Axial Thrust Bearing Research Articles

Theoretical and experimental analysis of the centrifugal micro hydrodynamic axial-thrust bearing

The novel centrifugal micro hydrodynamic axial-thrust bearing has been demonstrated to substantially mitigate the wear in hydrodynamic suspension micropumps. To further elevate the bearing performance, the flow mechanism is systematically analyzed via numerical simulations and experiments in this work. The effects of various properties of bearing on the performance are explored and explained. Results indicate that the load capacity augments with the growth of inlet-suction flow rate and with the reduction of rotational speed. Meanwhile, it initially decreases and then increases as fluid film thickness expands. Further, the bearing exhibits proper stiffness and adaptable anti-abrasion when thickness maintains 0.3 mm. This study provides a profound understanding of centrifugal micro hydrodynamic axial-Thrust bearing, and identifies its optimization measures.

Experimental and Simulated Investigation of Lubrication Characteristics of a Water-Lubricated Bearing in a Single-Screw Compressor

Water-lubricated single-screw compressors (WSSCs) have developed rapidly in recent years because they can supply oil-free compressed air at considerably low costs. However, a major technical obstacle is that the conventional bearing arrangement of a star wheel shaft is prone to wear failure, which makes it difficult for WSSCs to run properly for long periods of time. To solve this problem, a star wheel thrust bearing with new liquid groove was proposed in this paper. Pulsating forces (i.e., bearing forces) acting on a star wheel shaft by compressing air were calculated through the dynamic analysis of the star wheel shaft system. A mathematical model of hydraulic water films in the bearing sliding clearance was established to describe the influence of water injection pressure on water film pressure distribution and its bearing capacity. Lubrication characteristics were compared between two types of hydrostatic thrust bearings (HTBs) with different grooves to illustrate that the new structure is more suitable for WSSCs. The reasonability of the proposed model and simulation results were verified using an axial thrust bearing test rig developed by the authors. In addition, variation parameters of hydrostatic film thickness between the sliding surfaces of the star wheel axial thrust bearing were measured. The results show that the instability of the water film thickness and axial vibration of the star wheel were suppressed, thereby avoiding the contact of solid materials between the end face of the axial thrust bearing. This study provides a structural optimization pattern of star wheel axial thrust bearings used in water-lubricated single-screw compressors.

Analysis and Treatment of Turbine’s Increasing Shaft Displacement and Thrust Bearing’s Burning Loss

In this paper, the writer is to analyze the causes of axial displacement and thrust bearing temperature according to the relevant factors affecting the axial force of turbine and provides treatments. It can be used for reference for units with this phenomenon or axial force increasing.

Finite element method modeling of crankshaft axial impact measurements

It has been recently discovered that there is a periodical axial impact phenomenon in a running engine crankshaft. Bending of the shaft causes significant extension of the crankshaft and impact to the engine block through the axial thrust bearing. The aim of this work is to study impact-induced energy fluctuations in a complex-shaped Wärtsilä sixteen vee 32 engine crankshaft by using an explicit finite element method (FEM) during the first 25 ms after impact. Using the FEM allows us to study real components used in industry, and analyze their dynamics in the transient phase. In conclusion, we found interesting results that can be used as guidelines for a full-scale crankshaft measurement instrumentation plan. The full-scale measurements will be performed later in the Wärtsilä Oy facility at Vaasa, Finland. The main finding is that a substantive amount of energy is trapped in the head region and the first two crank pins of the crankshaft, which can affect crankshaft durability regarding high-cycle fatigue.

수소전기차용 공기압축기 에어포일 스러스트 베어링 2-FSI 해석

A hydrogen-electric car is a fuel-cell vehicle that reacts hydrogen fuel with oxygen in the air to generate electricity to drive the traction motor. An air compressor is a device that compresses air and supplies it to the fuel cell stack. These generally use two types of airfoil bearings: The first is journal bearing, the second a thrust bearing. In this paper, axial thrust bearings are analyzed using 2-Way fluid-structure interactions (FSI). To determine the validity of the 2-Way FSI analysis, a solid thrust bearing was fabricated and the torque was measured. For 60 kr/min 70 kr/min and 80 kr/min rotations, loads were applied at 10 N, 15 N, and 20 N and the resulting torque was measured. For the 2-Way FSI analysis, a 1/6 split model was selected, the turbulence model was Menter’s Shear Stress Trasport (SST), and 10 meshes were made in the air gap using a system coupling condition moving the solid and fluid parts simultaneously. The 2-Way FSI analysis result showed the error within 7.3 %, proving its validity.

