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The opposed piston two-stroke (OP2S) engine architecture is widely recognized for its improved fuel efficiency relative to a four-stroke engine. Achates Power Inc. seeks to demonstrate the market readiness of the OP2S engine by proving competitive in other important areas, one of which is oil consumption. Achieving oil consumption competitive to modern four-stroke engines is thus a key step in bringing OP2S technology to market. Two-stroke engines have historically suffered from higher engine lube oil consumption and subsequent emissions and durability challenges. This is primarily due to two main features of traditional two-stroke engines; the direct interaction of the piston skirt and rings with the intake and/or exhaust ports, which results in a direct leak path for lube oil to the combustion chamber and/or exhaust manifold, and crankcase-scavenged architectures which entrain oil into air being pumped through the crankcase.

This paper presents analytical and measured results on the effects of injection pattern design on piston thermal management in an Opposed-Piston, Two-Stroke (OP2S) diesel engine. The OP2S architecture investigated in this work comprises two opposing pistons forming an asymmetric combustion chamber with two opposing injectors mounted on the cylinder wall. This unique configuration offers opportunities to tailor the injection pattern to control the combustion heat flux and resulting temperatures on the piston surfaces while optimizing combustion simultaneously. This study utilizes three-dimensional (3D) computational fluid dynamics (CFD) with state-of-the-art spray, turbulence and combustion models that include detailed chemistry to simulate the in-cylinder combustion and the associated flame/wall interactions. In addition, the measurements comprise a real-time thermocouple system, which allows for up to 14 locations to be monitored and recorded on the intake and exhaust pistons.