Although ignition by hot surfaces has received some attention in the past, most of the data refer to flat surfaces and hot wires. The effect of 'local confinement' around the ignition source on the ignition process has not been extensively studied. The investigations of two well known accidents, the Tunnel Summit fire and the Piper Alpha disaster, showed that more data and knowledge about the ignition mechanism by heated surfaces are needed. In both cases, ignition at hot surfaces of complex geometry was identified as a possible cause of the fire, but the temperature was much lower than 900<SUP>o</SUP>C, the temperature considered necessary for ignition of a vapour/air mixture at a hot surface. There have been a number of studies of ignition by hot surfaces, in which the ignition sources were hot spheres, wires and strips. In all these studies the ignition sources were unconfined. However, it is important to understand the influence of the 'local confinement' around the ignition source on the ignition mechanism. The work described in this thesis is confined to the ignition of a flammable vapour/air mixture at a hot surface. The objective of the experimental work was to generate new data which could be used to help understand the effect of 'local confinement' on the ignition of flammable mixture at a hot surface. Electrically heated nichrome strips were used as the ignition source, and measurements were made of the effect of 'local confinement' on the minimum temperature required to cause ignition of a 3% propane/air mixture. It was found that the ignition temperature decreased as the depth of the confinement was increased. The results obtained were analysed using the thermal theory of Frank-Kamenetskii.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:649745 |
| Date | January 1994 |
| Creators | Duarte, Dayse Cavalcanti de Lemos |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/13727 |
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