The effect of initial diameter on free droplet combustion with spherical flame
- Noritz Corp., Tokyo (Japan). Research Lab.
Two kinds of experiments have been conducted to study the effect of the initial droplet diameter on the burning behavior of a single free droplet with a spherical flame. One is performed under microgravity, which is realized in a freely falling chamber to establish a spherical flame around a large droplet of about 400-{micro}m initial diameter. The other is to investigate the combustion of small droplet under normal gravity, whose initial diameter is about 70 {micro}m. The small droplet is injected up vertically and ignited by an electric spark after passing through the apex of its trajectory. Even under normal gravity, for such a small droplet, a spherical flame, can be observed through the image intensifier. In this study, the fuel used is n-heptane as sooting fuel. The time dependence of the squared droplet diameter is categorized into two types with the initial droplet diameter. (1) The so-called d{sup 2} law is established for the entire period of burning, except for the initial period, where the droplet diameter is not changed markedly. This type can be observed for large droplets in the microgravity experiment. (2) The evaporation constant decreases at the later period of burning after the d{sup 2} law is held. This type can be observed for small droplets in the experiment under normal gravity. It is recognized that extinction occurs around the time when the evaporation constant begins to decrease. Soot formation tends to be enhanced as the initial droplet diameter is increased, and the no-soot formation can be observed for a small droplet of about 70-{micro}m initial diameter.
- OSTI ID:
- 93189
- Report Number(s):
- CONF-940711--
- Country of Publication:
- United States
- Language:
- English
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