Experimental study of simultaneous effects of porous medium and biodiesel application on spray and combustion characteristics of gasoline–biodiesel blends

Controllability of combustion characteristics in combustion systems, specifically for internal combustion engines, is vital for environmental compliance. This study experimentally investigated the simultaneous effects of the porous medium (PM) application and biodiesel addition on the spray and combustion characteristics of the gasoline–biodiesel blended fuel. A ring-shaped metal PM with 10 or 20 pores per inch pore density (PPI) is installed in a constant-volume combustion chamber for fuel injection through it. Varied blends of gasoline–biodiesel fuel (volume fraction: 5–15%) are tested at three different temperatures (750–1050 K). The results showed that the blended fuel spray interaction with the PM enhanced the fuel dispersion within the combustion chamber. The spray-projected area fraction increased by 4.4% and 28.2%, with the 10 and 20 PPI PM. The porous medium lowered the combustion pressure, temperature, heat release rate, extended ignition delay, and prolonged combustion duration, facilitating homogeneous combustion. The pressure decrease was around 12% and 59%, and the ignition delay increase was 223% and 263% for the 10 and 20 PPI PM. Conversely, biodiesel addition increased the combustion pressure, temperature, and heat release rate while reducing the ignition delay time. While the pressure increase was more than 100%, the PM reduced it by around 50%. The ignition delay reduction was around 50%, but the PM could increase it from 5 to 218%. Therefore, PM and biodiesel applications can be combined to address high emissions of gasoline–biodiesel blended fuel in free-spray combustion and the prolonged ignition delay associated with PM.