Controlled Transpiration Cooling of the Anode in a High Intensity Arc

A high intensity arc plasma torch with controlled transpiration cooling of the anode has been developed. The plenum chamber surrounding the porous anode is subdivided into several independent compartments which allow for individual control of the pressure and of the ensuing mass flow rates through the corresponding anode segments. In this way, the inherent instabilities of transpiration cooling may be alleviated. Arc performance characteristics are determined utilizing a porous carbon anode and argon at atmospheric pressure as working fluid. It is shown that the temperature distribution of the porous anode segments depends only on the transpiring mass flow rate and on the pressure drop through the porous material. Theoretical predictions compare favorably with experimental results. By using a two-step temperature model, the arc attachment size on a particular anode segment may be estimated. The torch efficiency which is a measure of the effectiveness of transpiration cooling on net anode losses and the mean enthalpy of the emanating plasma jet are measured as a function of mass flow rate and power input.