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Impact of multiple injection strategies on efficiency and combustion characteristics in an optical PPC engine
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on April 14, 2020 by SAE International in United States
The partially premixed combustion (PPC) concept is regarded as an intermediate process between the fully mixed Homogeneous charge compression ignition (HCCI) combustion and compression ignition (CI) combustion. It is also a combination of auto-ignition mode, a fuel-rich premixed mode, and a diffusion combustion mode. To achieve high efficiency and low soot emission, the in-cylinder mixture process and combustion behavior of PPC are still to be further explored using laser diagnostic. In this paper, a combined combustion deriving from three stages (HCCI stage, transition stage, PPC stage) was achieved by using multiple injection strategies changing from -220° to -8° after top dead center (ATDC) in an optical heavy-duty CI engine. To analyze the interaction between different combustion modes from HCCI, PPC, and CI, the natural luminosity of combustion was captured by high speed camera. The result shows that piston bowl and cylinder wall play an important role on mixture process in the transition stage and PPC stage. Besides, the interaction between different combustion modes result in different ignition behavior, combustion propagation and gross indicated efficiency.