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High reliability is required for the permanent magnet brushless DC motor (PM-BLDCM) in an electrical pump of hypersonic vehicle. The PM-BLDCM is a short-time duty motor with high-power-density. Since thermal equilibrium is not reached for the PM-BLDCM, the temperature distribution is not uniform and there is a risk of local overheating. The winding is a main heat source and its insulation is thermally sensitive, so reducing the winding temperature rise is the key to the improvement of the reliability. In order to reduce the winding temperature rise, an electromagnetic-thermal integrated design optimization method is proposed. The method is based on electromagnetic analysis and thermal transient analysis. The requirements and constraints of electromagnetic and thermal design are considered in this method. The split ratio and the maximum flux density in stator lamination, which are highly relevant to the windings temperature rise, are optimized analytically. The analytical results are verified by finite element analysis (FEA) and experiments. The maximum error between the analytical and the FEA results is 4%. The errors between the analytical and measured windings temperature rise are less than 8%. It can be proved that the method can obtain the optimal design accurately to reduce the winding temperature rise.

To explore the pressure distribution characteristics of pump chambers, and the law governing the axial force in a particle-laden flow centrifugal pump, a semi-open impeller centrifugal pump was selected as the research object. The particle model and heterogeneous model were used to develop the numerical calculations of the particle-laden flow field within the centrifugal pump. For the liquid phase we adopted the shear–stress–transport (SST) turbulence model, while for the solid phase we adopted the discrete phase zero equation model. The external characteristics, pressure distribution and axial forces were compared and analyzed (1) for a constant solid particle diameter, d, of 0.1 mm and particle volume fractions, Cv, of 0, 1, 5, and 10%, and (2) for a constant particle volume fraction, Cv, of 10% and solid particle diameters, d, of 0, 0.01, 0.1, and 0.5 mm. The correlations between the particle volume fractions and solid particle diameters with the pump chamber pressure distributions and axial forces were obtained. The results show that when Cv increased from 1–10%, or d from 0.01–0.5 mm, the pump head and efficiency decreased continuously under the same flow rate. At the same time, larger particle volume fractions resulted in larger pressures at the same radius, while for larger solid particle diameters, smaller pressures were obtained at the same radius. Under the same flow rate, when Cv increased from 1–10%, the total axial force of the centrifugal pump increased, but it was smaller than what was achieved under the clean-water condition. When d increased from 0.01 to 0.5 mm, the total axial force of the centrifugal pump decreased. This study provides a reference for the calculation and balance of the total axial force in a particle-laden flow centrifugal pump.

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