高压喷嘴内部空化流动的数值模拟研究

高压柴油喷嘴入口流动分离产生的局部低压会诱发空化现象。该文利用k-ω SST 两方程湍流模型和k-kl-ω湍流/转捩模型对某喷嘴内无空化及空化流动进行数值模拟。结果表明k-kl-ω模型可有效预测喷嘴入口回流区分离转捩过程, 且喷孔内空化流的空泡位置、形态及出口质量流量与实验结果吻合很好, 能更准确模拟喷嘴内空化流动, 而k-ω SST 模型忽略了分离转捩过程, 难以预测喷嘴内部的初生空化及流动特性。进而采用k-kl-ω模型探讨了喷嘴入口回流区流动结构及转捩过程对空化初生及发展的影响, 揭示出回流区长度、压力及脉动能强度分布特性, 为深入研究喷嘴射流雾化机理提供依据。

NUMERICAL SIMULATION OF INTERNAL FLOW AND CAVITATION OF A DIESEL NOZZLE

Cavitation phenomenon inside a high-pressure diesel nozzle is usually induced by the relative pressure region formed by flow separation along with laminar-turbulent transition. In the present paper, the k-ω SST two-equation turbulence model and k-kl-ω turbulence model taking account of laminar-turbulent transition were employed to simulate the non-cavitation and cavitation flow in a diesel nozzle. Compared with the k-ω SST model that disregards the laminar-turbulent transition effects and accordingly fails to predict the incipient cavitation, the k-kl-ω turbulent model predicted the location and shape of incipient cavitation bubble well with the experimental results, as well as the mass flow rate at the nozzle outlet. Further, the internal flow characteristics, including the length of recirculation region, pressure, fluctuation energy distributions, were investigated utilizing the k-kl-ω model, which provides the insight of liquid fuel jet atomization phenomena and corresponding mechanism.