Shock Tube Sensors

The Hanson Group commonly uses laser absorption sensors to monitor transient, radical species (e.g., CH, OH, CH₃) and stable species (e.g., CH₄, C₂H₄, H₂O, CO, CO₂, NH₃, NO, NO₂, etc.) as they react in the controlled, high-temperature (500–10,000+ K) environment generated by a shock tube [1].

Deploying multiple in situ laser sensors in a single shock tube experiment allows us to monitor temperature, species time-histories, and chemical reactions with high time-resolution (10s of MHz), thereby providing valuable insight into the energy conversion pathways that govern modern-day and next-generation energy systems and fuels [2]. Lasers in the infrared (IR) region (1–12 μm) are used to target the rovibrational absorption transitions of molecules, while ultraviolet (UV) and visible laser diagnostics (210–614 nm) leverage strong electronic transitions of molecules to provide access to species without a permanent dipole moment (e.g., O₂), or species at very low concentrations.

The figure below highlights the broad range of laser diagnostics in the Hanson Lab that can be paired with shock tube experiments and shows typical data obtained from a tunable diode laser absorption experiment. The ongoing development of new laser sensors and shock tube measurement techniques allows us to continually extend our scientific understanding of chemistry in combustion, hypersonic flight, and advanced energy systems.

diagram of pieces involved in a shock tube experiment — Schematic showing alignment of multiple laser diagnostics in a shock tube experiment, options for laser diagnostic systems, and representative results from a wavelength-scanned diagnostic. The numerous types of laser absorption sensors in the Hanson Group cover large portions of the infrared and ultraviolet spectra, thus enabling measurement of chemical species relevant to advanced engineering systems.

To learn more, check out some of our publications:

[1] R.K. Hanson, D.F. Davidson, “Recent advances in laser absorption and shock tube methods for studies of combustion chemistry,” Progress in Energy and Combustion Science, Vol. 44 (2014), pp. 103–114. DOI: 10.1016/j.pecs.2014.05.001

[2] R. Choudhary, V. Boddapati, S. Clees, J.J. Girard, Y. Peng, J. Shao, D.F. Davidson, and R.K. Hanson, “Shock tube study of ethanol pyrolysis I: Multi-species time-history measurements,” Combustion and Flame, In Press, Available online 23 June 2021, 111553. DOI: 10.1016/j.combustflame.2021.111553