Abstract
The quality of fuel and air mixing depends immensely on the type of bowl shape used for the piston and directly affects an engine's performance and emissions. In this study, the effects of piston bowl designs on the combustion and emissions in a hydrogen-diesel dual-fuel engine with a direct injection (DI) have been investigated. Using numerical simulations, typically three different piston bowls have been analyzed considering engine performance parameters as indicators. Investigation has been aimed for better performance of the engine, lower cost of fuel, and improved emission characteristics. Among different piston bowls studied in this work, it has been observed that the w-type and re-entrant piston bowls increased the cylinder power by 1.27% and 2.65%, respectively, and decreased the indicated specific fuel oil consumption (ISFOC) by 1.04% and 1.63% compared to the U-type bowl, respectively. Among these bowls, much of the NO emissions could be reduced by 25.59% for the w-type bowl and 46.09% for the re-entrant bowl, because of the lower peak temperature compared with the U-type bowl. Changing the piston bowl also has effect on soot emissions and CO(2) emissions. Considering these results, it is recommended to use the re-entrant piston bowl in a four-stroke diesel engine in order to avail enhanced engine performance, reduced fuel consumption, and decreased NO emission.