Numerical simulation of combustion and emission characteristics in a H₂-Diesel dual-fuel DICI engine with a coaxial dual-layer nozzle

The study employs CFD modeling to assess the combustion performance of a diesel engine equipped with coaxial dual-layer nozzles for direct gas-phase hydrogen injection. The dual-layer nozzle allows separate injections of diesel and hydrogen. This research compares the combustion characteristics of CDL-H₂DDI engines and CDC engines, and subsequently examines the effects of varying hydrogen injection methods (hydrogen-diesel spray angle, HIT, HID, and hydrogen nozzle diameter) on fuel mixing and combustion characteristics in a hydrogen-diesel blend. The study finds that CDL-H₂DDI engines, with the addition of hydrogen, exhibit higher cylinder pressure peaks and RoHR, while promoting soot oxidation and increasing NOx due to the high-temperature combustion. Appropriate hydrogen-diesel spray angles, HIT, hydrogen nozzle diameter and HID reduction can enhance fuel mixing, accelerate mixed-combustion processes, and reduce soot production; however, this may also lead to varying degrees of NOx increase. The study provides technical insights into the optimization design of CDL-H₂DDI engines.