Numerical Simulation and Experimental Research on Passive Hydrodynamic Bearing in a Blood Pump

The current research of hydrodynamic bearing in blood pump mainly focuses on the bearing structure design.Compared with the typical plane slider bearing and Rayleigh step bearing,spiral groove bearing has excellent performance in load-carrying capacity.However,the load-carrying capacity would decrease significantly with increasing flow rate in conventional designs.In this paper,the special treatment is made to the upper spiral groove bearing to make sure that both the circulatory flowing and load-carrying capacity are high.Three-dimensional computational fluid dynamics(CFD) models in the space between rotor and shaft are developed by using FLUENT software.Effects of groove number,film height and groove depth on load-carrying capacity of the spiral groove bearings are investigated by orthogonal experiment design.The experimental results show that film height is the most remarkable factor to the load-carrying capacity.The variation tendency of load-carrying capacity reveals that the best combination of geometry is the one with groove number of 8,film height 0.03 mm and groove depth 0.08 mm.The velocity and pressure distributions in spiral groove bearings are also analyzed,and the analysis result shows that the distributions are in conformity with the design of the blood pump based on the principle of hydrodynamic bearing.The displacement of the rotor with the best combination parameters is tested by using laser displacement sensors,the testing result shows that the suspending performance is satisfactory both in axial and radial directions.This research proposes a bearing design method which has sufficient load-carrying capacity to support rotor as an effective passive hydrodynamic bearing.

Effects of Dimensional Tolerances on the Friction Power Loss of Hydrodynamic Journal Bearing System

According to the dimensional tolerances on hydrodynamic journal bearing system, a nonlinear oil film force model was established,and the Reynolds' equation was solved by adopting finite difference method. In order to fulfill different dimensional tolerances in the system,adopting 2kfactor design and using the eccentricity ratio corresponding to the stability critical curve,the effects of the friction power loss brought by the dimensional tolerances of the dynamic viscosity,bearing width,bearing diameter and journal diameter were analyzed. The effect on dynamic characteristics of the hydrodynamic journal bearing system was quantitatively analyzed,and the nonlinear dynamic analysis, modeling and calculation methods were studied while considering the manufacturing tolerances. The results show that in contrast to the impacts of the tolerances in journal diameter,dynamic viscosity and bearing width,the bearing diameter tolerance would lead to the rise in the power loss, and the dimensional tolerances have different degrees of impacts on the journal bearing system. The friction power loss decreased as the eccentricity ratio increased, and when the eccentricity ratio was 0. 695 the power loss came to the minimum.The investigation would find the best solution and reduce energy consumption,then control varieties of nonlinear dynamical behavior effectively,and provide a theoretical basis for hydrodynamic journal bearing system in parameter design.

Application of the Non-Stationary Oil Film Force Database

The technique of non stationary oil film force database for hydrodynamic bearing is introduced and its potential applications in nonlinear rotor dynamics are demonstrated. Through simulations of the locus of the shaft center aided by the database technique, nonlinear stability analysis can be performed and the natural frequency can be obtained as well. The easiness of 'assembling' the individual bush forces from the database to form the bearing force, makes it very convenient to evaluate the stability of various types of journal bearings. Examples are demonstrated to show how the database technique makes it possible to get technically abundant simulation results at the expense of very short calculation time.

Transformation between polar and rectangular coordinates of stiffness and dampness parameters in hydrodynamic journal bearings

The stiffness and dampness parameters of journal bearings are required in rectangular coordinates for analyzing the stability boundary and threshold speed of oil film bearings.On solving the Reynolds equation,the oil film force is always obtained in polar coordinates;thus,the stiffness and dampness parameters can be easily obtained in polar coordinates.Therefore,the transformation between the polar and rectangular coordinates of journal bearing stiffness and dampness parameters is discussed in this study.

Friction and wear performance of polyether ether ketone(PEEK)polymers in three lubrication regimes

This experimental study investigates the friction and wear of three coatings commonly used in industrial applications,particularly in hydrodynamic bearings.The three materials under investigation were Babbitt,polyether ether ketone(PEEK)reinforced with 15%carbon fibers,and PEEK reinforced with 20%carbon fibers.The first polymer material was extruded,while the other was produced by fused deposition modelling(FDM).The materials were subjected to sliding tests in a pin-on-disc configuration,with a steel ball serving as the counter surface.The tests were conducted at room temperature,with a load of 10 N and under three different lubrication conditions:dry,grease,and oil.The linear speed was set at 0.3 m/s for the dry and semi-solid lubrication tests,while for the oil tests,the speed was set at 0.25 m/s.The greases used had consistency grades of NGLI 000 and NGLI 2.An ISO VG 68 circulation oil was used for the oil lubrication tests.Additionally,thermodynamic analyses were performed under the most severe conditions(i.e.,dry)to investigate the steel-Babbitt and steel-PEEK contact.

Comparison between the volumetric flow rate and pressure distribution for different kinds of sliding thrust bearing

In this paper a hydrodynamic journal sliding bearing,forming with two nonparallel surfaces that the lower surface moves with a unidirectional velocity and the upper surface is stationary shaped with exponential geometry is verified mathematically.The values of volumetric flow rate and distribution of pressure for incompressible lubricant flow between two supports in several conditions of velocity with different variables are determined.The results indicate that by increasing the amount of constant(m),the maximum oil pressure in the bearing will face an extreme decrease,and also by increasing theαcoefficient,the rate of volumetric flow rate will decrease.

Performance behaviour of elliptical-bore journal bearings lubricated with solid granular particulates

Journal bearings operating in hot environments and at high temperatures experience accelerated degra- dation of lubricating oils. In such situations, dry granular particulates have emerged as potential media for providing lubrication in journal bearings in place of lubricating oils. Granular particulates do not degrade thermally, even at considerably high temperatures. This work explores the static and dynamic perfor- mance characteristics of elliptical-bore journal bearings lubricated with granular particulates. It is found that a bearing lubricated with a larger size （2 μm） particles offers better performance compared with that using smaller size （1μm） particles. Bore ellipticity reduces the load-carrying capacity and increases side leakage and the coefficient of friction; however, rotor stability is marginally improved at low eccentricity ratios （〈0.6）, followed by significant improvement at high eccentricity ratios （〉0.6）.