Laminar Flame Speed Measurements

Laminar flame speed is a fundamental combustion property that characterizes both the global combustion kinetics and important transport properties (thermal and diffusion) of a flammable mixture.

Several techniques are commonly used to experimentally measure laminar flame speeds, but they all struggle to reach the high unburned-gas temperatures (>800 K) frequently encountered in current and next-generation engines.

In the Hanson Group, we have overcome this limitation through our development of the shock-tube flame speed method [1,2]. Through the combined use of a side-wall-imaging shock tube as an impulse heater, a nanosecond laser to ignite an outwardly expanding flame, and high-speed schlieren imaging to track the flame’s propagation, we have performed laminar flame speed measurements for a variety of fuels including methane [1], propane [3], n-heptane [4], iso-octane [4,5], ethanol [5], and ammonia [6] at the highest temperatures ever reported (>1,000 K). Using this novel technique, our group is able to study and provide new insights into the flame behavior of conventional and alternative fuels at previously unexplored, high-temperature conditions.

Laminar flame speed measurements at unburned-gas temperatures up to 1,020 K for iso-octane and ethanol. Lower temperature (<700 K) literature data show good agreement with results obtained using the shock-tube flame speed method; comparison between our high-temperature measurements with various power-law flame speed correlations found in the literature reveals major inadequacies in those correlations’ ability to extrapolate high-temperature flame speeds. The shock tube flame speed method allowed us to report the first flame speed correlations for iso-octane and ethanol which are experimentally validated for unburned-gas temperatures exceeding 1,000 K.

To learn more, check out some of our publications:

[1] A. M. Ferris, A. J. Susa, D. F. Davidson, and R. K. Hanson, “High-temperature laminar flame speed measurements in a shock tube,” Combustion and Flame, Vol. 205 (2019) pp. 241–252. DOI: 10.1016/j.combustflame.2019.04.007

[2] A. J. Susa, L. Zheng, and R.K. Hanson. "Measurements of propane-O2-Ar laminar flame speeds at temperatures exceeding 1,000 K in a shock tube," Proceedings of the Combustion Institute, Vol. 39 (2023) pp. 1793-1802. DOI: 10.1016/j.proci.2022.07.191.

[3] L. Zheng, Z. Nygaard, M. Figueroa-Labastida, A.J. Susa, A.M. Ferris, and R.K. Hanson. "Atmospheric-pressure shock-tube measurements of high-temperature propane laminar flame speed across multiple equivalence ratios." Combust and Flame, Vol. 251 (2023). DOI: 10.1016/j.combustflame.2023.112726.

[4] L. Zheng, A.J. Susa, Z. Nygaard, A.M. Ferris, and R.K. Hanson. "Laminar Flame Speed Measurements of Primary Reference Fuels at Extreme Temperatures," Proceedings of the ASME 2022 ICE Forward Conference. (2022). DOI: 10.1115/ICEF2022-90501

[5] L. Zheng, M. Figueroa-Labastida, Z. Nygaard, A.M. Ferris, and R.K. Hanson. "Laminar flame speed measurements of ethanol, iso-octane, and their binary blends at temperatures up to 1,020 K behind reflected shock waves⋆." Manuscript under Review at Fuel 2023.

[6] M. Figueroa-Labastida, L. Zheng, A.M. Ferris, and R.K. Hanson. "High-temperature ammonia flame speed measurements behind reflected shock waves." 13th U.S. National Combustion Meeting , 2023.