DEVELOPMENT OF BOUNDARY/MIXED FRICTION MODELS FOR CYLINDER BLOCK/VALVE PLATE INTERFACE IN A NOVEL AEROSPACE ELECTRO-HYDROSTATIC MODULE

The highly compact Electro-Hydrostatic Module (EHM) is the key technology of future Electro-Hydrostatic Actuation (EHA) in the aerospace industry. Improving the frictional performance of the critical friction pairs is crucial for EHM. To address this issue, this study develops a specific friction model for the cylinder block/valve plate interface that combines rotor dynamics with boundary/mixed friction characteristics. The boundary/mixed friction properties of the interface are characterized by combining a viscous friction model based on Reynolds lubrication theory and the measurement results of a special simulated friction experiment of cylinder block/valve plate. A finite element model for the rotor dynamics is developed, and the rotor models under a wide range of rotational speeds are determined by harmonic response analysis. By merging the rotor dynamics model with the friction model through the exchange of rotor model data and bearing parameters, the coupling effects of rotor vortices and oil film hydrodynamics at the cylinder block/valve plate interface are simulated. The model's accuracy is verified through experiments to be 85%. It is found that the integrated structure has a critical speed near 20000 rpm through simulation analysis, and the interface friction characteristics near the critical speed are significantly increased. From the perspective of the two critical attributes of reliability and efficiency, this study provides theoretical reference points for the structural optimization of the novel EHM.