Analysis And Application Of Negative Pressure Protection Measures For Long Distance Cross-sea Pipeline Transmission Systems

Water transfer engineering is one of the most effective engineering measures to optimize the allocation of water resources and to guarantee basic water in water-scarce areas.Among the water transfer projects,the pressurized water transfer project of the cross-sea pipeline has received greater attention with the development of the marine economy.In order to improve the negative pressure protection ability in the transition process of the trans-sea pipeline pressurized water transmission system and to provide a reference basis for the selection of water hammer protection measures in the trans-sea pipeline,this paper analyses the negative pressure protection effect of the transition process of the long distance trans-sea pipeline water supply project for different negative pressure protection measures:based on the water hammer characteristic line method and the water transmission system hydraulic element control equation for association,the trans-sea pipeline transition process is established The process calculation model,the development of the corresponding application software,numerical simulation as the main research method,the loss of power to the trans-sea pressurized water transmission system for the loss of pumping state numerical simulation,to explore the effect of a variety of water hammer protection measures for the trans-sea pipeline for joint protection.The analysis and application is also combined with actual engineering for more complex practical engineering situations.The research in this thesis has led to the following results:(1)Analysis of the hydraulic dynamic characteristics of various types of hydraulic components that may be encountered in water hammer calculations for long-distance cross-sea pipeline transmission systems,and the establishment of various types of boundary condition equations.The compatibility equations with water hammer are coupled to construct a simulation model of the hydraulic transition process of the long-distance cross-sea pipeline water transmission system.(2)Based on the established mathematical model of the hydraulic transition process of the long-distance cross-sea pipeline transmission system,the programming language is applied to develop the hydraulic transition process calculation program.The program can be configured to splice the hydraulic components available in the long-distance cross-sea pipeline transmission project:air valve,pressure regulating tower,one-way water replenishment tower,air tank and intake and exhaust valve.It can be easily and quickly configured and spliced to obtain accurate simulation results of the hydraulic transition process of long-distance cross-sea pipeline transmission system.(3)Using the generality of the hydraulic transition process calculation program,the use of different negative pressure protection measures on the long-distance cross-sea pipeline water transmission project of the pump loss of power conditions to analyze and study the effect of protection,the combination of the use of pressure regulating tower,one-way water replenishment tower,air tank protection measures,the conclusion that the joint protection measures on the cross-sea pipeline water hammer has a positive protective effect.(4)The transition process analysis and calculation was carried out with the example of Zhoushan city mainland water diversion Lanshan pumping station-Golden Bay reservoir water supply project,put forward the engineering measures of negative pressure protection,proposed after the pump valve according to the "two sections of the folding law" to close.The research results show that for cross-sea projects,a single water hammer protection measure is often difficult to effectively carry out water hammer protection for the whole pipeline.Joint measures need to be considered to protect against negative pressure.For this project,increasing the rotational inertia of the pumping unit and setting up an underground air tank and a one-way water replenishment tower at the sea inlet is less difficult to construct,less costly and has the best protection effect.