Simulation Modeling And Leakage Fault Diagnosis Of Complex Central Heating-Network

The development of urban central heating system in China has been gradually mature.While the level of automation is still low from the short of controlling experience towards heating system.Some operation faults often occur,such as the hydraulic imbalance,leakage and so on.Building establishing hydraulic working-condition simulation model and leakage diagnosis model according to the complexity of heating-network topology is proposed though this thesis with the goal of understanding the operation rules of urban central heating system clearly,simplifying the modeling of heating-network reasonably,and diagnosing leakage locations of heating-network.This method is applicable to the actual heating-network universally.The simulation modeling of heating-network is conducted based on the network-graph theory,Kirchhoff’s law,ring-network leveling.The actual urban central heating-network in Shandong Province is adopted as the research object.The modeling scheme according to the complexity of heating-network topology is proposed.The hydraulic intersection locations are determined,which combines the flow direction and minimum closure error towards ring heating-network.In order to highlight the hydraulic characteristics of the ring network and verify the accuracy of the proposed method for determining the hydraulic intersection location,three kinds of hydraulic working-condition simulation models are built in terms of three complexity levels of heating-network,which are primary model,secondary model and tertiary model respectively.After that,the simulation model is verified for the three normal operating working-conditions,and the results show that for any simulation model,the absolute value of maximum relative error for the simulated and actual pressure of the heat source and the user is less than 10%,which proves the effectiveness of the simulation model.In addition,the more complex heating-network topology is,the lower simulation error with the higher cost of modeling.Then,the hydraulic simulation model of the ring-network is adopted to verify the hydraulic intersection location method.The results show that for the three conditions,the maximum error absolute value for the flow rate of users and pipe sections and the corresponding actual flow rate in the simulation model after the judgment of the hydraulic intersection location is less than 0.1m~3/h,which proves the method could determine the hydraulic intersection location accurately with the ensuring of the effectiveness of the simulation model.Finally,based on the established simulation model of hydraulic conditions,the research towards leakage fault diagnosis of actual central heating-network is conducted.In this thesis,a graded leakage diagnosis method based on the variable point theory CUSUM is proposed in order to diagnose the leakage faults of the heating-network efficiently.In order to verify the effectiveness of this method to diagnose heating-network leakage,four one-point leak conditions and four two-point leak conditions are selected to research.The results show that the leakage start time could be accurately diagnosed under all leakage conditions,and the leak alarm signal could be issued within 80s.In addition,the absolute value of the maximum relative error between the simulated and actual leak flow is less than 10%.For the leakage conditions studied in this thesis,the diagnostic accuracy of the leakage location could reach 75%,which proves the effectiveness of the CUSUM leakage fault diagnosis method in leakage alarm,leakage flow calculation and leak location diagnosis,which could be applied to the actual heating-network leak detection.