Atkinson cycle

Thermodynamic cycle The Atkinson-cycle engine is a type of internal combustion engine invented by James Atkinson in 1882. The Atkinson cycle is designed to provide efficiency at the expense of power density. A variation of this approach is used in some modern automobile engines. While originally seen exclusively in hybrid electric applications such as the earlier-generation Toyota Prius, later hybrids and some non-hybrid vehicles now feature engines with variable valve timing. Variable valve timing can run in the Atkinson cycle as a part-time operating regimen, giving good economy while running in Atkinson cycle mode, and conventional power density when running in conventional Otto cycle mode. Design Atkinson produced three different designs that had a short compression stroke and a longer expansion stroke. The first Atkinson-cycle engine, the differential engine, used opposed pistons. The second and best-known design was the cycle engine, which used an over-center arm to create four piston strokes in one crankshaft revolution. This unusual reciprocating engine had the intake, compression, power, and exhaust strokes of the four-stroke cycle in a single turn of the crankshaft, and w