Supercritical nitrogen free jet investigated by spontaneous Raman scattering

The injection of fuel and oxidizer in high pressure rocket combustion chambers is simulated in a model experiment dedicated to investigate the phenomenology of coaxial injection at supercritical pressures. Cryogenic nitrogen is injected in a pressurized reservoir of N-2 at ambient temperature at 4 MPa and 6 MPa, above the critical pressure for nitrogen of 3.4 MPa. The radial density distribution of the N-2 is determined by spontaneous Raman-scattering, from the measured densities temperature distributions are derived. The radial density and temperature profiles are analyzed as a function of the distance from the injector for x/D = 1 to 30. The influence of density gradients, internal field effects and interference effects on the performance of the Raman technique when applied to turbulent high density flows is discussed.