ABSTRACT
This chapter discusses the possible port and valve scavenging arrangements and the relevant prior experience with these arrangements, with focus on the simplest approach: the use of scavenge and exhaust ports. It explores the geometric design issues of the intake and exhaust systems relevant to optimizing the gas exchange process and focuses on minimizing short-circuiting through the exhaust port, and backflows through the inlet and scavenge ports. In a simple two-stroke engine, the opening and closing times of the ports are fixed and are symmetrical about the BC crank position. The port timings are optimized at well-defined conditions of operation where excellent performance is most important. A reed valve is constructed of flexible leaf springs, of cantilever design, typically made of thin spring steel, firmly anchored at one end and free to deflect substantially at the other end under load. The objective of installing a reed valve at the intake port is to improve low-speed engine operation by eliminating backflows.
