EVAPORATION OF MULTICOMPONENT DROP ARRAYS

The conventional fuels that are used in the field of transportation ar e primarily composed of two or more components. Each component evapora tes, mixes with hot oxidant gases, ignites, and burns. Since euaporati on is the precursor of the sequence of events leading to combustion, t he evaporation studies on the multicomponent drops are essentialfor de termining the governing parameters of spray evaporation. While single- component drop studies have been carried out extensively in the past, very limited literature exists on the multicomponent array evaporation . The present paper deals with the evaporation of multicomponent fuel droplets in an array using the recently developed point source method (PSM). First, the quasisteady (OS) evaporation of an isolated, multico mponent droplet is briefly analyzed. The resultant governing equations , along with Raoult's law and the Cox-Antoine relation, constitute the set of equations needed to arrive at the solutions for: (1) the dropl et surface temperature, (2) the evaporation rate of each species, and (3) the vapor mass fraction of each species at the droplet surface. Th e PSM, which treats the droplet as a point mass source and heat sink, is then adopted to obtain an analytic expression for the evaporation r ate of a multicomponent droplet in an array of liquid droplets. Defini ng the correction factor (eta) as a ratio of the evaporation of a drop in an array to the evaporation rate of a similar isolated multicompon ent drop, an expression for the correction factor is obtained. The res ults of the point source method (PSM) are then compared with those obt ained elsewhere for a three-drop array that uses the method of images (MOI). Excellent agreement is obtained. The treatment is then extended to a binary drop array to study the effect of interdrop spacing on va porization. When the drops are close to each other, the evaporation ra te of the droplet in the array containing the larger percentage of vol atiles is higher than the rate under isolated conditions (eta > 1). Th e results qualitatively confirm the experimental data reported elsewhe re. Parametric results were obtained for the effect of changing the co mposition on the correction factor and finally critical drop compositi ons in the binary array are given for which eta > 1. Even though the r esults for the average correction factor of the whole array of 2 to 9 drops obtained using PSM are almost the same as the results from MOI, the correction factor of the center drop under severe interaction may deviate from those results obtained with MOI.