Wojciech Litwin

Influence of Surface Roughness Topography on Properties of Water-Lubricated Polymer Bearings: Experimental Research

Surface smoothness of journal and bushing has significant influence on properties of sliding bearings. Relevant literature contains a number of theoretical works connected with the subject of surface roughness pattern and height. Calculations based on various models indicate that the structure of sliding surface influences bearings hydrodynamic properties. One of the main conclusions is that roughness transversal to the sliding direction can increase hydrodynamic capacity of a bearing (H. Christensen and K. Tonder, 1973, Journal of Lubrication Technology, Vol. 4, pp 166–172). In bearings lubricated by a low-viscosity liquid such as water, the influence of roughness is of particular importance. This is due to low hydrodynamic film thickness and the resulting limited hydrodynamic capacity of these types of bearings. In fact, these are the reasons for deciding to conduct experimental research aimed at verifying the influence of roughness pattern on bearing properties. Research conducted for a selected group of polymer materials demonstrates strong influence of roughness height on movement resistance and working properties of bearings. No significant influence of roughness pattern on working parameters was observed. Furthermore, the running-in process for this type of bearing material is rapid. The sliding surface becomes smoothed out in just a few hours of work, significantly reducing all of the coefficients of friction.

Water-lubricated bearings of ship propeller shafts - problems, experimental tests and theoretical investigations

Water-lubricated bearings of ship propeller shafts - problems, experimental tests and theoretical investigations In recent years can be met ships whose propeller shaft polymer bearings are lubricated with water. It results from simplicity and associated low cost of such solution which is also environmentally friendly as no risk of pollution is involved. However the solution is not free of disadvantages. The main problem is intensive wear of bush material, occurring in certain cases. It very often results from errors of improper design and machining and mounting operations. Another problem is a limited value of its hydrodynamic load-carrying capacity, resulting from low viscosity of water used as a lubricating medium. As results from the performed research investigations, bearing of the kind is a highly sensitive unit. Problems of choosing a suitable bearing clearance, designing an optimum bush geometry, selecting a proper bush material are crucial for lifitime of the bearing.

Water-Lubricated Sintered Bronze Journal Bearings—Theoretical and Experimental Research

Water-lubricated bearings have been used for many years in shipbuilding, hydropower, and other industries because of their advantages, including extensive serviceable life, low coefficient of friction, longevity of shaft sleeve, good abrasion resistance, low maintenance required, unit simplicity, no danger of pollution, and low price. Various types of water-lubricated sliding bearings have been tested at the Technical University of Gdansk, including stiff composite bearings, ceramic bearings, as well as elastic polymer ones. It was unequivocally determined that a properly designed hydrodynamic water-lubricated journal bearing may function under a hydrodynamic regime in the conditions of typical loads and speeds found in practical applications. In this article, the authors present an attempt at researching the possibility of more extensive use of other stiff bush bearings, represented by bronze bush bearings. The aim of the research was to investigate stiff metal bearings, as solutions offering theoretically greater load bearing capacity than comparable elastic bearings, capable of replacing typical polymer and rubber bearings in certain applications. Based on the conducted research, it can be concluded that bronze bearings may constitute an interesting alternative to nonmetallic bearings. Although they require a hardened journal surface, they offer a greater load-bearing capacity, durability, and lower movement resistance levels. These bearings are particularly advantageous when used with journals of relatively small diameters working under heavy loads.

