Evaluating the effect of combustion duration on combustion behavior, pollutant formation and residual gas ratio in a propane-fueled spark-ignition engine under varying load regimes

This research investigates the influence of combustion duration on combustion characteristics, emissions, and residual gas in a propane-fueled spark ignition engine under varying load conditions (25%, 50%, and 100%). Utilizing a two-cylinder engine equipped with a control dynamometer and supported by simulations conducted with AVL-Boost software, the study explores combustion durations ranging from 40 to 80 degrees crank angle. The study integrates simulation and experimental methods to address challenges in measuring key parameters such as residual gas and effective release energy under different conditions. Moreover, key performance metrics, including effective release energy, brake mean effective pressure (BMEP), brake-specific energy consumption (BSEC), hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxides (NO_x), were systematically analyzed. The results reveal that combustion duration significantly impacts engine performance and emissions, with longer durations improving combustion efficiency at lower loads but increasing BSEC. Residual gas ratio (RGR) varied more prominently at higher loads, indicating its strong interdependence with combustion characteristics. Optimal combustion durations were identified for each load, balancing performance and emissions. At lower loads, longer combustion durations reduced HC and CO emissions but exhibited fluctuations in NOx emissions. Conversely, at higher loads, shorter combustion durations were more effective in minimizing emissions.