15-04-2017, 03:24 PM
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 the power density or total power drawn per unit of displacement per rotation. A modern variant of this approach is used in some modern car engines. Although originally seen exclusively in hybrid electric applications such as the Toyota Prius, some non-hybrid cars now feature engines that can run on the Atkinson cycle as a part-time operating regimen, giving good economy while running in the Atkinson cycle As a normal cycle engine. Mazda Skyactiv models that offer this capability include the Mazda 3 and MX-5.
The Atkinson cycle delays the closing of the intake valve until the piston has completed 20 to 30 percent of its upward stroke in the compression stroke. As a result, part of the fresh charge is returned to the intake manifold by the upward piston so that the cylinder is never completely filled (hence the reduction of power at low speed). The reward comes after ignition when the piston begins to descend in the blow of expansion (also called power). Consistent with Atkinson's original thinking, the shortened intake stroke combined with a full-length expansion stroke compresses more work from every fuel increase.