Experimental investigation on flame spread over liquids using holographic interferometry

The increasing probability and occurrence of accidents from using and transporting liquid fuel has focused attention on their combustible properties. Liquid spills from aircraft or automobile accidents are examples usually result in losses of life.; Research on flame spread over liquids have not reached the level of maturity that has been done on solid fuel. The convective motion in the liquid phase increase the complexity of the phenomenon.; Detailed temperature measurement of the condensed phase is important for the study of flame spread over liquid fuel pools. This measurement requires high spatial resolution near the interface between liquid and gas phases, where a steep temperature gradient is formed that controls the heat-transfer interaction between the two phases. We developed a holographic interferometry (HI) technique that is non-intrusive and is capable of detecting almost simultaneously a sudden and minute temperature change occurring in a distributed area. Along with these HI measurements, we developed a laser-sheet particle-track flow visualization system (LSPT). Both techniques (HI and LSPT) were applied simultaneously to obtain detailed temperature and velocity profiles in the liquid. An infrared IR thermography technique was also applied to measure the liquid surface temperature.; Using those concurrent measurements, we were able to better understand the mechanism of the flame spread over liquids, a phenomenon that is currently not well understood. The major findings include: (1) Combining HI and LSPT techniques proved to be an effective tool for obtaining detailed temperature and velocity maps simultaneously of the fuel-gas interface, (2) Only one vortex, driven by the coupling effect of the surface tension and the buoyancy forces, was observed ahead of the flame in the liquid phase at sub-flash temperature, (3) Increasing the effect of dimensionality (2D to 3D) in a tray wider than 10 mm caused twin surface side flow which suggested that the next generation of the flame spread study needs to be both transient and three-dimensional, (4) Effect of the ambient conditions on the rate and the mechanism of the flame spread over liquids were found to be minor and (5) Confirming that the controlling mechanism of the uniform flame spread over liquids is the liquid phase convection ahead of the flame.