Air-Fuel Mixture Matching Characteristics in the Swirl Combustion Chamber of an Opposed-Piston Two-Stroke Diesel Engine

The opposed-piston two-stroke (OP2S) diesel engine is attracting growing interest from research institutions worldwide due to its high power density, superior balance, and potential for high thermal efficiency. This engine configuration is particularly well-suited for small-scale specialized applications, such as auxiliary power units and unmanned aerial vehicles. Nevertheless, OP2S engines still face challenges, including inefficient spatial utilization of the air-fuel mixture and elevated thermal loads on the exhaust piston. To address these issues, a dedicated swirl combustion chamber system for OP2S engines was designed and developed. The influence of the arc ridge depth on the air-fuel mixture matching characteristics was systematically studied. The findings reveal that as the arc ridge depth increases, the air-fuel mixture homogeneity deteriorates, and the combustion duration initially decreases before rising. Concurrently, the thermal load on the exhaust side is reduced, resulting in lower heat transfer losses. By implementing the optimized dual-swirl combustion chamber system, the engine's indicated thermal efficiency can surpass 50%.