Extending the operational range of hydrogen diesel RCCI mode through charge temperature and injection strategy optimization guided by coupled chemical kinetics model

This study presents a validated detailed chemical kinetics-based computational model to investigate and overcome the operational limits of hydrogen-diesel reactivity-controlled compression ignition (HDRCCI) mode. Hydrogen’s (H 2 ) high diffusivity and wide flammability limits facilitate cleaner combustion, but its chemical activity simultaneously introduces kinetic constraints (knocking, excessive pressure rise rates, and misfire limits). Chemical kinetics analysis reveals that increased H 2 activity/consumption of OH radicals ( \(\:{\text{H}}_{2}+\text{O}\text{H}\leftrightarrow\:{\text{H}}_{2}\text{O}+\text{H}\) ) inhibit the cool flame at high hydrogen energy ratio (HER), which leads to misfire at HER = 41%. It is demonstrated that this critical misfire can be resolved by either increasing charge temperature (340 K) or application of a twin-pulse injection strategy. These optimizations not only restore stable combustion, leading to enhanced indicated thermal efficiency (ITE), but also sustain the goal of low-emission performance (around 92% lower soot and low NO X at optimized conditions). Overall, these findings define a viable and extended operational map for highly efficient, low NO X HDRCCI operation.