Critical Charge for the Direct Initiation of Detonation in Gaseous Fuel-Air Mixtures

摘要

This paper describes the results of measurements of the critical initiation energy for hydrogen-air mixtures performed in a large-scale facility at Sandia National Laboratories. These results for hydrogen-air mixtures, in conjunction with earlier measurements carried out on a smaller scale by Elsworth and together with Elsworth's measurements covering a range of other fuels, are used to assess the accuracy of existing phenomenological models. A comprehensive review of the theoretical models used to predict the critical initiation energy of unconfined detonation in reactive mixtures is presented as well. Three initiation energy models, namely, the surface energy model of Lee, the cell energy model of Vasiliev and Grigoriev, and the detonation kernel model of Ramamurthi and Lee are found to correlate well with the experimental critical charge data for hydrogen-air, ethane-air, propane-air and butane-air mixtures. For ethylene-air mixtures, none of the existing models predict the whole range of initiation energy data. From examination of the hydrogen-air data, the calculated explosion length R sub 0 , for critical conditions is of the order of R sub 0 approx. =1.5 d/sub c/, where d/sub c/ is the critical tube diameter. This is compatible with the reinitiation distance of approx.2 d/sub c/ for the critical tube situation observed by Ungut, et al. The correlation R sub 0 approx. =1.5 d/sub c/ provides a better estimate of the critical initiation energy than can be obtained from direct measurements which are influenced by the characteristics of the initiation source. 46 refs., 3 figs., 3 tabs. (ERA citation 10:042876)