Based on the mutual coupling effect among the compressor, the air cooler and pipes in the system of natural gas pipeline, innovatively with the goal of minimum energy consumption, this paper established a combined operation optimization model of the air cooler and compressor through the optimization of the switching scheme of compressors and air coolers, which can greatly reduce the production energy consumption of the pipeline system. Moreover, when the air temperature is taken as an optimization variable, the most proper temperature to start the air cooler of each compressor station can be worked out to guide the optimized operation of the pipeline, which is of high value for promotion and application. The case analysis of west-east natural gas pipeline II showed that among genetic algorithm (GA), particle swarm optimization (PSO), and simulated annealing (SA) algorithm that are used to solve the optimization model, the genetic algorithm is the fastest, and the simulated annealing algorithm the slowest, but the optimization results of the simulated annealing algorithm is the best, in which the reduced production energy consumption accounted for 33.77%, testifying the practicability and creativity of the optimization model. INDEX TERMS Natural gas pipeline, air cooler, compressor, operation optimization, algorithm.

A pipeline operation optimization model with minimum energy consumption as the objective function was established based on the dynamic programming method. The model was applied to a 3840 km gas pipeline whose designed pipeline capacity was 170 3 10 8 t/a. There were 40 stations in the line, including 22 compressor stations and 32 compressors. The solution time was controlled within 60 s to show that the algorithm was fast and effective. The number of startingup compressors in the optimized scheme is two more than that in the actual operation scheme, and the total pressure drop of the pipeline decreased by 3.40 MPa, the average efficiency of the gas turbine units increased by 4.234%, the average efficiency of the electric drive units increased by 4.875%, and the power decreased by 18,720.38 kW, confirming the validity and feasibility of the optimization model.

In view of the complicated heat transfer calculation for air coolers and the difficulty of directly calculating the exit temperature of natural gas in a compressor station, taking the dry air cooler of model GP12 × 3-6-258-13.0S-S-23.4/DR-Ia configured in the West-East Natural Gas Pipeline II as an example, a three-dimensional simplified model of the air cooler is established. The model is used to simulate a temperature flow field of a dry air cooler-finned tube based on Fluent flow field analysis software. This paper studies the cooling effect of the dry air cooler-finned tube on high-temperature and high-pressure natural gas at compressor outlet. By comparing and analyzing the relationships among natural gas mass flow, inlet air temperature, inlet natural gas temperature, and outlet natural gas temperature for an air cooler, the formula of temperature drop of dry air cooler to natural gas is fitted, and the fitting formula is verified by field operation data. The results show that the average error between the fitting results and the actual data is less than 1.5%, which proves the correctness of the fitting formula and greatly simplifies the heat transfer calculation process for air coolers. K E Y W O R D Sdry air coolers, finned tube, optimization, outlet natural gas temperature

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