中文摘要：

为提高喷嘴的雾化性能,得到理想的雾滴粒径和均匀的雾云分布,该文首先对超音速雾化喷嘴的雾化原理进行了分析,应用拉瓦尔喷管超音速原理,对雾化喷嘴内部阀芯的锥形结构作了改进,结合Fluent流体动力学软件,分析了拉瓦尔式阀芯结构内部流场速度分布规律,然后通过喷雾试验对比分析了改进前后喷嘴的雾化效果,并探究了不同运行参数对拉瓦尔式结构喷嘴雾化性能的影响规律。数值仿真结果表明,拉瓦尔式阀芯能够产生超音速气流,对增大气液两相速度差具有显著效果;试验结果表明,改进后的拉瓦尔式喷嘴在雾化性能和效果上优于原锥形式喷嘴,气压和气液压力比的增大以及水压的减小均有利于雾滴粒径的减小,其中气液压力比在0-3区间内,雾滴粒径下降幅度高达90.56%,当气液压力比为6时,雾滴粒径达到最小值18.52μm。该文研究内容可为超音速雾化喷嘴进一步研究以及新型喷雾设备的研发提供参考。

英文摘要：

Atomizing nozzle is a crucial part of spray device. And it is widely applied in many fields such as agricultural spraying, plant cooling and dust suppression. Moreover, the atomizing performance of nozzle has a great influence on the size and velocity of droplet, and the flow distribution. In order to improve the atomizing performance of the supersonic atomizing nozzle, atomizing principle of the supersonic atomizing nozzle is analyzed in this paper, and it is found that the velocity difference of air phase and water phase has a great effect on the atomizing performance. The spool structure of the atomizing nozzle is changed according to the supersonic principle of Laval nozzle when it is tapered before. The key size of Laval-style structure is important to its accelerated performance, the air inlet diameter is 4.5 mm, the throat diameter is 1.5 mm, the spool outlet diameter is 3.5 mm, the water inlet diameter is 0.9 mm, the subsonic contraction period length is 3.3 mm, the supersonic expansion period length is 6.2 mm, and the expansion period cone angle is 10°. A three-dimensional （3D） geometry model of Laval-style spool is built, supersonic can be achieved while the air pass through the nozzle, and velocity distributions law of the nozzle flow field is obtained by using computational fluid dynamics software Fluent. Furthermore, a test bench is built for atomization and the atomizing testing is carried out. The atomizing effect of nozzle is analyzed and compared before and after the spool structure being changed, and the atomizing performance influence rule of Laval-style atomizing nozzle is studied under different operational parameters. The numerical simulation results show that the velocity within most parts of the nozzle can reach supersonic and the velocity difference of air phase and water phase is significantly increased. In addition, the results of atomization testing indicate that the change of spool structure and the operational parameters have a great influence on atomizing performance, and the L