Investigation of Sub- and Supercritical LOX/Methane Injection Using Optical Diagnostics

Abstract

The DLR Institute of Space Propulsion at Lampoldshausen has been working on dierent aspects of oxygen/methane combustion for a couple of years. Within this framework, the European High Pressure Research and Technology Test Facility P8 was equipped with a methane fluid system as a first step to enable single injector investigations of high pressure methane injection and combustion processes. The fluid system provides ambient temperature methane at flow rates up to 1 kg/s and at combustion chamber pressures up to 10 MPa. The measurement system has been adapted to the new fluid system to provide a precise determination of injection conditions. Hence, the P8 now allows investigations of LOX/CH4 combustion chamber processes under realistic rocket engine conditions. For the first operational tests, a single injector windowed rocket combustion chamber was operated at various steady-state conditions in the sub-, near- and supercritical regime with respect to the critical pressure of oxygen. The propellants were injected through a single shear coaxial injector element at temperatures of about 120 K and 275 K, respectively. High speed optical diagnostic techniques such as flame emission spectroscopy and shadowgraphy have been applied in the near injector region to assess injection and atomization behavior as well as flame anchoring and stabilization. The paper describes the modifications of fluid and MCC systems at P8 and presents preliminary results of the first test campaign.