Experimental study on the combustion characteristics of LOX/LCH4 pintle injectors

[Display omitted] •The flash boiling of liquid oxygen/liquid methane under supercritical condition was completely captured.•Five main evolutionary patterns of the flame core during ignition were observed by the backlit photography technique.•The skip distance should not be smaller than the pintle diameter, so as to avoid low combustion efficiency. Oxidizer-centered pintle injectors under different skip distance conditions for liquid oxygen/liquid methane (LOX/LCH4) rocket engines were used as the test objects to analyze their combustion characteristics. The experimental time sequence and the images of the combustion process were given, and the comparisons of combustion efficiency and combustion chamber pressure among different skip distance scenarios were presented. Experimental results indicated that during ignition, the flame core experienced the formation, the reversed development, the diffusion, the enhancement, and the extinction successively in 149.0508 ms. The spray angle of the LOX stabilized prior to the steady combustion in the quasi-steady combustion process. Large skip distance could contribute to high combustion efficiency and small amplitude of the combustion chamber pressure. The skip distance should not be smaller than the pintle diameter in order to avoid low combustion efficiency. The characteristic length of the combustion chamber should be relatively large when the skip distance was large, so as to enhance the mixing of the gases and improve the combustion efficiency.