LOX/CH_4 Hot-Flow Testing of Dual-Bell Nozzles with Rapid-Expansion Extension

摘要

Hot-flow testings with subscale dual-bell nozzle models were conducted. The primary nozzle model had a relativelylarge initial expansion angle in the extension nozzle section. The propellant was liquid oxygen and gaseous methane.Wall distributions of pressure,temperature,and heat flux distributions along the extension nozzle were measured tocharacterize the effect of the mixture ratio and combustion chamber pressure on the separation transition. The wallpressure for the primary test model indicated that the separation transition took place at nearly a constant nozzlepressure ratio and independently of the mixture ratio. Differently,a test model with a smaller expansion angle,whichwas also tested for a comparison,showed that the separation transition took place dependently on the mixture ratio.Comparison of the separation transition condition with some existing criteria found that one of the causes of thedependency on the mixture ratio was related to the separation pressure in the inflection region. Additionally,stronghysteresis was observed for the test model with a smaller extension angle. The heat flux transducer data indicated thatthe wall heat flux at the inflection point at the separation transition had a linear relationship with the mixture ratio.