Simulation study on the effect of intake charge temperature and ignition timing on the performance of a converted biogas engine

This study conducts a simulation analysis of the performance and emission characteristics of a biogas-fueled engine using the thermodynamic simulation tool AVL Boost. The original diesel engine model was modified by lowering the compression ratio and enhancing mixture formation to enable operation with biogas. Key engine parameters such as airflow mass, brake torque and power, fuel consumption, emission outputs, and in-cylinder parameters were evaluated. The simulation results indicate that, under biogas operation, NOx emissions decrease significantly, while CO emissions rise compared to diesel-fueled operation. Although the engine’s brake power shows a decline when fueled by biogas, fuel efficiency demonstrates an improvement trend. Additionally, the impact of ignition timing and charge temperature on engine behavior was examined. Findings suggest that the optimal ignition timing for biogas engines should be set between 11° and 19° crank angle before top dead center. The intake charge temperature affects the combustion process and the engine's output power. Ideally, the intake air temperature should be maintained below 50°C to ensure optimal engine performance and technical reliability.