Electrical behaviour of ceramic composite materials for aero-engine igniters

High energy igniters are extensively used in aero-engines and this study describes the specific ceramic composite materials used at the igniter tips. These ceramics favour the formation of a plasma-like process on their surfaces under an electrical field not exceeding 1 kV mm−1. The elevated temperature which is reached, and the high energy released during sparks are very favourable for engine ignition, even when internal engine temperature, pressure and fuel flow are unfavourable. Currently used ceramics and possible igniter designs are described. For composite ceramics, the physical mechanisms involved during sparking are presented, together with the high temperature and pressure effect in engines. Degradation mechanisms of materials are also examined to understand the operational life of igniters when working conditions vary. Problems associated with continuous ignition and the type of surface discharge materials are also discussed.