- Author
- Kashiwagi, T. | Mell, W. E. | Baum, H. R.
- Title
- Theoretical Study on Ignition, Transition, Flame Spread in Multidimensional Configuration in Zeromicrogravity. [Slide Presentation]
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Book or Conf
- Microgravity Combustion International Seminar. Presentation No. 8. Proceedings. Host Organizations: Institute of Fluid Science/Tokoku Univ. (IFS), New Energy and Industrial Technology Development Organization (NEDO), Japan Space Utilization Promotion Center (JSUP), Japan Microgravity Center (JAMIC), Ministry of International Trade and Industry (MITI), National Aeronautics and Space Admin. (NASA). August 19-20, 1999, Japan, 68-76 p., 1999
- Keywords
- microgravity | ignition | flame spread | spacecraft
- Abstract
- In the inhabited quarters of orbiting spacecraft, fire is a greatly feared hazard. A momentary ignition might be tolerable but a material which permits a transition from a localized ignition to flame spread would significantly increase the fire hazard in a spacecraft If the transition does not take place, fire growth does not occur. Therefore, it is critical to understand what process controls the transition. Many previous works have studied ignition and flame spread separately or were limited to a two-dimensional configuration. In this study, time-dependent phenomena of the transition over a thermally thin sample is studied theoretically in the two- and three-dimensional configurations to understand the difference in the transition process between the two different configurations. Furthermore, localized ignition is initiated at the center portion of thermally thin paper sample instead of at one end of the sample. Thus, the transition to flame spread could occur either toward upstream or downstream or both directions simultaneously with an external flow. In this presentation, the difference in the transition between in the three-dimensional configuration (ignited to produce a small circle shape flame front) and in the two-dimensional configuration (ignited across the sample to produce a line shape flame front) is explained with the numerically calculated data. It was found that the two-dimensional flame quenched more easily than the three-dimensional flame during the transition period. Significant diffusion of oxygen from the sides (in a direction perpendicular to the imposed flow) to the centerline plane occurred in the three-dimensional case. On the other hand, oxygen supply to the two-dimensional flame could only occur within the centerline plane. Once flame spread was established, there was little difference between the three-dimensional and two-dimensional flames due to decreased curvature of the three-dimensional flame. A small experimental chamber is always required to conduct tests in a microgravity environment due to limited available space. This raises a question of an appropriate sample width to study flame spread in the two-dimensional configuration. This question is examined by comparing the numerically calculated results based on the two-dimensional code and three-dimensional code with ignition across the sample width. The results show two important edge effects with a finite width sample; one is heat loss to a sample holder and the other is enhanced oxygen supply from outer flow to the edges of flame. These effects become significant for narrow samples.