Adaptive PCCI combustion using micro-variable circular-orifice (MVCO) fuel injector - Key enabling technologies for high efficiency clean diesel engines

This paper presents the latest results for a new high efficiency clean diesel combustion system - Adaptive PCCI Combustion (a premixed charge compression ignition mixed-mode combustion) using a micro-variable circular orifice (MVCO) fuel injector. Key characteristics of the new combustion system such as low NOx and soot emissions, high fuel efficiency, increased engine torque are presented through KIVA simulation results. While early premixed charge compression ignition (PCCI) combustion reduces engine-out NOx and soot, it's limited to partial loads by known issues such as combustion control, high HC and CO, and high pressure rise rate, etc. Conventional combustion is well controlled diffusion combustion but comes with high NOx and soot. Leveraging the key merits of PCCI and conventional combustion in a practical engine is both meaningful and challenging. A new Adaptive PCCI combustion system, which couples early PCCI with an Accelerated Diffusion Combustion (ADC) in the same power cycle, successfully merges the merits of early PCCI and diffusion combustion for different operating conditions. The Adaptive PCCI reduces the drawbacks of each combustion mode, produces low emissions and high efficiency with stable combustion simultaneously. Conventional fixed-spray-angle fuel injectors have to be compromised for dual-mode combustion. An injector with variable spray angle and spray pattern is much desirable. MVCO injector provides variable spray angles and spray patterns with a low-cost structure. The MVCO minimizes surface-wetting and oil dilution, and enables practical combustion optimization for broad loads, speeds, and injection timings.