Synergistic Impact of Dual Split Injection on the Combustion, and Emission Characteristics of Crdi Diesel Engine Fueled with Carbon Black Nanoparticle-Enriched Dairy Scum Biodiesel B20 Blend

Abstract

This study investigates the combined influence of dual split injection and carbon-black nanoparticle enrichment on the performance, combustion, and emission characteristics of a single-cylinder CRDI diesel engine fueled with dairy-scum biodiesel (DSOBD) blends. Experiments were conducted at varying injection timings, pilot–main mass fractions, and loads, comparing single injection with optimized dual split injection. Results show that the optimized split injection strategy—main injection at 14° BTDC and pilot injection at 7° BTDC with a 90:10 mass fraction—achieved up to 8.6% higher brake thermal efficiency (BTE) and 6–7% lower brake specific fuel consumption (BSFC) than single injection. Carbon-black nanoparticle addition shortened ignition delay (ID) by 18%, reduced combustion duration (CD) by 12%, and increased peak pressure (PP) by 4–5%, indicating faster and more efficient combustion. At full load, the optimized split strategy reduced smoke opacity by 23.1%, HC emissions by 15–17%, CO emissions by 12–14%, and NOx emissions by 8–10% compared to single-injection biodiesel operation. These improvements are attributed to enhanced atomization, better air–fuel mixing, and controlled combustion phasing. The findings confirm that integrating carbon-black nanoparticles with dairy-scum biodiesel under optimized dual split injection delivers a balanced improvement in efficiency and emissions, offering a viable pathway for sustainable CRDI diesel engine operation.