旋转式阻尼喷头水滴及水量分布试验与模型研究

发布时间：2018-03-13 17:04

本文选题：旋转式阻尼喷头　切入点：散水齿　出处：《江苏大学》2017年硕士论文　论文类型：学位论文

【摘要】：旋转式阻尼喷头由于具有射程远,喷灌均匀性高及抗风性强等诸多优点,所以越来越多地应用于农业生产。深入研究旋转式阻尼喷头水滴直径分布、动能分布和水量分布等规律对提高喷头喷洒质量有重要意义。本文通过试验研究了旋转式阻尼喷头喷洒水滴分布特性,建立了喷洒水滴运动模型,最后掌握了不同风速范围下水量分布规律及模型。本文主要研究成果如下:(1)对旋转式阻尼喷头水滴直径和动能分布规律进行了试验研究,分析了散水齿、喷嘴直径对水滴直径、动能分布的影响规律,并建立了相应模型。结果表明:散水齿对射程中段的水滴平均直径影响较大,对射程初始段和末段水滴平均直径影响较小;散水齿使末端水滴平均直径范围变小,使同一段距离的单位体积动能增加幅度变大。无散水齿时,近喷头处,喷嘴直径对水滴平均直径和动能强度影响较小;在喷头射程末端处,喷嘴直径对水滴平均直径和动能强度影响较大;有散水齿时,喷嘴直径对沿径向水滴平均直径分布和动能强度影响较小。建立相关模型的拟合系数均大于0.90。(2)提出了空气阻力模型、弹道轨迹模型、喷洒速度及射程模型和水滴蒸发模型综合条件下的水滴运动的仿真方法。采用Park公式计算空气阻力系数C,结合牛顿第二定律得到适用于旋转式阻尼喷头的弹道轨迹模型。在静止条件下水滴蒸发模型的基础上,引入折算薄膜概念推导出运动条件下水滴蒸发模型。通过试验建立了有散水齿条件下旋转式阻尼喷头水滴速度和喷洒射程模型,模型拟合系数均在0.80以上。综合上述模型,提出了模拟水滴运动及分布仿真方法。(3)通过试验研究了不同风速下布置方式、喷嘴直径、工作压力、安装高度和喷头间距对组合喷灌均匀性的影响。结果表明:不同风速下,矩形布置均比三角形布置更适用于实际工程;喷头间距对组合喷灌均匀性影响较大。低风速和中风速下,工作压力和喷嘴直径对组合喷灌均匀性有显著影响,安装高度对组合喷灌均匀性影响较小。高风速下,喷头的组合喷灌均匀系数小于75%,说明该喷头不宜在高风速下工作。不同风速下,压力为250kPa以下时,组合喷灌均匀系数随着风速的增大而减小。(4)分析了不同风速下点喷灌强度变化规律,建立了不同风速下水量分布模型。结果表明:低风速下,随着距喷头距离的增加,点喷灌强度在近喷头范围内逐渐增高,末端会出现骤降的现象;工作压力和喷嘴直径等影响因素会产生交互作用。中风速下,总体上点喷灌强度随着距喷头距离的增加先增加后降低。不同条件下,点喷灌强度峰值都出现在射程的后半段。高风速下,随着距喷头距离增加,点喷灌强度呈锯齿状波动。低风速和中风速下水量分布模型拟合系数均为0.90以上,为旋转式阻尼喷头在工程应用中提供了参考。
[Abstract]:The rotary damping sprinkler has many advantages, such as long range, high uniformity of sprinkler irrigation and strong wind resistance, so it is more and more used in agricultural production. The distribution of kinetic energy and water is of great significance to the improvement of spray quality. In this paper, the spray droplet distribution characteristics of rotary damping sprinkler are studied experimentally, and the spray droplet motion model is established. Finally, the distribution law and model of water volume in different wind speed range are grasped. The main research results in this paper are as follows: 1) the distribution of water droplet diameter and kinetic energy of rotary damping nozzle is studied experimentally, and the distribution of water droplet diameter and nozzle diameter to water droplet diameter are analyzed. The influence of kinetic energy distribution on the average diameter of water droplets in the middle part of range is greater than that in the initial and final stages of range. The mean diameter range of the water droplets at the end decreases and the kinetic energy per unit volume increases at the same distance. When there is no dispersed water teeth, the nozzle diameter has little effect on the average diameter and kinetic energy intensity of the water droplets near the nozzle. At the end of the nozzle range, the nozzle diameter has a great influence on the average diameter and kinetic energy intensity of water droplets. The nozzle diameter has little effect on the average diameter distribution and kinetic energy intensity along radial water droplets. The fitting coefficients of the relevant models are all greater than 0.90.2.) the air resistance model and trajectory model are proposed. The simulation method of droplet movement under the conditions of spray velocity and range model and droplet evaporation model is presented. The air drag coefficient C is calculated by Park formula, and the trajectory suitable for rotary damping sprinkler is obtained by combining Newton's second law. Trace model. Based on the evaporation model of water droplets under static conditions, The model of water droplet evaporation under moving conditions is derived by introducing the concept of reduced film. The model of droplet velocity and spray range of rotary damped sprinkler head under the condition of scattered water teeth is established through experiments. The fitting coefficient of the model is above 0.80. The simulation method of water droplet movement and distribution is put forward. The effects of different wind speed arrangement, nozzle diameter, working pressure, installation height and nozzle spacing on the uniformity of combined sprinkler irrigation are studied experimentally. The rectangular arrangement is more suitable than the triangular arrangement for practical projects, the space between the sprinklers has a greater effect on the uniformity of the combined sprinkler irrigation, and the working pressure and nozzle diameter have significant effects on the uniformity of the combined sprinkler irrigation under the low and medium wind speeds. The installation height has little effect on the uniformity of combined sprinkler irrigation. Under high wind speed, the uniformity coefficient of combined sprinkler nozzle is less than 75, which indicates that the nozzle is not suitable for working under high wind speed. Under different wind speed, the pressure is below 250kPa, The uniform coefficient of combined sprinkler irrigation decreases with the increase of wind speed. (4) the variation law of sprinkler intensity under different wind speed is analyzed, and the distribution model of water volume of different wind speed is established. The results show that under low wind speed, with the increase of distance from sprinkler head, The intensity of sprinkler irrigation increases gradually in the range of near sprinkler head, the phenomenon of sudden drop will occur at the end of the sprinkler, the influence factors such as working pressure and nozzle diameter will interact. Under different conditions, the peak value of sprinkler intensity appears in the second half of the range. At high wind speed, with the increase of the distance from the sprinkler head, the peak value of the point sprinkler intensity increases with the increase of the distance from the sprinkler head. The distribution coefficient of low wind speed and middle wind speed is above 0.90, which provides a reference for the application of rotary damping sprinkler.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S277.94

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