Development of a High Speed Gas Bearing Test Rig to Measure Rotordynamic Force Coefficients

2011 ◽  
Vol 133 (10) ◽  
Author(s):  
J. Jeffrey Moore ◽  
Andrew Lerche ◽  
Timothy Allison ◽  
David L. Ransom ◽  
Daniel Lubell
Keyword(s):  
High Speed ◽  
High Amplitude ◽  
Fluid Film ◽  
Test Rig ◽  
Force Coefficient ◽  
Gas Bearings ◽  
Foil Bearings ◽  
Fluid Film Bearings ◽  
Wide Range ◽  
Gas Bearing

The use of gas bearings has increased over the past several decades to include microturbines, air cycle machines, and hermetically sealed compressors and turbines. Gas bearings have many advantages over traditional bearings, such as rolling element or oil lubricated fluid film bearings, including longer life, ability to use the process fluid, no contamination of the process with lubricants, accommodating high shaft speeds, and operation over a wide range of temperatures. Unlike fluid film bearings that utilize oil, gas lubricated bearings generate very little damping from the gas itself. Therefore, successful bearing designs such as foil bearings utilize damping features on the bearing to improve the damping generated. Similar to oil bearings, gas bearing designers strive to develop gas bearings with good rotordynamic stability. Gas bearings are challenging to design, requiring a fully coupled thermo-elastic, hydrodynamic analysis including complex nonlinear mechanisms such as Coulomb friction. There is a surprisingly low amount of rotordynamic force coefficient measurement in the literature despite the need to verify the model predictions and the stability of the bearing. This paper describes the development and testing of a 60,000 rpm gas bearing test rig and presents measured stiffness and damping coefficients for a 57 mm foil type bearing. The design of the rig overcomes many challenges in making this measurement by developing a patented, high-frequency, high-amplitude shaker system, resulting in excitation over most of the subsynchronous range.

Development of a High Speed Gas Bearing Test Rig to Measure Rotordynamic Force Coefficients

2010 ◽  
Author(s):  
J. Jeffrey Moore ◽  
Andrew Lerche ◽  
Timothy Allison ◽  
David L. Ransom ◽  
Daniel Lubell
Keyword(s):  
High Speed ◽  
High Amplitude ◽  
Fluid Film ◽  
Test Rig ◽  
Force Coefficient ◽  
Gas Bearings ◽  
Foil Bearings ◽  
Fluid Film Bearings ◽  
Wide Range ◽  
Gas Bearing

The use of gas bearings has increased over the last several decades to include microturbines, air cycle machines, and hermetically sealed compressors and turbines. Gas bearings have many advantages over traditional bearings, such as rolling element or oil lubricated fluid film bearings, including longer life, ability to use the process fluid, no contamination of the process with lubricants, accommodating high shaft speeds, and operation over a wide range of temperatures. Unlike fluid film bearings that utilize oil, gas lubricated bearings generate very little damping from the gas itself. Therefore, successful bearing designs such as foil bearings utilize damping features on the bearing to improve the damping generated. Similar to oil bearings, gas bearing designers strive to develop gas bearings with good rotordynamic stability. Gas bearings are challenging to design requiring a fully coupled thermo-elastic, hydrodynamic analysis including complex non-linear mechanisms such as Coulomb friction. There is a surprisingly low amount of rotordynamic force coefficient measurement in the literature despite the need to verify the model predictions and the stability of the bearing. This paper describes the development and testing of a 60,000 rpm gas bearing test rig and presents measured stiffness and damping coefficients for a 57 mm foil type bearing. The design of the rig overcomes many challenges in making this measurement by developing a patented, high-frequency, high-amplitude shaker system resulting in excitation over most of the subsynchronous range.

