Response of droplet parameters to liquid viscosity in the flow field of an air-blast sprayer

The physical properties of sprayed droplets such as viscosity affect their deposition on the target.In order to understand the response characteristics of droplet parameters to the viscosity of a spray solution,a three-dimensional model of the external flow field of an air-blast sprayer based on computational fluid dynamics(CFD)was established according to the actual spray range and the sprayer duct structure.The change rules of droplet diameter and droplet density with distance under different viscosities of the spray solution in the flow field were obtained through numerical solution of the CFD model.The reliability of the model was verified by a chi-squared test comparing the numerical calculations with the results of field experiments.The results showed that the change rule of droplet parameters in an airflow field under different values of the spray solution viscosity was consistent.With the increase in the axial distance,the droplet size decreased initially,then increased,and finally decreased,while the droplet density gradually decreased.Moreover,the greater the spray solution viscosity,the shorter the conveying distance of the droplets in the axial direction,although viscosity was helpful in reducing the droplet drift.In addition,at the same axis distance,with the increased viscosity of the spray solution,the droplet size increased,and the sedimentation of the droplets was more rapid,while the density of the droplets decreased.The results provided a new framework for the study of air-blast spraying technology and serve as a reference for the optimization of the sprayer structure and the preparation method for spray solutions.

垃圾填埋场用除臭风炮喷雾特性的研究

除臭风炮是垃圾填埋场除臭的常用设备,能够有效缓解垃圾填埋场臭气外溢的问题。但在实际应用过程中存在除臭药液喷洒不均、喷射不及,风炮俯仰角控制不合理等问题。针对这些问题,对除臭风炮的喷雾特性进行研究,运用计算流体动力学理论(CFD)结合牛顿定律对除臭风炮喷雾过程中的气相和液相进行了理论分析,并通过FLUENT进行仿真,分析了风炮风速、风炮俯仰角等因素对雾滴分布均匀性和覆盖率等指标的影响,其间有实验数据加以佐证。结果表明,风速增大可以增大雾滴射程并改善雾滴的分布均匀性,雾滴降落的密集区域随着风炮俯仰角增加会先增大后减小,在45°左右达到最大值;为增加雾滴分布均匀性,风炮俯仰角的角速度控制应呈现中间大两头小的趋势。

Simulation and experimental research on droplet flow characteristics and deposition in airflow field

In order to study the motion law of droplet flow under the airflow action of long-range air-blast sprayers,a CFD-based 3D model was established for the air-blast sprayer duct and its external airflow field,and the discrete phase model was introduced to simulate the motion of droplet flow in the airflow.The simulation data of the droplet flow trajectory,droplet flow parameters and droplet deposition were obtained by establishing the monitoring sections and bilateral coupling calculation in the airflow field.Results showed that gravity had an obvious effect on droplets and large droplets settled faster.Some of the larger droplets were formed by polymerization in droplets motion.The smaller droplets were transported further along with the airflow,and the long-range sprayer has a significant effect on the directional transport of small droplets.Besides,the spraying swath in the direction perpendicular to the range enlarged gradually with the increase of the spraying range.At the end of the range,the diffuse and drifting of the droplets were dominant.Given that the outlet airflow velocity of the sprayer duct was 25.01 m/s and the spray pressure 1.8 MPa,the maximum motion distances of aerosol,mist,fine mist and coarse mist in the airflow field were 18.5 m,19.5 m,17.5 m and 10.5 m,respectively.Droplet size and number as well as number density and volume density of droplet flow on all monitoring sections showed a regression function with changes in the distance of the spraying range.The simulation results of the model adopted in this paper were verified by Chi-square test between the simulation results of the droplet deposition and the spray measurement results.Research results provide a new method for the study of orchard air-blast spraying technology and references for the optimization of spraying technology.