Study On Hydraulic Parameters And Key Design In The Vacuum Sewer System

As a new drainage technology, vacuum sewer system is a favorable add to the traditional gravity drainage system. The researches on basic theory and engineering practice of vacuum sewer system of foreign countries are relative mature, but still not sufficient in china. Therefore, study on hydraulic parameters and key design in the vacuum sewer system has a positive theoretical and engineering significance.Environmental, technical and economic and other reference factors of choice for vacuum sewer system, and the work procedures and design steps after project is selected is firstly pointed out in the paper. Then the design approaches of design flow and trunk diameter are given out; different definition and different design approaches of air-water ratio is specified, and it is deduced that system energy consumption is mainly from vacuum pump, and aggrandizes with the increase of air-water ratio. based on the different situations of system, the composition of vacuum pipe pressure loss,the mechanism of generation and the limit conditions it should meet are described,;four calculation approaches (Modified Hazen-Williams,A-H,Dukler and Duan Jinming) of vacuum pipe friction loss are summarized and deduced respectively based on single-phase flow, homogeneous flow, phase flow, and drift flow models. Experiment shows that the foreign classic formula (Modified Hazen-Williams) is closer to the experimental results, and the two-phase coefficient increases with the increase of air-water ratio.Lastly, combining theoretical researches and engineering experiences at home and abroad, the key technologies when the specific installation of vacuum pipeline are summarized, including the vertical section design of the pipeline, pipe connections and some other important considerations. And then, some new design approaches are put forward when vacuum pipeline through a barrier due to the disadvantages of big vacuum loss in the traditional design,Finally, the work principles of the equipments in the vacuum station are introduced, and then according to the different vacuum generating device, the vacuum station is divided into three types, performance characteristics of vacuum pump station and cam pump station are compared. The theoretical derivation of the design parameters of the equipments is given and the principles which should be referred to are pointed out when equipments selection in the paper. Meanwhile, basing on an outbuilding vacuum sewer system example project, the application of the design methods given in the paper for system parameter design and equipments selection is specified. The final calculation results successfully demonstrate that the specific design approaches provided in the paper are of feasibility and guidance in the actual project.