Influence of Diluents and Inhibitors on Detonations

摘要

The present paper reports on a series of experiments performed to determine the influence of chemical inhibitors and diluents on the detonability of fuel-air and fuel-oxygen mixtures. The influence of adding small amounts (1 to 3%) of CF sub 3 Br, CF sub 4 and CO sub 2 to ethylene-air mixtures was determined by performing large scale critical tube diameter tests. The results of these tests show that the inhibition effect of CF sub 3 Br on detonations is not nearly as dramatic as it is on flames. For detonations, the relatively chemically inert diluent CO sub 2 is found to be a better inhibitor than CF sub 3 Br. Similar laboratory test with ethylene-oxygen and hydrogen-oxygen mixtures confirm the results obtained for fuel-air mixtures. In fact, the addition of small amounts of CF sub 3 Br to these fuel-oxygen mixtures has a small sensitizing effect, whereas the influence of CO sub 2 is similar to that observed for fuel-air mixtures. The results are compared with the prediction of a detailed chemical kinetic model for the oxidation and inhibition processes. For CF sub 3 Br, it is found that a chemical kinetic scheme derived from flame data predicts a detonation inhibiting effect much larger than that observed. Possible modifications of this scheme to obtain a consistent description of CF sub 3 Br inhibition are proposed and discussed. (ERA citation 09:034163)