The process of admitting air and expelling exhaust gas is known as scavenging. The three main types of scavenging for two stroke engines are cross flow, uniflow and loop flow. Notice on the below image that the cross flow and loop flow scavenging designs use ports only, whilst the uniflow design uses valves (for exhaust) and ports (for inlet).

There is three main scavenge method used in a two-stroke diesel engine. To better understand its application and working we will consider two stroke marine diesel engines. The three main scavenging types are; loop, uniflow, and cross-flow. loop and cross-flow don’t require a dedicated exhaust valve while the uniflow scavenging method does.