The modern diesel engines equipped with an advanced fuel injection system up to ultrahigh injection pressure of 300 MPa are under development at present. The impact of injection pressure on fuel spray characteristics such as spray penetration and spray cone angle has been widely concerned in previous studies. However, it is still lack of the detailed investigation on the turbulent dispersion of small droplets produced by a high-pressure injector due to the limited capability of optical diagnostic techniques to simultaneously measure the two phases. Droplet dispersion due to turbulence plays a major role in high-velocity fuel spray mixing and combustion processes involving group evaporation of droplets. Thus, the effect of different injection pressures on droplet dispersion in nonevaporating diesel sprays was investigated using the Euler-Lagrange framework with large eddy simulation (LES) implemented in an open-source code OpenFOAM. Size-dependent instantaneous radial motion and dispersion characteristics of droplets dominated by large-scale turbulent structures within a polydisperse downstream spray were analyzed in detail. Results show that increasing injection pressure can modestly promote the radial dispersion of most droplets with diameter of 2 ~ 12 µm further downstream at the late stage of injection. This could be the result of the increasing interaction time of droplets with larger turbulent structures due to the increase of spray penetration with increasing injection pressure. However, increasing injection pressure has no significant impact on the strength of droplet-turbulence interaction in terms of slip velocity between droplet and gas phases and this could be quantitatively explained by the droplet Stokes number (St) estimated in this study. The most droplets with 0.1 < St < 10 tend to move and concentrate further radially outward, leading to droplet clustering. Thus, the effect of injection pressure on droplet-turbulence interaction is much less than its influence on droplet size for high-velocity fuel sprays, indicating that the ultrahigh injection pressure has much less important impact on the spatial inhomogeneity of droplet distribution than its influence on the evaporation rate of individual droplets.

目前正在开发配备先进燃料喷射系统的现代柴油发动机，该系统可达到300 MPa的超高喷射压力。在先前的研究中，喷射压力对诸如喷雾渗透和喷雾锥角之类的燃料喷雾特性的影响已被广泛关注。然而，由于光学诊断技术同时测量两相的能力有限，因此仍然缺乏对高压喷射器产生的小液滴湍流分散的详细研究。由于湍流引起的液滴分散在涉及液滴的群蒸发的高速燃料喷雾混合和燃烧过程中起着重要作用。从而，使用在开放源代码OpenFOAM中实现的带有大涡流仿真（LES）的Euler-Lagrange框架，研究了不同喷射压力对非蒸发柴油机喷雾中液滴分散的影响。详细分析了多分散下游喷雾中以大规模湍流结构为主的液滴的尺寸依赖性瞬时径向运动和分散特性。结果表明，增加注射压力可以适度地促进大多数直径为2〜12 µm的液滴在注射后期向下游的径向分散。这可能是由于随着喷射压力的增加喷雾渗透性的增加，具有较大湍流结构的液滴相互作用时间增加的结果。然而，St）在这项研究中估计。0.1 < St <10的液滴最多 会移动并径向向外进一步集中，从而导致液滴聚集。因此，喷射压力对液滴-湍流相互作用的影响远小于其对高速燃料喷雾的液滴尺寸的影响，表明超高喷射压力对液滴分布的空间不均匀性的影响远小于其对液滴分布的影响。单个液滴的蒸发速率。