A new, friction controlled, piston actuated diaphragmless shock tube driver

Abstract

A new friction operated single piston shock tube driver design that is capable of generating shock waves of Mach number 1.1 to 2 is presented. By using different test gases and evacuating the driven section Mach 5 shock waves can easily be produced. The driver is efficient with shock wave Mach numbers within 9% of that predicted by ideal shock tube theory and the non-dimensional formation length lies between 20 and 40. The brake pad mechanism, that restrains the piston until tests commence, removes the necessity of venting an auxiliary chamber rapidly, thus speeding up the displacement of the piston. It is believed that the design is a practical, simple and cost effective way of generating reproducible shock tube tests with very short test turn around times, while removing the necessity of using a diaphragm and exposing the test gases to the atmosphere. Results for three pistons with masses of 4.4, 0.71 and 0.38 kg (brass, PVC and hollow aluminium respectively) with driver gauge pressures of between 2 and 50 bar (Mach 1.2 to 2) are given.