Papers by Keyword: Diffusion Flame

Abstract: Diffusion flame burners are mainly used in industries over premixed flame burners for safety considerations. But the combustion process in a diffusion flame is not complete and the flame is usually in bright yellow in colour in contrast to the premixed flame which gives a bluish flame. To improve the combustion process in a diffusion flame burner a novel approach, using chevrons has been carried out. The chevrons are found to reduce the aero-acoustic noise in the exhaust jets of aircraft engines by allowing better mixing of the exhaust gas with the ambient air. The similar concept is used here where the tips of the burners are cut in the form of chevrons. Experimental investigations are carried out on burners with three and four chevrons in addition to a standard burner using LPG as the fuel. The results indicate that with the introduction of chevrons the diffusion flame becomes more compact. The premixed region, in the diffusion flame, where the air and fuel is mixed well is found to increase by nearly 100 % with the usage of chevrons, indicating better mixing of fuel and air. The results also indicate that increasing the number of chevrons from three to four does not show much variation. Further experiments are to be carried out to determine the improved fuel consumption with the usage of chevrons.

Abstract: Diffusion combustion of propane and air in a rotational combustor was simulated by three-dimensional numerical model based on FLUENT. Influence of centrifugal field on the flame shapes and temperatures were discussed under various jet angles changing in the plane perpendicular to the rotational axis. The flame is compressed when the value of jet angle θ is less 90°, otherwise, the flame is stretched when |θ|>90°. When θ<90°, the deflection of flame becomes larger with an increase of θ. As contrasted to positive θ cases, the zones of high temperature in combustion chamber corresponding to negative are larger, and the maximal flame temperatures are likewise larger. The negative jet angle is useful to flame stability. External fluid is an important factor influence the distribution of temperature in combustion chamber.

Abstract: The present research experimentally investigated the effect of different water droplet size on the burning behavior and extinction condition of concentric jet premixed and diffusion flame. Water droplet stream in line with flowing air from lower duct. The burning behavior of concentric jet flame was observed and the extinction of flame was gained by decreasing the flow rate of fuel until the flame exthinguised. The results showed that the burning behavior of concentric jet diffusion and premixed flame had the same tendency. Different water droplet size influenced the burning behavior of flame. Decreasing the water droplet size, luminosity of the flame became thin as well as reducing the flame height. However, the inhibition effect of water droplet was stronger for diffusion flame compared to premixed flame. For smaller water droplet size, water droplet was four times more effective for suppressing the diffusion flame than premixed flame

Abstract: Abstract. temperature and species distributions of an atmosphere coflow laminar CH₄/air diffusion flame was studied by numerical simulation. We solve the steady equations for the species mass fraction, energy, momentum with detailed gas-phase reaction mechanism and complex thermal and transport properties to predict the velocity, temperature, species distributions for different dilute level. Results indicated that the predicted temperature and species are in excellent with available experiment date at different dilute level. In addition, it is indicated that adding N₂ in the fuel has a significant influence on the flame temperature and species distribution.