Ignition Delay Time Measurements

Accurate knowledge of the time-scale associated with chemical reactions and heat release is essential for accurately sizing and designing next-generation energy systems.

From spark-ignited internal combustion engines to combustion chambers for the next-generation supercritical CO₂ (sCO₂) gas turbines, a critical metric that is often used for quantifying this chemical time scale is called the ignition delay time (IDT).

Our lab has pioneered the use of shock tubes in measuring IDTs for a wide variety of fuels, ranging from hydrogen and light gaseous hydrocarbons to heavier liquid fuels (including gasoline, jet fuels, biofuels, and rocket fuels). By combining pressure measurements with fuel concentration monitoring using targeted lasers, OH* emission, and high-speed imaging [1], we have measured and reported high-quality IDTs for these fuels. Some of these measurements have been conducted at extreme pressures, in excess of 300 atm [2,3]!

In addition to providing insight into the behavior of fuels under engine-relevant conditions, these measurements also serve as targets for the validation of chemical kinetic models being developed for these fuels.

graphs from ignition delay time measurement experiments — (Left) Time histories of pressure, OH* emission, and laser absorption in a typical ignition experiment [4]. (Right) Variation of IDT with temperature and pressure for a high-performance gasoline [3]

To learn more, check out some of our publications:

[1] J. Shao, R. Choudhary, A.J. Susa, D.F. Davidson, and R. K. Hanson, “High-speed imaging of n-heptane ignition in a high-pressure shock tube,” Proceedings of the Combustion Institute, Vol. 38(1) (2021), pp.911–918. DOI: 10.1016/j.proci.2020.06.158

[2] J. Shao, R. Choudhary, D.F. Davidson, R.K. Hanson, S. Barak, and S. Vasu, “Ignition delay times of methane and hydrogen highly diluted in carbon dioxide at high pressures up to 300 atm,” Proceedings of the Combustion Institute, Vol. 37(4) (2019), pp.4555–4562. DOI: 10.1016/j.proci.2018.08.002

[3] D.F. Davidson, J.K. Shao, R. Choudhary, M. Mehl, N. Obrecht, and R.K. Hanson, “Ignition delay time measurements and modeling for gasoline at very high pressures,” Proceedings of the Combustion Institute, Vol. 37(4) (2019), pp.4885–4892. DOI: 10.1016/j.proci.2018.08.032

[4] ] 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 II: Rate constant measurements and modeling,” Combustion and Flame, Vol. 233 (2021), p.111554. DOI: 10.1016/j.combustflame.2021.111554