Shock tubes are tools to study the kinetics of gas-phase chemical reactions at high temperatures. In most shock tubes, a diaphragm separates a high-pressure gas, called the driver, from a low-pressure gas, called the test gas. When the diaphragm ruptures, the driver gas pushes into the test gas, generating a shock wave that propagates through the tube at supersonic speed, sometimes heating and compressing the test gas to combustion temperatures. Instruments placed at the end of the tube then measure reaction kinetics.

However, experiments using diaphragm-based shock tubes can take up to an hour to set up for each shock, which limits data collection. Additionally, no two diaphragms rupture exactly the same way, so each shock is unique, which prevents signal averaging.

Building on recent innovations in diaphragmless shock tubes, Fuller et al. designed, constructed, and successfully tested a next-generation, fully automated, diaphragmless full-size shock tube.

The new shock tube divides the gases with an automated seal plate instead of a diaphragm. Although the new device can’t generate shocks as strong as diaphragm-based shock tubes, it can produce a shock wave every minute. The seal plate design also enables the creation of identical shock waves, allowing signal averaging.

Author Franklin Goldsmith said that this efficient, highly reproducible system will let researchers explore aspects of low signal chemistry that are only accessible with signal averaging. It could also act as proxy system for an internal combustion engine to test for cleaner, more efficient fuels.

Source: “A modular, multi-diagnostic, automated shock tube for gas-phase chemistry,” by Mark E. Fuller, Mal Skowron, Robert S. Tranter, and C. Franklin Goldsmith, Review of Scientific Instruments (2019). The article can be accessed at