Low Temperature Combustion: Cool Flames and Warm Flames

抄録

One of the greatest challenges in combustion today is to reduce carbon emissions by increasing energy conversion efficiency and using low carbon alternative fuels. Reduction of thermal heat loss and control of ignition timing using low temperature combustion at higher pressure and lean burn conditions are critical to the development of future advanced engines and low carbon fuels. In this paper, an overview of the recent progress in understanding low temperature flames such as the cool flames, warm flames, and hot flames as well as the double flames, multi-stage flames, and auto-ignition assisted flames will be presented. Special focus will be placed in the dynamics and burning limits of these low temperature flames. The phenomenological definition of cool flame, warm flame, and hot flame will be described. Three temperature dependent chain-branching pathways which correspond, respectively, to the cool, warm, and hot flame regimes will be summarized. The flammability limit diagrams for both premixed and non-premixed cool flames, warm flames, and hot flames will be presented. The effects of chemical sensitization and wall quenching on cool flames will be discussed. Furthermore, the auto-ignition assisted cool flame propagation in auto-igniting mixtures at engine conditions will be presented. The impact of cool flames on turbulent combustion and engine knock formation will be briefly discussed. A brief summary and future research of low temperature combustion under engine conditions will be made.