The design of a canned ceramic oval converter, 77mm by 146.8mm, is described along with subsequent demonstration of its high temperature (1050°C) durability. A new mat deterioration phenomenon was recognized, and will be described. The mat deterioration results from sintering of the vermiculite and glass fiber structure when exposed to temperatures greater than approximately 1000°C. Due to the extremely high temperature experienced in the supporting mat of an oval converter exposed to 1050°C, an alternative mat configuration was utilized to eliminate potential mat sintering.
An inner layer of non-intumescent mat (1500g/m2) was used in conjunction with an outer layer of intumescent mat (3100g/m2). The inner mat provided sufficient thermal protection to the outer intumescent mat, maintaining considerable holding pressure on the ceramic substrate. A tourniquet closure technique was developed to uniformly compress a hybrid mat system around the entire perimeter of the oval converter. It is typically difficult to fully compress mat systems, in the region of the minor axis, due to the geometric effects of its flat radius of curvature.
The durability of the oval design was demonstrated both by 1050°C hot vibration at 75g, and additionally by 1050°C Resistive Thermal Exposure (RTE) testing. Two samples passed 100 hours of 1050°C, 75g engine hot vibration testing with no visible degradation and no significant loss in residual shear strength as measured with a 550°C hot push test. Three additional sets of samples were each hot push tested following 0, 50, and 100 hours of RTE aging. Results for the samples subjected to RTE were comparable for all exposure times, and overall showed little change in residual shear strength as compared to the as-prepared components. Results of this work demonstrate that it is possible to utilize mat mounted oval ceramic substrates at temperatures greater than 1050°C.