Experimental Study On Flame Morphology And Transformation Characteristics Of Pure Propane And Hydrogen-doped Propane Under Micro-scale Conditions

Compared with traditional batteries,micro power devices have the advantages of long energy supply time,small volume,and high energy density,which make these devices give high hopes in solving the problem of MEMS power,and gradually become a research hotspot.As the micro combustor,a core component of the micro motive device,stable combustion of its fuel determines the efficiency and power output of the entire device.For the flame in the micro combustor faced with short residence time,excessive heat loss caused by flame quenching and unstable phenomenon occurred.Many measures are used to improve the stability of the combustion process,including blended combustion and internal optimization of the burner structure.For this reason,a micro-planar combustor was designed at the same time.Pure propane and hydrogen additional of propane were selected as the research object,and the high-speed digital camera combined with infrared thermal imager was used to analyze the flame morphology and its transformation law.The research results obtained are as follows:(1)Dynamic flame patterns of a propane/air mixture in a micro-planar quartz glass combustor are studied using a high-speed digital camera.Six types of flames are found: FREI,W-shaped,flat-shaped,U-shaped,inclined and X-shaped.The distribution region of all of these flame patterns are drawn based on the experimental results obtained for an inlet velocity range of 11–89 cm/s and an equivalence ratio of 0.5–1.2.(2)The areas are composed of absolutely stable,relatively stable,and absolutely unstable regions.In addition,the velocity range of the flame will overlap due to the hysteresis phenomenon.Secondly,a slight addition or reduction of equivalence ratio can significantly change the patterns of FREI and W-shaped flames.Finally,it is found that a range of absolute stability is not directly proportional to channel length,and a reduction in channel height will lead to the decrease in the numbers of flame patterns.In addition,a detailed analysis of flame variation frequency,flame position,and other characteristics of the FREI,inclined flame,and X-shaped flame have been investigated.(3)Based on the study of pure propane,the characteristics and implementation effects of hydrogen blended propane combustion process were discussed.The results show that the hydrogen addition combustion method overcomes the shortcomings of propane flame instability in micro combustion,greatly improves the steady-state flow rate range,and suppresses the absolute stable area reduction that may be caused by the hysteresis phenomenon.At the same time,hydrogen addition can also slow down the change of flame morphology by fixing flame position and stabilizing the high temperature region,thereby suppressing the formation of unstable flames.Finally,different hydrogen addition ratios have different effects on U-shaped flame morphology.The larger the hydrogen addition ratio,the smaller the U-shaped flame location and thickness.