A diagnostic for measuring H2O2 concentration in a shock tube using tunable laser absorption near 7.8 μm

Hydrogen peroxide was measured in a shock tube via absorption spectra of the ν6 (asymmetric HOO bending) fundamental band using a lead–salt diode laser tuned to 7845.63 nm. At this wavelength, there is minimal interference from water absorption at combustion temperatures and pressures, even for water levels that are more than two orders of magnitude larger than the H2O2 concentration. For obtaining a calibration of the laser absorption technique, a robust method of hydrogen peroxide delivery was employed so that a standard H2O2–H2O mixture could be used as the source, but with high certainty as to the initial concentration of H2O2. The initial amount of hydrogen peroxide was measured using a water absorption laser diagnostic to measure the water concentration in conjunction with the known thermodynamics of the vapor mixture, highly diluted in argon. Measurements were made with argon as the bath gas at temperatures ranging from 292 to 1296 K and a pressure range of 0.05–1.43 atm, resulting in a calibration for the absorption coefficient of H2O2 at 7845.63 nm. To the authors’ knowledge, this study marks the first successful measurement of H2O2 concentration in a shock tube using tunable laser absorption in the infrared.