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Publisher : Elsevier - Science Direct (الزویر - ساینس دایرکت)
Journal : Simulation Modelling Practice and Theory, Volume 19, Issue 1, January 2011, Pages 196–212
This paper focuses on developing a simulation model for the analysis of transmission pipeline network system (TPNS) with detailed characteristics of compressor stations. Compressor station is the key element in the TPNS since it provides energy to keep the gas moving. The simulation model is used to create a system that simulates TPNS with different configurations to get pressure and flow parameters. The mathematical formulations for the TPNS simulation were derived from the principles of flow of fluid through pipe, mass balance and compressor characteristics. In order to determine the unknown pressure and flow parameters, a visual C++ code was developed based on Newton–Raphson solution technique. Using the parameters obtained, the model evaluates the energy consumption for various configurations in order to guide for the selection of optimal TPNS. Results from the evaluations of the model with the existing TPNS and comparison with the existing approaches showed that the developed simulation model enabled to determine the operational parameters with less than 10 iterations. Hence, the simulation model could assist in decisions regarding the design and operations of the TPNS.
Natural gas is becoming one of the most widely used sources of energy in the world due to its environmental friendly characteristics. Usually, the location of natural gas resources and the place where the gas is needed for various applications are far apart. As a result, the gas has to be moved from deposit and production sites to consumers either by trucks in the form of liquefied natural gas (LNG) or through pipeline network systems. As reported in , short distances gas transportation by pipelines is more economical than LNG transportation. The LNG transportation incurs liquefaction costs irrespective of the distance over which it is moved. As a result, the development of transmission pipeline network system (TPNS) for natural gas is a key issue in order to satisfy the ever growing demand from the various customers . When the gas moves by using the TPNS, the gas flows through pipes and various devices such as regulators, valves, and compressors. The pressure of the gas is reduced mainly due to friction with the wall of the pipe and heat transfer between the gas and the surroundings. Compressor stations are usually installed to boost the pressure of the gas and keep the gas moving to the required destinations. It is estimated that 3–5% of the gas transported is consumed by the compressors in order to compensate for the lost pressure of the gas  and . This is actually a huge amount of gas especially for the network transmitting large volume of gas. At the current price, this represents a significant amount of cost for the nation operating large pipeline network system. For instance, considering the US TPNS, Wu  indicated that a 1% improvement on the performance of the transmission pipeline network system could result a saving of 48.6 million dollars. Carter  also presented that the cost of natural gas burned to power the transportation of the remaining gas for the year 1998 is equivalent to roughly 2 billion dollars for US transmission system. Investigation on various TPNS indicated that the overall operating cost of the system is highly dependent upon the operating cost of the compressor stations which represents between 25% and 50% of the total company’s operating budget  and . Hence, compressor station is considered as one of the basic elements in TPNS.
نتیجه گیری انگلیسی
In order to analyze the various configurations of natural gas pipeline transmission network system, a simulation model was developed by incorporating the detailed parameters of the compressors. Speed of the compressor, flow rate, suction pressure, discharge pressures and suction temperature are included in the general compressor equation. These are critical elements which affect the performance of the transmission system. The developed TPNS simulation model enabled to determine pressure and flow parameters of the network under various conditions. The results for the unknown pressure and flow parameters were obtained with less than 10 iterations. From the convergence graphs of both the pressure and flow variables, it is observed that it took only from 4 to 6 iterations for the solution to get stable. The maximum relative percentage error at the end of the 10th iteration was less than 10−11. The performance of the system which includes, power consumption, compression ratio and flow capacity could be analyzed based on the parameters obtained. As a result, the model could assist in decisions regarding the design and operations of the pipeline network. The results of the TPNS simulation model were compared with two other models based on various pipeline network configurations. In the first case, the simulation model was compared to an exhaustive optimization technique based on gunbarrel pipeline networks system. The model yielded close solutions of nodal pressures with less than 1.8% absolute parentage errors. The comparison based on looped pipeline network also showed that, the TPNS simulation model was able to provide solutions to nodal pressures and flow variables with mean absolute error of 5.10% between the two methods.