Simulation of the transient flow in a natural gas compression system using a high-order upwind scheme considering the real-gas behaviors

• A high-order upwind scheme for real gas was proposed to solve the governing equations of pipe flow.
• Quasi-steady methods were used to model the elements such as compressor or valve.
• Simulation of the transient pipe flow after the sudden closure of a downstream.
• Transient simulation of the surge avoidance system after the ESD of compressor.

The transient flow in a pipe flow network was numerically simulated to study the performance of the surge avoidance system in a natural gas compression station. The simulation was performed based on a combined approach that the flow in the pipe was simulated using a finite volume method with a high-order upwind scheme considering the real-gas behaviors and the behaviors of elements (e.g., compressor and valve) were evaluated using quasi-steady models. In the pipe flow simulation, characteristic boundary conditions were used to couple with the quasi-steady modeling of elements. The numerical scheme for the pipe flow simulation was first used to predict the rapid transients in a single pipe after the sudden closure of a downstream valve. The predicted distributions of the flow properties indicated that the present numerical scheme was capable of simulating the pipe flow under extreme flow conditions with high order of accuracy. The present approach was further used to simulate the transient flow during the emergency shutdown of compressor in an experimental piping network. Simulation results, including traces of operating points and histories of pressures at both sides of the compressor, were compared to the corresponding experimental data, and an agreement with a maximum deviation less than 10% was obtained in the primary control stage. The agreement proved the accuracy of the present approach for the simulation of the transient flow in a piping network and its validity in evaluating the performance of the surge avoidance system in a natural gas compressor station.