Further Developments in Scavenging Analysis for Two-Cycle Engines

In 1968 Professor Alfred Jante published an SAE paper detailing a method of assessing the scavenging behaviour of a two-cycle engine. It was a simple technique involving motoring the engine and measuring the (cylinder head removed) velocity contours at the cylinder head level using pitot tubes. It attracted wide attention in industry, but with varying degrees of acceptance and results. This paper attempts to establish in a logical manner and with a considerable’ volume of experimental data that the method proposed by Jante has real relevance, but to obtain acceptable accuracy in terms of predicting good and bad scavenging for particular engine cylinders the results have to be analysed rather more carefully and completely than the approach adopted by Jante. The experimental work describes motoring and firing tests on one engine with many engine. cylinders of differing scavenging layouts and correlates the scavenge tests motoring with the firing tests which include measured scavenge and trapping efficiency values, cylinder pressure diagrams together with the usual engine performance parameters.