Effect of Milk Scum biodiesel addition and hydrogen energy share on the performance of reactivity‐controlled compression ignition engine

Abstract Reactivity Controlled Compression Ignition (RCCI) engines are a promising way to decarbonize the internal combustion engine industry. Despite this extensive literature covering dual‐fuel setups, a critical knowledge gap persists regarding the steady‐state combustion behavior of highly specific, waste‐derived oxygenated lipids when paired directly with carbon‐free LRFs. To address this gap, the current study focuses on the waste‐to‐wealth principle of utilizing Milk Scum biodiesel and mineral diesel (as a High‐Reactivity Fuel) and hydrogen (as an LRF) to achieve the minimum carbon‐based emissions. Experimentally, performance and emissions were measured using a constant‐rpm diesel engine with a compression ratio of 18, fuel injection pressure of 500 bar, fuel injection time of 23 bTDC, and common‐rail direct‐injected (B10, B15, and B20) and port‐injected hydrogen (0.077 and 0.121 kg/h) at 25%, 50%, 75% and 100% engine loads. The measurements indicate that the RCCI optimality (0.121 kg/h H 2 , B10 blend) achieved a maximum Brake Thermal Efficiency of 31.2% and 10–15% lower Brake Specific Fuel Consumption under high‐load conditions. Moreover, this hydrogen‐enriched RCCI mode achieved average reductions in CO, HC, NOx, and smoke emissions of 24%, 27%, 35%, and 40%, respectively. Interestingly, while the overall experimental matrix yielded an average NOx reduction of 35%, the optimum RCCI B10 configuration at 100% load inhibited peak NOx formation by more than 60% compared with the baseline diesel mode at the same load.