Study On The Fast,Accurate And Robust Simulation Method For A Complex Natural Gas Pipeline Network And Its Application

With the fast construction of natural gas pipeline,nationwide natural gas pipeline network will be popular in our country.The nationwide pipeline network,especially the loop structure in the network,makes the flow condition more complicated,and brings great difficulty for operation management,scheduling and allocation.Flow simulation is one of the core technologies in natural gas pipeline network industry,and it is of great significance to conduct study on advanced simulation method for natural gas pipeline network is of great significance.On the basis of comprehensive analysis of topological structure in natural gas pipeline network,mathematical models are respectively established for each element in the pipeline network by analyzing their respective function.And the complete mathematical model of natural gas pipeline network is further constructed.Then,the mathematical model is discretized based on linearization technique,and the decoupling method is employed to enhance the efficiency of hydraulic and thermodynamic calculation.In addition,one fast,accurate and robust simulation algorithm is developed for natural gas pipeline network simulation.The influence on the computation accuracy and speed of different combinations of basic solving variables is investigated by qualitative analysis of solving procedures and quantitative comparisons of calculation time.It is found that time consumptions of simulations vary greatly when different variables are chosen as basic solving variables.The main reason is that the calculation procedures of the coefficients in discrete equations are different.The density-velocity couple is found to be the best basic solving variables.The primary adaptive simulation method for natural gas pipeline network simulation is developed,which is based on the combination of local error control and multilevel grid system.Then,improvements are made for the prediction of time step,interpolation of pressure and relocation of spatial grid in the improved adaptive simulation method.It is found that,through the primary adaptive simulation method,real-time adjustment of time step and spatial grid system are achieved to allocate the calculation resources on demand,which lead to the great decrease of time consumption in the simulation while the accuracy is ensured.The sensitivity,accuracy and robustness are further improved in the improved adaptive simulation method.The highly efficient solving algorithm for large sparse matrix is proposed based on “divide and conquer method”.This algorithm can separate the large sparse matrixes into several block-shape and band-shape small matrixes,and then we employ chasing method and conjugate gradient method to solve the small matrixes.Such algorithm for solving large sparse matrixes is simple,practicable,efficient,and effective to overcome the low speed problem of traditional methods.Through large numbers of cases,the simulation result by the present method is found to be in good agreement with that by Stoner Pipeline Simulator(SPS),which is the well-known international commercial pipeline simulation software,moreover the present method is two times faster than SPS in computation speed.Besides,the time consumptions linearly increase as the number of grid and pipeline network elements increases,which means that the proposed algorithm could deal with the expansion of pipeline network scale.Based on the above studies,a program for pipeline network simulation is developed and the program is testified by data in literatures as well as measured data.Then,the program is applied to one actual pipeline network.Through large amount of simulations and analysis,the influences of operation plan change and accident on operation characteristics are identified,which can offer significant guide to safe management as well as efficient operation of natural gas pipeline network.