Analytical and Experimental Study of Hydroinertia Gas Bearings for Micromachine Gas Turbines

2005 ◽  
Author(s):  
Kousuke Isomura ◽  
Shin-ichi Togo ◽  
Kousuke Hikichi ◽  
Satoshi Goto ◽  
Shuji Tanaka
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
Load Capacity ◽  
Stable Operation ◽  
Test Rig ◽  
Suction Force ◽  
Gas Bearings ◽  
Bearing Stiffness ◽  
Gas Bearing

Hydro-inertia gas bearing is a type of static air bearing, which supports the rotor by suction force generated by supersonic flow in large bearing clearance [1]. A tool to analyze the flow inside the clearance of hydroinertia gas bearings have been developed, and validated by experiment. A tool to estimate the load capacity and the bearing stiffness of the hydroinertia gas bearing based on experimental data has also been developed. A micro spinner test rig has been fabricated to test an hydroinertia gas bearings designed by the developed tools, and stable operation of 4mm diameter shaft at 1,200,000 rpm has successfully been achieved. A micro-high-speed bearing test rig to test a rotor for micromachine gas turbine has been designed and fabricated. Current micromachine gas turbine’s configuration requires a rotor with 10mm diameter compressor and turbine impellers on each end of 4mm diameter shaft to operate stably at 870,000rpm. Based on the achievement of stable operation at the high-speed of 1,200,000 rpm, hydro-inertia gas bearing has been selected as a candidate for both the bearings for micromachine gas turbine. Currently, the rotor speed as high as 770,000rpm has been achieved in this test rig.

scholarly journals Improvement of Tilting-Pad Journal Bearing Operating Characteristics by Application of Eddy Grooves

Lubricants ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 18
Author(s):  
Eckhard Schüler ◽  
Olaf Berner
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Load Capacity ◽  
Fluid Film ◽  
Operating Characteristics ◽  
Fluid Film Bearings ◽  
Tilting Pad ◽  
Bearing Load ◽  
Bearing Loads ◽  
Tilting Pad Journal Bearing

In high speed, high load fluid-film bearings, the laminar-turbulent flow transition can lead to a considerable reduction of the maximum bearing temperatures, due to a homogenization of the fluid-film temperature in radial direction. Since this phenomenon only occurs significantly in large bearings or at very high sliding speeds, means to achieve the effect at lower speeds have been investigated in the past. This paper shows an experimental investigation of this effect and how it can be used for smaller bearings by optimized eddy grooves, machined into the bearing surface. The investigations were carried out on a Miba journal bearing test rig with Ø120 mm shaft diameter at speeds between 50 m/s–110 m/s and at specific bearing loads up to 4.0 MPa. To investigate the potential of this technology, additional temperature probes were installed at the crucial position directly in the sliding surface of an up-to-date tilting pad journal bearing. The results show that the achieved surface temperature reduction with the optimized eddy grooves is significant and represents a considerable enhancement of bearing load capacity. This increase in performance opens new options for the design of bearings and related turbomachinery applications.

Paper 3: Recent Developments in Fluid Film Lubrication Theory

1967 ◽  
Vol 182 (1) ◽  
pp. 36-50 ◽  
Author(s):  
T. Lloyd ◽  
H. McCallion
Keyword(s):  
Finite Difference ◽  
High Speed ◽  
Lubrication Theory ◽  
Fluid Film ◽  
Special Topic ◽  
Finite Difference Schemes ◽  
Great Activity ◽  
Wide Range ◽  
Film Lubrication ◽  
Fluid Film Lubrication

Developments in high-speed electronic computers have greatly influenced the progress in fluid film lubrication over the past ten years. Static and dynamic oil film parameters have been computed for a wide range of finite geometries, for hydrostatic and hydrodynamic bearings lubricated by compressible and incompressible lubricants. These are either sufficient in themselves or else act as a yardstick against which approximate formulas may be tested. Much use has been made of iterative finite difference schemes, which are particularly well suited to digital computers, and these methods are now more fully understood. Other methods of solution include direct inversion of finite difference matrices and solution by expression of the pressure by some infinite series, a finite number of terms of which give adequate representation. Besides the increase in design data available, there has been substantial progress through a re-examination of the effects of modifying some of the assumptions inherent in most of the available solutions of the Reynolds equation. These include the assumption of constant lubricant viscosity, of rigid surfaces and of laminar flow. Major progress has been witnessed in two fields. The interaction of the lubricant film with elastic boundaries has been shown to be of prime importance in highly loaded contacts such as gears. This has led to the development of the special topic of elastohydrodynamic lubrication theory. The applicability of gas bearings in such growing industries as computers, space vehicles and nuclear reactors has resulted in great activity and progress in this field.