Porosity Effect of Sintered Steel on the Frictional Performance of Conformal and Nonconformal Lubricated Contacts

The effect of surface topography on lubricated systems plays a crucial role in terms of friction performance, because surface micro-irregularities can improve the load-carrying capacity of mechanical parts in lubricated conformal and nonconformal contacts. Sintered materials, which can be applied to manufacturing several mechanical components such as gears, axial thrust bearings, and disc brake pads, are interesting candidates, because they present pores that could be somewhat compared to microcavities produced by surface texturing techniques. This work aims at studying the influence of surface pores originated from the sintering process on the frictional performance of lubricated contacts under different lubrication regimes and slide-to-roll ratios (SRR). The research contributes to understanding how random micro-irregularities could change lubrication conditions and promote effects similar to those of more expensive and precise surface features produced by texturing techniques. The experimental results showed that a decrease in porosity led to a reduction in the coefficient of friction. Furthermore, less porous samples promoted friction reduction compared to nonporous materials due to the probable additional load support caused by small-scale surface pores. Therefore, in addition to the traditional appeal of the use of sintered materials to reduce production costs, the present contribution reveals that this type of material could also be used to reduce friction in contacting mechanical components operating under certain tribological conditions.

A Gas Lubricant Combined Support-sealing Node

The purpose of the research provided in this article is to develop a gas-dynamic device capable of performing the functions of support sealing, unloading devices for axial thrust bearings and damping of axial vibrations of the rotor. Some kinds of seals applied in supports of aircraft engines are known. A face gas-dynamic seal is one of the most effective and standard technology solution for compressors. As the basic element of the developed device, a face gas-dynamic seal with spiral grooves is considered. It also includes the fundamental mathematical calculation of such devices and the experimental research outcomes that form the basis of which such devices can be produced and adapted for use.

Heat transfer in a cavity with rotating disk in turbulent regime

Subject of Research.The paper considers turbulent flow and heat exchange in a closed axisymmetric cavity with a rotating disk, which is a model of two-way axial thrust bearing, as well as the other important elements of turbomachines, for example, blade ring labyrinth seals of axial compressor stage. Method. The flow and heat transfer characteristics are studied depending on the relative gap between the fixed housing and the rotating disc and the Reynolds number. Comparison of the local and integral flow characteristics obtained on the basis of various models of turbulence with the data of physical experiment is given. Main Results. The flow structure and heat transfer characteristics are studied depending on the relative gap between the fixed body and the rotating disc and the Reynolds number. Comparison of the local and integral characteristics of the flow with the data of the physical experiment shows that the best matching is given by the application of the k-ε model with Kato-Launder corrections for the turbulence production term and the corrections to the curvature of the streamlines, as well as the two-layer k-ε / k-1 turbulence model. The application of the Spalart-Allmares turbulence model and the Reynolds stress transfer model leads to significant errors in calculating the heat flux distribution over the stator surface. Practical Relevance. The considered problem is a model problem and it gives the possibility to make a conclusion about the applicability of various flow models and models of turbulence in such units of compressors and gas turbines as seals of the blade ring, axial and radial gas and liquid bearings, rotating heat exchangers.

Formation of nanosized grain structure in martensitic 100Cr6 bearing steels upon rolling contact loading studied by atom probe tomography

To understand the origin of white etching cracks (WECs), a systematic microstructural characterisation in the regions affected from the near-surface region down to the subsurface layers where WECs occur is necessary. As a starting point, we focus on the near-surface region of an axial thrust bearing, made of martensitic 100Cr6 steel, to study the influence of rolling contact loading on the microstructure and the resulting distributions of the major alloying elements C and Cr using atom probe tomography. We find that upon rolling contact loading the original plate-like martensitic structure evolves into a nanosized equiaxed grain structure with C segregation up to 5 at.-% at the grain boundaries. Cementite particles, located at grain boundaries and triple junctions, undergo spheroidisation. The originally homogeneously distributed Cr becomes enriched in spheroidised cementite particles. The microstructural changes give strong hints that rolling contact loading induces plastic deformation and an increased temperature on the near-surface region.This paper is part of a Themed Issue on Recent developments in bearing steels.

