CARS thermometry in high pressure rocket combustors

Coherent anti-Stokes Raman spectroscopy (CARS) has been used to investigate high pressure cryogenic liquid oxygen/gaseous hydrogen (LOX/GH2) flames at pressures up to 6.5 MPa. The method employs two synchronized broadband CARS systems to probe simultaneously H2 and H2O. Temperature is deduced from the H2 and H2O CARS profiles while the H2O concentration is deduced from the modulation from the resonant the H2O resonant signal superimposed on the nonresonant background signal. Details of the modeling of the CARS spectra at high pressure and the data reduction are discussed. Problems issued from the presence of liquid phase are also investigated. The results demonstrate the applicability and usefulness of CARS for investigating cryogenic combustion under representative rocket model combustor regimes where the pressure range is above the supercritical condition (P>5.04 MPa).