Transpiration Cooling of the Constrictor Walls of an Electric High-Intensity Arc

In this paper transpiration cooling of a porous tube exposed to a high-temperature plasma is discussed. The plasma is generated by a high-intensity d-c arc which reaches a thermally and hydrodynamically fully developed state in the porous constrictor tube. From an energy balance over a tube cross section in this regime using a semiempirical relationship between pressure drop and mass flow rate across the porous wall, the temperature distribution in the porous material as well as local heat fluxes are determined. Properties of the porous material which are of particular importance for the performance of a transpiration-cooled arc arc determined independently. The experiments provide a check on the reliability of these data. Analytical predictions of arc and constrictor performance are compared with experimental results. A large discrepancy exists in most of the results which is mainly attributed to turbulent-flow components in the tube which, in turn, can be confirmed by other diagnostic measurements. Finally, various sources for possible errors are discussed and the limitations imposed on the performance of a transpiration-cooled arc by imperfections of porous materials and the technology involved are indicated.