Saeid dousti senior technical fellow rotor bearing. Modeling of gas foil bearings for sco2 turbomachinery. The tribology group has developed advanced and efficient computational models for the analysis and design of processfluid film bearings hydrostatic and hydrodynamic, gas bearings including foil bearings, gas damper and labyrinth seals, tilting pad bearings and squeeze film dampers. Barber nichols deploys foil gas bearings operating on supercritical co2 sco2 turbomachinery international septoct 2012. Since 2003, xdot has focused on several specialties including foil bearing applications, analysis tool development, bearing shape optimization, and friction damping. Foil bearings development mechanical solutions inc. Foil bearings are selfgenerating, compliant hydrodynamics bearings. Abstract this paper presents selected numerical models of foil bearings developed in a few research centres around the world. Influence of geometric parameters on the bump foil bearing. Pdf development of the foil bearing technology researchgate. New testing capabilities are needed in order to foster thrust foil air bearing technology development and aid its transition into future oilfree gas turbines. Pdf application of foil bearings to helium turbocompressor.
The foil forming process includes stamping and heat treatment of metal sheets of a certain thickness. All calculations are performed in a consistent calculation model. Xdot has developed a unique, high performance foil bearing configuration to meet the needs of machines being developed by our customers. We also have strong research and development efforts related to a variety of rotordynamic, bearing, and high speed machinery topics. To validate these new foilbearing capabilities, nasa set out to.
Essentially, the viability of these bearings within the automotive market has become a reality with individualized bearing designs. Pure refrigerant lubrication technology in oilfree centrifugal compressors. The suitable technical abilities, which mean a highefficiency computer working station with the adequate software and dedicated test stands, are also essential. Pure refrigerant lubrication technology in oilfree. Xdot engineering consultants and staff xdot engineering. Compliant foil bearings technology and their application to high. Foil air bearings encounter contact at very low speeds during startup and shut down prior to the development of the hydrodynamic gas film and. This work is concerned with the development and the implementation of a foil air journal bearing model.
The thermo hydrodynamic flow models account for fluid inertia and variable properties, flow turbulence in exotic bearing geometries. Development of the bearing technology with deformable elements of the bearing sleeve utilization are presented in the paper. To address one such need, concepts nrec has developed a tool for the preliminary design of actively cooled, axial turbine blades, called ctaads. Design, fabrication, and performance of foil gas thrust. Nov 01, 2014 other companies, such as barber nichols and capstone turbine, are involved in gas bearing development. Foil bearing advantages make them ideal for application in technologically. Miniaturization of gas foil bearings has been explored using silicon parts with marginal success. Each bearing is designed for a specific application which required october 20. San andres measurements of rotordynamic performance in a hot rotor gas foil bearing system by. Research shows that during shaft startup the foil bearing needs to develop the gas film layer to effectively support the shaft. These projects blend improving our ability to address todays consulting needs, with developing technology and capabilities for tomorrows problems. A significant effort was spent toward materials and coating development for capabilities to 1200 f. A new approach to the analysis of wide foil bearings is investigated. Foil air bearings are selfacting hydrodynamic bearings that use ambient air as the lubricant instead of oil.
A foil bearing, also known as a foilair bearing, is a type of air bearing. Technical development path for gas foil bearings ntrs nasa. Compliant air foil bearings are used in a wide variety of applications. A spring model to estimate the stiffness of compression springs was developed and showed a good level of agreement with the experimental results. Gas foil bearing coating behavior in environments relevant to. An improved bulkflow analysis for interlocking labyrinth gas seals.
Dynamic response of a rotor air bearing system due to base induced periodic motions by. This research focuses on development of foil gas thrust bearing test rig which will operate at high temperature and speed. These elements form together the thrust foil bearing structure fig. San andres study of impact of orbit path whirl ratio and clearance on the flow field and rotordynamci coefficients for a smooth annular seal by.
This results in a hard, wearresistant coating that meets the life and temperature requirements of the bearing. In fact, initial development costs remain unreasonably high for new applications, with a common perception of many in the industry that foil bearing design remains a black art. Pdf development of the bearing technology with deformable elements of the. On the manufacturing of compliant foil bearings sciencedirect. Lowfriction coatings are used on bearing surfaces in order to facilitate rotation during these periods. If the sommerfeld number is greater than 6, the bearing system is a good candidate for foil bearings. The influences of bump foil structure parameters on the. The equation of motion for a finite length of tape is coupled to the transient lubrication equation for the air film between th. At high shaft rotational speed these bearings allow the shaft to ride on a cushion of air. Giri agrawal who is an industry renowned pioneer in highspeed foil gas bearing. Foil or a set of foils with the viscoelastic properties comprise the. Miti 4 th generation compliant foil bearings have unlimited speed potential, high load carrying capacity, can operate under temperature extremes from cryogenic to 650c, have low power loss and long life.
