What do we know about long laminar plasma jets?*
Xi Chen1, Wenxia Pan2, Xian Meng2, Kai Cheng1, Dong-Yan Xu1, and Chengkang Wu2
1Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China; 2Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, China
Abstract: Silent and stable long laminar plasma jets can be generated in a rather wide range of working parameters. The laminar flow state can be maintained even if considerable parameter fluctuations exist in the laminar plasma jet or if there is an impact of laterally injected particulate matter and its carrier gas. The attractive special features of laminar plasma jets include extremely low noise level, less entrainment of ambient air, much longer and adjustable high-temperature region length, and smaller axial gradient of plasma parameters. Modeling results show that the laminar plasma jet length increases with increasing jet inlet velocity or temperature and the effect of natural convection on laminar plasma jet characteristics can be ignored, consistent with experimental observations. The large difference between laminar and turbulent plasma jet characteristics is revealed to be due to their different laws of surrounding gas entrainment. Besides the promising applications of the laminar plasma jet to remelting and cladding strengthening of the metallic surface and to thermal barrier coating preparation, it is expected that the laminar plasma jet can become a rather ideal object for the basic studies of thermal plasma science owing to the nonexistence of the complexity caused by turbulence.
Keywords: thermal plasma jets; jet flow state; jet characteristics; carrier-gas impact; ambient air entrainment; buoyancy effects; applications; experiments; modeling.
*Paper presented at the 17th International Symposium on Plasma Chemistry (ISPC 17), Toronto, Ontario, Canada, 7-12 August 2005. Other presentations are published in this issue, pp. 1093-1298.