Research Initiation Awards: Spherically-Symmetrical Combustion of Unsupported Droplets Under Normal-Gravity Conditions

本文将研制一种独特的滴管实验装置，用于研究自由下落液滴的球对称蒸发和燃烧。该装置的设计是基于这样一个原理，即通过使用适当形状的管子加速气体，可以显著降低气体中重力引起的压力梯度。随着气体移动的液滴将经历大大减少的浮力和强制对流环境，从而促进球形对称性。该装置将用于在迄今尚未实验实现的条件下研究近乎球形对称的液滴蒸发和燃烧（即在大气压下最初直径= 100微米的液滴燃烧）。实验研究将集中在1。2.烃类液滴的燃烧与熄灭；2 .瞬态液滴和火焰直径的测量；具有强烈烟尘倾向的液滴的燃烧和破裂。拟议的设施将允许在以前未达到的条件下研究许多基本和实际的液滴燃烧和蒸发现象。所获得的数据将有助于检验现有的理论，并将提供诸如熄灭条件、瞬态汽化速率和瞬态火焰生长等现象的基本信息。这项工作的结果将对科学界（从所获得的基本信息中），以及一般的燃烧和喷雾社区有用，可能允许改进的实际燃烧装置被开发出来。

A unique drop-tube experimental apparatus to promote spherically-symmetric evaporation and combustion of freely- falling droplets will be developed and constructed. The design of the apparatus is based upon the principle that gravitationally-induced pressure gradients in gases may be significantly reduced by accelerating the gases with properly contoured tubes. Droplets traveling with the gases will experience greatly reduced buoyancy and forced convection environments, thereby promoting spherical symmetry. The apparatus will be used to study nearly spherically-symmetrical droplet evaporation and combustion under conditions that have heretofore not been experimentally achieved (i.e., combustion of droplets initially = 100 um in diameter at atmospheric pressure). Experimental studies will focus on 1. combustion and extinction of hydrocarbon droplets, 2. measurements of transient droplet and flame diameters, and 3. combustion and disruption of droplets with strong sooting tendencies. The proposed facility will allow many fundamental and practical droplet combustion and evaporation phenomena to be studied under conditions previously unattained. The data obtained will be useful for testing existing theories, and will provide fundamental information on phenomena such as extinction conditions, transient vaporization rates, and transient flame growth. Results from the work will be useful to the scientific community (from the fundamental information gained), and also to the combustion and spray communities in general, possibly allowing improved practical combustion devices to be developed.