Adam Czaban

MODELS OF VISCOSITY CHARACTERISTICS ŋ=ŋ(B) OF FERRO-OIL WITH DIFFERENT CONCENTRATION OF MAGNETIC PARTICLES IN THE PRESENCE OF EXTERNAL MAGNETIC FIELD

The purpose of this article is to determine, identify and describe the viscosity characteristics of the ferro-oil with different concentrations of magnetic particles in the presence of an external magnetic field interaction. These characteristics are defined in the context of magnetic induction changes. These rheological tests were performed on a Physica MCR 301 rheometer. It was used a measuring system ‘plate to plate’ type which was armed with magneto-rheological research system MRD 180/1T. The tests were performed for the selected temperature of the medium i.e. 90°C, the shear rate changes were carried from 0 to 1000 1/s. Changes of the magnetic field intensity value were ranged from 0 to 500 mT. The selected concentrations of magnetic particles in a ferro-oil were 1%, 2%, 4%, 6% and 8% and the tested ferro-oil was product of FerroTec of Unterensingen (Germany), which is a mixture of colloidal mineral motor oil Penzzoil’s LongLife Golds SAE 15W-40 with Fe3O4 magnetic particles and the surfactant. Analyses of the results, identify and matching characteristic were calculated using STATISTICA software. It has been proposed three categories of functions mapping the waveforms of the results obtained experimentally: the exponential function, logarithmic with basis of the normal and the polynomial function.

GENERALIZED NEWTONIAN FLUIDS AS LUBRICANTS IN THE HYDRODYNAMIC CONICAL BEARINGS – A CFD ANALYSIS

Opracowanie ze środkow MNiSW w ramach umowy 812/P-DUN/2016 na dzialalnośc upowszechniającą nauke.

The influence of the microgrooves on the hydrodynamic pressure distribution and load carrying capacity of the conical slide bearing

The aim of this work is to determine the hydrodynamic pressure distribution in oil film and the load carrying capacities of conical slide micro bearings with grooved sleeves. The results for some bearings examples are presented. For the bearings taken into account, the Reynolds equation was solved by the method of Finite Differences. In the calculations, the Reynolds boundary condition was applied. The simulation was performed for the conical slide micro bearings with the groves parallel to the cone generating line. The function of lubrication gap height for the conical slide bearings with sleeves covered with microgrooves was assumed on the basis of existing papers. The results obtained for the analogous bearings without the microgrooves are also shown, therefore the influence of microgrooves on the conical slide micro bearings can be observed. On the basis of the results, one can conclude, that applying microgrooves on the bearing sleeve surface causes the increase of the value of hydrodynamic pressure and longitudinal and transverse components of the load carrying capacity of the bearing. Furthermore, the effect of the microgrooves and their impact is noticeable in graphs of hydrodynamic pressure distribution. The applied method of investigation of the impact of microgrooves on a bearing operation is simpler and less expensive than the experimental studies, however it is necessary to verify that the results obtained with this method are correct and whether in fact applying microgrooves, besides form facilitate lubrication, causes the improvement in bearing operating parameters.

Surface topography of operated slide journal micro - bearings used in computer fans

In this paper authors present results of measurements of slide journal bearings surface topography measured with a profilometer and an atomic force microscope (AFM). Surface topography of investigated bearings (i.e. journals and sleeves) was measured using the Hommeltester T8000R60 profilometer. The results of these measurements give information about micro-grooves dimensions and location. Measurements of surface topography were made for journals and sleeves of slide journal micro-bearings from personal computers fans, with the Atomic Force Microscope NT-206 produced in MTM in Minsk, Republic of Belarus. The results of measurements of surface topography were presented in the form of surface topography maps, threedimensional graphs and some examples of selected cross-sections of investigated surfaces in the form of profile graphs. The values of profile roughness parameters Ra and Rq and the distance between maximum peak height and maximum valley depth are presented as well. The application SurfaceXplorer® was used for processing and visualization of the data obtained from AFM NT-206, which besides from generating 2D, 3D and profile diagrams, was used to calculate and draw graphs of height distribution. In this research authors used two identical sets of micro-bearings. The investigated bearings are: a) Kama Flow SP0825FDB12H fan with grooved surface of bearing sleeve, b) Xilence Case fan which sleeve surface was without grooves. First set of that micro-bearings functioned for a year at rated RPM continuously (i.e. 24 hours a day). Second set of the same micro-bearings also functioned for a year at rated RPM, but in intermittent mode (i.e. 15 minutes on, 15 minutes off). On the surfaces of studied micro-bearings some microgrooves can be found in form of herringbone, with depth about 1-2 m and width 100-150 m. Received information about microgrooves geometry will help to develop proper theory of hydrodynamic lubrication for micro-bearings with microgrooves and allows determining how the mode of operating affects on the wear of co-operating surfaces.

CFD analysis of hydrodynamic lubrication of slide conical bearing with consideration of the bearing shaft and sleeve surface roughness

In this work is shown the result of CFD simulation of hydrodynamic conical bearing lubrication with consideration of the effect of the bearing shaft and sleeve surface roughness. The oil flow in a bearing lubrication gap largely depend on the condition of the cooperating surfaces of a bearing. Surface irregularities are formed already at the manufacturing process and furthermore the quality of the surface may change during operation of a bearing. In this work, as a parameter describing surface condition, the Ks roughness height parameter was taken (i.e. sand-grain roughness height). The hydrodynamic pressure distribution in lubrication gaps of investigated bearings were calculated by using the commercial CFD software ANSYS Academic Research for fluid flow phenomenon (Fluent). Calculations were conducted for bearings without misalignment. The Ostwald-de Waele model for non-Newtonian fluids was adopted in this simulation. The coefficients of Ostwald-de Waele relationship were determined by application of the least squares approximation method and fitting curves described by this model to the experimental data, obtained for some motor oils, presented in previous work. The calculated hydrodynamic pressure distributions were compared with the data obtained for corresponding bearings, but assuming that bearings have smooth surfaces and there is no slip on surfaces. This paper presents results for bearings with different rotational speeds and of different bearing gap heights.