基于气液比调控的新型两相流喷头设计与试验

Design and Experimental Investigation of Novel Air-Liquid Two-phase Nozzle with Independently Controlled Air-to-Liquid Ratio

摘要:

空气诱导喷头是农业施药常用的雾化部件，通过文丘里效应吸入空气，使喷雾过程呈气液两相流特征，从而改变雾滴粒径分布。气液比（Air-to-liquid mass ratio，ALR）是影响喷头雾化特性的重要参数，但空气诱导喷头的ALR难以作为独立变量进行调控。为研究ALR对喷雾雾化特性的影响，本研究基于空气诱导喷头的结构特征，通过改变气体供给方式，设计了一种ALR可独立调节的两相流喷头，并采用激光粒度仪对不同ALR条件下喷头的雾滴体积中径（Volume median diameter，VMD）及粒径分布特性进行了测试与分析。结果表明，当ALR为0~0.005时，VMD随ALR增大而增大；当ALR为0.005~0.01时，VMD随ALR增大而快速减小；当ALR高于0.01时，VMD下降速率显著放缓并趋于稳定。基于ALR大于0.005试验数据，建立了VMD与ALR的关联模型，模型决定系数（R2）不小于0.91，能够有效表征不同工况下雾滴粒径的变化趋势。粒径分布结果表明，ALR变化可显著影响雾滴粒径小于150 μm的累积体积分数，从而改变喷雾潜在飘移风险。研究结果为农业施药两相流喷头雾化行为理解及喷头设计提供了理论依据。

Abstract:

Air induction nozzles introduce air through the Venturi effect and generate air-liquid two-phase sprays, thereby altering droplet size distribution during agricultural applications. The air-to-liquid mass ratio (ALR) is a key parameter governing atomization characteristic; however, in conventional air induction nozzles, ALR is strongly coupled with structural parameters and cannot be independently controlled. To investigate the specific role of ALR in spray atomization, an ALR-adjustable air-liquid two-phase nozzle was developed by modifying the air supply mode while maintaining the original liquid flow structure. Droplet size distribution and volume median diameter (VMD) under different ALR conditions were measured by using a laser particle size analyzer. The results indicated that atomization characteristics exhibited distinct stage-dependent variations with increasing ALR. When ALR was below 0.005, VMD increased with ALR; when ALR ranged from 0.005 to 0.01, VMD decreased sharply; and when ALR exceeded 0.01, the decreasing rate of VMD slowed and gradually stabilized. Based on experimental data for ALR > 0.005, a correlation model between VMD and ALR was established, with coefficients of determination (R2) no less than 0.91, demonstrating strong agreement with measured data. Furthermore, variations in ALR significantly influenced the cumulative volume fraction of droplets less than 150 μm, which was closely related to spray drift potential. These findings can provide theoretical support for understanding the atomization behavior of air-liquid two-phase nozzles and offer guidance for the design and optimization of spray systems in agricultural applications.