Research On Dissimilar Hydraulic Conditions Structure Of Branched Heating Network And Identification Of Pipe Friction Parameters

District heating systems is indispensable in northern China,which has large scale and complex structure.Therefore,it is important to establish an accurate and reasonable hydraulic simulation system for operation management and fault diagnosis of heating system.The key problem to establish the hydraulic simulation system is to obtain the friction parameters of the pipeline,because it is difficult to obtain the friction parameters of the pipeline in the heating network.In this paper,the identification method based on generalized inverse theory was used to study the identification calculation under different hydraulic conditions.The influence of different hydraulic conditions on the identification calculation was analyzed to find a hydraulic condition adjustment method that can improve the identification accuracy.In this paper,the hydraulic calculation model of the fluid network of the heating system was established based on the laws of mass conservation and energy conservation.Then the solving steps of the node analysis method were introduced;Then,the system observability theory and Moore-Penrose generalized inverse theory that need to be used in the friction parameters identification were introduced,and the friction parameters identification method of branched heating network under multiple hydraulic conditions was derived.Due to the fact that some users in the branched heating network have some similar conditions with equal ratio and consistent imbalance,when there are some similar conditions,it will lead to identification does not meet the observability conditions.Therefore,this paper proposes a user valve regulation method for branched heating network to construct non-similar conditions.Based on the established theoretical model of branched heating network,the accuracy of the identification method based on the generalized inverse theory under this identification model was first verified.In addition,the conditions of partial similar working conditions and the conditions considering observation error were studied,and it is pointed out that in order to ensure the identification accuracy,the identification conditions need to be non-similar hydraulic conditions.In order to improve the identification accuracy under the condition of considering the observation error,the identification of different numbers of non-similar hydraulic conditions was studied.The results showed that increasing the number of non-similar hydraulic conditions can improve the identification accuracy.With the increase of the number of non-similar hydraulic conditions,the average identification error decreased from 39.23% to 3.07%.Then,considering the observation error,the influence of the pipe network size on the identification results was studied in this paper.After analyzing the identification results,a construction method of non-similar hydraulic conditions after optimizing the adjustment mode was proposed,and the construction method of non-similar hydraulic conditions after optimizing the adjustment mode was verified under the conditions of large-scale pipe network and different instrument accuracy.The average identification error in large-scale pipe network is 8.39%.When the instrument accuracy is high,the identification error is less than 5%.When the instrument accuracy is low,the identification error can also be less than 20%and most of the identification results are less than 5%.The results showed that the construction method of non-similar hydraulic conditions after optimizing the regulation mode can significantly improve the identification accuracy and the identification effect.