【作者】 刘海星；

【导师】 王彤；

【作者基本信息】 长安大学 ， 市政工程， 2010， 硕士

【摘要】 给水管网是给水系统的重要组成部分,净化后的水经过错综复杂的地下管网,达到用户终端。一般给水厂出水水质都能达到国家规定的生活饮用水卫生标准,但通过给水管网送至用户时,水在给水管网中停留一段时间,在此期间会受到二次污染。管网中的“生长环”是造成二次污染的重要原因,清除“生长环”有利于提高供水水质和管道通水能力。对几种管道清洗方法对比得出,气压脉冲法是一种非常好的管道冲洗方法。提高气压脉冲法的冲洗效率,对减少管网水质的二次污染有重要的理论和实际意义。“生长环”是多种无机物、有机物、微生物的混合物。生长环的形成机制复杂,既受到物理沉淀、管道电化学腐蚀、化学稳定性、生物稳定性的影响,对金属管而言,也受到铁细菌、硫酸盐还原菌的腐蚀作用。“生长环”不仅影响给水管网水质,而且随着管道管龄的增长,“生长环”逐渐加厚,内壁粗糙,凹凸不平,增大了管道阻力系数,缩小了过水断面面积,从而直接影响管道的通水能力、供水水压,增加了供水能耗及漏耗。通过自行设计搭建的试验平台,对气压脉冲管道冲洗法的脉冲规律进行了研究。试验结果表明,确定供气压力和供水流量一定的情况下,保持停气时间不变,充气时间变化,初始流速、压力迅速增大,后期增速缓慢,且在充气时间为5s的时候,流速、压力达到极大值。保持充气时间不变,随着停气时间的增长,管内的流速、压力呈线性增大趋势,管道内水流紊动加剧,冲洗效果增强；供气压力一定的情况下,改变供水流量,得到供水流量与管道中水流流速、压力之间呈线性关系；供水流量一定的情况下,改变供气压力,得到供气压力与管道中水流流速、压力之间也呈线性关系。对实验管道进行气液两相数值模拟研究。针对实验管段,分别建立入口直管和弯管的网格模型。利用非稳态分离求解方法,对入口直管处气、水两相流进行数值模拟,在0.0005s、0.0010s、0.0015s和0.0020s时显示实时结果。对气、水两相流的流型进行分析,研究得出在一定边界条件下,实验管段会形成“弹状流”,分析了“弹状流”的能量转化过程、尾部涡流现象及其对“生长环”的去除作用。利用稳态求解器计算弯管流场,分析弯管内外侧所受压力,及管内流速的分布情况,研究证明弯管对“生长环”去除有一定影响。更多还原

【Abstract】 Water supply network is an important component of water supply systems. Purified water goes through the intricate network of underground pipes to users. General water treated by plants can meet the drinking water health standards. But sent to the user through the water supply network, the water has been stayed in the water supply network for a period of time. During this period water will be subjected to the secondary pollution. In pipe networks "growth ring" is an important factor to cause secondary pollution, so clearing the "growth rings" will help improve water quality and the capacity of pipes carrying water. Comparison of several methods of cleaning pipes, barometric pulse flushing is a very good method. Improving the efficiency of flushing of barometric pulse method, it has the important theoretical and practical significance to reduce secondary pollution in water supply network."Growth ring" is a mixture which consists of variety of inorganic matter, organic matter, and microbe. The formation mechanism of the growth ring is complex, not only effects of physically precipitation, pipeline electrochemical corrosion, chemical stability, and biological stability, in terms of the metal pipe, but also corrosion by iron bacteria, sulfate-reducing bacteria. Growth rings affect the water quality, and with the growth of pipe age, thickening and increasing roughness of wall, so increasing pipe resistance coefficient, reducing the cross section area, directly affecting the capacity of the pipeline transmission and head, and increasing energy consumption and leakage consumption.By designed and built the test platform, the pulses pattern of barometric pulse flushing method is studied. The results show that in a condition of the gas pressure and water flow and maintaining the time of filling air, with changes of the time of stopping air, flow velocity and head sharply increase at the beginning, and later steadily rise. When the time of filling air is 5s, the velocity and head reach the maximum. Remaining unchanged time of filling air, with the stopped time growth, the velocity and head increase linearly in the pipes. In a certain value of gas pressure, with the increase of water flow, velocity and head in the pipes are linear relation. In a certain value of the flow, with the increase of gas pressure, velocity and head in the pipes are also linear relation. Study on numerical simulation of two-phase gas-liquid in the experimental pipe. For the experimental pipe sections, grid models of the entrance straight section and the bend section are established respectively. Used separate non-steady solution method, numerical simulation is processed of two-phase gas-liquid in entrance straight section. Display real-time results at 0.0005s,0.0010s,0.0015s, and 0.0020s. The flow pattern of two-phase gas-liquid analyzing, a "slug flow" will be formed in some boundary conditions. The theory of "slug flow" explains the energy conversion process, its tail vortex and the effect of removing "growth rings". Calculate the flow field of bend section with steady-state solver, and analysis pressure and velocity within the pipe. Experiments demonstrate that the elbows of pipes affect to remove "growth rings" at a certain extent.更多还原