Transient Analysis Of Natural Gas Systems

The regional distribution of natural gas resource is unbalance in China, so the research of natural gas transmission and distribution engineering play an important part in energy industry. The accuracy of hydraulic analysis of natural gas pipe networks affects the engineering, investment and reliability of pipe networks greatly. The parameters of the natural gas networks are variational, so transient analysis plays a dominant role in the hydraulic analysis.The transient flow model of natural gas systems is founded based on the momentum equation and continuity equation for transient flow and the state equation of natural gas. The settlement about some boundary conditions and initial conditions in natural gas systems are proposed. Transient flows of natural gas systems under different conditions are simulated and analyzed by two numerical algorithms. The compute programs of the two methods have been compiled with compute language C++.Up to now, the Method of Characteristics (MOC) is the main method used to numerically solve the control equations of the gas transient flow in pipelines. This method has preciseness theory and the physics meaning is definitude, so that it is convenient to programme in computer with high accuracy. The MOC is easy to deal with all kinds of boundary conditions and need a little computer memory spaces. The ratio of the time step and the distance step is restricted by the stability condition in MOC, so that the time step is limited. Comparatively, the calculation of slow transient using the MOC takes much time for complex gas network systems.The MOC including inertial multiplier is presented in this paper. By using the inertial multiplier, it is flexible to choose the time step and able to satisfy the computation precision under different transient conditions. It is good for the design and the operation of natural gas systems.