Purpose
Multitilting-pad journal bearings (MTPJBs) used in large-scale hydraulic turbines often suffer from complex operating conditions, which greatly influence the overall performance of the rotating machine. The purpose of this study is to establish a thermal-elastic-hydrodynamic lubrication model for MTPJBs that can predict the static and dynamic characteristics of high-speed and heavy-load MTPJBs under different operating conditions.
Design/methodology/approach
A thermo-elasto-hydrodynamic lubrication model considering the turbulence effect is proposed for high-speed and heavy-load TPJBs, which is solved using the coupled finite difference method and finite element method. The model considered the turbulence effect, thermal energy diffusion, viscosity–temperature–pressure relationship and elastic deformation of the pads. The influences of the operating conditions on static and dynamic characteristics of tilting pad journal bearings were analyzed in depth.
Findings
The operating conditions have a strong effect on the static properties of the bearings. The dynamic characteristics of the TPJB were the most influenced by the shaft speed. The effects of the load direction on the dynamic properties of the TPJB were much stronger than those of the static characteristics.
Originality/value
This study used analytical methods and models to provide theoretical guidance for evaluating lubricating characteristics, assembling conditions and overall health.
Purpose
In high-pressure pumps, due to the interaction of asperities on the upper and lower surfaces, the piston–cylinder interface suffers severe lubrication and sealing problems during mixed lubrication. This study aims to establish a mixed thermo-elastohydrodynamic (EHD) model for the lubrication gap to determine how working conditions affect the lubricating characteristics and sealing performance of the interface.
Design/methodology/approach
A mixed thermo-EHD lubrication model is established to investigate the lubricating characteristics and sealing performance of the interface between the piston and cylinder. The model considers piston tilting, thermal effect, surface roughness and bushing deformation. The interface lubricating characteristics and sealing performance under different working conditions are calculated by the proposed numerical model.
Findings
A higher inlet pressure contributes to an increase in the minimum film thickness. Increased shaft speed can significantly reduce the minimum film thickness, resulting in severe wear. Compared to roughness, the impact of the thermal effect on the interface sealing performance is more significant.
Originality/value
The proposed lubrication model in this study offers a theoretical framework to evaluate the lubricating characteristics and sealing performance at the lubrication gap. Furthermore, the results provide references for properly selecting piston-cylinder surface processing parameters.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2023-0072/
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