Laser Absorption Spectroscopy of Carbon Monoxide near 4.97 μm for Temperature and Species Measurements in Hydrocarbon-Fueled Rockets

摘要

In this work, a novel thermometry and species measurement sensor for rocket combustion flows was developed based on laser absorption spectroscopy (LAS) of nascent carbon monoxide (CO). The optical strategy enables non-intrusive, in situ measurements in hydrocarbon-fueled rockets by probing rovibrational transitions in the P-branch of the fundamental infrared absorption band of CO, near 4.97 μm. Initial measurements were conducted at atmospheric pressure with a two-line scanned-wavelength direction absorption (DA) technique at the exit plane of a PMMA - GOx hybrid rocket motor to correlate both path-integrated and spatially resolved plume temperature and CO concentration to estimated O/F ratio and combustion completeness. Measurements of CO concentration were also conducted at pressures up to 60 atm on a single-element-injector RP-2-GOx rocket combustor at the Air Force Research Laboratory in Edwards, CA. Noise rejection in this harsher environment was achieved by using a scanned-wavelength modulation spectroscopy (WMS) technique. Data collected in both applications highlight the potential utility of the mid-infrared LAS strategy in studying a wide-range of fuel-rich hydrocarbon rocket flows.