Propagation Characteristics of the Shock Wave in Small Diameter Tubes at Atmospheric Initial Driven Pressure

Recently, the micro-shock waves have attracted attention of researchers in several fields of science. It is well known that the shear stress and the heat transfer between a test gas and a wall lead to significant deviations from the normal theory of a shock wave propagating in a small diameter shock tube[1][2]. In our previous research, we developed a diaphragmless driver section using a rubber valve, and estimated the valve opening characteristics[3]. In addition, the shock wave measurements in the driver pressure range from 0.1 to 0.2 MPa were made in 1 and 3 mm inner diameter shock tubes with rubber valves, while the shock wave measurements in small diameter tubes were performed at a relatively low driver pressure[4][5][6]. At relatively high driver pressures over 0.5 MPa, shock wave measurements using the diaphragmless driver section with the rubber valve are very difficult to perform, because of the structural properties of the section. The technique of two pistons for diaphragmless driver section, which was invented and applied by Oguchi, et al.[7] and Maeno, et al.[8]. Its technique is successfully used especially in the larger diameter shock tube and initial pressure ratio, and has some accomplishments[9][10]. They concluded that, the diaphragmless driver section with two pistons is capable of producing the shock waves and is very convenient at the driver pressure range from 0.3 to 0.9 MPa, and there are some advantages over the convential shock tube as high reproducibility, and so on. However, there are no reports about applying this technique for generation of the shock wave in the small diameter tube. In this study, we simultaneously measured the velocities of shock waves and the density ratios across the shock wave, generated by originally developed diaphragmless driver section with two pistons, propagating in 2 and 3 mm inner diameter tubes by using laser differential interferometer.