CARS Temperature Mapping in a Cryogenic LOX-H2 Rocket Combustion Chamber under Supercritical Conditions

Abstract

Coherent anti-Stokes Raman spectroscopy (CARS) was applied for temperature measurements in a highöpressure cryogenic liquid oxygen-hydrogen rocket model combustor. The combustor was operated at 6 MPa, above the supercritical pressure of the propellants. H2 and H2O molecules were probed simultaneously using a dual-boradband CARS setup and degenerate CARS setup with a single dye laser. The diagnostic set-up at the test site was adapted to the high level of cibrations exprienced during tests by several measures: the laser system was positioned in a separate room next to the test cell, a heavy-duty tri-axial translation stage for positioning the beam guiding optics and focusing lenses in the test cell was specially designed to be insensitive to vibrational excitation. The combustor was operated at two hydrogen injection temperatures, 65 and 117 K. In the low hydrogen temperature tests no CARS signal could be obtained. At a higher hydrogen temperature (-117 K), successful temperature mapping of the flame was performed at two cross-sections, 50 and 80 mm downstream of the injector. Bimodal temperature distributions were observed at the 80 mm position, indicating strong flame and flow oscillations.