Experimental study of a free piston linear alternator with an opposed piston combustion chamber

Abstract

This study focuses on the comparison of oil lubricated and dry lubricated pistons and there influence on the combustion process of free-piston engine with an opposed piston combustion chamber. The free-piston engine, which is developed by the German Aerospace Centre, works with a two-stroke principle and the dry lubrication is designed to eliminate the pollution caused by traditional oil lubrication in engines with scavenging ports. The introduction into opposed piston combustion, free piston engines and dry lubrica-tion is kept brief and is followed by a description of the test bench setup. The experi-mental results for a selection of operational points of both the oil and dry lubrication are compared. The key questions of the study are the influence regarding blow-by and possible impact on the combustion process. The observed differences are analysed and the initial assumptions discussed. The dry lubrication concept shows a reasonable in-dicated combustion efficiency of and the carbon piston rings are operated at a maximum frequency of 18.5 Hz. Some difficulties in the comparison need to be acknowledged which are based on the dry lubrication design. In combination with the results the dry lubrication concept is revised and the outlook adds suggestions towards future research.