Numerical study of the impact of piston bowl geometry on emissions and combustion properties in diesel engine fueled with aqueous ammonia and diesel mixture

Numerous research studies have been conducted to enhance fuel economy and reduce emissions by converting diesel engines to run on aqueous ammonia-diesel (AAD) blends. However, only a few studies have investigated the effect of the piston bowl geometry on combustion efficiency and emissions from AAD blends. This study investigated the effect of piston bowl geometry on the combustion efficiency of a diesel engine fueled with AAD blends. Five different types of piston bowls, namely the Double lip (Case 1), 10D100 (Case 2), Mexican hat (Case 3), Inveco F1C Rollbuch (Case 4), and Peugeot DW 10 (Case 5), were used. Diesel-RK software was used for modeling and simulating the fuel combustion inside the diesel engine. Based on the numerical findings, with the same combustion chamber, the results show that the NOx emission, smoke level, and peak pressure reduced with increased engine speed from 2000 to 3000 rpm, whereas peak temperature, CO₂, and PM emissions increased. Moreover, among all designs, Case 5 achieved the highest combustion performance, with peak pressure and temperature, along with the lowest PM and smoke. However, it produced the highest NOx emissions. In contrast, Case 1 yielded the lowest NOx, peak pressure, and temperature, but the highest PM, indicating poor combustion. Case 3 achieves the second-highest peak pressure (53.13 bar at 2000 rpm and 52.61 bar at 3000 rpm) and second-highest temperature (1886.8 K at 2000 rpm and 1914 K at 3000 rpm), and only moderately elevated NOx. Case 3 offers the best overall emission balance while maintaining high combustion efficiency, making it the most suitable piston bowl geometry for sustainable operation with AAD blends.