Abstract

Porous silicon carbide (SiC) ceramics are promising materials for liquid fuel evaporator tubes in gas turbine combustors. For evaporator tubes with four different design variations (two-layer concept and three continuous porosity gradients) finite element method calculations were made to determinate the thermal stresses due to the temperature gradient during steady state and transient operation, By comparing the local stress distribution with the local strength it could be shown that a tailored porosity gradient is necessary to meet the local stress/strength requirements. For tubes with such continuous porosity gradients a new processing route based on pressure filtration has to be developed, The formation of one and more dimensional wax concentration gradients in the filter cake (corresponding to porosity and pore size gradients after sintering) is adjusted by controlling the composition of a mixture of SiC- and SiC-wax slips (slurries) and the filtration pressure. The design concept of a laboratory casting apparatus which uses this new concept and an experimental/numerical method for the derivation of the process parameters is also described in this paper.