Laser-based CO concentration and temperature measurements in high-pressure shock-tube studies of n -heptane partial oxidation

This paper presents a laser-based absorption technique for measuring temperature and CO concentration in high-pressure shock tubes. Two fundamental vibrations of CO ( v " = 0, P8, 4.73 µm and v " = 1, R21, 4.56 µm) were selected for high-temperature sensitivity with a reduced influence from pressure broadening compared to previous work. Single-pass absorption (80 mm path length) was measured with two quantum-cascade lasers. The technique was demonstrated by measuring time-resolved temperature for non-reactive mixtures at 1100–1960 K and 1.2–9.7 bar. During partial oxidation of n -heptane, temperature and CO concentrations were measured with 4 µs time resolution at 1360–1670 K and 5.8–8.2 bar. Interference from broadband CO 2 absorption was quantified and subtracted. Measured data in the burnout state are in excellent agreement with predictions from kinetics mechanisms (Mehl et al. Proc Combust Inst 33:193, 2011; Zhang et al. Combust Flame 172:116, 2016) over the entire range of operating conditions, which validates the performance of the current laser-absorption technique in reactive-mixture measurements. Additionally, time-resolved temperature and CO-concentration measurements agree well with predictions based on the Mehl et al. mechanism.