Advances and challenges in droplet and spray combustion. I. Toward a unified theory of droplet aerothermochemistry

Major theoretical accomplishments in droplets and sprays in the twentieth c entury are reviewed in this two-part article, with emphasis focused upon th e evolution of scientific concepts, paradigms and methodologies. A structur al spray theory, which was developed from an early view of isolated droplet s, has evolved in to a new view that the interacting droplet and meso-scale structures and clusters of many-droplet systems are also fundamental entit ies in practical sprays. The first part of this work addresses the major co ncepts in analytical developments, which serve as the framework of modern t heories of an isolated and interacting droplet. Outstanding issues and crit ical bottlenecks that have prevented further advancement of the existing an alytical theory of droplet physics are examined, and an emerging research t rend in a unified theory of droplet phenomena discussed. Recent accomplishm ents and future prospects of a unified theory are presented to complement t he status of this special branch of droplet science and its future applicat ion. (C) 2000 Elsevier Science Ltd. All rights reserved.