An Opposed-Piston Diesel Engine

Abstract

Typical conventional diesel engine designs are based on arrangements of single piston and cylinder sets placed sequentially either in-line or offset (“V”) along the crankshaft. The development of other engines, such as the opposed piston type, has been motivated by potential advantages seen in such designs, which may not be viable in conventional in-line or V engine arrangements. Several alternatives to conventional engine design have been investigated in the past and some aspects of these designs have been utilized by engine manufacturers. The design and development of a proof-of-concept opposed piston diesel engine is summarized in this paper. An overview of opposed-piston engines is presented from early developments to current designs. The engine developed in this work is a two stroke and uses four pistons, which move in two parallel cylinders that straddle a single crankshaft. A prechamber equipped with a single fuel injector connects the two cylinders, forming a single combustion chamber. The methodology of the engine development process is discussed along with details of component design. Experimental evaluations of the assembled proof-of-concept engine were used for determining feasibility of the design concept. An electric dynamometer was used to motor the engine and for loading purposes. The dynamometer is instrumented for monitoring both speed and torque. Engine parameters measured include air flow rate, fuel consumption rate, inlet air and exhaust temperatures, and instantaneous cylinder gas pressure as a function of crank position. The results of several testing runs are presented and discussed.