The generation of triggered shock-waves in shock-tubes with exploding wires

The University of Missouri-Columbia Center for Physical and Power Electronics has implemented the use of exploding wires to trigger the diaphragm in a 20.3 cm diameter PVC shock tube. The shock tube is partitioned into two segments: the driver side and the driven side. The high pressure driver side is partitioned from the low pressure side by a 0.127 mm thick Mylar sheet with an exploding wire attached to it. The shock wave is generated in the tube by pressurizing the driver side of the shock tube to 30.5 psig and discharging the energy from an 11uF capacitor bank into a 30 AWG copper wire. The 9.8 cm long wire vaporizes as 4.95 kJ of stored energy is discharged into it at a peak current of 3 kA. The wire, which is attached to the Mylar, behaves like a fuse; puncturing the Mylar diaphragm as it vaporizes. This catastrophic failure results in the low jitter generation of a shock wave whereby experiments can be timed to the arrival of the shock wave. The key benefit to minimizing the jitter of shock-wave generation allows for better timing for shock-wave diagnostics and functionality. Through experimentation, shock-wave jitter times of approximately 32 µs have been observed. This jitter provides sufficient timing capabilities to efficiently capture data, as well as synchronize external events designed to interact with the shock wave. The diagnostic suite used to analyze the characteristics of the shock wave and the exploding wire includes: a schlieren setup, a phantom V7.3 high speed camera, Kistler 603B1 pressure transducers, a Tektronix TDS2024C oscilloscope, a Northstar PVM-6 high voltage probe, and a Stangenes SI-5009 current probe. The characteristics of the shock tube, as well as the exploding wire for these experiments, are reported.