预燃室直喷汽油机湍射流预燃室燃烧机理研究

This study utilized CONVERGE CFD to investigate the ignition process and combustion characteristics of passive turbulent jet pre-chambers (PC) in GDI engines. The results indicated that it took approximately 110° CA after the start of injection (SOI) for a rich mixture to effectively enter the PC. The concentration and duration of the entering rich mixture determined the actual equivalence ratio (ER) in the pre-chamber. The actual ER in the PC was always lower than that in the main-chamber (MC)，which approached 1 when the overall ER exceeded 1.2，resulting in optimal jet ignition effects. The hot jet was able to retaine a high content of free radicals after passing through the nozzles, and the ignition mechanism in MC was the propagation of the flame from PC into the MC without quenching. Increasing the intake air temperature (IAT) in the range of 30—70 ℃ improved the actual ER in the PC. However，further increasing the IAT sped up the spray mixing，hence reducing the ER of the rich mixture entering the PC. Additionally，the density decreased，leading to smaller pressure differences and jet velocities. Therefore，when the IAT deviated from the optimal value of 70 ℃，the jet duration was prolonged, and the effect of the jet on accelerating the main chamber combustion diminished.