Intrinsic features of micro-scale flames are presented by surveying the vast previous and on-going works owing to its flame structure, and potential future and academic impact brought by micro-scale flames are summarized accordingly. The role of (micro) burner is pronounced when the flame size is minimized and variety of unique features, including excess enthalpy combustion, thus appear to improve the stability. Within the miniaturized flame, the major transport process is mainly dominated by diffusion so that the limiting micro-scale flames tend to be “spherical” irrespective of the flame type (both premixed and non-premixed flame). At the small-scale limit, the concept of flame sheet model (i.e., zero-thickness of the flame zone) is no longer valid, rather, the flame thickness becomes the same order to the characteristic length of transport. In this way, the micro-scale flame can be one of fundamental tools to investigate the basic nature of the flame. In order to clarify the unresolved issues related on the micro-scale flames, past works are briefly categorized and future challenges to be done with our best knowledge are also presented. Furthermore, potential of “new” research category driven by micro-scale flame study, named “high-Knudsen number reacting flow”, is additionally introduced. Due to the fact that there is missinglink to diagnose such small-scale flames directly, interdisciplinary cooperation with researchers in other fields (likely, micromachine, nano-scale technology) is highly encouraged.
View full abstract