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Flame stabilization in the near-injector region of a subscale liquid propellant rocket combustion chamber has been investigated using optical diagnostics. Several different single shear coaxial injectors have been used to inject liquid oxygen (LOX) and methane at relevant operating conditions. Three main operating points cover the range of sub-, near-, and superciritical conditions with respect to the thermodynamic cirtical point of oxygen. Whereas liquid temperatures of about 270 K. Similar to previous investigations performed with LOX/H2 combustion, spontaneous OH chemiluminescene has been detected to characterize the flame anchoring zone near the LOX post tip. Theoretical considerations have indicated that the binary mixture of oxygen and methane shows and entirely different behaviour compared with the oxygen/hydrogen system. This is believed to have an influence on the spray evolution and mixing characteristics at supercritical conditions. The experimental investigation includes both the ignition transient a well as the steady-state operating points. It has been detected that the LOX/CH4 flame shows very similar characteristics in comparison with LOX/H2 flame at similar operating conditions. Critical flame stabilization at the startup transient has been found during all hot runs. At steady-state conditions, the influence of the injection parameters on the flame shape is comparable to previous LOX/Hydrogen investigations.
Lux et al. (Tue,) studied this question.