Showing papers in "Combustion and Flame in 2006"

TL;DR: In this article, the laminar burning velocities and Markstein lengths of natural gas-hydrogen-air flames were obtained at various ratios of hydrogen to natural gas (volume fraction from 0 to 100%) and equivalence ratios.

TL;DR: This article showed that the initial structure alone alone does not dictate the reactivity of diesel soot and rather the initial oxygen groups have a strong influence on the oxidation rate, leading to the formation of graphene ribbon structures.

TL;DR: In this article, a combustion-driven entrained flow reactor equipped with an optical particle-sizing pyrometry diagnostic and a rapid-quench sampling probe has been used for this investigation.

TL;DR: In this article, a two-stage reduction strategy and using the kinetic responses of autoignition and perfectly stirred reactor (PSR) with extensive parametric variations as the criteria in eliminating unimportant species were successfully reduced to skeletal mechanisms consisting of 188 and 233 species, respectively.

TL;DR: In this article, a relatively small detailed mechanism has been developed for the combustion of various fuels, mainly hydrocarbons, in air or oxygen-inert mixtures, which has been tested previously for autoignition, premixed-flame burning velocities, and structures and extinction of diffusion flames and of partially premixed flames.

TL;DR: In this paper, the authors report spatially resolved two-dimensional measurements of a quantity closely related to heat release rate, which is a fundamental property of great importance for the theoretical and experimental elucidation of unsteady flame behaviors such as combustion noise, combustion instabilities, and pulsed combustion.

TL;DR: A gas turbine model combustor for swirling CH 4 /air diffusion flames at atmospheric pressure with good optical access for detailed laser measurements is discussed in this article, where three flames with thermal powers between 76 and 349 kW and overall equivalence ratios between 055 and 075 were investigated.

TL;DR: In this paper, the kinetic parameters governing the thermal and oxidative degradation of flexible polyurethane foam are determined using thermogravimetric data and a genetic algorithm using a lumped model of solid mass loss based on Arrhenius-type reaction rates.

TL;DR: In this paper, the influence of thermal stratification on autoignition at constant volume and high pressure is studied by direct numerical simulation (DNS) with detailed hydrogen/air chemistry with a view to providing better understanding and modeling of combustion processes in homogeneous charge compression-ignition engines.

TL;DR: In this article, the conditions for application of the directed relation graph (DRG) method in skeletal reduction of mechanisms with vastly different time scales were systematically analyzed, and it was found that the existence of quasi-steady state species induces no additional restriction on the application of DRG.

TL;DR: In this article, experimental measurements on the combustion of nanoaluminum particles behind reflected shock waves in a shock tube were performed at elevated pressures (4-32 atm) and temperatures (1200-2100 K) in the oxidizers oxygen and carbon dioxide, with nitrogen also present.

TL;DR: An algorithm is developed to generate simplified kinetic mechanisms from a given detailed one, able to replicate the dynamics of a user-specified set of species when a finite set of sampling points, D, in the chemistry configuration space is given.

TL;DR: In this article, the effect of reaction chamber configuration on the resulting aerodynamics and temperature field was investigated using a creviced piston and a flat piston under varying conditions, and it was shown that the flat piston design leads to significant mixing of the cold vortex with the hot core region, which causes alternate hot and cold regions inside the combustion chamber.

TL;DR: In this article, the authors systematically investigated diesel emissions at different engine loads and speeds by rapid thermophoretic sampling followed by direct transmission electron microscope (TEM) visualization, which provided new, accurate, and relevant data on diesel particulates compared to the abundant past studies involving questionable mobility sizing measurements.

TL;DR: In this article, a gas turbine model combustor for swirling CH{sub 4}/air diffusion flames at atmospheric pressure with good optical access for detailed laser measurements is discussed, and three flames with thermal powers between 7.6 and 34.9 kW and overall equivalence ratios between 0.55 and 0.75 were investigated.

TL;DR: In this paper, the applicability of one-step irreversible Arrhenius kinetics with unity reaction order to the numerical description of partially premixed hydrocarbon combustion was explored, where planar premixed flames were used in the selection of the three model parameters: the heat of reaction q, the activation temperature T a, and the preexponential factor B. The resulting chemistry description is able to reproduce propagation velocities of diluted and undiluted flames accurately over the whole flammability limit.

TL;DR: In this article, the authors used a high-speed camera and planar laser-induced fluorescence of a cylindrical shape with a propagating edge upstream to study the effects of the jet velocity and air premixing of the fuel stream on the ignition probability.

TL;DR: In this paper, an experimental study on combustion instability is presented with focus on oxy-fuel type combustion, where an acoustic model of the system coupled with a time-lag based flame model made it possible to elucidate the acoustic mode selection in the system as a function of laminar flame speed and Reynolds number.

TL;DR: In this article, a flamelet combustion model based on the G equation combustion model was developed and implemented to improve the prediction accuracy of the spark ignition and combustion processes in spark ignition engines.

TL;DR: In this paper, the influence of hydrogen addition to the fuel of an atmosphere pressure coflow laminar ethylene-air diffusion flame on soot formation was studied by numerical simulation.

TL;DR: In this article, a chemical-kinetic mechanism is presented for autoignition, deflagration, detonation, and diffusion flames of a number of different fuels. But the mechanism is restricted to pressures below about 100 atm, temperatures above about 1000 K, and equivalence ratios less than about 3 for premixed systems, thereby excluding soot formation and low-temperature fuel-peroxide chemistry.

TL;DR: In this paper, a combined experimental and modeling study was conducted to understand the pathways by which the addition of ethanol to fuel-rich ethylene flames causes reductions in PAH and soot.

TL;DR: In this article, a stochastic approach is used to obtain soot particle size distributions (PSDs) and the sensitivity of the PSDs to the parameters defining parts of the soot model, such as soot inception, particle and PAH collision efficiency and enhancement, and surface activity is investigated.

TL;DR: In this paper, the Eulerian stochastic field method is applied to the solution of the modeled evolution equation for the subgrid joint probability density function (JPDF) of the reacting scalars in a large eddy simulation (LES) of a piloted methane/air diffusion flame (Sandia Flame D).

TL;DR: In this paper, the authors investigated the conversion of methane to hydrogen within a porous media reactor over the fuel-rich equivalence ratio range of 1.5 to 5, and showed that a thick, high-temperature zone, which promotes steam reforming, is preferred to maximize conversion efficiency.

TL;DR: In this paper, the CxHy PAH products of premixed and diffusion flame processes, which also occur in the unsteady diesel combustion, range in mass from 128 u (two rings, x = 10, y = 8 ) to beyond 350 u (eight rings, X = 28, y = 14 ).

TL;DR: In this article, the main reaction paths of low-temperature co-oxidation are discussed according to current knowledge of the oxidation paths of pure hydrocarbons, and the influence of toluene on the temperature coefficient of the first stage of ignition of isooctane cannot be accounted for by the current theories of low temperature autoignition.

TL;DR: In this paper, the effect of pressure on soot formation and the structure of the temperature field was studied in coflow propane-air laminar diffusion flames over the pressure range of 0.1 to 0.73 MPa in a high-pressure combustion chamber.

TL;DR: In this paper, the influence of thermal stratification on autoignition at constant volume and high pressure is studied by direct numerical simulation (DNS) with detailed hydrogen/air chemistry.

TL;DR: In this paper, the authors used laser-induced breakdown spectroscopy (LIBS) for direct measurement of atomic species over a wide range of mixture fractions of C3H8, CH4, and CO2 in air.