Method of characteristics for the problems of stages of the serviceability check of elementary section of a gas pipeline for operation

The article is devoted to modeling the gas-dynamic state of an elementary section of a gas pipeline during gas injection and its outflow through the choke in the final section of the pipe and to solving these problems using the method of characteristics. The subject of the study is the gas-dynamic state of an elementary horizontal section of a gas pipeline in the process of checking its serviceability for operation. The processes of gas injection into the section and gas outflow from it, considered in the article, were modeled using the N.E. Zhukovsky formula on gas outflow into unbounded space in a framework of the short pipeline approach. The original equations are linearized by introducing the mass flow rate of gas and waves traveling in two directions. When solving the problem, the method of characteristics was applied; numerical results were obtained and analyzed using an analytical solution to the problem. The research methods are based on the laws of conservation of momentum and gas mass, the d’Alembert method for solving a system of hyperbolic equations and the methods of conducting a computational experiment. An analytical solution to the problem with a rupture caused by an instantaneous change in the gas pressure at the end of the section is obtained. It is shown that the process proceeds with the formation of compression and rarefaction waves, and their multiple reflections at the ends of the section. The gas in the section tends to a state of rest with time, and the changes in the mass flow rate and gas pressure are of exponential nature.

DEVELOPMENT OF ANALYTICAL APPROACHES FOR DETERMINATION OF STORAGE CAPACITY OF RELIEF GAS PIPELINE TAKINGINTO ACCOUNT INERTIA FORCE

New analytic formulas were obtained for storage capacity of the elementary section of the gas pipeline, taking into account the inertia of gas and linear change of leveling height of pipeline route. On their basis numerical simulation and analysis of change of this indicator in length at various static conditions of functioning of the gas pipeline were conducted.