Design optimization and active control of unsteady flow in large-scale annular linear induction pumps

This study addresses the issue of unstable flow in large-scale annular linear induction pumps (ALIPs), with a focus on optimizing their design and enhancing performance. Utilizing the ALIP model developed by Toshiba Corporation as a reference, the design process employs the equivalent circuit method to improve the hydraulic performance of high-flow ALIP systems. A comparison of various hydraulic and excitation structure parameters facilitated the identification of an optimal design scheme. A numerical simulation of the ALIP’s internal magneto-fluid coupling field was then conducted, based on magnetohydrodynamic (MHD) theory. The simulation results were validated against experimental data, confirming the model’s accuracy. Further simulations under various operational conditions were performed to analyze the distribution and magnitude of the axial Lorentz force (FL) and the axial pressure gradient across different flow rates and currents. The analysis indicated that the unstable flow primarily results from inverse pressure gradients, which are caused by the uneven distribution of these forces. To mitigate this issue, the study proposes the addition of a regulating coil winding to the inner stator. This addition significantly reduces the uneven distribution of magnetic fields and pressure gradients. These coils generate a compensating magnetic field that enhances FL within the electromagnetic section, thereby improving the axial force on the magnetic fluid. The results demonstrate that this active regulation method markedly reduces unsteady flow phenomena, stabilizes fluid movement, and offers a novel design strategy for large-scale ALIP systems. The ratio of the area of the regulating coils to that of the driving coils is only 0.33, which minimally increases the pump dimension. Additionally, the energy conversion rate of different regulation currents between the inner and outer regulation coils was compared. It was found that variations in the regulation current alter the total efficiency of the ALIP by no more than 1%, indicating that the control coil winding consumes minimal energy and that the stability of the magnetic fluid can be effectively controlled, making this approach feasible for engineering applications.