Formation, levitation and evaporation of unsupported liquid fuel droplet clusters

Evaporation and combustion experiments using arrays of droplets seek to provide a link between single droplet phenomena and the behavior of complex spray systems. Both single droplet and droplet array studies have been conducted in microgravity to better isolate the droplet interaction phenomena and eliminate or reduce the confounding effects of buoyancy-induced convection. In most experiments involving droplet arrays, the droplets are supported on fibers to keep them stationary and close together prior to combustion. The presence of the fiber, however, disturbs the combustion process by introducing a source of heat transfer and asymmetry into the configuration. As the number of drops in a droplet array increases, supporting the drops on fibers becomes less practical because of the cumulative effect of the fibers on the combustion process.; In this thesis, recent works related to the single drop and droplet array evaporation and combustion, unsupported droplet and droplet cluster formation, and microgravity combustion experiments are reviewed. A unique experiment in which unsupported droplet clusters are formed in normal gravity has been developed and the design concepts and test results are presented and discussed. The results of droplet cluster formation and levitation tests and investigations of the acoustic field are also presented. The current 1-g equipment has been used to investigate the inter-droplet effects of a droplet cluster supported in an acoustic field. Droplet size, inter-droplet distance and evaporation rate were measured and compared with theoretical models. It was found that the single droplet evaporation results are consistent with previous studies and compared well with the single droplet evaporation models. Direct experimental results of multiple droplet evaporation were obtained and compared with a point source method. Based on the 1-g test results, the experimental apparatus will be incorporated into a drop tower rig where experiments can be performed in a microgravity environment.