This foil gas bearing uses a series of compression springs as a compliant structure instead of corrugated bump foils. Design principles for large foil bearings based on scaling. Under the top foil petals, there are bump foil segments. Currently, the fields of application are more extensive but still. For this purpose, the numerical procedure resolving the reynolds equation for compressible.
The boundary condition is that both the top foil and the bump foil are welded to the bearing sleeve. Chen is a graduate of national taiwan university and. To validate these new foil bearing capabilities, nasa set out to demonstrate the use of foil air bearings. This paper is an attempt to shed light into the foil bearing manufacturing knowhow. Both air and oil are fluids that can perform the job of separating moving metal parts. Application of tribology in foil bearing technology. This innovative test rig offers a revolutionary, oilfree platform to advance the development of hydrodynamic, compliant foil thrust bearing technologies over a broad range of applications. Foil air bearings for turbochargers turbomachinery blog. Computeraided engineering software for specialized design. The development of foil bearings began in the early 1970s to provide rotational.
These challenges include bearing surface velocities above current industrial applications, the need for small compact bearing sizes with thin material sections foils and small well controlled clearances. Erik swanson began his career at the virginia tech rotordynamics lab and at mohawk innovative technology. During operation, the rotating shaft of an oilfree high speed turbomachine is supported on a thin, self generated film of high pressure air or gas. The foil bearing was tested, and the maximum rotation speed of 642,000 rpm, which was limited by turbine performance, was recorded.
An experimental program was initiated to elucidate the behavior of coated. Commercialization of gas foil bearings in mega watt scale applications necessitate the development of simple tools for estimating bearing design parameters such as load capacity, radial clearance, and support structure stiffness, etc. Conversely, during startup and shutdown, the shaft rides along the foil bearing surface. His current research focuses on the development of foil gas bearings for highspeed turbomachinery and hybrid magnetic bearings for blood pumps and momentum energystorage flywheel systems. Development and application of integrated aerodynamic. Garrett airesearch air cycle machine foil bearings were first installed as original equipment in 1969 in the dc10 s environmental control systems. The axstream bearing module is used to determine hydrodynamic and mechanical characteristics for different types of hydrodynamic journal and thrust bearings as well as auxiliary component characteristics such as seals, squeeze film dampers, etc. On the manufacturing of compliant foil bearings infoscience. The thrust foil bearing lifting surface is divided into a few segments known as petals fig. Foil bearing foil bearings were first developed in the late 1950s by airesearch mfg. Simplified thermohydrodynamic analysis of rigid geometry journal bearings. Turbomachinery is the most common application because foil bearings operate at high speed. Guidelines for determining foil bearing applicability.
Development and application of multiphysics simulation tools for foil thrust bearings operating with carbon dioxide. The effect of nonlinear pivot stiffness on tilting pad bearing dynamic force coefficients. A bearing system s sommerfeld number is the the quickest way to determine if foil bearings might make sense. Introduction replaced the clear plastic film with sheet metal, studded with foil gas bearing technology evolved from rigid gas. One of the objectives was to validate their thermomechanical behavior at high temperatures 1,2. Specialized design computeraided engineering software. The question now becomes whether the foil gas bearing manufacturers can penetrate the market from a largerscale and create a standard for these turbocharger setups to run free of oil altogether. Foil or a set of foils with the viscoelastic properties comprise the deformable element. A foil bearing, also known as a foil air bearing, is a type of air bearing. In foil bearing systems, the main manufacturing complication is the fabrication of the bump foil, as the sleeve and the rotor can be manufactured with good accuracy. Xdot engineering and analysis gas foil bearings and. Fea model of the analyzed foil bearing was developed by. Models development requires an intensive teamwork of scientists, who deal with the modelling as well as with the experiments. Foil bearing provides compliant support and moderate coulomb friction for rotorbearing system, which is conducive to stability and reliability of high speed.
In this paper, a deformation model of bump foil is established by using elastic mechanics theory. Dynamic performances of foil bearing supporting a jeffcot. It is expected that a better understanding of foil gas bearing development path will aid in future development and progress towards more advanced applications. This common foil bearing application provides oilfree air for highspeed systems such as fuel cell blowers and turbochargers. Technical development path for foil gas bearings dr. An experimental program was initiated to elucidate the behavior of coated bearing foils in the harsh environments of this system. Foil bearings are not a commercially available product that can simply be ordered from a catalog. Pdf application of a compliant foil bearing for the. Other companies, such as barber nichols and capstone turbine, are involved in gas bearing development.
