Computational study of the effects of the throat diameter of the piston bowl for the performance and emissions of a high-speed direct-injection diesel engine

different throat diameters associated with different re-entrant lips using an experimentally validated KIVA3V-based computational fluid dynamics (CFD) program. In order to investigate individually the effects of the throat diameter and the re-entrant lip shape with the minimum interactive effects on other parameters, the bowl pip height and width were changed in order to maintain the same bowl height and volume. Three bowls, namely the baseline bowl, a bowl with increased throat diameter with limited pip height, and a bowl with increased throat diameter with the same pip height as the baseline, were investigated at the three speeds 4000 r/min maximum power, 2000 r/min maximum torque with three injector protrusions and three injection timings, and 1600 r/min part-load with two EGR fraction and injection timings respectively. It was found that the bowl with larger throat diameter and high pip has the best air-fuel mixing of all three bowls.