Dan Jiang

Analysis on design parameters of water-lubricated journal bearings under hydrodynamic lubrication

The article aims to investigate the relationship between eccentricity ratio and the Sommerfeld number based on hydrodynamic water-lubricated journal bearings. Considering the differences between water and oil, especially the difference in vapor pressure, the effect of cavitation on pressure distribution of water film is analyzed based on three boundary conditions and a cavitation model by computational fluid dynamics (CFD). The result shows that the three boundary conditions are all not suitable to replace cavitation model in numerical analysis of water-lubricated journal bearings. Then numerical analysis of journal bearings with different dimensions is undertaken with the cavitation model under different working conditions. Based on the analysis, a reference is produced for designing water-lubricated journal bearings under hydrodynamic lubrication. At last, the reference is verified by experiments.

Study of the lubrication performance of water-lubricated journal bearings with CFD and FSI method

Purpose Water lubrication is significant for its environmental friendliness. Composite journal bearing is liable to deform for the huge pressure of water film. This paper aims to study the influence of elastic deformation on how lubrication functions in water-lubricated journal bearings and to provide references for designing composite journal bearings. Design/methodology/approach The combination of computational fluid dynamics and fluid-structure interaction is adopted in this paper to study the lubrication performance of water-lubricated compliant journal bearings. The influences of elasticity modulus and Poisson’s ratio on load-carrying capacity and elastic deformation are studied for different rotational speeds. Predictions in this work are compared with the published experimental results, and the present work agrees well with the experimental results. Findings A reference whether elastic deformation should be considered for composite journal bearings is proposed under different working conditions. Besides, a reference to determine water-lubricated plain journal bearings dimensions under different loads and rotational speeds is developed with the effect of both elastic deformation and cavitation being accounted. Originality/value The present research provides references as to whether elastic deformation should be considered in operation and to determine compliant journal bearings’ dimensions in the design process.

Tribological behavior of hybrid PTFE/Kevlar fabric composites with different weave densities

Purpose – The purpose of this paper is to achieve attractive fabric composites with excellent tribological performance and investigate the wear mechanisms of these fabric composites sliding against bearing steel pins under dry sliding process. Design/methodology/approach – Five different weave density composites were prepared, and the tribological behaviors of these composites were studied at different testing conditions. Scanning electron microscopy, laser microscopy (three-dimensional profile measurements) and energy-dispersive X-ray spectrometry were used to analyze the worn surface morphology, wear volume and elemental content of the transfer films, respectively. Findings – The composite weave density serves an important influence on tribological behavior. Generally, the wear rate of each composite increased with increasing weave density, and the friction coefficient of each composite decreased with increasing weave density. Originality/value – Nanoparticle-filled hybrid polytetrafluoroethylene/Kevlar fabric composites with proper weave density have exhibited superior tribological properties in dry sliding conditions. The results that obtained in this paper may offer a reference for others who intend to achieve attractive fabric composites with excellent tribological performance.

Comparison of the Lubrication Performances of Water-Lubricated and Oil-Lubricated Plain Journal Bearings

Water-lubricated bearings have attracted increasing attention in recent years because of their environmental sustainability, simplified design, low cost, good cooling performance and low coefficient of friction. To show the characteristic of water lubrication more clearly, this paper quantitatively compares the lubrication performances of water-lubrication plain journal bearing and oil-lubricated plain journal bearing using CFD method. Bearing length, friction coefficients, power losses and temperature rises are obtained under the same working condition. Results show that water-lubricated bearing needs to be 3.4 times longer than oil-lubricated bearing, but its friction coefficient and power loss are only 11.7% of those of oil-lubricated bearing and its maximum temperature rise is less than 2 K, much lower than 96.76 K corresponding to oil lubrication.

Pipe Routing Approach for Aircraft Engines Based on Ant Colony Optimization

AbstractAircraft engines usually contain a lot of pipes and cables whose routing design greatly affects engine performance and reliability. In this paper a pipe routing approach for aircraft engines based on ant colony optimization is proposed, which contains improvements in three aspects. First, constraints over aircraft engine pipe routing are formulated and classified with respect to nine aspects. Second, a fan annual mesh of the layout space is developed, and two-mesh division is conducted to store and update environmental information about the layout space. Every unit obtained by the layout space modeling has been assigned a potential value to meet constraints and represent different areas in the layout space. Third, an improved ant colony optimization is developed for pipe routing, which includes the classification of ant colony, rank mechanism updating rule of pheromone intensity, and a dynamic updating rule of heuristic information. Every ant can search for 26 adjacent units in random directions a...

A Study of the Static/Kinetic Friction Behavior of PTFE-Based Fabric Composites

ABSTRACT Three different polytetrafluoroethylene (PTFE)-based fabric composites were prepared. The static/kinetic friction behaviors of these composites under different loads and speeds were studied. A 3D laser microscope and profile measurement apparatus were used for analysis of the morphology and weave structure of the composites, and the contact temperature of these composites under different loads and speeds was monitored continuously using a high-precision thermal resistor. In addition, a dynamic mechanical analysis (DMA) apparatus was used to explore the thermal and mechanical properties of PTFE-based fabric composites. The results demonstrated that speed/load, weave structure, and fiber form have an important influence on static and kinetic friction behavior of the fabric composites. Generally, the static friction coefficient is greater than the kinetic friction coefficient, except when considering light load conditions. Under light load conditions, the static friction coefficient is equal to the kinetic friction coefficient. In addition, the kinetic friction coefficient first increased and then decreased with increased speed, but the static coefficient increased first and then remained at an almost constant value. At all sliding speeds, the static and kinetic friction coefficients of tape yarn composites are better than those of the multifilament yarn composites. Weave structure has no effect on the static friction coefficient, but it has a significant influence on the kinetic friction coefficient.

Researches on Friction Performance of Water-Lubricated Polymer Composite Journal Bearings Based on Experiments

A composite which is PTFE as a matrix with PEEK and carbon fiber as fillers is developed to fabricate the bush of water-lubricated journal bearings. The bush is fabricated with a new structure that a relatively large straight groove is opened in its upper part. A water-lubricated journal bearing made up of the bush and a steel sleeve is studied using purposed-built test rig. It is shown that the test bearing operates under hydrodynamic lubrication for almost all of the given conditions. The composite developed in the work is a promising material for water-lubricated journal bearings, and the new structure can be well used in water-lubricated journal bearings.