分流对冲与多级扩容组合式自动集沙仪及其内流场特性研究

发布时间：2018-03-21 21:50

本文选题：土壤风蚀　切入点：集沙仪　出处：《内蒙古农业大学》2016年博士论文　论文类型：学位论文

【摘要】：开展土壤风蚀研究必须借助于先进的研究手段与方法,以获得大量而精确的风蚀数据。集沙仪能够采集土壤风蚀过程中随风搬运的可蚀性颗粒,是观测风沙流结构和研究风沙运动规律的关键设备,对研究风沙运动的物理机制,揭示土壤风蚀的发生、发展和演化规律,有效防治土壤风蚀具有十分重要的作用。随着自动控制技术的广泛应用,研制具有较高测量精度和较高集沙效率的新型自动集沙仪,提高观测数据的连续性、科学性和可靠性,满足复杂多变的野外风蚀观测需求,成为相关研究领域重点内容。针对自动集沙仪存在的因强风风力对称重传感器产生冲击而影响测试数据的精确性以及风沙在集沙仪内部的高效分离等问题,提出气流分流对冲与多级扩容组合以大幅降低集沙仪内气流速度的思路,采用理论分析、数值模拟、试验分析等方法,在研究利用分流对冲降速原理设计的初期风沙分离器的基础上,对分流对冲与多级扩容组合式集沙仪及其内流场特性进行研究。建立风沙分离器物理模型,分析气流降速、气固分离与内流场特性的关系,探究气流的能量损失规律和影响集沙效率的主要原因,揭示分流对冲与多级扩容组合降速机理,设计单通道采集数据的分流对冲与多级扩容组合式自动集沙仪,并测试其性能指标,为开发多通道采集数据、集沙效率更高的自动集沙仪提供理论与技术依据。研究主要结论如下：(1)利用气流分流对冲降速原理,设计了集沙仪的关键部件—初期风沙分离器。试验表明,排沙口气流的降速幅度为86.42%,可减缓排沙口气流对集沙盒下称重传感器的扰动；排气管气流的降速幅度为88.17%,可收集粒径大于0.032mm的土壤颗粒,进气口的等动力性为92.03%,基本符合等动力性要求；风速为9-18m/s时的平均集沙效率为89.6%。(2)依据管道的扩张降速理论,提出气流分流对冲与多级扩容组合降速法,设计了改进型风沙分离器。试验表明,排沙口气流的降速幅度为93.45%,排气管气流的降速幅度为89.98%,可收集粒径大于0.024mm的土壤颗粒,进气口的等动力性为94.74%,平均集沙效率为91.25%。(3)湍动能场内分布着大量的脉动气流,脉动气流从时均流中提取了较多的、易耗散的能量,是气流能量损失的主要组成部分；改进型风沙分离器内气流能量的大量损失和速度的大幅度降低归因于湍动能场的形成。(4)当风速、土壤粒径分布、采集时间等一定时,对于具有较高气固分离效率的改进型风沙分离器,若要进一步提高集沙效率,关键是提高其进气口的土样采集效率。(5)分流对冲与多级扩容组合式自动集沙仪具备了抗强风干扰性能,可实时、连续和远距离无线采集数据,自由旋转的起动风速为4.23m/s,平均集沙效率为90.42%,数据自动采集与无线传输系统的供电续航能力达31小时以上,无障碍时信号传输距离为208.51m,可满足土壤风蚀量的自动观测需求。
[Abstract]:Research on soil wind erosion must be carried out by advanced means and methods to obtain large and accurate wind erosion data. Sand collector can collect erodible particles transported with wind in the process of soil wind erosion. It is the key equipment to observe the structure of aeolian sand flow and to study the regularity of aeolian sand movement, to study the physical mechanism of aeolian sand movement and to reveal the law of occurrence, development and evolution of soil wind erosion. With the wide application of automatic control technology, a new type of automatic sand collector with higher measurement precision and higher efficiency of Gao Ji sand is developed to improve the continuity, scientificalness and reliability of observation data. To meet the needs of complex and changeable field wind erosion observation, It has become an important research area in the related fields. Aiming at the problem that the impact of the symmetrical heavy sensor of strong wind wind on the accuracy of test data and the high efficiency separation of sand in the sand collector, the automatic sand collector has some problems, such as the impact of the strong wind wind symmetric heavy sensor, and so on. In order to reduce the airflow velocity in the sand collector, the method of theoretical analysis, numerical simulation, experimental analysis and so on is put forward. Based on the study of the initial wind-sand separator designed by using the principle of shunt hedging and deceleration, the characteristics of the combined sand collector and its internal flow field are studied. The physical model of the wind-sand separator is established, and the airflow deceleration is analyzed. The relationship between gas-solid separation and the characteristics of internal flow field, the law of energy loss of air flow and the main reasons of affecting the efficiency of sand collection are discussed, and the mechanism of velocity reduction of the combination of shunt hedging and multistage expansion is revealed. In order to develop multi-channel data collection, a single channel automatic sand collecting instrument is designed, which is composed of shunt hedge and multistage expansion, and its performance index is tested. The main conclusions are as follows: (1) the key component of the sand collector, the primary wind-sand separator, has been designed by using the principle of flow separation, hedging and deceleration. The experimental results show that, The velocity drop range of the outlet airflow is 86.42, which can slow down the disturbance of the sand outlet airflow to the weighing sensor under sandboxie, and the velocity drop range of the exhaust pipe airflow is 88.17, which can collect soil particles with diameter larger than 0.032mm. The isodynamic property of the inlet is 92.03, which basically conforms to the requirement of isodynamic property, and the average sand collection efficiency when the wind speed is 9-18m/s is 89.60.2.According to the expansion and deceleration theory of the pipeline, the combined velocity reduction method of gas flow shunt and multistage expansion and capacity reduction is put forward. An improved wind-sand separator was designed. The test results show that the velocity reduction range of the outlet flow is 93.45 and that of the exhaust pipe is 89.98. The soil particles with diameter larger than 0.024mm can be collected. The isodynamic property of the inlet is 94.74 and the average sand collection efficiency is 91.25. 3) a large number of pulsating airflows are distributed in the turbulent kinetic energy field, and a large number of dissipative energy is extracted from the time-averaged flow, which is the main component of the energy loss of the airflow. The great loss of air energy and the decrease of velocity in the improved wind-sand separator are attributed to the formation of turbulent kinetic energy field. (4) when the wind speed, soil particle size distribution, collection time, etc., are fixed, For the improved wind-sand separator with higher gas-solid separation efficiency, if the sand collection efficiency is to be further improved, The key is to improve the collection efficiency of soil sample at its inlet. (5) the automatic sand collecting instrument combined with diffluence hedge and multistage expansion has the capability of resisting strong wind interference, and can collect data in real time, continuously and remotely. The starting wind speed of free rotation is 4.23 m / s, the average sand collection efficiency is 90.422.The power supply capacity of automatic data acquisition and wireless transmission system is more than 31 hours, and the signal transmission distance is 208.51 m when there is no obstacle, which can meet the demand of automatic observation of soil wind erosion.
【学位授予单位】：内蒙古农业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S237;S157.1

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