Pdf application of foil bearings to turbomachinery including. Using this design method, a foil bearing was designed, and its load capacity was estimated. A fully coupled elastohydrodynamic model for static. The versatility, ease of manufacture, and low cost of foil bearings are a few of the reasons foil bearing have been so thoroughly researched. The sandia sco 2 recompression closed brayton cycle rcbc utilizes a series of gas foil bearings in its turbinealternatorcompressors.
The results of recent design and development work on compliant air lubricated foil journal bearings to meet the requirements of new commercial aircraft. The test rig developed is equipped with thermocouple, optical probe, load cell which provides temperature, axial load, torque and high speed data by using ni labview. Christopher dellacorte nasa, glenn research center cleveland, ohio abstract foil gas bearings are in widespread commercial use in air cycle machines, turbocompressors and microturbine generators and are emerging in more challenging applications such as. Design of experiments techniques are used to quantify the effects of the different manufacturing parameters, as well as defining an optimum manufacturing procedure. Msi has decades of experience designing, building and testing foil bearings for a wide variety of systems, including for rotating machines that we design ourselves. With motors and generators running at higher and higher speeds and increased torque capacity, the need for a robust, highspeed, lowloss foil bearing design is clear. Some situations require additional, specialized software to complement the standard turbomachinery design workflow. The software allows rolling bearing supports to be analyzed in detail from single bearings via complex shaft or linear guidance systems to entire gear systems. In case of foil bearing with given dimensions, clearance governs the magnitude of pressure developed, whereas stiffness. The design activity included the development of analytical tools for the thrust and journal bearings and their use during the bearing test phase, for the purpose of increasing bearing load capacity.
Recent advances in bearing design, hightemperature surface coatings and computer modeling are enabling new applications of these bearings. The fabrication of foil bearings is challenging due to the dependence on sheet metal forming to produce the compliant structure. It is known from the published literature that the load capacity of foil bearings depend on the operating speed, viscosity of the medium, clearance, and stiffness of the foil apart from the geometric dimensions of the bearing. Both types of segment are welded to greater plate called the main foil. The development of foil bearings began in the early 1970s to provide rotational guidance of gas turbine shafts. The paper presents the application of a compliant foil bearing for estimation of the thrust force in a single stage radial blower under operational conditions. A computational model for tilting pad gas bearings porous type and performance evaluation of a carbongraphite porous type thrust bearing. Nasa engineers developed the rule of thumb guidelines for estimating foil bearing load capacity based on. A recently enacted program for the development of a high speed acm for a european commercial aircraft falcon 2000 provided the opportunity for developing a. Pressing needs for sealbearing software development. Bumptype gas foil bearing is a special type of sliding bearing, especially suitable for supporting rotors with light loads and high speeds. Because of this, we can support our customers with as much or as little of their machinery development effort as they like, from conceptual design to prototype testing. The development of reliable foil bearing numerical models still poses many problems. Dynamic response of selfacting foil bearings ibm journal.
Bearing analysis software turbomachinery design software. Miniaturization of gas foil bearings has been explored using silicon parts with. Application of tribology in foil bearing technology home. Rotor dynamics analysis would neither be complete nor reliable without accurate modeling of bearings. A fluidstructure interaction algorithm is proposed according to reynolds equation of compressible gas.
When subambient pressures occur in the gas film, the top foil will separate from the bump foil and deflect inward to the. There is generally a critical speed that is dependent on variables including bearing size, gas film clearance, etc. The use of air foil bearings for small gas turbine engines has been hampered by several significant technical challenges. A new foil bearing with compression springs is designed, built, analyzed, and tested.
Foil bearings were first developed in the late 1950s by airesearch mfg. A shaft is supported by a compliant, springloaded foil journal lining. This paper describes a new test apparatus capable of testing thrust foil air bearings up to 100 mm in diameter at. Foil bearing technology is utilized mostly in the highspeed turbo machines, such as. Computational analysis of foil air journal bearings using a. Development of a test rig for metal mesh foil gas bearing and measurements of structural stiffness and damping in a metal mesh bearing. This paper describes a new test apparatus capable of testing thrust foil air bearings up to 100 mm in diameter at speeds to 80,000 rpm and temperatures to 650 c 1200 f. Rotor dynamics and slide bearing department key words. Their compliant foils conform to the size and shape of the mating rotating shaft. Xdot is much more than just another engineering consultant. Research shows that during shaft startup the foil bearing needs to develop the gas film layer to. The power density of supercritical co2 is such that a 1 mw impeller is only 1. With the advent of new bearing designs, foil air bearings are now ready for higher temperature environments.