| While fossil fuels have a crisis of energy loss,they are also accompanied by various environmental pollution problems in the process of utilization and will cause serious harm to human health.This is a problem that China and the world need to deal with urgently.In view of these increasingly severe social conditions,it is necessary to rationally optimize combustion technology,improve energy combustion efficiency,and develop soot particle emission control technology.Exploring the combustion mechanism to achieve efficient combustion and exploring clean and reliable alternative energy sources are two important solutions.In the actual combustion system,the combustion behavior is extremely complicated due to changes in parameters such as temperature,air pressure and fluid state.Therefore,in order to facilitate the exploration of the combustion mechanism and simplify the combustion conditions,this paper builds a simple experimental platform based on the existing conditions,adopts propane and ethylene laminar diffusion flame as the research object and carries out a series of related experiments.This paper uses image processing technology and thermocouple temperature measurement method to accurately measure the flame height,cross-sectional area of flame blue area,flame surface area and flame temperature under different gas additives and their volume fractions.Aiming at the problem of laboratory environment and flame halo interference in the process of parameter extraction,this paper uses Matlab software to edit the program combined with the distribution characteristics of the gray value of the flame edge pixels in the flame image,and design a dynamic threshold method to realize the effectively segmentation of the flame area and the background,and use the "cylinder method" to calculate the flame area.In this paper,In this paper,the method which combines experimental means and theoretical analysis is used to further discuss the influence of different gas additives and their volume fractions on soot formation based on the obtained flame characteristic parameters.The results show that the influence of hydrogen on the flame height and flame surface area of propane and ethylene is significantly stronger than that of carbon dioxide and nitrogen.Because hydrogen is a combustible substance,the addition of hydrogen increases the volume flow of fuel.The airflow speed increases and the mixing speed with air slows down,so the flame will be elongated and the combustion heat release rate will be increased.It will increase the flame heat loss and affect the flame temperature,which in turn affects the soot formation.The cross-sectional area of the flame blue area expands upward with the increase of the volume fraction of the three gas additives.Among them,carbon dioxide has the greatest influence on the cross-sectional area of the flame blue area,followed by hydrogen.Therefore,it can be qualitatively judged that carbon dioxide is more effective than hydrogen in suppressing the formation of soot.The analysis shows that in addition to the thermal effect and dilution effect,carbon dioxide mainly suppresses the soot particle surface growth process by reducing the concentration of H radicals and suppresses the soot particle inception by increasing the concentration of OH radicals,while hydrogen mainly suppresses the soot particle inception by promoting the reverse progress of the dehydrogenation reaction.In the follow-up flame centerline temperature measurement,it is found that the cooling effect of carbon dioxide on the flame is the most significant,which provides favorable conditions for inhibiting soot nucleation. |
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