Influence of solid particle contamination on the wear process in water lubricated marine strut bearings with NBR and PTFE bushes

This paper reports on a study of the influence of solid particle contamination on the wear process in water-lubricated slide bearings (steel-acrylonitrile-butadiene rubber (NBR) and steel-polytetrafluoroethylene (PTFE)). To compare the wear of the shaft journal and bushes (NBR and PTFE) when lubricated with fresh water and contaminated water, an experiment was carried out to identify key factors that influence the state of wear of slide bearing. The amount of wear was checked by means of geometric structure measurements on the journals, namely, roughness profile measurements using both a contact profilometer and an optical microscope. The obtained results enabled correlations between the material comprising the sliding sleeve, roughness of the journals and contamination inside the water-lubricated slide bearings.

DEVELOPMENT OF A METHODOLOGY FOR CALCULATING THE PRESSURE DEVELOPMENT OF A METHOD FOR CALCULATING THE PRESSURE FIELD FOR THE NONISOTHERMAL FLOW OF A VISCOUS LIQUID IN GYROSTATIC BEARINGS WHEN PROCESSING LARGE-SIZED STEAM TURBINE SHAFTS

A mathematical model for calculating the pressure field of a hydrostatic support with an incomplete girth angle for a non-isothermal flow of a viscous working fluid using the iteration method is developed. The fundamental laws of hydrodynamics and the hydrodynamic theory of lubrication are used. The pressure field is calculated by jointly solving the Reynolds equation, the energy balance equation and the flow rate balance equation, as well as additional relationships for the thermophysical parameters of the working fluid, obtained by approximating the tabular values. The mathematical model of the pressure field takes into account all the characteristics and operating parameters of the hydrostatic support with an incomplete range angle, by setting the boundary conditions and geometric parameters of the working surface of the support liner. The developed system is solved by the numerical method of finite differences. A comparative analysis of the static characteristics of different designs of a hydrostatic support with an incomplete range angle is carried out. Recommendations are given on the choice of the number of pockets in the design of liners for a hydrostatic support with an incomplete range angle to ensure guaranteed floatation and maintain a given value of the working clearance in the fluid friction zone of the shaft journal and the bearing surface of the hydrostatic support liner when turning shafts of steam turbine.

Analysis of Contact Deformations in Support Systems Using Roller Prisms

This article presents the results of finite element analyses of the influence of reaction forces on stresses and strains at the contact points of the rollers of prism supports with cylindrical surfaces of the main journals of large-sized crankshafts. The analyses of strains and stresses, as well as the depth of their occurrences, in the case of the shaft journal and support rollers were carried out using Hertz contact theory and the finite element method. These calculation results proved to be highly consistent. Additionally, they provide a basis for stating that, in the case under consideration, permanent deformations do not significantly affect the values of the measured geometrical deviations nor the profile forms of the supported main crankshaft journals.

Modelling and Simulation Testing of Main Bearing Loads and Strains in Crankshafts Caused by Deviations in the Position of the Shaft Journal and Bearing Axes

This article presents the results of a simulation, testing the variation of main bearing loads and strains in crankshafts caused by geometrical deviations of the bearing system to justify the necessity and purposefulness of measurements of both the shape and axes position deviations of crankshaft journals. Measurements of these deviations at the existing level of applied measuring techniques are significantly limited. The research also accentuates the practical implementation of a measuring system equipped with the so-called flexible support system for the measured object, developed at the Maritime University of Szczecin. This system makes it possible to eliminate elastic deformations of the crankshaft due to its own weight, whereby the measurements of geometrical deformations of the crankshafts can be carried out with appropriate accuracy in conditions corresponding to the non-reference measurements when determining the object measured in counterpoints. The obtained results have fully confirmed the purposefulness of the conducted research and the validity of the theses.

Reducing the vibration of bearing units of electric vehicle asynchronous traction motors

The impact of the accuracy class of bearings, rotational speed, load, clearances, and fits on the vibration levels of electric motor bearing units is investigated. The ways to reduce the vibrations of mechanical origin are offered. The boundary vibration levels of asynchronous motors limited by vibration levels of 40 dB at a frequency of 5 Hz and 80 dB at a frequency of 10,000 Hz are determined. The effect of increasing the rotational speed and load on the vibration levels of bearing units has been determined, and reserves for reducing vibration while ensuring the optimum bearing preload on the shaft journal have been identified. It is established that the clearance between the cap and the bearing when it is fixed in the housing (primer) does not ensure the unambiguity of the bearing unit assembly, which results in a large variation in vibration levels compared with rigid and elastic fixation. The results of this research can be applied to all types of traction electric motors.

Calculation of lubricant flow in the slide bearing of the aviation engine reducer

A method has been developed for calculating the pressure distribution in a cylindrical slide bearing. We present the process of designing a heavy-duty slide bearing as a component of the reduction gearbox of a bypass turbojet engine as the object of our investigation. The process comprises the following stages: specification of the supporting structure; calculation of pressure distribution in the slide bearing for different eccentricities and angles of rotation of the shaft journal; calculation of the effect of shaft journal precession on pressure distribution; calculation of pressure distribution taking into account the channels of oil supply to the bearing. The results obtained in the experimental activities are given. The analysis carried out shows that the calculation helps to predict the location and size of pressure and rarefaction areas, to position the holes for oil supply, which will significantly improve the conditions of lubricant flow in the bearing.

Preliminary tests of the shaft journal grinding process on a four-axis milling machine

The article presents the results of preliminary tests of the shaft grinding process on a 4-axis AVIA VMC800 milling machine. The carried out tests are a preparation for the development of the face grinding process of a crankshaft pivots of ship engines. Measurements of selected shape errors of the face-ground journal were carried out in the paper.

ATTEMPT AT EVALUATING THE INFLUENCE OF BENDING STRESS ON SHAFT WEAR PROCESSES IN WATER LUBRICATED SLIDING BEARING WITH A RUBBER BUSHING

Water lubricated bearings find increasingly wide application in shipbuilding or the hydropower industry, with the popularity stemming from their numerous advantages. Unfortunately, as it turns out, water lubricated bearings do not always meet expectations, because, on occasion, they become subject to intense, premature wear, which requires costly repair. One of the still unexplained phenomena is the process of excessive bearing wear, in particular, that of shaft journal co-working with rubber bushings. The research goal was to evaluate the influence of shaft bending stress on the degree of its wear. Experimental tests were carried out on a purpose-designed test stand. The results of the first test series confirmed that the shaft bending stresses do have impact on the magnitude of wear.