Influence of main design parameters of ship propeller shaft water-lubricated bearings on their properties

Influence of main design parameters of ship propeller shaft water-lubricated bearings on their properties In recent years more and more frequently can be met ships in which propeller shaft water-lubricated polymer bearings have been applied. It results from their simplicity and associated relatively low initial and operational cost as compared with the complex classical sealed system based on oil-lubricated bearings. It is worth mentioning that the water-lubricated bearings are also environmentally friendly as no risk of pollution with lubricating oil used in classical systems, is involved. Design procedure of bearings in question based on materials made available by producers is relatively simple. However it turns out that choice of an appropriate sliding material, clearance value and optimum arrangement of lubricating grooves may greatly influence bearings properties. As results from the performed research investigations, bearing of the kind is a highly sensitive unit. Problems of choosing a suitable bearing clearance, designing an optimum bush geometry, selecting a proper bush material are crucial for life time of the bearing. In particular the problem is in forming hydrodynamical properties of bearing as owing to its operation in the fluid friction regime durability of bearings, the very responsible units of propulsion transmission system, can be greatly extended.

Influence of Shaft Misalignment on Water Lubricated Turbine Sliding Bearings with Various Bush Modules of Elasticity

Hydropower industry increasingly frequently uses water lubricated bearings in turbines. This stems from the lack of negative impact of such solution on the environment. The paper presents an analysis of the influence of shaft misalignment in a turbine with water lubricated main shaft bearing on its hydrodynamic capacity. The theoretical analysis was based on the results of calculations for experimentally verified elastohydrodynamic lubrication (EHL) model. The obtained results showed impact of the stiffness of bush material and the degree of misalignment on bearings hydrodynamic capacity.

Water Lubricated Marine Stern Tube Bearings: Attempt at Estimating Hydrodynamic Capacity

Water lubricated bearings are often installed on new build and modernized ships. The main reasons are unit simplicity, no danger of pollution and low price.Copyright

Water: An Extraordinary, Ordinary Lubrication Liquid. Influence of Water Salinity, Pressure and Temperature on Water Lubricated Bearings Properties

Lubrication liquid characteristic has significant influence on bearing properties and working conditions. In calculations of oil lubricated bearings oil viscosity changes resulting from increasing temperature are usually taken into consideration. In water lubricated bearings the isothermal model is usually applied. In most cases, it is a correct method because of negligible viscosity changes resulting from increasing pressure and temperature in the lubrication film. In reality, water has surprisingly unique properties. One of them is strong influence of pressure and temperature on viscosity. In addition, salinity of sea water influences viscosity, as well. Since typical ships can freely sail on all oceans, the sea-water temperature could change more than twenty degrees. This wide range of temperature change has influence on properties of water lubricated bearings.Copyright

Assessment of possible application of waterlubricated sintered brass slide bearing for marine propeller shaft

ABSTRACT Water-lubricated bearings have been applied to support ship screw shafts for over a hundered years. Development of plastic materials has caused that novel sliding polymers appeared available on the market and being approved by classification institutions, possible to be applied in shipbuilding. However in the subject - matter literature there is no reference to application of bearings fitted with metal or ceramic bushes in shipbuilding. Nevertheless they have important merits such as low resistance to motion, long service life or stability of form. But some doubts are evoked by their large value of shape elasticity module which can lead to local stress concentration at the bush edges in the case of non-axiality of bush and shaft axes. Hence this work has been aimed at the testing of a bearing made of bronze-graphite silter. In the work is presented a comparison of measurement results of resistance to motion , hydrodynamic pressure distributions in lubricating film as well as shaft axis trajectories of the bearing, with those made for a typical elastic polymer bearing. The measurement results have showed high quality of the tested material. In the opinion of these authors it could be applicable to bearing ship propeller shafts.

Marine Water Lubricated Stern Tube Bearings: Calculations and Measurements of Heavy Loaded Bearings

Water lubricated bearings are often used to support propeller shaft of modern ships. These environmentally friendly bearings are less expensive than those oil lubricated because of simplicity of the bearing unit and lower material costs [1].Copyright

Properties Comparison of Two Water Lubricated Rubber Bearings Based on Experimental Test

Water lubricated rubber bearings are used from many years in ship building and other industry because of their advantages such as: long serviceable life, low coefficient of friction, long life of shaft sleeve, good vibration damping, good abrasion resistance, low maintenance required, grit particles and other abrasives are expelled through the grooves [1,2,3,4].Copyright