling the production of NO in a Helmholtz-type pulse combustor, where cycle-resolved measurements of velocity and temperature in the combustion chamber were made.

TL;DR: In this article, absolute concentration measurements of hydroxyl radical have been made in a laminar, co-flowing methane-air diffusion flame using laser absorption and laser-induced fluorescence methods to probe the A2Σ+ ← X2Π transition.

TL;DR: In this article, a two-zone fluidized bed of silica sand heated externally to 1000°C was studied and the cross-flow factor was measured for secondary bubbles in the upper fuel-lean zone.

TL;DR: In this paper, asymptotic analysis is employed to extend an earlier model for the deflagration of nitramines to account for the presence of bubbles and droplets in a two-phase layer at the surface during combustion.

TL;DR: In this paper, soot volume fractions and mixture fractions, flame heights, and characteristic flame residence times were measured for turbulent acetylene, propylene, ethylene and propane diffusion flames burning in still air.

TL;DR: In this paper, a chemical kinetic model was used to calculate the homogeneous chemical kinetic ignition delay time for conditions typical of an operating pulse combustor, and a fluid dynamic mixing model for a transient jet of cold reactants to mix with an ambient environment of hot products to an ignition temperature.

TL;DR: In this article, the dispersion of the optical properties of absorbing submicronic aerosols, starting from the simultaneous measurements of the scattering and extinction coefficients in the near UV and visible, was evaluated.

TL;DR: In this article, a detailed model for the steady-state combustion of a coal particle considering both surface oxidation and volatile combustion is presented, and the homogeneous ignition temperature is determined as the gas temperature at which the mass consumption rate of the particle shows a jump.

TL;DR: In this article, a numerical model has been developed to study the sensitivity of a pulse combustor's performance to changes in the relative timing between several of the dominant physical processes, such as acoustics, fluid mixing, and chemical kinetics.

TL;DR: In this article, a two-phase model appropriate for describing the detonation of granulated solid propellants or explosives is presented, which satisfies the principle that the mixture mass, momentum, and energy are conserved.