The twin-screw multiphase pump shows a significant phenomenon of fluid–thermal–structure physics field coupling. The method of studying dynamics, thermodynamic characteristics, and deformation of the screw pump is biased from the actual boundary conditions without considering multi-field coupling. To enhance the calculation accuracy of the twin-screw pump integrated deformation field and further determine the clearances between rotors and pump liner, the fluid–thermal–structure coupling calculation is completed by ANSYS WORKBENCH. The calculation results of the leakage rate are verified by experiments. The moving reference frame dynamic mesh method is used in the fluid domain numerical simulation, and the non-equilibrium wall function method is used to solve the boundary layer. The rotor and pump liner deformations and their influences on volumetric efficiency are studied under different gas volume fractions. The optimal installation clearances are proposed to reduce the leakage flow rate and prevent the rotor from sticking due to large deformation. The results show that the calculated results of the leakage rate are in good agreement with the experimental values, and the average deviation is less than 4%. The research program effectively ensures the calculation accuracy and efficiency of the whole model and provides an important basis for the optimal design of the twin-screw pump.
During on-site operation under wet gas compression, the volumetric efficiency of a twin-screw pump decreases sharply, the temperature in the pump rises significantly, severe vibration and even jamming can occur. To solve the problems caused by wet gas compression structurally, a method for optimizing the design of a decompression screw is proposed in this paper based on the characteristics of a twin-screw pump and screw compressor. A fluid–solid multi-field thermal-coupling scheme is used to calculate the pressure, temperature, deformation, outflow, and volumetric efficiency of a screw pump before and after optimization. The average deviation between the calculated outflow and the experimental results was no more than 5%, demonstrating the accuracy of the calculation. After optimization, the return flow between the pump stages was significantly reduced and the outflow had increased. When the pressure difference between the inlet and outlet was 1 MPa, the maximum increase was about 18%. With an increase of the gas volume fraction from 95% to 99%, the average increase of the volumetric efficiency was about 14%. The temperature rise in the chambers at all levels and the temperature difference between the inlet and outlet of the decompression screw pump were lower than those of a traditional screw pump. The deformations at the three clearances were also less than those of a traditional screw pump, which helps to avoid jamming caused by thermal expansion.
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