Droplet spacing on drag measurement and burning rate for isothermal and reacting conditions

To understand the effects of droplet interaction on the drag coefficient an d vaporization process, our experiment investigated the nonreacting and com bustion history of a single stream of monosized droplets. Continuous monosi zed streams of fuel droplets were injected into quiescent surrounding air. An electronic device designed to modulate the droplet spacing C (ratio of i nterdroplet spacing to droplet diameter) was used, Measurements of droplet diameter, droplet velocity, and droplet temperature were performed using no nintrusive laser interoferometry. Ethanol was used as the simulation fluid throughout the experiment. The droplet stream was investigated in cold cond itions to study the influence of droplet spacing on the drag coefficient. T he data compiled for an extensive range of parameters (Re, droplet spacing) were compared with previous correlations from the literature. We propose a ne iv correlation that improves the prediction of the drag coefficient for a large range of spacing parameter 2 < C < 40. For reacting conditions the droplet stream was ignited by a heated coil. The results of the first tria l do not agree with the correlation established for cold conditions, theref ore we formulated a new one valid for burning droplets. We also examine the effects of interaction in accordance with the spacing parameter. These res ults show that the classical "D-2 law" does not apply rigorously for intera cting droplets, and so a corrective factor for burning rate was determined.