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Science and Technology of Energetic Materials

Vol.77, No.4 (2016)

Research paper

Experimental study on acceleration of projectile by a gaseous detonation-driven gas gun using a light gas
Shinichi Maeda, Shoichiro Kanno, Isshu Yoshiki, and Tetsuro Obara
p.79-85

Abstract

Experiments were conducted to investigate the gaseous detonation-driven gas gun in which the driving source was the high-pressure combustion products behind the detonation waves propagating inside the simple straight tube (called detonation tube), and demonstrated that the acceleration of the projectile reached to the supersonic or hypersonic speeds. As the simplest configuration, the single-stage gun was tested directly connecting the detonation tube with the launch tube. When the detonation wave was driven by the hydrogen-oxygen mixture, the gun could accelerate the spherical projectile of 4.76 mm diameter and 52 mg mass up to 1400 m s-1. The dilution of the hydrogen-oxygen mixture with the helium gas within 30% of the volumetric fraction had an insignificant effect on the projectile acceleration, and the reason was explained from the thermodynamic properties of the combustion products. However, the increase of the dilution rate to 40% caused to increase the projectile velocity up to 1600 m s-1. This was owing to the arrival of the overdriven detonation at the launch tube, because the location of the detonation transition shifted to the downstream section of the detonation tube. In these experiments, the detonation-driven gas gun could obtain experimentally two to three times the projectile velocities compared to the theoretical velocities of the conventional single-stage light-gas gun driven by the pure hydrogen or helium gas under the same gun geometry and the filling pressure. The two-stage gun driven by the hydrogen-oxygen detonation was also tested by using the same detonation tube. The pump tube was added downstream of the detonation tube to compress the pure helium gas using the free piston driven by the detonation products. The detonation driver successfully established the pumping process of the helium gas in the pump tube. The velocities obtained in this study were up to around 2500 m s-1, and these results were about 1.8 times higher than the velocities of the single-stage gun using the same detonation driver.

Keywords

gaseous detonation, gas gun, shock wave, supersonic combustion, supersonic flow

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