Development of a Small Diameter Shock Tube and Measurement of Basic Characteristics

Abstract

In this study, we developed a diaphragmless driver section with two pistons to generate the shock wave in small diameter tubes. An optical system using a He-Ne laser is constructed for the definition of a main piston opening time. The trajectories of main piston are measured under the several initial driver pressures. Additionally, the motion equation for the main piston is derived from a simple motion model. Moreover, the laser differential interferometer is constructed for the contactless measurement of the shock waves. The shock waves generated by our diaphragmless driver section, propagating in 2 and 3 mm inner diameter tubes are measured by the laser differential interferometer. The Mach number of the shock wave and the density ratio across the shock wave can be calculated by the interference signal obtained from the shock wave measurement. Additionally, the Mach number distributions along the axial direction of the tubes and the relation between the shock wave location and time (shock wave diagram) are obtained. Consequently, it is attributed to the fact that the friction effect between the test gas and the inner wall of the tubes becomes larger with decreasing the inner diameter of the tube.