A SiC-CuG-Cu insulator for MHD generator channels

New SiC ceramics insulator, which have been developed by the ETL, Hitachi Ltd. and Hokkaido University, show excellent performance, and can be operated as non-slagging and slagging insulators for open-cycle MHD generator channels. This insulator element is composed of SiC ceramics (HITACERAM SC101), a water cooling copper substrate and a compliant layer made of copper-carbon composite material (CuC). The SiC-CuC-Cu bonding element showed a high permissible heat flux. However, the problem of oxidation of the CuC compliant has been observed under high heat fluxes and long-duration operating conditions. Also, drastic heat impact due to sudden heating up and cooling down combustion will cause a degradation and exfolidation of the CuC compliant layer. In this paper, the authors first point out the problems of the SiC-CuC-Cu insulator elements tested under both safe and extreme conditions. Next, they show the test results using the improved SiC-Cu-G-Cu elements. They show the effectiveness of the SiC-CuG-Cu elements as regards to permissible heat flux, safe thermal shock conditions, electrical leakage and breakdown characteristics between adjacent elements