An experimental investigation of a microturbine simulated rotor supported on multileaf gas foil bearings with backing bump foils

2017 ◽  
Vol 232 (9) ◽  
pp. 1169-1180 ◽  
Author(s):  
Bo Zhang ◽  
Shemiao Qi ◽  
Sheng Feng ◽  
Haipeng Geng ◽  
Yanhua Sun ◽  
...  
Keyword(s):  
High Speed ◽  
Preliminary Test ◽  
Journal Bearings ◽  
Rotating Machinery ◽  
System Stability ◽  
Test Rig ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Simulated System ◽  
First Time

Two multileaf gas foil journal bearings with backing bump foils and one set of gas foil thrust bearings were designed, fabricated, and used in a 100 kW class microturbine simulated rotor system to ensure stability of the system. Meanwhile, a preliminary test rig had been built to verify the simulated system stability. The rotor synchronous and subsynchronous responses were well controlled by using of the gas foil bearings. It is on the multileaf gas foil bearings with backing bump foils that the test was conducted and verified for the first time in open literatures. The success in the experiments shows that the design and fabrication of the rotor and the gas foil bearings can provide a useful guide to the development of the advanced high speed rotating machinery.

Subsynchronous Vibration Patterns Under Reduced Oil Supply Flow Rates

2017 ◽  
Author(s):  
B. R. Nichols ◽  
R. L. Fittro ◽  
C. P. Goyne
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Operating Conditions ◽  
System Stability ◽  
Supporting Evidence ◽  
Test Rig ◽  
Flow Rates ◽  
Oil Supply ◽  
Bending Mode ◽  
Wide Range

Many high-speed, rotating machines across a wide range of industrial applications depend on fluid film bearings to provide both static support of the rotor and to introduce stabilizing damping forces into the system through a developed hydrodynamic film wedge. Reduced oil supply flow rate to the bearings can cause cavitation, or a lack of a fully developed film layer, at the leading edge of the bearing pads. Reducing oil flow has the well-documented effects of higher bearing operating temperatures and decreased power losses due to shear forces. While machine efficiency may be improved with reduced lubricant flow, little experimental data on its effects on system stability and performance can be found in the literature. This study looks at overall system performance of a test rig operating under reduced oil supply flow rates by observing steady-state bearing performance indicators and baseline vibrational response of the shaft. The test rig used in this study was designed to be dynamically similar to a high-speed industrial compressor. It consists of a 1.55 m long, flexible rotor supported by two tilting pad bearings with a nominal diameter of 70 mm and a span of 1.2 m. The first bending mode is located at approximately 5,000 rpm. The tiling-pad bearings consist of five pads in a vintage, flooded bearing housing with a length to diameter ratio of 0.75, preload of 0.3, and a load-between-pad configuration. Tests were conducted over a number of operating speeds, ranging from 8,000 to 12,000 rpm, and bearing loads, while systematically reducing the oil supply flow rates provided to the bearings under each condition. For nearly all operating conditions, a low amplitude, broadband subsynchronous vibration pattern was observed in the frequency domain from approximately 0–75 Hz. When the test rig was operated at running speeds above its first bending mode, a distinctive subsynchronous peak emerged from the broadband pattern at approximately half of the running speed and at the first bending mode of the shaft. This vibration signature is often considered a classic sign of rotordynamic instability attributed to oil whip and shaft whirl phenomena. For low and moderate load conditions, the amplitude of this 0.5x subsynchronous peak increased with decreasing oil supply flow rate at all operating speeds. Under the high load condition, the subsynchronous peak was largely attenuated. A discussion on the possible sources of this subsynchronous vibration including self-excited instability and pad flutter forced vibration is provided with supporting evidence from thermoelastohydrodynamic (TEHD) bearing modeling results. Implications of reduced oil supply flow rate on system stability and operational limits are also discussed.

