Interference Effects During Burning in Air for Two Stationary N-Heptane Droplets

Citation

Rex, James Foster (1955) Interference Effects During Burning in Air for Two Stationary N-Heptane Droplets. Engineer's thesis, California Institute of Technology. doi:10.7907/334Z-RA03. https://resolver.caltech.edu/CaltechETD:etd-01202004-145717

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstraact is included in .pdf document. In order to gain some understanding of droplet interference during burning, experiments have been conducted for the determination of the evaporation constant and flame shapes of two closely spaced n-heptane droplets burning in air. Droplets of approximately the same and of different diameters were used at various distances between the droplet centers. Experimental results on flame shapes and evaporation constants for closely spaced droplets show somewhat surprising behavior. Thus the apparent flame shape changes very little during the burning of the droplet. The square of the droplet diameter decreases linearly with time for fixed spacing between droplet centers, at least within the experimental limits of accuracy. Since geometrically different conditions are produced continuously during burning, the observed independence of the slope of plots for the square of droplet diameter vs time is not obviously expected. Furthermore, for droplets of different average initial diameters [...], the frequency, [...], where [...] is the usual evaporation constant, is well represented as a universal function of the initial spacing between droplet centers ([...]) or adjacent droplet surfaces ([...]). The evaporation constant [...] for constant [...], and the frequency [...] for arbitrary values of [...], increase at first as [...] is reduced and then decrease again. For large values of [...], [...] approaches the numerical value measured in studies on the burning of single droplets. This behavior can be understood in terms of a competition between heat losses to the outside from the flame front surrounding a single droplet, which decrease as the droplets are brought together, and oxygen-deficient atmospheres, which are more likely to occur for very small values of [...]. Although an acceptable empirical correlation of experimental measurements has been obtained, the processes which determine interference during droplet burning are as yet not understood. In view of the possible practical importance of interference during burning in sprays, additional laboratory studies on the burning of simple geometric arrays, other than two droplets, appear to be indicated.

Thesis Files