The Working Theory And Design Method Of The Compress Unit In Multiphase Pump

As a new technology used for multiphase product in oil field, R&D on helico-axial multiphase pump become a hot topic nowadays.This paper discussed the present research progress of multiphase pump, such as the current situation of hydraulic design for axial pump, the design theory for vane and the numerical calculation for interior flow field. Some problem which should be resolved urgently was proposed, including lack of perfect theory basis, the improvement on design method and so on.Combined with theory, design, experiment, and numerical calculation, work theory of multiphase pump was firstly discussed, and then based on which, the design method was presented. Finally the theory and design method was verified by finite element calculation.Main contents as follows were researched:⑴Theory of compress units for multiphase pump and mechanism of multiphase transportation were conducted systemically, external characteristic of multiphase pump was analyzed. In addition, the relationship between characteristic parameter, multiphase transportation capability and structural parameter, operating parameter, mixed liquid parameter was put forward firstly, and then the related formula was raised, which can provide theory basis for the design of multiphase pump;⑵On the basis of theory research, this paper presented a new design method of the structural parameter for compress unit, as a reference to the design of meridian plane.⑶According to the inverse theory, taking inlet velocity torque as controlled variable, formula was deduced to calculate the velocity gradient of meridian plane, design method of vane shape in compress unit was provided; Meanwhile, according to quasi-three dimensional direct theory, gas and liquid equation running in the multiphase pump was also deduced separately. And a method to carry on the quasi-three dimensional numerical calculation of interior flow field was proposed, which provided basis for the vane shape optimization with multi-objective genetic algorithm. The feasibility of both methods was verified by experiments.⑷With the theory of multi-objective genetic algorithm, Optimization of vane shape in compress unit was carried on. According to the comparison analysis of multi-objective optimization, combined with the multiphase transportation capability and efficiency of multiphase pump, a trade-off design method was proposed, which obtained the best multiphase capability while the efficiency is not lower than the primary requirement. While, the variable tendency of vane shape to fulfill different objective was analyzed and proved to be instructive for the further study.⑸Working theory and design method developed here was proved by numerical calculation and experiments. With the result of lab experiments for multiphase pump, a method to do numerical analysis on the flow field of compress unit was developed, which researched on the flowing rule of gas and liquid in compress unit, simulated the characteristics of multiphase pump and optimized the structural parameter of compress unit. Finally, the working theory and design method of compress unit were improved and optimized according to the numerical analysis result.