ID#: 135
Abstract Title: DDT in Methane-Air Mixtures
Session Title: DDT
Session Date: 7/31/01
Session Start Time: 8:30 AM
Contributing Author: Dorofeev, S.B.
Organization: RRC - Kurchatov Institute
Country: Russia
Authors: M. Kuznetsov, G. Ciccarelli, S. Dorofeev, V. Alekseev, Yu. Yankin, T.H. Kim
Short Abstract: Considering the common use of methane gas in the chemical process industry there is a lack of detonation phenomena data in the literature for methane-air mixtures. This is due to the relatively low detonation sensitivity of methane-air, and thus the need for large-scale apparatus. Experimental results from a study on the critical condition for DDT in methane-air mixtures are presented in this paper. Tests were performed in two different detonation tubes, one with an inner-diameter of 174-mm and the other 520-mm inner-diameter. With a blockage ratio (BR) of 0.3, propagation in the quasi-detonation regime was observed for mixtures with 8, 9.5, 10.5, and 12 % CH4 in the 520-mm tube and 9.5 and 11% CH4 in the 174-mm tube. In tests with a BR= 0.6, propagation DDT was not achieved in either tube for any methane-air mixture. The results indicate that for a blockage ratio of 0.3 the critical condition for DDT can be characterized by the d/lambda = 1 criterion proposed by Peraldi et al. However, for BR = 0.6 it was found that the critical value was significantly higher. The data also shows that the critical condition for DDT can be better described by L/lambda = 7, where L is a characteristic size for of the channel volume between orifice plates which depends on the orifice plate dimensions and spacing. This is in good agreement with previous data obtained for other hydrocarbon and hydrogen mixtures with irregular detonation cellular structure.