Clearance leakage flow on aviation oil pump performance: Entropy generation and thermal–fluid–structure interaction analysis

This study, based on the eddy current identification method and combined with the thermal-fluid-solid (three-field coupling) characteristics, systematically investigates the influence of the end and radial clearance in aviation gear pumps on the leakage flow characteristics. By constructing a vortex dynamics analysis framework, the evolution law of the leakage vortex structure is mainly revealed, and the influence mechanism of clearance changes on the spatiotemporal evolution of energy loss and dissipation in the pump body under the coupling of multiple physical fields is quantitatively clarified. Four typical vortices are observed within the end face clearance of 0.02 mm and the radial clearance of 0.04 mm: opposite vortex, angular vortex, outlet vortex, and tooth vortex. Among them, the evolution of radial pairs of vortices and tooth vortices is affected by frictional flow and rotational effects (the circumferential velocity vector and the Lamb vector gradient determine the rotational direction), and angular vortices are controlled by the pressure gradient in the meshing region. The evolution of the inlet and outlet vortex structures and the turbulent kinetic energy shows obvious time-varying characteristics. Meanwhile, a three-dimensional model of the changes in end face and radial clearance was established, revealing the influence mechanism of a temperature change of 200 °C and a pressure change of 5 MPa on the clearance size. This provides a theoretical basis and innovative guidance for the improvement of leakage and active control of the aviation external meshing gear pump.