Editing Diesel engine (section)

==Low heat rejection engines==
A special class of prototype internal combustion [[piston engine]]s has been developed over several decades with the goal of improving efficiency by reducing heat loss.<ref name="Papers on adiabatic engines" /> These engines are variously called adiabatic engines; due to better approximation of adiabatic expansion; low heat rejection engines, or high temperature engines.<ref name="Schwarz_1993" /> They are generally piston engines with combustion chamber parts lined with ceramic thermal barrier coatings.<ref name="BRYZIK_1993" /> Some make use of pistons and other parts made of titanium which has a low thermal conductivity<ref name="Danielson_1993" /> and density. Some designs are able to eliminate the use of a cooling system and associated parasitic losses altogether.<ref name="Nanlin_1993" /> Developing lubricants able to withstand the higher temperatures involved has been a major barrier to commercialization.<ref name="Kamo_1995" />