Diffusion flame

About: Diffusion flame is a research topic. Over the lifetime, 9266 publications have been published within this topic receiving 233522 citations.

Aliphatic C–H and oxygenated surface functional groups of diesel in-cylinder soot: Characterizations and impact on soot oxidation behavior

Abstract: This paper reports the characteristics of surface functional groups (SFGs) and oxidation reactivity of in-cylinder soot during the diesel combustion process and discusses the correlation between SFGs and the oxidation reactivity of soot Test soot samples were obtained from a total cylinder sampling system SFGs and the apparent activation energy for the soot oxidation were determined by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis Results reveal that the concentrations of aliphatic C–H, C–OH and C O groups are dependent on the combustion stages The ratio of aromatic C C to aliphatic C–H groups rapidly increases in the premixed combustion phase, indicating significant loss of aliphatic C–H groups from the soot surface As the combustion proceeds, the ratio of the two groups gradually increases, following an earlier drop during the diffusion combustion phase In contrast, the concentration of both C–OH and C O groups shows a bimodal distribution during the combustion process, with the concentrations peaking in the premixed and diffusion combustion stages, respectively The apparent activation energies for the oxidation of soot collected under the applied engine operating conditions are observed in the range of 12212–1582 kJ mol −1 at various crank angles, revealing a similar variation to that of aliphatic C–H groups Aliphatic C–H groups are a more important factor in governing soot oxidation reactivity than the oxygenated SFGs

Basic Considerations in the Combustion of Hydrocarbon Fuels with Air

Abstract: Basic combustion research is collected, collated, and interpreted as it applies to flight propulsion. The following fundamental processes are treated in separate chapters: atomization and evaporation of liquid fuels, flow and mixing processes in combustion chambers, ignition and flammability of hydrocarbon fuels, laminar flame propagation, turbulent flames, flame stabilization, diffusion flames, oscillations in combustors, and smoke and coke formation in the combustion of hydrocarbon-air mixtures. Theoretical background, basic experimental data, and practical significance to flight propulsion are presented.

On-line flicker measurement of gaseous flames by image processing and spectral analysis

Abstract: The flicker of a flame is an important physical parameter associated with the characteristics of a combustion process. This paper presents a novel instrumentation system developed for on-line continuous flicker measurements of combustion flames. The system comprises a high-speed CCD camera, a frame grabber and associated image processing software. The flicker signal was obtained by processing the radiation intensity of individual pixels within the luminous region of a flame image. Power spectral density analysis was performed to obtain the frequency components of the flicker signal. The quantitative flicker of a flame is defined in terms of weighted spectral components in the frequency domain and this definition has been proven to be well suited to quantification of the flickering characteristics of a flame. A tungsten lamp driven by a frequency-varying power supply was employed to calibrate the measurement system. The calibration results show that the system is capable of measung the flicker of an unknown light source with a relative error no greater than 3% . The system developed has been utilized to investigate the relationship between the flicker of a diffusion flame and the burner diameter, and to study the effect of the equivalence ratio on the flicker of a premixed flame under a range of combustion conditions. The experimental results obtained by both motion image analysis and spectral analysis have demonstrated that the flicker of a diffusion flame depends predominantly on the burner diameter. It has also been found that the flicker of a premixed flame varies with the equivalence ratio and a peak flicker exists for a given air flow rate.