Development of a Stratified Scavenging System for Small Capacity Two-Stroke Engines

The application of low cost stratified scavenging systems to the two-stroke engine is described. Previous results from multi-stream systems tested at The Queen's University of Belfast are reviewed and results from single- and double-entry air-head engines are presented.

The most promising results relate to a 270cm³ single cylinder cross-scavenged engine with the single-entry air-head system. Effective trapping was obtained by injecting fuel into the crankcase and inducing air through an inlet at the top of the transfer ducts. The results showed significant improvements over the standard homogeneous scavenged engine. The brake specific fuel consumption was reduced by up to 22% and the brake specific hydrocarbons by up to 55%.