Abstract
Sliding bearings are the main kinematic pair of a Stirling engine, and one of the main sources of friction power loss and excitation force. There is a coupling effect between the lubrication state and the excitation force. In this paper, the dynamic model of a Sapphire bearing fatigue test bed, which includes thermo-elasto-hydrodynamic (EHD) property, is established and the accuracy of the model is verified by the experimental data. Based on the model, the effects of the load, the oil supply temperature, the oil supply pressure, the bearing clearance on the tribological and dynamic characteristics are studied. With an increase in the load, the orbital path of the journal moves downward, the lubrication state changes from the full hydrodynamic lubrication to the boundary lubrication, the friction power loss increases, and the bearing excitation frequency increases. Due to the decrease of the oil viscosity, the hydraulic friction power loss decreases, but the friction power loss derived from the asperity contact increase, so does the total friction power loss. With the increase of the radial clearance, the shape of the orbital path and the minimum oil film thickness remain unchanged. The increase of the bearing clearance results in the collisions between the journal and bearing bush, thus the amplitude of the frequency multiplication component in the bearing load increases, and the asperity and the total friction power loss increase.
Highlights
Journal bearings are widely used in Stirling engines, and they are the major kinematic pairs and the key source of power loss and vibration
Due to the impact of the oil film, the pressure between the journal pin and the bearing bush can be transferred through two parts, which are the hydrodynamic pressure borne by the lubricating oil and the asperity pressure created by the asperity contact
The results show that the errors of the modal frequencies of the shaft and connecting rod condensation body with the finite element model are less than 1%, which shows that the dynamic characteristics of the reduced model and the finite element model are consistent
Summary
Journal bearings are widely used in Stirling engines, and they are the major kinematic pairs and the key source of power loss and vibration. A multibody dynamic model of the Sapphire bearing fatigue test bed (hereinafter called ‘the test bed’) is established by using the DOFs reduced method and the TEHD method, considering the influence of the contact surface morphology and the temperature on the lubrication characteristics. On this basis, the change in the law of the lubrication and the dynamic characteristics under the different working conditions is analyzed to provide guidance for optimizing the tribological and dynamic performance of the main bearings for the Stirling engine
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