Abstract
We recently developed two different optical techniques in order to simultaneously measure transient 2-D profiles of velocity, temperature and fuel concentration that were generated by a spreading flame over liquid fuels. One technique employs a particle-track system combined with a laser-sheet system (PTLS) and a high speed camera, while the other technique employs a dual wavelength holographic interferometry (DWHI). The PTLS system revealed transient 2-D profiles of flame induced flow, while DWHI revealed 2-D profiles of fuel concentration over liquids. In this paper we present a series of velocity profiles for a pulsating flame spread over propanol and concentration profiles for gaseous propanol determined with PTLS and DWHI respectively. Other researchers have predicted the formation of small twin circulations, one a gas-phase circulation just ahead of the flame’s leading edge, and the other a small liquid circulation just underneath the gas-phase circulation. Our PTLS results confirmed these predictions, i.e., the formation of 5–10 millimeter diameter circulation in the gas phase and an accompanying approximately 20 millimeter diameter liquid circulation. Based on these data, we offer a phenomenological explanation of the mechanism of pulsating flame spread. In addition, we show that DWHI is a very promising technique for measuring transient fuel-concentration profiles over liquids.
