摘要
结合工程实例,对长距离重力流输水工程中减压消能技术进行了分析,介绍了减压阀的设置方式,并对其口径选择及配套设施进行了分析。根据可调式减压阀的特点,结合典型工程实例,对减压方案进行了比选,采用两级减压方案较为经济合理。利用KYpipe2010水锤分析软件进行了数学模拟计算,通过对稳态分析我们发现,设计在正常运行工况下,一、二级减压阀减压比均小于3,发生气蚀的可能性很小;在极端小流量工况下二级减压阀后减压比大于3,气蚀系数为0.52,阀后会出现气蚀现象,为防止气蚀发生,在二级减压阀处并联一个小口径的网孔套筒式调节阀(DN400),在小流量及极端小流量工况下,关闭大的减压阀,开启网孔套筒式调节阀,防止气蚀破坏;通过对关阀水锤计算,可以看出,末端关阀和减压阀的关闭存在一定的时间差,末端关阀时间应大于到减压阀处的压力波的传导时间,以确保减压阀正常关闭,达到减压效果。
The paper uses project cases to analyze the pressure reduction and energy dissipation technologies applied in long-distance gravitational flow water transport projects, introduce the placement modes of pressure reduction valves and make analysis on the diameter selection and supportive facilities of the valves. According to the characteristics of adjustable pressure reduction valves, the paper compares pressure reduction plans based on typical projects and believes that the two-stage pressure reduction plan is economical and reasonable. The KYpipe2010 water hammer analysis software is used in the mathematical simulation computing. By means of the steady state analysis, we have found out that, under the normal operation work condition, the pressure reduction ratios of the 1st and 2nd-stage pressure reduction were lower than 3, and the probability for cavitation erosion was quite low; under the extreme low flow work condition, the pressure reduction ratio after the 2nd-stage pressure reduction was higher than 3, and the cavitation erosion coefficient was 0.52. So, cavitation erosion may occur after the valve. In order to avoid the occurrence of cavitation erosion, a small-diameter mesh sleeve adjustment valve （DN400） is installed at the 2nd-stage pressure reduction valve in parallel. In case of small flow or extreme low flow conditions, the major pressure reduction valve will be closed while the mesh sleeve adjustment valve be opened to avoid the damages caused by cavitation erosion. By means of the computation on the water hammer when closing the valve, we may see that there is a time difference between the closing of the valve at the pipeline end and the closing of the pressure reduction valve. The time for closing the valve at the pipeline end should be longer than the time that the pressure wave reaches the pressure reduction valve in order to secure the normal closing of the pressure reduction valve and achieve the pressure reduction effect.
出处
《中国农村水利水电》
北大核心
2017年第10期143-147,152,共6页
China Rural Water and Hydropower
关键词
长距离
重力流
减压阀
关阀时间
long distance, gravitational flow, pressure reduction valve, valve-closing time
