Study On Bearing Capacity Of High-pressure Loop Network On Basis Of Region-scale Gas Load Characteristics

It is known to all that energy is one of the indispensable material bases in supporting social and economical development.As the demand for clean energy keeps growing,natural gas is going to play a crucial role in the future scene of energy consumption.Natural gas will be widely used in multiple fields such as urban gas supply,industrial fuel and manufacture process,especially in the promising urban gas supply field.In order to step up the pace of adjusting energy structure and achieve the goal of using green and low-carbon sources as the main energy,our country's need in natural gas will maintain a remarkable increasing tendency in the near future.With the advent of an upgraded energy consumption era,the energy market supply tend to be diversified and demand side gradually takes the dominant position.Thus gassing operation companies have to actively reform the supply-demand pattern,start a new energy production-supply-consumption mode from the perspective of demand side and strengthen the coordination and support capability of pipeline networks.A lot of medium-sized and large-sized cities have constructed comprehensive pipeline networks in the form of “X+1+X”,and established linked response mechanism among multiple stages of pipeline networks.High-pressure loop pipeline network serves as the lifeline of energy supply in a city,while connecting to sub-high-pressure or middle-pressure pipeline networks by download points(a.k.a.district regulation stations).Its main task is to indirectly supply gas to the end users from different districts,as well as adjusting the unevenness of hourly consumption.However,end users in the radiation range of each download point have various characteristics in gas consumption,which will directly affect the running condition of the whole transportation and transmission system,hence the extreme complexity of inherent operation laws in the high-pressure loop pipeline network.Studying the bearing capacity of high-pressure loop pipeline network is relevant to whether the demand at each download point under regular running condition is satisfied and whether the system's capability of gas storage and peak shaving in the peak hour is enough.Normally,traditional hydraulic analysis of a pipeline network takes planning as its goal and explores the network's operation laws at different gas supply capabilities from the perspective of supply side.As of now,most scholars simply analyzed gas load or network's running condition alone,ignoring the interaction between network and end users.From a systematical point of view,this dissertation emphasized on the interrelationship and interaction between the gas loads of network system and end users.During the shifting process of dominant position from supply side to demand side in the gas consumption market,oriented to the end users' demand,the network's bearing capacity was comprehensively studied by the means of hydraulic analysis.In the radiation range of each download point,various quantitative and qualitative factors that affect gas consumption lead to different characteristics of gas load.With the introduction of the concepts of region-scale and effective temperature,the spatial scale of gas load research was defined and the influence degree of thermal inertia on daily gas load was quantified.Besides,composing state and running condition of gas load under region-scale is analyzed through a practical case.The daily gas load under urban region-scale is normally periodic and has a nonlinear relationship with effective temperature and some other factors.After closely investigating historical load data,as well as some other main factors,an optimized combination of two models — nonlinear regression analysis and BP neural network — was set up to explore the inherent laws and changing trends of gas load.Then comparisons of forcasting accuracy between the optimized combination model and singular prediction models were made.With the expansion of urban gas consumption scale and the increase of gas users' numbers and types,higher requirements for the quantity and quality of urban gas supply were brought up than before,hence the trend of constructing a comprehensive network with multiple-source input and multiple-region output.Steady supply from upstream,uneven consumption of end users and the randomness of storage and venting inside the loop pipeline network,all these factors contribute to the extreme complexity of inherent running condition in the natural gas transportation and transmission system.A mathematical model of multiple-source input and multiple-region output was built,and green software based on Java programming language was developed,which is able to analyze the response laws to different gas consumption demands of the gas network and to trace the gas quality at each download point,respectively at certain gas supply pressure and certain supply flow.The outer-ring high-pressure network of CQ was studied in this paper to analyze its bearing capacity.It was shown that XP regulation station and YL regulation station have the lowest pressure in the network,which means special monitoring and adjustment are needed in the future to avoid a shortage of gas.What's more,the outer-loop pipeline network's theoretical gas storage capacity was found out to be less than the hourly peak-shaving demand of 2020 in CQ.In order to achieve the balance of gas supply and demand,other gas storage facilities and an emergency plan of gas supply are needed.