Quantitative mapping mechanism between thermo-flow coupled characteristics and cutting performance of oxygen-propane cutting nozzles

The present study is founded upon the theoretical framework of isentropic flow, and it puts forward a structural enhancement, of the Laval type, for the oxygen channel of a commercial straight-tube oxygen-propane cutting nozzle. Initially, numerical simulation methods were utilised to examine the preheating flame characteristics of the designed nozzle and the thermal-fluid coupling mechanism between the preheating flame and the cutting oxygen jet. The validation of the simulation results was achieved through the execution of in-situ testing experiments. The study indicates that the characteristics of the cutting oxygen jet are the key factors determining the cutting performance of the flame nozzles. The protective effect of the preheating flame has been shown to significantly improve the flow field characteristics of the oxygen jet (e.g., extending the length of the unmixed high-purity oxygen jet and the length of the velocity core zone). The improved nozzle was finally prototyped and tested on a 332 mm-thick ship engine crankshaft forging (S34MnV steel) under design conditions. This process was successful in revealing and establishing a quantitative mapping relationship between the coupled flow field characteristics and the cutting performance of the nozzle. • The temperature and velocity fields of the cutting flame were investigated using thermocouples and high temperature resistant anemometers for fixed point testing. • The characteristics of the cutting flame combustion temperature field, velocity field, turbulent kinetic energy, mass fraction of oxygen-propane gas and its combustion products were investigated to reveal the mechanism of cutting thickness and performance of the oxygen-propane cutting nozzle. • By studying the oxygen cutting jet with or without preheated flame protection, the protective effect of the preheated flame on the oxygen cutting jet is revealed, and the mechanism of heat flow coupling between the cutting oxygen and the preheated flame is tentatively explored. • The present study aims to verify the process of flame cutting through the crankshaft of a marine crankshaft. The objective is to reveal the mapping relationship between the flame combustion characteristics of the cutting nozzle and the cutting thickness.