Since the early inception of the adiabatic diesel engine in 1974, marked progress has taken place as a result of research efforts performed all over the world. The use of ceramics for heat engines in production applications has been limited to date, but is growing. Ceramic use for production heat engine has included: combustion prechambers, turbochargers, exhaust port liners, top piston ring inserts, glow plugs, oxygen sensors; and additional high temperature friction and wear components. The potential advantages of an adiabatic engine vary greatly with specific application (i.e., commercial vs. military, stationary vs. vehicular, etc.), and thus, a better understanding of the strengths and weaknesses (and associated risks) of advanced adiabatic concepts with respect to materials, tribology, cost, and payoff must be obtained. As an example, installed vehicular fuel economy for a low heat rejection adiabatic engine can vary from at least 10% improvement to well over 20% depending on application and engine configuration.
In the U.S., key research efforts within the adiabatic engine area include: high temperature tribology, brittle material fracture analysis, stochastic finite element stress analysis, transient heat transfer, and methods of designing engine components with ceramic/metal interfaces. Careful characterization of ceramic materials, techniques for low cost machinery/processing of the ceramics, and non-destructive evaluations are also underway. In Japan, the monolithic ceramic engine has been the predominant approach. However, at high output engine conditions, current monolithic ceramics have not lived up to expectations with respect to reliability and cost. In the U.S. and Europe ceramic coatings are drawing greater interest because of low cost and high reliability potential. The trend toward ceramic material/engine manufacturer consortiums appears to be growing on a worldwide basis, with success in the future most likely achieved by those working toward a common goal.