Tag Archives: transport of natural gas
The main gas pipelines are the body of the gas transmission system. The main share of expenses of energy resources in the pipeline transport of gas belongs to this part of the system. Characteristics of the pipeline network, also as the set technological tasks, are defining factors for an operating mode of other equipment of system which settles down generally at compressor stations.
In this regard, it is very important to provide possibility of calculation of an operating mode of the main gas pipeline with sufficient degree of accuracy. For this purpose you have to consider all significant factors which influence operation of the main gas pipeline. The method of calculation shouldn’t contain insoluble difficulties of mathematical character.
In spite of the simple construction of the gas pipeline at first sight, it contains difficult processes of movement, friction, interaction with gravitation, internal and external heat exchange. These processes, as a rule, change in time therefore they are non-stationary.
The gas transmission system has the difficult scheme where simple gas pipelines are united in a transport network, the operating mode of all elements is interconnected.
The specified complexity of processes has rather difficult mathematical description of all these processes by means of the corresponding models, in this regard; obtaining decisions is accompanied by difficulties of mathematical character. Simplification of models for the avoidance of the specified difficulties can reduce their compliance to the described object.
The author of this work considers existing methods of calculation of simple gas pipelines, does their analysis.
The author classifies models concerning a scope.
The author revealed construction stages for all considered universal models.
By results of the research the author draws a conclusion about the necessity of the solution of the question of mathematical modeling of gas movement in the main gas pipeline and notes the productive directions of further researches of this subject.
The author of this work offers the way of definition of the internal calculating error of methods of the gas pipeline hydraulic calculation. The offered way is applicable both to stationary model, and to the most general case – to the model describing non-stationary process. This way is shown on the calculation of the known system of the equations which describes non-stationary process by “the way with variable coefficients”. But this way of calculation was considerably modified by the author for the accounting of heat exchange, and for gravity influences. But this way of calculation was considerably modified by the author for the accounting of heat exchange, and for gravity influences. The initial “way with variable coefficients” didn’t consider these factors that attracted considerable errors. The mentioned adjustment is described in detail by the author in the other publication. The offered way of definition of the internal calculating error of methods of the gas pipeline hydraulic calculation includes the analysis on each component of the initial equation of movement of compressed liquid. The author gives formulas for definition of influence of all factors entering this equation. The main thing of definition of an internal calculating error is the comparison of the sum of influence from all factors which sizes are received as a result of calculation for the chosen method with basic data for the same calculation. These data are provided to a uniform scale for possibility of carrying out procedure of comparison. As such scale the size of change of gas pressure in the course of its movement on the gas pipeline is accepted. The author defines changes of pressure according to the following factors: change of gas energy in volume because of not stationarity of process, change of kinetic energy of gas, influence of friction forces and weight. The sum of changes of all these factors pressure is compared with the general pressure difference on the gas pipeline that is set in basic data of calculation. Their distinction defines an internal calculating error of the estimated method. The offered way is shown on calculation of the concrete example. The author shows settlement ratios for all counted parameters, and results of calculation, are presented by numbers or graphically for the offered example.
Development of the calculation method of the non-stationary not isothermal operating mode of the main gas pipeline
The author of the work shows the necessity of the accounting of heat exchange for calculation of the really functioning gas pipeline. The concrete example shows that if heat exchange isn’t considered, calculation is made incorrectly. As known methods of the decision of the equations system, that describe non-stationary operating mode of the gas pipeline, don’t consider heat exchange and gravity influence, the author shows the necessity of development of the method which considers both these factors. For a start the author chooses the known “way with variable coefficients” which is used for the approximate decision of the equations system and which describes movement of gas on the pipeline. This way considers variability of parameters. However this way, as well as others, doesn’t consider heat exchange and gravity influence. For the solution of this problem the author suggests to use variability of parameters of the “way with variable coefficients” for addition of the specified factors accounting. The process of heat exchange and some other necessary parameters, for example, coefficient of hydraulic resistance, the author counts by means of system of ratios which is widely known in stationary modes calculations. Application of the offered method is shown on calculation of a concrete example. For all counted parameters settlement ratios are given, and results of calculation, in relation to the reviewed example, the author gives with the help of numbers or graphically in comparison for different stages of calculation. For calculation of expenses of power, ratios which are applied to non-stationary process are presented. These ratios are necessary for an assessment of power efficiency of applied regime decisions and their optimization which are the key research of problems in this direction.
The author of the work offers the way of delimitation of preferable application of a stationary model, and the model which describes non-stationary process of the gas pipeline operation. Scientifically reasonable choice of a settlement model is the key question for the gas pipelines calculation. The importance of such differentiation in practice is that it makes sense to use simpler stationary model if variability of parameters is not big and doesn’t entail inadmissible errors. The author of the work shows this way on concrete models: standard calculation of a stationary operating mode of the gas pipeline, offered, for example, in norms of design and the calculation of the well-known system of the equations which describes non-stationary process by “the way with variable coefficients”. This way of calculation was significantly modified by the author for the accounting of the heat exchange, and also, for gravity influence. The specified adjustment is described in detail in the other publication of the author. In the offered way of differentiation of scopes of stationary and non-stationary models of the gas pipeline hydraulic calculation, the comparison of results of calculation of both models according to the same regime data is used. Results of calculation of both models have to be compared in sizes of the calculated losses of energy of gas compression in the gas pipeline. The choice, for example, of this parameter is caused by that in the solution of the specific objective concerning the gas transport, the size of losses of energy of gas compression in the gas pipeline defines the main part of expenses of energy carriers at the compressor station. Therefore it is the key indicator in an assessment of an operating mode of the gas transmission system and in the choice of the most economically expedient option of an operating mode. The essence of definition of the required border consists in that the distinctions of results of calculation for both methods which are exposed to differentiation, are comparable to errors of these methods. The application of the offered way is shown on calculation of the concrete example. For all counted parameters, settlement ratios are offered, and results of calculation, for the reviewed example, presented by numbers or graphically.
The author of this work analyzes features of collaboration of gas cooling knot and the main gas pipeline; structure, scheme and way of regulation of work of gas cooling knot. The author shows basic formulas for calculation of parameters of operation of the main gas pipeline, the device of air cooling of gas, technical and economic indicators of operation of gas-distributing units on compressor station of the main gas pipeline. All possible options of sequence of turning on of fans on devices of gas air cooling are studied in this article. These options are estimated from the economic point of view. The author points to the most economically expedient option, when at the exit of compressor station you at first turn on one fan on each device, then – the others, if necessary for fall of temperature of gas. The author does calculation of several options of collaboration of AVO gas and the gas pipeline at different sizes of a commercial consumption of gas, temperature of external air and number of the switched-on fans. Results of calculations are presented in the form of charts of expenses. The received charts showed unequal tendencies for different cases. Therefore the author draws a conclusion about need of development of a way of finding of economically expedient option of turning on of AVO fans taking into account a technological mode of the gas pipeline. The regularities concerning dependence of expenses on a site of the gas pipeline from reference temperature of gas, are formulated and shown on examples in this article. The author showed that schedules of dependences of expenses on a gas pipeline site from the reference temperature of gas at different sizes of a commercial consumption of gas look like proportional dependences in all range of changes of reference temperature of gas and temperature of atmospheric air. On the basis of research materials the author offers the scheme of ratios for a simple way of definition of an expedient mode of turning on of fans on the knot of gas air cooling taking into account a technological mode of the gas pipeline. The author gives the concrete examples which show economic feasibility of optimization of collaboration of knot of gas air cooling and the gas pipeline with application of the offered express method.