2020 Volume 62 Issue 201 Pages 218-227
Flame ball is a steady spherical flame observed under microgravity in a quiescent premixture. Flame ball does not propagate and is stabilized in extremely lean conditions. Molecular diffusions play essential roles for the stabilization of flame ball since no convection flow exists in a quiescent mixture. Flame ball was predicted analytically by Zeldovich in 1940’s while he himself concluded that it is unstable. Approximately forty years since its prediction, Dr. Ronney accidentally observed flame cells with slow propagation speed through short-duration microgravity experiments in U.S. Until early 2000’s, analytical studies with consideration of radiative heat loss, drop tower experiments at JAMIC and the subsequent Space-Shuttle experiments suggested that the existence of the ideal flame ball. Since 2010, our group has been focusing on the understandings of comprehensive combustion limits including relations between general propagating flame represented by low-speed counterflow premixed flames and flame ball. Through recent studies, some peculiar flame behaviors were confirmed experimentally and numerically. In this report, the recent studies related to flame ball as well as the history of related studies were summarized.
