The stratified charge engine is a hybrid internal combustion engine which combines features of the spark-ignition engine with a diesel. It usually has a bowl-in-piston combustion chamber design. The most successful designs of this type of machine have used the four-stroke cycle, whose concept is usually called direct injection stratified-charge engine. It can also be turbocharged to increase its power density.
In this type of machine, a high degree of air swirl is created during intake as there is an enhancement in the piston bowl during compression to achieve a fast fuel-air mixing. In a stratified charge engine, fuel is injected into the cylinder, tangentially into the bowl, during the latter stages of compression. Then a long-duration spark discharge ignites the developing fuel-air jet as it goes by the spark plug. The flame extends downstream, enveloping and consuming the fuel-air mixture. The process of mixing continues as the final stages of combustion are completed during expansion.
In some commercial multifueled engines, the fuel injector is set diagonally from the cylinder head from the upper left, injecting the fuel onto the hot bowl of the deep spherical piston bowl. The fuel flows around the wall of the bowl in a swirling pattern. Then it evaporates off the wall, get mixed with air, and is finally ignited by the discharge of the spark plug, which gets into the chamber vertically on the right. This particular engine is air-cooled, so the cylinder block and head are fitted with a series of metal fins, which help dissipate the heat. Fins increase the surface area.
Below, an schematic drawing of a M.A.N. high-speed, multifueled, four-cylinder, direct injection, stratified charge engine.
