Effect of Exit Wear Length on the Behavior of Coherent Jet

Abstract

The copper was the main manufacturing material to produce the coherent lance for enhancing the cooling effect. Due to the low hardness of copper and high-temperature environment, the exit of Laval nozzle would be worn off, resulting in suppressing the impaction ability of supersonic oxygen jet. In order to investigate the effect of wear length on the behavior of coherent jet, both high-temperature experiment and numerical simulation have been carried out, and the axial velocity, total temperature and oxygen fraction were measured in the experimental test to verify the accuracy of simulation model. Based on the result, the overexpand phenomenon was generated due to the Laval nozzle exit wear off, which improved the shock wave intensity at the tip of Laval nozzle, resulting in a lower axial velocity at the velocity potential core. With a longer wear length, the vorticity of the coherent jet periphery is increased, which causes more thermal energy of combustion flame being released prematurely near the coherent lance tip, leading to a shorter velocity potential core.