Testing of Felt-Ceramic Materials for Combustor Applications

The feasibility of using composite felt-ceramic materials as combustor liners was experimentally studied. The material consists of a porous felt pad sandwiched between a layer of ceramic and one of solid metal. Flat, rectangular test panels, which encompassed several design variations of the basic composite material, were tested, two at a time, in a premixed gas turbine combustor as sections of the combustor wall. Tests were conducted at combustor inlet conditions of 0.5 MPa and 533K with a reference velocity of 25 m/s. The panels were subjected to a hot gas temperature of 2170K with 1% of the total airflow used to film cool the ceramic surface of the test panel. In general, thin ceramic layers yield low ceramic stress levels with high felt-ceramic interface temperatures. On the other hand, thick ceramic layers result in low felt-ceramic interface temperatures but high ceramic stress levels. Extensive thermal cycling appears to cause material degradation, but for a limited number of cycles, the survivability of felt-ceramic materials, even under extremely severe combustor operating conditions, was conclusively demonstrated. Original contains color plates: All DTIC and NTIS reproductions will be in black and white.