Energy Conversion in a Gas Shock Tube: Theory and Experiments

Abstract

THE GAS SHOCK TUBE USED IN THESE EXPERIMENTS CONSISTS OF A LOW PRESSURE CHAMBER AND A HIGH PRESSURE CHAMBER, DIVIDED BY A METAL-DIAPHRAGM-TO- RUPTURE. IN CONTRAST TO THE SHOCK MODE OF OPERATION, WHERE INCIDENT AND REFLECTED SHOCKS IN THE LOW PRESSURE CHAMBER ARE STUDIED WHICH OCCUR WITHIN 3.5 MS, IN THIS WORK THE COMPRESSION MODE OF OPERATION WAS STUDIED, WHOSE MAXIMA OCCUR (IN THE LOW PRESSURE CHAMBER) ABOUT 9 MS AFTER RUPTURE. THEORETICAL ANALYSIS WAS DONE WITH THE FINITE ELEMENT COMPUTER CODE EURDYN-1M, WHERE THE COMPUTATION WAS CARRIED OUT TO 30 MS. THE COMPRESSION MODE WAS REINFORCED BY INSERTING ON THE LOW PRESSURE SIDE, JUST BEHIND THE DIAPHRAGM, A SMALL PISTON. IN THE CORRESPONDING ANALYSIS THE COMPUTATION TIME WAS UP TO 112 MS. RESULTS SHOWED THAT THE WORK DONE ON THE LOW PRESSURE GAS COULD BE APPROACHED WITH ADIABATIC COMPRESSION. IT WAS EXTRAPOLATED THAT AT HIGH PRESSURE LOADS, THE WORK DONE CORRESPONDED TO 1.5% OF THE POTENTIAL ENERGY IN THE HIGH PRESSURE CHAMBER WHEN NO PISTON WAS USED, AND TO 4% WHEN A PISTON WAS USED.