Theoretical and Experimental Loss and Efficiency Studies of a Magnetic Lead Screw

This paper investigates mechanical and magnetic losses in a magnetic lead screw (MLS). The MLS converts a low-speed high-force linear motion of a translator into a high-speed low-torque rotational motion of a rotor through helically shaped magnets. Initial tests performed with a novel 17-kN demonstrator and a simplified motor model showed an efficiency of only 80% at low load; however, it was expected that the efficiency should be above 95%. For understanding and future optimization, a detailed study of the loss in the MLS is presented with the aim of identifying and segregating various loss components that was not accounted for in previous results. This is done through theoretical loss calculations and various experiments. It is concluded that the linear guide is the dominating loss component in the MLS demonstrator, whereas the losses in the axial thrust bearing is not as dominant as expected; furthermore, an efficiency above 94% was measured.

Experimental investigation of the flow in a simplified model of water lubricated axial thrust bearing

In hydropower plants the axial thrust bearing takes up the hydraulic axial thrust of the runner and, in case of vertical shafts, the entire weight of all rotating masses. The use of water lubricated bearings can eliminate the oil leakage risk possibly contaminating the environment. A complex flow is generated by the smaller film thickness due to the lower viscosity of water compared with oil. Measurements on a simplified hydrostatic axial trust bearing model were accomplished for validating CFD analysis of water lubricated bearings. In this simplified model, fixed pads are implemented and the width of the gap was enlarged to create a higher resolution in space for the measurements. Most parts of the model were manufactured from acrylic glass to get optical access for measurement with PIV. The focus of these measurements is on the flow within the space between two pads. Additional to the PIV- measurement, the pressure on the wall of the rotating disk is captured by pressure transducers. The model bearing measurement results are presented for varied operating conditions.

Reduced-Friction Passive Magnetic Bearing: Innovative Design and Novel Characterization Technique

Friction is mostly unwanted in rotating machines. In order to reduce its impact on the system, the integration of magnetic bearings is frequently regarded as a valid solution. In rotating systems like flywheel energy storage systems (FESS), mechanical losses created by mechanical bearings greatly reduce the overall performance. Magnetic bearings are thus frequently integrated in FESS to eliminate mechanical losses. The simple design of passive magnetic bearings (PMBs), their inherent security, and their very low friction make them perfect candidates for FESS. The main objective, and most important contribution of this paper, is to document an innovative PMB that minimizes energy losses induced by the axial thrust bearing, and to document the methodology used to measure its stiffness and damping. Although PMBs are fairly well documented in literature, no other PMB is designed to reduce the friction generated by the thrust bearing. In order to promote their integration, it is critical to identify their mechanical properties such as stiffness and damping. Hence, another contribution of this paper is to propose a new way to easily characterize any magnetic bearing topology to replace available techniques that only provided the properties for a precise configuration of the bearing. The new technique provides an unprecedented mapping of the forces generated by complex combinations of permanent magnets. Experimental results show that the new PMB can be configured to effectively reduce the force applied to the thrust bearing, resulting in lower friction. This friction reduction is achieved while allowing the proper operation of the bearing. Results also show that the measured stiffness is different from those obtained analytically, suggesting that a magnetic bearing should always be characterized prior to its use.

