Molecular dynamics study on the Widom Line of binary mixture of methane and oxygen system

Liquid oxygen/liquid methane rockets are currently one of the most mature technologies among heavy-lift launch vehicles. However, the combustion of methane and oxygen is a complex transcritical process. The fluid crosses the Widom line can lead to heat transfer deterioration, thereby affecting the stability of combustion. This paper uses molecular dynamics (MD) simulations to calculate the Widom line of the methane-oxygen binary mixture with component changes and investigates the changes in microscopic structure of the mixture as it crosses the Widom line. The results of radial distribution function (RDF) indicate that the second peak exists in the liquid-like region, and when the binary mixture crosses the Widom line into the gas-like region, the second peaks of both components disappear simultaneously. This research findings provide a method for identifying the Widom line of binary mixtures and assist in engineering the identification of regions where heat transfer deterioration occurs during supercritical processes.