Broadband ultrafast-laser-absorption spectroscopy for multi-hydrocarbon measurements near 3.3 µm in flames.

This paper presents the development and application of a broadband ultrafast-laser-absorption-spectroscopy (ULAS) technique operating in the mid-infrared for simultaneous measurements of temperature, methane ( ), and propane ( ) mole fractions. Single-shot measurements targeting the C-H stretch fundamental vibration bands of and near 3.3 µm were acquired in both a heated gas cell up to ≈650 and laminar diffusion flames at 5 kHz. The average temperature error is 0.6%. The average species mole fraction errors are 5.4% for and 9.9% for . This demonstrates that ULAS is capable of providing high-fidelity hydrocarbon-based thermometry and simultaneous measurements of both large and small hydrocarbons in combustion gases.