Internal energy consumption analysis of counter-rotating axial-flow compressor based on entropy production theory

Abstract

Counter-rotating wet gas compressor is an ideal equipment for pressurizing natural gas in offshore gas fields. It has a compact structure, a wide range of operating conditions, and a certain liquid tolerance in the process of gas pressurization. However, due to the opposite rotation of the adjacent rotors, and the characteristics of the flow containing liquid, it is also easy to lead to flow separation in its interior and then produce obvious energy dissipation. In this paper, the numerical simulation of the internal flow field of counter-rotating axial-flow compressor under dry and wet conditions is carried out. The entropy production theory based on the second law of thermodynamics is introduced to analyze the energy consumption of the compressor, and the high energy consumption area in the internal flow field of the compressor is accurately located. Then, the energy consumption of this area is evaluated quantitatively and qualitatively. The entropy production and its proportion of each component under different working conditions, the distribution of the entropy production of each rotor along the flow direction, and the radial distribution under the near-stall state are obtained. The calculation results show that the entropy production of upstream rotor and downstream rotor in the total entropy production is 29.19%–31.41% and 59.48%–62.61% under dry gas conditions, respectively. Under wet conditions, the proportions are 28.20%–30.67% and 60.02%–63.33%, respectively. The wet gas droplets can increase the momentum input to the low energy region of 0.7–0.9 relative position of the suction surface of the upstream rotor and improve the flow field in this region. However, it can also exacerbate flow separation in the front middle of the downstream rotor, causing additional energy loss.