Model Tests on the Scavenging of Two-cycle Marine Diesel Engine

(Report 2. The Relation between Stroke-bore Ratio and Scavenging Efficiency)

Abstract

In two-cycle marine Diesel engine there is a movement which the efficiency of the engine power system including the propeller system is going to be improving by matching with the propeller efficiency. The reduction of engine revolution by means of the long stroke is also one way for it. It seems to be a problem to what extent the long stroke is possible in point of the scavenging action of this type of engine.
From such a back ground this paper reports the experimental results that the scavenging action in case of the long stroke of this type of engine was examined by the model. Two kind of tests were done, one is one cycle scavenging model test for surveying the relation between stroke-bore ratio and scavenging efficiency, another is steady flow scavenging tests for the relation between stroke-bore ratio and the flow in the model cylinder. From the results it was found that the change of the scavenging efficiency is not big up to the stroke-bore ratio 2.00, and the extreme reducing appears in case of that is more than the stroke-bore ratio 2.00. They are discussed in the relation among the stroke-bore ratio, the scavenging efficiency and the scavenge passages in the model cylinder.