Study On Transportation Function And Safety Of Air-light Hydrocarbon Mixing Gas Pipe Network

When the air-light hydrocarbon mixing gas is used as residential gas by the point distributed energy supply system,the transportation function and safety problems must be solved in the pipe network designed according to the specification of natural gas residential pipe network for transporting air-light hydrocarbon mixing gas.The research on the transportation function and safety of air-light hydrocarbon mixing gas in the small-scale civil residential pipe network is a basic scientific issue for new gas applications,and it is of great significance to the application of air-light hydrocarbon mixing gas.The transmission and safety theory of air-light hydrocarbon mixing gas pipe network is studied.Compared with the transmission of natural gas residential pipe network,the dew point problem is the main safety problem of air-light hydrocarbon mixing gas.Theoretically determined the form of the air-light hydrocarbon mixing gas transmission pipe network,analyzed the calculation of gas physical parameters,according to the flow law and safety requirements in the air-light hydrocarbon mixing gas pipe,established the continuity equation,motion equation,energy equation and state equation of the air-light hydrocarbon mixing gas.By means of theoretical derivation and software simulation,the pressure drop variation of air-light hydrocarbon mixing gas transported by natural gas residential pipe network is studied.A branched pipe network model for residential buildings was established,and the pressure drop formula for gas transportation in the pipe network model was theoretically deduced.Through the deduced pressure drop formula and Pipeline Studio simulation software,the pressure drop of natural gas and air-light hydrocarbon mixing gas was studied and compared,and the change rule and reason of the pressure drop of the two kinds of gas transporting were obtained.Under the same transportation conditions,the pressure drop of air-light hydrocarbon mixing gas obtained from theoretical pressure drop formula derivation and software simulation is about 2.4 times and 2.3 times of the average pressure drop of natural gas.When the natural gas pipe network of residential buildings is directly used to transport air-light hydrocarbon mixing gas,it is suggested to appropriately increase the transportation pressure.Taking the established air-light hydrocarbon mixing gas branched transmission and distribution pipe network system model as the research object,the change law of pressure drop from the air source to the farthest end of the pipeline and its influence on the transportation function of the most disadvantageous users at the farthest end of the pipeline are studied under different conveying pressure,different user loads and different number of the valve opening and closing in non-isothermal state.The pressure drop of air-light hydrocarbon mixing gas branch pipe network from the gas source to the farthest end of the pipe under different non-isothermal steady state transportation conditions was simulated,the transportation function of the pipe network was analyzed,and the improved gas source pressure was obtained,on the basis of the steady-state simulation,the transient simulation results of the transient pressure and flow rate of the farthest end users with the change of valve opening and closing were obtained,and the influence of the pressure and flow rate parameters on the user’s transportation function was analyzed.The results show that part of air-light hydrocarbon mixing gas users can not meet the transportation function designed according to the natural gas pipe network under the general transportation conditions and other transportation conditions,and can only meet the gas consumption of part of users after increasing the transportation pressure,the moment when the valve is opened and closed,it will cause the most disadvantageous user’s gas parameter fluctuation at the farthest end of the pipeline,under the premise of satisfying the user’s flow usage,the fluctuating pressure will exceed or be lower than the defined value to meet the user’s normal usage.The dew point safety of air-light hydrocarbon mixing gas pipe network with different number of users’valves opening and closing is studied.The phase equilibrium constant method is used to calculate the dew point of air-light hydrocarbon mixing gas under different mixing ratios and different pressures,the mixing ratio of air-light hydrocarbon mixing gas is determined,the dew-point safety of air-light hydrocarbon mixing gas at the end of the pipe network with different number of users at the opening and closing moment is studied and analyzed.The results show that the temperature of air-light hydrocarbon mixing gas is always above the dew point line,which ensures the safety of air-light hydrocarbon mixing gas transmission and distribution under the condition of the change of gas source transportation pressure and gas temperature.The study on the transportation function and safety of air-light hydrocarbon mixing gas pipe network can guide the applicability of air-light hydrocarbon mixing gas for natural gas pipe network and the transformation of natural gas pipe network,and play a certain reference role in improving the existing problems in the gas specification based on natural gas transportation.