Effects of natural convection on two stage ignition of an n-dodecane droplet
- Univ. of Tokyo (Japan). Dept. of Aeronautics and Astronautics
- Ishikawajima-Harima Heavy Industries Co., Ltd., Tokyo (Japan)
- Bremen Univ. (Germany)
The effects of natural convection on two-stage spontaneous ignition of a fuel droplet were studied experimentally. A suspended n-dodecane droplet of 0.7 mm in its initial diameter was employed. Ignition phenomena were observed by a fine thermocouple (0.025 mm) and by an interferometer so as to detect an invisible cool flame. A direct photographic method with a back light was also used to measure the droplet diameter. Ambient temperature was limited within the range where the cool flame can be observed (500 to around 800 K) and ambient pressure ranged between 0.1 and 1.0 MPa. Experiments were carried out under normal and microgravity conditions, and results were compared. Investigations were done mainly on the induction times it 0.2 and 1.0 MPa. Experiments showed longer first induction times (time to appearance of cool flame) under normal gravity than under microgravity in certain ambient conditions. Significant differences between critical temperatures, below which cool flame or hot flame does not appear, were also observed between the two gravity conditions. The induction times differed up to a factor of 3, and the critical temperature differed about 60 K. For the second stage, slightly increased induction times were observed under normal gravity conditions at 0.2 MPa. Differences observed between both gravity conditions can be explained by the effects of natural convection driven by the downward force due to the dense fuel vapor and by the buoyancy due to the cool flame.
- OSTI ID:
- 93193
- Report Number(s):
- CONF-940711-; TRN: IM9537%%236
- Resource Relation:
- Conference: 25. international symposium on combustion, Irvine, CA (United States), 31 Jul - 5 Aug 1994; Other Information: PBD: 1994; Related Information: Is Part Of Twenty-fifth symposium (international) on combustion; PB: 1838 p.
- Country of Publication:
- United States
- Language:
- English
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