Multiple cool flames in static, unstirred reactors under reduced-gravity and terrestrial conditions

Multiple cool flames have been observed experimentally in a static, unstirred reactor at reduced gravity in an equimolar n-butane–oxygen premixture diluted with helium. These are the first observations of sustained cool flame oscillations in a static reactor when transport is governed by diffusive fluxes of heat and species. To date, only single cool flames have been reported at reduced gravity, while oscillatory cool flames have long been observed in static reactors at terrestrial conditions. The results suggest that enhanced conduction heat transfer can provide the required heat loss to sustain cool flame oscillations.