This paper discusses the heat transfer process for a typical stator–rotor machinery-hydrodynamic retarder from the perspective of computational fluid dynamics and experimental means. Fluid cooling is an essential step in the working process of hydrodynamic retarders, and changes in viscosity along with temperature rise will affect the performance of braking. To investigate the heat transfer process of stator–rotor machinery, a novel computational fluid dynamics (CFD) method, combined with a dynamic thermophysical property transfer algorithm, is proposed. A heat-flow coupling numerical method with experimental verification is proposed, in which the density and the viscosity are variable with the temperature in an effectiveness–number of transfer units (P-NTU) method. The results show that the numerical results are in good agreement with the experimental data, with a 0.1–2.5% error. The influence of an asymmetric structure on heat transfer characteristics is discussed. The results show that the optimal braking performance, along with the liquid cooling performance, is achieved under outlets with an inlet passage set as 90 degrees.

In modeling the characteristics of a discharging valve in a hydrodynamic retarder, it is commonly required to determine the value of the flow area to calculate the force on the spool. However, the flow area often relies heavily on empirical or simulation data, which leads to increased uncertainty and computational cost, especially with the variation in the spool displacement. To overcome these shortcomings, Res-SE-U-Nets (networks that combine residual connections, squeeze-and-excitation blocks, and U-Net) are used to reconstruct the velocity field, and they have shown exceptional performance in image-to-image mapping tasks. The dataset of computational fluid dynamics (CFD) results for the velocity field is collected and verified using particle image velocimetry (PIV). The results show that Res-SE-U-Nets can capture the location information of the flow field using a training set of only 120 data points. By utilizing location information in velocity field reconstruction, the flow area can be directly obtained under different spool displacements and pressures to calculate the spool force. The valve characteristics calculated with this method show an error of less than 2% when compared with CFD results, which confirms the validity and effectiveness of this method. The proposed method, which utilizes location information extracted from flow field prediction results, is capable of calculating valve characteristics. This approach also demonstrates the feasibility of using Res-SE-U-Nets for flow field reconstruction.

The hydraulic torque converter is a critical component in high-power tracked vehicles such as bulldozers or bridge machines. Its axial force has a significant impact on the reliability and load-carrying capacity of the transmission system, which is greatly influenced by the charging oil conditions. To investigate the axial force characteristic of the torque converter and its charging oil effects, a computational fluid dynamics (CFD) method is established by considering inner and outer leakage regions, as well as inlet and outlet channels. Additionally, a novel axial force-testing method is proposed, and the axial force testing and validation experiments on the torque converter prototype have been completed. The research findings reveal that changes in oil viscosity resulting from variations in charging oil temperature have a considerable impact on the axial force of the torque converter. The axial force of the pump and turbine decreases as the temperature increases due to varying pressure sensitivity among different components. The influence of charging oil pressure on axial force follows a linear relationship, with its magnitude determined by the axial unbalanced area of the hydraulic torque converter during its design and development. In addition, a formula for the axial force of the hydraulic torque converter is proposed under different charging oil pressures. Furthermore, a novel suppression of axial force has been proposed without altering the structure, which has been validated as an effective method. The results lay a theoretical foundation for the research and suppression of axial forces in hydraulic torque converters, and they also have an engineering application value in the design of high-reliability and long-life converters.