Finite element thermal and stress analyses of thin cylindrical rings of variable geometry subjected to high heat flux conditions

The main objective of the present magnetohydrodynamic (MHD) research at The University of Tennessee Space Institute (UTSI) is to achieve long duration testing of components of the Coal Fired Flow Facility (CFFF). This requires that the water-cooled nozzle and circular aerodynamic duct of the upstream flow train be extremely durable. These upstream components are designed with a cooling-ring structure that is subject to high heat flux and pressure loadings. A thermal analysis and stress analysis of these cooling rings were performed using commercial finite element software. Two thermal loading conditions were studied; start-up and operating conditions.

The computer analysis indicated that metal surface temperatures on the plasma side of the ring were cool enough to support a solid slag layer. The rings with refractory-filled grooves developed significantly thinner slag layers. Predicted temperatures were not consistent with thermocouple measurements. High compressive stresses were predicted, indicating that plastic behavior of these rings is possible. Test results indicate that ring failures have occurred along the grooves of these rings.