: Detonation, a shock wave supported energetically by chemical reactions in flames, is a most dangerous form of flame propagation through explosive media. Interruption of detonation is, therefore, an important technique to prevent serious disasters in such processes as flammable gas conveying pipelines. Gases are seldom premised with air, but atmospheric air often invades into gas lines through various leak processes. It would be better to consider that an ignition of explosive mixture leads finally to a detonation in a long line, and to insert effective detonation arrester in such pipelines to minimize the resulting damages.
    This report describes about the decaying of a detonation wave by inserting a perforated plate in a detonating tube, and the direct interruption of detonation by layered wire gauzes supported with a perforated plate. Experiments are carried out in a 1-inch tube (Fig.1), and the arrester housing (Fig.2) contains wire gauzes and/or a perforated plate under test. Combustible mixture used is that of stoichiometric hydrogen-air with initial pressures below 1 kg/cm² (G). After the ignition of the mixture at the far end of the tube, flame is so accelerated by a spiral insertion as to develop to an incidental detonation wave onto the arrester housing.
    To determine the effect of perforated plate on detonation decaying, plates in Fig.3 are tested. Each plate is specified by a diameter of one hole D ₀ and a number of equi-diameter holes N. An average flame speed V _a.b between two points, one before and the other after the tested plate, is measured by the ion-gap method. If detonation is decayed through the plate, V _a.b differs from the detonation velocity depending on the degree of decaying. Main results are as follows ;
  (1) For each plate V _a.b is not effected by the initial gas pressure. For plates with one hole, D ₀ can be related with V _a.b as shown in Fig.7. From this relation, a corresponding single hole diameter (D _E) of each plate with N ≥ 2 can be given ; D _E is defined as a hole diameter of the plate with N = 1 which gives the same V _a.b as that measured for the plate under consideration.
  (2) The relation between D _E and D ( = √N D ₀) shows that the degree of decaying is determined by a total open area of holes for plates with rather larger D , and that plates with suber 5 decay detonations more effectively than estimated from N and D ₀ of those plates. Thus, D _E can be used to denote the relative degree of detonation decaying by any perforated plate (Fig.8).
  (3) D _E is also related to the flow resistance of each plate, but because of the dependency of the flow resistance on N and D ₀, the relation between D _E and the flow resistance is found to be nearly same as that between D _E and D .
  (4) As a whole, a perforated plate with a large number of holes of suber diameter may practically be useful from the standpoints of the effect on detonation decaying and the flow resistance togas flows.
    Flame quenching abilities of wire gauzes are studied for commercial filter gauzes (Table 1). They are not so strong as to stand against repeated shock pressures by themselves that they must be supported by a perforated plate. As flames more easily pass through gauzes for higher initial gas pressures, the maximum initial pressure which gives three successive quenchings is denied as the Limiting Safe Pressure (L.S.P.) to compare a relative quenching ability of gauzes. Thus, a high L.S.P. means a high quenching ability of gauzes.
    Main results on detonation quenchings are as follows ;
  (1) The open area of holes of a supporting perforated plate effects largely on the flame quenching : decreasing D always increases the L.S.P. (Fig.9).
  (2) Effects of the thickness of layered gauzes on the L.S.P. are more distinct for larger holes in supporting plates (Fig.10). The rate of increasing the L.S.P. gradually decreases as the thickness of the gauze layer increases. Five packs of gauze supported by an adequate perforated plate will quench all flames of hydrogen-air detonations under studied conditions.
  (3) Flow resistances of packed gauzes with a perforated plate can be related with the L.S.P. (Fig.13). For more than three packs of gauze, the flow resistance gives a little influence on quenching abilities.
    From these results the mechanism of detonation quenching may be roughly assumed ; the first process is a decaying of a detonation wave at the entrance into the surface of wire gauzes, and the second is a process of flame quenching or heat losses to gauze metals. Thus, detonation arresters are said to be flame arresters with mechanical structures for detonation decaying.