Experimenta land analytical characterization of GO ₂/GCH ₄ injector combustion flowfield

The characteristics of combustion flowfield in GO ₂/GCH ₄ injector combustor were investigated in this study. A total of four single-element shear coaxial injectors, a tri-coaxial injector and a swirl coaxial injector were designed and fabricated with different design parameters. The combustion flow fields of these injectors were examined in a windowed combustion chamber with two quartz windows allowing for optical access. The flame was captured by high speed photograph, and the near-field steady-state flame structure was captured by digital camera. One shear coaxial injector was hot-tested in different pressure by changing the mass flow rate to investigate the chamber pressure influence on the combustion flowfield. Additionally, the temperatures along the chamber wall were measured with thermocouples in the hot fire tests. The effect of injector design parameters on the combustor temperature distribution was analyzed. The CFD model developed by us was verified through the imaging results acquired by the optical diagnostics technology. The results show that the combustion performance, the temperature of the chamber wall and the near-field flame are influenced significantly by the injector design parameters. The transient images captured by the high speed photograph show that the gaseous oxygen/gaseous methane combustion flowfield is highly turbulent and the shear layer is unsteady. The low-frequency and intermediate- frequency instabilities occured when the oxygen pressure drop is lower than 3%Pc, and the instabilities can be effectively restrained by improving the oxygen pressure drop. For the same injector, the stability combustion, instability combustion and instability frequency are all similar. Furthermore, the instabilities are sensitive to the oxygen pressure drop and are insensitive to the fuel pressure drop.