Induction times to thermal ignition in systems with distributed temperatures: An experimental test of theoretical interpretations
✍ Scribed by T. Boddington; J.F. Griffiths; K. Hasegawa
- Publisher
- Elsevier Science
- Year
- 1984
- Tongue
- English
- Weight
- 565 KB
- Volume
- 55
- Category
- Article
- ISSN
- 0010-2180
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✦ Synopsis
Experimental data are presented which show how induction times to ignition in a nonadiahatic system decrease as Frank-Kamenetskii's dimensionless parameter ( ) is raised. The data were obtained from the spontaneous ignition of methyl nitrate vapor at very low pressure in a closed spherical vessel. Heat transfer occurs solely by conduction.
Comparisons are made with the predictions from two recent theoretical interpretations of induction times. Each relates time to ignition to Frank-Kamenetskii's 6. An empirical expression derived by Boddington, Feng, and Gray is applicable at marginally supercritical conditions; it is extremely conveoient to exploit and is found to be in very good agreement with experimental measurements. Careful allowance for the time due to heating up ~or assembly) of the reactant system is found to be necessary. The upper and lower bounds predicted by Bebemes and Kassoy are more appropriate to conditions very far from criticality, where induction times approach the adiabatic limit. Experimental tests in this realm are not easy because reactant assembly becomes a substantial proportion of the elapsed time. A significant discrepancy between numerically computed times to ignition that are exploited in these theoretical interpretations is revealed.