Demonstration of High Compression Ratio Combustion Systems for Heavy-Duty Diesel Engine with Improved Efficiency and Lower Emissions

Advanced diesel combustion systems continue to push the peak cylinder pressure limit of engines upward to allow high-efficiency combustion with high compression ratios (CR). The air-standard Otto and Diesel cycles indicate increased compression ratios lead to higher cycle efficiency. The study presented here describes the development and demonstration of a high-efficiency diesel combustion system. The study used both computational and experimental tools to develop the combustion system fully. Computational fluid dynamics (CFD) simulations were carried out to evaluate combustion with two combustion systems at a compression ratio of 22:1 with a Wave piston design (based on the production Volvo Wave piston). Analysis of combustion performance and emissions were performed to confirm the improvements these piston designs offered relative to the baseline combustion system for the engine. Companion single-cylinder engine (SCE) experiments were performed to validate the simulation results. The combustion profiles showed good agreement between the experimental and computational results. Indicated thermal efficiency was increased by almost one percentage point with the high compression ratio pistons. Further testing on a multi-cylinder engine verified the engine brake thermal efficiency improvement.