A oxygen lance jet examination system with coherent jet oxygen lance Laval nozzle containing central main hole and 16 auxiliary holes is used to study the oxygen jet central velocity weakening rule

measure the coherent jet produced with accompanying flow of helium at ambient temperature to replace shielding gas burning at high temperature and the coherent jet simulated by flowing air in main hole and flowing shielding gas produced from oxygen and propane in both side auxiliary holes at high temperature. Results show that the characteristics of coherent jet are better than that of traditional jet

at ambient temperature with increasing the pressure of entrance helium the axial weakening of central jet is slowing to get longer length of supersonic jet region than that of traditional jet; at high temperature the length of circle flame can be changed by adjusting burning gas and oxygen flow rate while according to melting real condition it is available to change the length of main jet and meet the requirement of melting process.