Multi-objective optimization of performance and emissions for hydrogen-powered CI engines in dual-fuel mode using RSM-fuzzy techniques

Abstract

Environmental concerns and the demand for fossil fuels have driven the exploration of hydrogen as an alternative fuel. Its clean-burning properties can enhance engine performance and meet strict emission standards in Diesel-Hydrogen dual-fuel mode. This study investigates the performance of a 4-stroke Single-Cylinder dual-fuel CI engines operating with hydrogen as a supplementary fuel and diesel being the primary fuel at varying loads (20%, 40%, 60%, 80%, and 100%). The results demonstrate a maximum Brake Thermal Efficiency improvement of 23% at full load under the DH3 strategy, though Nitrogen Oxide emissions peak at 7.5 g/kW-h at full load. SOOT emissions remain low at lower loads but increase at higher loads, especially for DH3. Unburnt Hydrocarbons emissions are higher with hydrogen enrichment at low loads, with peaks of 29 and 22 g/kWh for DH1 and DH2, respectively. Advanced injection strategies, particularly DH4, improve efficiency and control Unburnt Hydrocarbons and SOOT emissions, though Nitrogen Oxide emissions rise at higher loads. Additionally, the study develops a predictive model using Response Surface Methodology to evaluate engine performance and emissions. To enhance the model’s accuracy and robustness under varying operating conditions, fuzzy optimization is integrated. This approach addresses the challenges of nonlinear relationships and complex data inherent in engine performance modeling. The results indicated that at 40% load and an injection timing of 6500 µs (DH2), the engine performance was optimized. The corresponding values of Brake Thermal Efficiency, Volumetric efficiency, Unburnt Hydrocarbons, Nitrogen Oxide, and SOOT emissions were found to be 18.46%, 70.85%, 21.5 g/kW·h, 0.93 g/kW·h, and 0.05 g/kW·h, respectively. These findings highlight the optimal operating conditions that balance performance and emissions under the specified load and injection timing.