| Diode-laser sensors have been developed for monitoring gas properties (e.g., temperature, pressure, velocity, and species concentrations) in relatively harsh (high-pressure, high-temperature, multiphase, and transient) combustion flows. The sensors have been applied to study an experimental propulsion concept, the pulse detonation engine (PDE), with the goal of enhancing PDE development and modeling efforts.; Optically harsh environments present many challenges, including severely broadened absorption features, limited spectroscopic data, extinction, and beam steering. To enable quantitative measurements in the midst of these challenges, two advanced sensing strategies have been fostered: wavelength multiplexing and broad wavelength scanning. Both strategies attempt to recover broad spectral information with fast time response (coined, “all spectra, all the time”), enabling straightforward measurement of high-pressure absorbers as well as rejection of both spectrally broadband and slowly varying noises. Wavelength multiplexing has been employed to measure H2O mole fraction and temperature in PDEs; broad wavelength scanning has been employed to measure C2H4 fuel in PDEs, gas temperature and pressure in Cs-seeded PDEs, high pressure and nonuniform-temperature O2 in static cells, and high pressure H2O in static cells. The sensors demonstrated in static cells are modeled after successful PDE sensors but are intended to support measurements in other harsh environments such as gas turbine and piston engines. |
