銃口に於ける高壓瓦斯及び壓縮波の運動に就て

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By means of high-speed kinematography, we have studied on some phenomena which occur in the neibourhood of the muzzle when the rifle is fired, such as the motion of powder gases and the propagation of compressed waves accompanied therewith. The method of high-speed kinematography is almost the same as that previously reported by one of the authers, and it utilizes the illumination of high frequency electric sparks as the light source of Schlieren photography. We can take several thousands pictures in a second, of which the time of exposure is less than half a microsecond. The rifle used in the experiments is specially made and the bullet is of 7.8mm in its diameter. The initial velocity of the bullets varies from 310m/sec to 460m/sec, according to the quantities of gunpowder primed (see Table 1). From the photographs we have taken, it can be seen that there are, in general classification, five stages of the phenomena at the moment of firing, that is: 1) First of all there emerges a compression wave A (Pl. 1, 2. Photo. 1-4) from the muzzle and propagates nearly spherically. The ratio of the initial speed of the wave A to that of the sound wave in air is 1.44 in mean (Table 2). But as the wave proceeds about 70cm from the muzzle the speed approaches that of the sound wave (Table 3). 2) At the same time as the compression wave A appears, a narrow jet B issues out of the muzzle with a high speed. And the photographs show that this jet B has a sort of periodic formation (see Pl. 1, 4. Photo. 2, 7, 8). The distances (λ_1, λ_2, ....in Table 4, given in cm) between each successive periodic pattern seem to diminish as it proceeds. The relations between the distance B of the jet from the muzzle and the time are shown in Fig.7-12, the origin of time being taken at the instant at which the rear end of the bullet just appeared in front of the muzzle. 3) When the front of the jet B reaches some distance from the muzzle, the bullet comes out of the barrel and flies away with a nearly uniform velocity. 4) Following the bullet, the high-pressure powder gases C, which have propelled the bullet through the barrel, effuse into the atmosphere with a high velocity which exceed the ordinary sound velocity in air. 5) An intense compression wave D (see Pl. 1, 2. Photo. 1, 2, 3, 4), caused by the violent effusion of the powder gases, propagates in every direction with a velocity of several hundreds meters per second, which after a few thousandth of a second reduces nearly to the ordinary sound velocity. The relations between the distance of the head of D from the muzzle (see Fig.19) and the time are shown in Fig.22-27. The velocity of the wave front of this kind is nearly expressed in the form: V=V_T+V_0e<-αt>, where V_T is the velocity of sound wave at temperature T, and α and V_0 are constants. The numerical values of these are given in Table 6, the units of length and time being cm and sec respectively. Minute descriptions about several aspects are given and some discussions on the results are tried.
宇宙航空研究開発機構の論文

銃口に於ける高壓瓦斯及び壓縮波の運動に就て

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