Effect of injection pressure on low-temperature fuel atomization characteristics of diesel engines under cold start conditions

Exploring the atomization characteristics and spray impingement characteristics of low-temperature fuel under different injection pressures has important practical significance for improving the cold start performance of diesel engines. In this study, based on LIEF-PIV combined laser testing technology, a fuel atomization experimental system for diesel engine cold start was established. The concentration and velocity fields of low-temperature fuel with the temperature from 20 to -40 degrees C were experimentally analyzed within the injection pressures of 40-80MPa. The results showed that the increase of injection pressure increased the initial kinetic energy of the diesel droplets, whereas the concentration gradient of spray decreased significantly. Meanwhile, the mixing effect of spray and ambient gas increased. When the fuel temperature decreased from 0 degrees C to -20 degrees C, the values of the average equivalence ratio in the near-wall region decreased from 0.52 to 0.21. The change of injection pressure had an obvious effect on the macro morphology of wall-impinging spray and the flow characteristics of the fuel/air mixture. When the injection pressure increased from 40MPa to 80MPa, the difference of maximum turbulent kinetic energy among various temperatures increased from 0.66 m2/s2 to 0.90 m2/s2.