The Study On Transient Characteristics And Safety Protection Of Pressure Piping System

So far, channel hydraulic pipeline and piping hydraulic pipeline were two ways which were mostly used in large flow and long distance water supply project. Channel hydraulic pipeline was relatively old, and there was a great flow of water seepage and evaporation, which was unfavorable to sustainable development of water resource. But piping hydraulic pipeline was a new water transport ways, which had obvious advantages and had been widely adopted within the scope of industrial water and city life water in the world. Although the piping hydraulic pipeline had obvious advantages, it always caused transient high pressure or low pressure in pipeline because of suddenly closed and opened of valve and suddenly stopped of pump in the pressure pipeline water supply, which seriously damaged the safety of pipeline and caused significant economic losses and the safety accident. Therefore, the study of hydraulic transient theory of water transport pipeline, looking for methods of control and protect of hydraulic transients, was of great significance to ensure the safe operation of the project. With the continuous development of modern large-scale and long-distance water transport project, people had paid more and more attention the transient characteristics and security research of water transport systems.This paper was based on the background of pressure pipeline system, focused on the IAB friction model to simulate the hydraulic transient, and put forward Simpson method to integral the model friction term, and verified the proposed unsteady friction model by using model test; it studied a variety of commonly used protective measures applicable conditions and working principle, and gave its boundary conditions; in addition, it also discovered and resolved the exist problems in simulating water supply engineering based on transient model.Study work and achievements was include as follows:(1)This study elaborated research status of domesticand abroad about the transient friction model and security protection and identified existing problems and deficiencies.(2) Based on the understanding of researching pipeline hydraulic transient required a more accurate model,-qualitative analysis was carried out for several classes of transient friction model, and gives the Simpson treatment and discrete grid of friction term of IAB friction model;By using the model test, qualitative analyzing the consistent level between simulation results and actual measured pressure value of quasi-steady friction model and IAB unsteady friction model, and comparative analysis of advantages and disadvantages of two models.(3) Through conducting the numerical example to Brunone friction coefficient k value that calculated by two empirical formulas espectively, verifying the accuracy of the coefficient k of the original empirical formula, and studying the influence of the coefficient k on IAB model.(4) On the basis of the IAB model, studying the relationship between closing valve time and maximum indirect water hammer and its occurring moment by simulating the different closing valve time;The influence of time step At which calculated by Simpson difference grid on the simulation precision,and putting forward the scope of the reasonable value of At.(5) Discussing the protection mechanism and working principle of safety measures of a variety of transient flow in detail, and giving the boundary conditions, to provide the basis for the choice of safety protection schemes.(6) Combining the IAB friction mode with the boundary condition of safety protection measures, to develop the decision supporting system of the safe operation of the pressure pipeline water conveyance project, and through the engineering examples to conduct the computer simulation of hydraulic transient process of the project, to put forward the safe and reasonable operation way of water conveyance system, and to verify the validity of the system software.