Progress on high temperature air heater development for MHD systems

Progress in the development of regenerative air heaters for directly- and indirectly-fired MHD systems is reviewed. For directly-fired heaters, major developmental problems are associated with the corrosion of refractories and the deposition of seed or slag. Simulations of MHD gas heating and air cooling cycles have shown that dense, low porosity materials are needed to withstand corrosion, and a fusion cast structure of magnesia grains imbedded in a magnesia/alumina spinel matrix is being investigated. Testing of a small-scale simulated heater has revealed the conditions under which seed deposition can be prevented. The developmental needs of separately-fired heaters depend on whether the fuel burned is clean or dirty. Work is in progress on slag deposition in heater passages and refractory corrosion due to slag attack in heaters fueled with dirty fuel. If a clean fuel is burned, current hot blast stove technology can be utilized at air temperatures up to 1644 K, however development of materials for higher temperatures is needed. Valves for MHD heaters are also under investigation