Investigation of the supersonic jet impingement into vacuum chamber induced by cryogenic helium leakage

Leakage of cryogenic helium into a vacuum chamber can induce supersonic jet impingement, posing risks of local overpressure and overheating that threaten stability and safety. However, the localized effects resulting from jet impingement remain insufficiently explored. A two-dimensional axisymmetric model with the SST k-ω turbulence model and the real gas model is established to investigate flow and heat transfer characteristics of supersonic impinging jets from thermal shield helium leakage. Two key factors are evaluated, including dimensionless impingement distance ( L p / D = 5–120) and surface shape (flat, convex, and concave). Results indicate that increasing L p / D from 5 to 120 reduces the secondary peaks in velocity, temperature, pressure, and heat flux profiles. The dimensionless impingement distance strongly affects the Mach disk sizes in the nearfield region ( L p / D = 5 and 10). At L p / D = 100 and a central angle of 90°, the convex surface reduces the average Nusselt number by 8.68% compared with the flat surface, while the concave surface increases it by 12.78%, indicating that the convex surface is superior in overheating risk mitigation. Moreover, the average heat flux on the target surface consistently exceeds the reference value (10 kW/m 2 ) for the liquid helium film boiling threshold, while the wall pressure remains below 100 kPa, indicating that overheating risk arises prior to overpressure risk during loss of coolant accidents. These findings can provide references for the risk assessment and thermal protection design of superconducting magnets, as well as the optimization of component layouts in cryostats. • Cryogenic helium supersonic jet impingement in vacuum is studied with real gas effects. • Increasing L p / D from 5 to 120 suppresses secondary peaks of pressure and heat flux. • Convex surface reduces Nu by 8.68% compared to the flat surface at L p / D =100. • Overheating risk arises prior to overpressure in vacuum chambers during a loss of coolant accident.