A Study of Propagating Detonation Waves in Narrow Channels

Abstract

Detonation cell width and velocity deficit, both implicitly include the wall effects, are investigated to obtain insight on propagating detonation waves in narrow channels. The total length of the 50.5 mm i.d. detonation tube is 5350 mm, which comprises of several sections including a 850 mm long driver section and a 1500 mm long test section. The detonation in the test section is initiated via a detonating driver gas, which bursts a thin diaphragm separating these two sections. The velocity deficits predicted by the boundary layer displacement theory developed by Murray were compared to those obtained experimentally. Good agreements are found between the theoretical predictions and the experimentally obtained velocity deficits for all the channel dimensions studied for the present gaseous systems. However, the experimentally measured cell widths are found to be larger than those evaluated from the induction zone length calculated by the ZND model. This gives a basis to conclude that the extinction of some of the triple points, which leads to form larger cellular structures inside the channel as compared to the original one measured before the channel entrance, may be made by the boundary layer developed at the wall surfaces. To approximate the experimental cell width (λ_m) in the channel through the predicted cell width (λ_P), a relation λ_m=Bλ_P was found in this study where the value of B is slightly dependent on the reaction model. B was evaluated to be 1.2 using Lutz et al.'s reaction model and 1.3 using GRI Mech 3.0.