清扫车气力输送系统设计与吸嘴流场仿真

发布时间：2019-06-29 15:25

【摘要】：近年来,经济发展迅速,城市化进程加快,给城市环卫工作带来了压力。而人们的环保意识逐步加强,对环境质量的要求越来越高。同时,我国公路总里程逐年增加,高速公路总里程也升至世界第一。机械化,现代化的道路清扫方式成为道路养护必然的发展趋势。政府对环卫工作越来越重视,投入不断增大。道路清扫车凭借其清扫效果好,清扫成本低等优势,成为了道路环卫的主要工具,得到了广泛应用。因此,清扫车市场十分广阔,技术水平也快速发展。本文首先研究了空气的物理性质、流动规律以及尘粒的物理性质和一些参数。尘粒在气流中主要受到的力有:气流阻力、上升力、冲击力及重力。其中,冲击力对尘粒的起动起主导的作用。通过对尘粒受力分析,得到了尘粒的起动机理,简而言之即气流速度超过尘粒的起动速度后,尘粒滚动而相互碰撞,受到冲击力起跳。而后计算出两个重要的参数:尘粒的起动速度以及尘粒的悬浮速度,为后面气力输送系统的设计、仿真以及结构优化提供了理论和数据支持。然后对气力输送系统两个最重要的部件的设计理论进行了研究。吸嘴的设计要做到符合清扫车行业标准、结构合理、气流速度分布合理、流场能量损失小等原则。对吸嘴各个结构参数进行了分析。对于其中最重要的参数收缩角α,研究了它影响流场气流速度分布和压力损失的原理。这对分析吸嘴流场以及对吸嘴结构进行优化至关重要。接着通过对风机风量风压的计算,得到风机的选择原则。吸嘴内流场能量损失有两种:局部损失和沿程损失。其中局部损失来源于吸嘴和风道连接处的形状变化,比如收缩角处,气流在形状变化的位置流向急剧变化,形成涡流,这也是流场分布不合理的主要原因,因此在优化结构设计时也要针对减小局部损失这个问题,使吸嘴内空气流动尽量平滑,减小气流方向急剧变化的情况,从而对吸嘴的形状进行改善。对本文研究的吸嘴进行了仿真,从仿真结果可以看出,当前吸嘴流场分布存在不合理之处,会导致吸尘效率降低,需要改变吸嘴结构使气流分布更合理。最后根据减少局部损失这个原则,对吸嘴肩部两个结构不合理之处进行了改进。修改模型后重新仿真。证明了改进后的结构更有利于尘粒加速和起动,并大大减少了能量消耗,提高了清扫效率。
[Abstract]:In recent years, the rapid development of economy and the acceleration of urbanization have brought pressure to the work of urban sanitation. However, people's awareness of environmental protection is gradually strengthened, and the requirements for environmental quality are getting higher and higher. At the same time, the total mileage of highway in our country increases year by year, and the total mileage of expressway also rises to the first in the world. Mechanization and modernization of road cleaning have become the inevitable development trend of road maintenance. The government pays more and more attention to sanitation work and invests more and more. Because of its good cleaning effect and low cleaning cost, road sweeper has become the main tool of road sanitation and has been widely used. Therefore, the market of sweeper is very broad, and the technical level is also developing rapidly. In this paper, the physical properties of air, the flow law, the physical properties and some parameters of dust particles are studied. The main forces of dust particles in the air flow are: airflow resistance, lift force, impact force and gravity. Among them, the impact force plays a leading role in the starting of dust particles. Through the analysis of the force acting on the dust particles, the starting mechanism of the dust particles is obtained. In short, after the air flow velocity exceeds the starting speed of the dust particles, the dust particles roll and collide with each other, and are taken off by the impact force. Then two important parameters are calculated: the starting speed of dust particles and the suspension speed of dust particles, which provides theoretical and data support for the design, simulation and structural optimization of the rear pneumatic conveying system. Then the design theory of two most important components of pneumatic conveying system is studied. The design of suction nozzle should meet the standards of cleaning car industry, the structure is reasonable, the distribution of air flow velocity is reasonable, and the energy loss of flow field is small. The structural parameters of the suction nozzle are analyzed. For the most important parameter shrinkage angle 伪, the principle that it affects the velocity distribution and pressure loss of flow field is studied. This is very important for analyzing the flow field of suction nozzle and optimizing the structure of suction nozzle. Then through the calculation of fan air volume and wind pressure, the selection principle of fan is obtained. There are two kinds of energy loss in the flow field in the suction nozzle: local loss and along-way loss. Among them, the local loss comes from the shape change at the connection between the suction nozzle and the air duct, such as the sharp change of the flow direction in the shape change position and the formation of vortex current, which is also the main reason for the unreasonable distribution of the flow field. Therefore, in optimizing the structural design, we should also aim at reducing the local loss, make the air flow in the suction nozzle as smooth as possible and reduce the sharp change of the direction of the air flow. In order to improve the shape of the suction nozzle. The suction nozzle studied in this paper is simulated. From the simulation results, it can be seen that the current flow field distribution of the suction nozzle is unreasonable, which will lead to the decrease of the cleaning efficiency, and it is necessary to change the suction nozzle structure to make the air flow distribution more reasonable. Finally, according to the principle of reducing local loss, the unreasonable structure of suction nozzle shoulder is improved. Modify the model and re-simulate. It is proved that the improved structure is more beneficial to the acceleration and starting of dust particles, and greatly reduces the energy consumption and improves the cleaning efficiency.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U469.691

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