Numerical investigation of Fuel Fraction and Dwell Time in Compression Ignition Engines Using Diesel-Biodiesel Blends

Homogeneous charge compression ignition (HCCI) engines offer an advanced combustion strategy to enhance thermal efficiency and reduce emissions. However, challenges remain in achieving mixture homogeneity and controlling the combustion phase. A split injection strategy, utilizing reactive control compression techniques, enhances the combustion process in HCCI engines. This paper focused on investigation of two key parameters; (i) dwell timing and fuel fraction in the second injection pulse and (ii) their effects on combustion, performance, and emissions characteristics across various diesel-biodiesel blend proportions in a direct injection diesel engine (DIDE). The study employed the Diesel-RK software to simulate compression ignition engine performance, providing a reliable numerical model for evaluating fuel operation under different conditions. In the split injection strategy, the first pulse injection timing was fixed at 40° CA BTDC, while the dwell time between the first and second pulses varied at 5°, 10°, 15°, 20°, and 25° CA respectively. Additionally, the fuel fraction in the second pulse was adjusted to 90%, 80%, 70%, and 60%, with the remaining fuel injected during the first pulse. The investigation also considered the effects of four fuel compositions: B0, B20, B40, and B100. The results demonstrated that the proposed methodology significantly influences compression ignition engine characteristics. Increasing the dwell time to 25° CA resulted in reductions of 14.4% in ICP, 6.3% in ICT, 9.1% in HRR, 5.7% in SFC, 10.6% in NOx, and 9.4% in CO₂ compared to 5° CA. Furthermore, NOx emissions were minimized by increasing dwell times and reducing the fuel fraction in the second pulse. The study also found that increasing the fuel fraction in the second pulse slightly increased ICP, ICT, HRR, and NOx, while SFC, ID, and CO₂ decreased. The second injection pulse lacked sufficient time for proper mixing with the charged air, influencing combustion efficiency. This paper suggests optimizing dwell time and fuel fraction in split injection strategies to enhance combustion efficiency and emissions control in diesel-biodiesel blends. The dwell time and fuel fraction adjustments play a crucial role in improving the performance and sustainability of DIDE.