Shock Wave Pressure and Velocity Measuring Using a Novel Optic Sensor in a Newly Designed Diaphragm-less Shock Tube

Abstract

This paper suggests a new optical system for measuring shock wave characteristic that is installed in a shock tube. This shock tube has an innovative pneumatic rapid opening valve designed to open from the center of the tube to the corners. In this measurement system, a plate has placed in front of the shock wave. The plate displacement has measured during a collision by measuring the amount of light reflectance change. Then these optical data have converted to a voltage. After calibration with the help of a piezoresistive sensor in the shock tube and showing its voltage-pressure relation, the shock wave pressure diagram has been demonstrated, which contains the wave’s positive and negative parts. Also, the delay time in this system is investigated. In addition to the shock wave velocity, the system can measure the timing and velocity opening of the pneumatic valve replaced in the shock tube. The velocity is also calculated theoretically and compared with the experimental results. The unique feature of this automatic valve is its opening from the center of the tube to the corners, like a camera aperture, which is best suited for opening the valve and resulting wave uniformity. Also, the alignment of the driver and the driven prevented gas perturbation due to the redirection or rotation. This problem has seen in most recently used valves. Finally, the planar shock wave formation has been investigated.