Experimental and theoretical study on downward flame spread over uninhibited PMMA slabs under different pressure environments. (25th May 2018)

• Record Type: Journal Article
• Authors: Zhao, Kun; Zhou, Xiaodong; Liu, Xueqiang; Tang, Wei; Gollner, Michael; Peng, Fei; Yang, Lizhong
• Is Part Of: Applied thermal engineering. Volume 136(2018)
• Page Start: 1
• Page End: 8
• Publication Date: 2018-05-25
• Subjects: Downward flame spread -- Side-edge effects -- Parallel-slab -- Heat transfer -- Ambient pressure; Heat engineering -- Periodicals; Heating -- Equipment and supplies -- Periodicals; Periodicals; 621.40205
• DOI: 10.1016/j.applthermaleng.2018.02.059
• Languages: English
• ISSNs: 1359-4311

Abstract

Highlights: 3-D downward flame spread rate is decided by the ignition at side-edge. A thermal model is established to predict 3-D downward flame spread rate. The angle of the pyrolysis front changes greatly with sample separation distance. Abstract: This paper presents an experimental and theoretical study of side-edge effects on downward flame spread over two parallel polymethyl methacrylate (PMMA) slabs under different pressure environments. Identical experiments of downward flame spread over thin PMMA slabs with side-edges unrestrained were conducted at different altitudes in Hefei (102 kPa), Geermu (73.2 kPa) and Lhasa (66.3 kPa). Experimental results show that the flame spread rate is controlled by ignition along the side-edge, rather than at the center of the samples, for experiments with both single and two parallel slabs. Based on these results, a thermal model is developed which describes flame spread along the edge and quantitatively agrees with experimental results. In the parallel-slab case, convective heating appears to influence the spread rate only when the separation distance is very small, with radiative heating playing a more important role as separation distance increases. The angle of the pyrolysis front, formed between the faster side-edge spread and slower center-region spread, hardly changes with pressure, but changes significantly with separation distance, due to differing modes of heat transfer between the side-edge and center region. In addition, variations of flame height with pressure and separation distance are reasonably interpreted from diffusion flame theory.