气吸式射流喷头内部瞬态流场数值模拟与气液两相流变特性研究

Numerical Simulation of Internal Transient Flow Field and Air-Liquid Two-phase Flow Characteristics on Air-induction Nozzle

摘要:

气吸式射流喷头（Air-induction nozzle,AIN）具备特殊的文丘里结构，在降低农药雾滴飘移概率、实现精准施药等技术领域得到了广泛应用。为探明气吸式射流喷头内部气液两相瞬态流动分布及文丘里几何结构参数对气液比的影响规律，本文采用TD型文丘里管、ST型扇形喷嘴组合的射流喷头进行数值模拟及气液比预测模型探究。基于开放型进、出口边界条件，采用VOF模型、Realizable湍流控制方法，对TD-ST组合气吸式射流喷头进行数值模拟，研究结果表明：组合式AIN瞬态流动特性由文丘里管几何参数决定，内部速度和压力在文丘里角处发生显著扩散变化。相同ST型喷嘴下，气液两相流中气相体积分数随TD文丘里管喉管尺寸增大而减小。TD03-ST06型组合式AIN在压力0.6 MPa下气体体积流量达到最大值（0.0092 L/min）。通过设计进气量测量系统，建立气液比回归模型，依据模型可明晰喉管尺寸与喷雾参数对气液比的影响规律，方差分析结果表明该模型适用于TD-ST型组合式AIN喷头气液比预测。阐明了AIN内部气液耦合规律，为量化分析喷头几何参数、喷雾参数与气液比间的关系提供了参考。

Abstract:

Air-induction nozzles (AINs) feature a unique Venturi structure, which has led to their widespread application in technical fields such as reducing pesticide droplet drift and achieving precise application.To investigate the transient two-phase flow distribution within the air-induction jet nozzle and the influence of Venturi geometric parameters on the air-to-liquid ratio numerical simulations and a predictive model for the air-liquid ratio were developed by using a jet nozzle comprising a TD-type Venturi tube and an ST-type fan-shaped nozzle.Based on the VOF model and the realizable k-ε turbulence scheme, numerical simulations of the TD-ST composite air-induction nozzle were conducted using open-type inlet and outlet boundary conditions.The results indicated that the transient flow characteristics of the composite AIN were determined by the geometric parameters of the Venturi tube, with significant diffusion changes in internal velocity and pressure occurring at the Venturi angle.For the same ST nozzle model, the gas phase content in the gas-liquid two-phase flow was decreased as the throat size of the TD Venturi tube increased.The gas volumetric flow rate of the TD03-ST06 combined AIN reached a maximum value of 0.0092 L/min at 0.6 MPa.By designing an air intake measurement system, a gas-liquid ratio regression model was established.Based on this model, the influence of throat dimensions and spray parameters on the gas-liquid ratio can be clearly elucidated.Analysis of variance confirmed that this model was suitable for predicting the gas-liquid ratio of TD-ST composite AIN nozzles.The research result elucidated the gas-liquid coupling mechanisms within AINs, providing a reference for the quantitative analysis of the relationship between nozzle geometric parameters, spray parameters and the gas-liquid ratio.