Experimental identification of turbocharger mechanical friction losses

Understanding the friction losses of automotive turbochargers is a key parameter in assessing properly the mechanical efficiency of these machines. Current turbochargers are mostly equipped with oil bearings: two journal bearings and one double-acting axial thrust bearing. In order to know on which element improvement efforts have to be focused, it is important to determine their contribution to the total friction losses. This will also make it possible to calibrate the computation models of friction losses of the bearings separately. Measuring the friction losses of a turbocharger is not easy and existing methods measure only the total losses due to the association of journal and thrust bearings. A novel turbocharger test bench equipped with a highly accurate torquemeter and a magnetic axial load device has been developed. Measuring methodologies have been fine-tuned to measure the total friction losses, the influence of axial load on the thrust bearing, and the mechanical friction losses of the journal bearings alone. The experimental device and measuring methods are detailed in this paper. Experimental results are presented and analysed. The influence of axial load, oil inlet pressure and the distribution of friction power and oil mass flow between thrust bearing and journal bearings are discussed.

Analysis and Control of Nonsalient Permanent Magnet Axial Gap Self-Bearing Motor

This paper deals with a nonsalient permanent magnet axial gap self-bearing motor (AGBM), which is an electrical combination of an axial thrust bearing and an axial flux motor. A method for controlling the axial position and the rotating speed of the motor is also discussed. First, the development of the AGBM is briefly reviewed. The axial force and the rotating torque are then analyzed theoretically to establish an exact mathematical model for the motor. Finally, a modern control structure is derived to give the AGBM drive good dynamic behavior to make it suitable for practical application in industry. To demonstrate the proposed technique, a surface-mounted four-pole AGBM has been constructed and tested. The experimental results confirm that the motor works stably with the proposed vector control. Moreover, the AGBM can simultaneously provide noncontact levitation and rotation. This makes it an ideal replacement for conventional mechanical bearing motors in equipment used in harsh environments.

Modeling and Control of Salient-Pole Permanent Magnet Axial-Gap Self-Bearing Motor

This paper will introduce an inset-type axial-gap self-bearing motor (AGBM), which is an electrical combination of an axial thrust-bearing and an axial flux motor. A method for controlling the axial position and the rotating speed of the AGBM without the influence of reluctance torque is also discussed. First, the axial force and the motoring torque are analyzed theoretically, and then, the control method is derived. To demonstrate the proposed technique, an inset two-pole AGBM has been constructed and tested. The experimental results confirm that the motor works stably with the proposed vector control. Moreover, the rotating torque and the axial force can be controlled independently as well.

Superconducting energy storage flywheel—An attractive technology for energy storage

Flywheel energy storage (FES) can have energy fed in the rotational mass of a flywheel, store it as kinetic energy, and release out upon demand. The superconducting energy storage flywheel comprising of magnetic and superconducting bearings is fit for energy storage on account of its high efficiency, long cycle life, wide operating temperature range and so on. According to the high temperature superconducting (HTS) cooling mode, there are zero field cooling (ZFC) bearings and field cooling (FC) bearings. In practice, the superconducting bearings are formed by field-cooled superconductors and permanent magnets (PMs) generally. With respect to the forces between a permanent magnet and a superconductor, there are axial (thrust) bearings and radial (journal) bearings. Accordingly, there are two main types of high-temperature superconducting energy storage flywheels, and if a system comprising both the thrust bearing and the radial bearing will have the characteristics of both types of bearings. Magnetic force, magnetic stiffness and damping are these three main parameters to describe the levitation characteristics. Arrangement and shape of superconductors, thickness of superconductor, superconducting flux creep and critical current density of the superconductor affect the magnetic levitation force of these superconducting bearings. The key factors of FES technology, such as flywheel material, geometry, length and its support system were described, which directly influence the amount of energy storage and flywheel specific energy. All these results presented in this paper indicate that the superconducting energy storage flywheel is an ideal form of energy storage and an attractive technology for energy storage.

