Recent advances in the application of nonintrusive diagnostics to propulsion ground testing

Abstract

Laser-based diagnostics offer many advantages for the remote, nonintrusive measurement of gas flow properties in propulsion devices undergoing ground testing. This review concentrates on selected recent advances in diagnostics for gas turbines, aod advanced propulsion devices such as ramjets, scramjets, and rockets. Techniques discussed are intended for the determination of temperature, velocity, and species concentration. The UTRC mobile coherent antiStokes Raman spectracopy (CARS) instrument has been modified for simultaneous, multiple species, wave mixing. Strategies have been recently developed for using this configuration for measurement of temperature and species concentrations in bydrogenfair combustion systems. Fiber optic Raman thermometry (FORT) is appropriate Cor ground testing of the space shuttle main engine (SSME) preburner. Fensibility demonstrations imply that temperature realizations can be made in 10 ma in the hot, high pressure, hydrogen preburner wing a cw argon ion laser. Other approaches b e ing developed w relevant to SSME exhaust and hydrogenfueled =ramjet combustor probing. Raman thermometry using a pulsed uv laser is appropriate to these lower pressure applications. Supersonic velocimetry along a line has been ncently demonstrated by imaging OH fluorescence. In this timcof-flight approach, a line of OH radicals are produced transvem to the flow direction by uv-laser photodissociation of raker. The OH so tagged is detected after convection by inducing fluorescence with a second laser and imaging its position with a two dimensional detector. Planar laser-induced Buonscence (PLIF) diagnostics are being applied to propulsion device testing by use of a recently constructed, hardened, mobile imaging laser and digital detection system.