Dual-Band Mid-Infrared Imaging for Measurement of Fuel Concentration and Temperature in a Supersonic Cavity
Abstract
A dual-band mid-infrared absorption imaging method is demonstrated for spatially resolved measurement of ethylene concentration and temperature in a Mach-2 cavity flow. The method used narrowband filters selected to exploit the differing in-band temperature sensitivities of ethylene absorption, together with a broadband infrared source and high-frame-rate mid-wave infrared camera. Temperature-dependent, filter-weighted absorption cross-sections were used to measure two-dimensional ethylene number density and temperature fields. Measurements were obtained for cavity, curtain, and discrete fuel-injection configurations, including cases with the leading edge of a quasi-steady shock near the cavity. Cavity equivalence ratio measurements agreed well with independent extractive measurements and reproduced trends previously observed using hyperspectral imaging. A complementary single-band implementation using a temperature-independent filter provided instantaneous ethylene concentration fields at 100 Hz and revealed intermittent reductions in cavity equivalence ratio associated with plume deflection by the shock train leading edge. The dual-band approach provides quantitative full-field measurements with substantially simpler spectral instrumentation than hyperspectral imaging while retaining flexibility for time-resolved flow measurements.
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BibTeX
@misc{hahn2026dualband,
title = {{Dual-Band Mid-Infrared Imaging for Measurement of Fuel Concentration and Temperature in a Supersonic Cavity}},
author = {Loren C. Hahn and Erik L. Braun and Brendan J. McGann and Katherine C. Opacich and Timothy M. Ombrello},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.03341},
eprint = {2611.03341},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.03341},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Dual-Band Mid-Infrared Imaging for Measurement of Fuel Concentration and Temperature in a Supersonic Cavity
AU - Loren C. Hahn
AU - Erik L. Braun
AU - Brendan J. McGann
AU - Katherine C. Opacich
AU - Timothy M. Ombrello
PY - 2026
DA - 2026/11/02
PB - arXiv
DO - 10.48550/arxiv.2611.03341
UR - https://arxiv.org/abs/2611.03341
AB - A dual-band mid-infrared absorption imaging method is demonstrated for spatially resolved measurement of ethylene concentration and temperature in a Mach-2 cavity flow. The method used narrowband filters selected to exploit the differing in-band temperature sensitivities of ethylene absorption, together with a broadband infrared source and high-frame-rate mid-wave infrared camera. Temperature-dependent, filter-weighted absorption cross-sections were used to measure two-dimensional ethylene number density and temperature fields. Measurements were obtained for cavity, curtain, and discrete fuel-injection configurations, including cases with the leading edge of a quasi-steady shock near the cavity. Cavity equivalence ratio measurements agreed well with independent extractive measurements and reproduced trends previously observed using hyperspectral imaging. A complementary single-band implementation using a temperature-independent filter provided instantaneous ethylene concentration fields at 100 Hz and revealed intermittent reductions in cavity equivalence ratio associated with plume deflection by the shock train leading edge. The dual-band approach provides quantitative full-field measurements with substantially simpler spectral instrumentation than hyperspectral imaging while retaining flexibility for time-resolved flow measurements.
ER -