Surface contact analysis in axial thrust bearings based on different numerical interpolation approaches

The simulation of moving parts in combustion engines and power trains by means of flexible multi-body dynamics requires complex computation techniques for the contact areas. Understanding surface interactions in detail is of great value for new products and can reduce the development time and costs significantly. Modelling of lubricated contacts, which exist in slider bearings (axial and radial) and in the cylinder kit (piston, rings, and cylinder liner) are challenging tasks. Here, the simulation models have rough discretizations of the body surfaces and fine oil-film discretizations. Although body surfaces are usually given by finite element method (FEM) meshes, the non-linear reaction force of the loaded oil-film is determined by integrating the lubricant pressure field on the hydrodynamic mesh. The pressure is commonly calculated by solving a type of Reynolds equation in the gap between the contacting surfaces. The combination of different types of meshes of the body surfaces and the oil-film highly affects the quality of the results. Interpolation and integration approaches have to be capable of dealing with the high sensitivity of algorithms used for elastohydrodynamic contacts. This paper presents an analysis of numerically simulated contacts in axial slider bearings for combustion engines. A surface contact algorithm with different numerical interpolation approaches for the clearance gap and its time derivative is utilized to investigate the elastohydrodynamic behaviour of axial thrust bearings. Thereby, the complete set of equations for moving and elastic bodies and oil-film reaction forces have to be solved in time domain to obtain the actual shape of the deformed clearance. The numerical interpolation approaches comprise the Fritsch-Butland interpolation with the Brodlie-derivative-formulation as well as generalized cubic spline functions. The investigations consider effects of inclined crankshafts as they occur in axial thrust bearings of combustion engines. Detailed results are shown applying linear and tetragonal FEM meshes for the surfaces of the contacting bodies.

Active Control of Axial-flow Fan Noise Using Magnetic Bearings

In this paper we present a novel approach to reducing blade-rate noise of axial-flow fans. By using magnetic bearings as a noise control actuator, it is possible to collocate the anti-noise source with the disturbance noise source. This approach allows for global noise reduction throughout the sound field. A DC motor connected to a fan by a short rigid shaft was used to demonstrate this approach. The shaft was supported in the radial and axial directions by magnetic bearings. The bearings provide position control of the shaft and fan; this position control can be used to vibrate the fan at a desired frequency and amplitude. Controlled vibration of the fan allows its use as a speaker in an active noise control scheme. Noise control was implemented on a dedicated digital signal processor using a least mean square algorithm. The output of the noise control algorithm supplies the position commands for the magnetic bearing controller. Experimental data showed that by actuating the axial thrust bearing, the noise output of a fan could be reduced by 4 dB at the error microphone, and 3 dB at points away from the error microphone.

Voltage Sags Compensation Using a Superconducting Flywheel Energy Storage System

This paper presents a voltage sag compensator, which uses a flywheel energy storage system with superconducting magnetic axial thrust bearing (SMB) and a permanent magnet radial bearing (PMB). The SMB was built with Nd-Fe-B magnet and YBCO superconducting blocks, refrigerated with liquid Nitrogen. The magnets are assembled with magnetic flux shapers in order to increase the levitation force and the stiffness. The radial PMB is used to positioning the vertically arranged switched reluctance machine (SRM) used as motor/generator. Simulations of the power electronics and SRM show that the system can work up to 30,000 rpm supplying the required energy during disturbances.

HEARTWARE - A NOVEL MINIATURIZED PASSIVE MAGLEV CENTRIFUGAL VAD

A long term mechanical assist device must have the following attributes to be successful in a large patient population: capability of full ventricular support; small size and optimized fit; hemocompatibility; highly reliable, wearless design; high power efficiency. Heartware has developed a miniaturized passively magnetically suspended centrifugal VAD, which has a displaced volume of 50 cc and weighs 145 grams. The pump has a short integrated inflow cannula and an axial height less than one inch. The size of the device coupled with the perpendicular relationship of outflow to the inflow allows for intrapericardial pump placement and fast implantation. The short axial height is achieved through a proprietary design that integrates the motor into a wide-bladed impeller. Wearless pump design is achieved via a combination of passive radial magnetic bearings, which also provide axial preload, and shrouded axial hydrodynamic thrust bearings. Enhanced reliability is achieved via the simplicity of the impeller suspension system, as well as by redundant stators and a fatigue resistant driveline. The pump can provide 2 to 12 litershin of flow at 2500 rpm. Through the novel motor and impeller integration, the pump is highly power efficient requiring only 4.5 Watts to deliver 5 I/min flow against 100 mmHg. The Heartware VAD promises to be an easily implantable, highly reliable, long term, mechanical ventricular assist device suitable for a large patient population.