Spatially Resolved Water Measurements in a Scramjet Combustor Using Diode Laser Absorption

Abstract

A two-color tunable diode laser sensor for detection of absorption near was used to simultaneously determine temperature, column density, and velocity in a direct-connect scramjet combustor. Axial and transverse spatial resolutions were achieved by translating the measurement line of sight across and along the flowpath with measurements spanning six axial planes and 24 measurement lines of sight in each plane. Results are presented for a uniform noncombusting -seeded case as well as for air combustion at equivalence ratios of 0.17 and 0.46. A combination of wavelength-modulation spectroscopy and scanned-wavelength direct absorption were used to mitigate nonuniform gas conditions along the measurement line of sight present in the combustion cases. Comparisons of tunable diode laser absorption spectroscopy measurements with computational fluid dynamics simulations are included and illustrate the use of line-of-sight tunable diode laser absorption spectroscopy to validate computational efforts. Additional comparisons with coherent anti-Stokes Raman scattering measurements in the same model scramjet corroborate many key findings from tunable diode laser absorption spectroscopy.