Investigation of hydrogen influence on compression ignition engine fuelled with pyrolysis blends using experimental and RSM methods

This study experimentally investigates the performance, combustion, and emission characteristics of a single-cylinder diesel engine operated in dual-fuel mode using pyrolysis oil and gaseous hydrogen. Four fuel combinations were examined: neat diesel (100D), diesel–hydrogen (50D50H), diesel–pyrolysis oil (90D10P), and diesel–pyrolysis oil with hydrogen enrichment (90D10P + 50 LPH). The engine was operated at a constant speed of 1,500 rpm under varying load conditions (0–100%), and the results were analysed using response surface methodology (RSM). The 50D50H blend achieved the highest brake thermal efficiency, showing a 21.4% improvement over neat diesel, along with a minimum brake-specific fuel consumption of 0.22 kg/kWh. The maximum in-cylinder pressure (69 bar) and peak heat release rate (75 J/CA) were observed for the 90D10P + 50 LPH blend. Emission analysis indicated that this blend produced the lowest carbon monoxide, carbon dioxide, hydrocarbon, and nitrogen oxide emissions among all tested fuels, while the lowest NOx emission of 350 ppm was recorded for the 50D50H blend. Statistical validation using analysis of variance (ANOVA) yielded regression coefficients (R2) between 0.8 and 1, demonstrating strong agreement between experimental results and model predictions. The findings confirm that the combined application of pyrolysis oil and hydrogen in dual-fuel operation significantly enhances engine efficiency while effectively reducing exhaust emissions.