Stability-Optimized Clearance Configuration of Fluid-Film Bearings

2006 ◽  
Vol 129 (1) ◽  
pp. 106-111 ◽  
Author(s):  
Koichi Matsuda ◽  
Shinya Kijimoto ◽  
Yoichi Kanemitsu
Keyword(s):  
Fourier Series ◽  
Load Capacity ◽  
Fluid Film ◽  
Eccentricity Ratio ◽  
Rotating Speed ◽  
Fluid Film Bearings ◽  
Wide Range ◽  
Jeffcott Rotor ◽  
The Stability ◽  
Frequency Ratios

The whirl instability occurs at higher rotating speeds for a full circular fluid-film journal bearing, and many types of clearance configuration have been proposed to solve this instability problem. A clearance configuration of fluid-film journal bearings is optimized in a sense of enhancing the stability of the full circular bearing at high rotational speeds. A performance index is chosen as the sum of the squared whirl-frequency ratios over a wide range of eccentricity ratios, and a Fourier series is used to represent an arbitrary clearance configuration of fluid-film bearings. An optimization problem is then formulated to find the Fourier coefficients to minimize the index. The designed bearing has a clearance configuration similar to that of an offset two-lobe bearing for smaller length-to-diameter ratios. It is shown that the designed bearing cannot destabilize the Jeffcott rotor at any high rotating speed for a wide range of eccentricity ratio. The load capacity of the designed bearings is nearly in the same magnitude as that of the full circular bearing for smaller length-to-diameter ratios. The whirl-frequency ratios of the designed bearing are very sensitive to truncating higher terms of the Fourier series for some eccentricity ratio. The designed bearings successfully enhance the stability of a full circular bearing and are free from the whirl instability.

Foil Bearings Makes Oil-Free Turbocharger Possible

2005 ◽  
Author(s):  
Crystal A. Heshmat ◽  
Hooshang Heshmat ◽  
Mark J. Valco ◽  
Kevin C. Radil ◽  
Christopher Della Corte
Keyword(s):  
High Speed ◽  
Solid Lubricant ◽  
Load Capacity ◽  
Maximum Load ◽  
Solid Lubricant Coating ◽  
Foil Bearings ◽  
Wide Range ◽  
Rotor Bearing ◽  
Component Development ◽  
Bearing System

This paper describes an oil-free, 150 Hp turbocharger that was successfully operated with compliant foil bearings in a range of pitch and roll angles, including vertical operation, thereby demonstrating its viability for aircraft applications. On a gas test stand the turbocharger was operated to 120,000 rpm, under extreme conditions. In addition, the compliant foil bearing-supported turbocharger successfully tolerated shock and vibration of 40 g. Advanced technologies have been applied to the second generation of this turbocharger, shown in Figure 1, including self acting, compliant foil hydrodynamic air bearings with advanced coatings capable, of operation above 815 °C (1500°F). Journal foil bearings with maximum load capacity up to 670 kPa (97 psi) were used in conjunction with thrust foil bearings capable of maximum loads to 570 kPa (83 psi). Bearing component development tests demonstrated 30,000 start stop cycles at 815 °C (1500°F) with a newly developed, solid lubricant coating, KOROLON™. KOROLON™ exhibits a coefficient of friction of less than 0.1 at a wide range of temperatures. Current-designed foil bearings with KOROLON™ have immensely decreased turbolag, allowing acceleration from rest to over 100,000 rpm in less than 2 seconds. Advanced bearing stiffness maintained rotor total axial end-to-end motion within 100 microns (0.004 inch). Total radial static and dynamic motion was controlled within 25 microns (0.001 inch). Development of this high speed turbomachine included bearing and solid lubricant component development tests, rotor-bearing dynamic simulator qualification and gas stand tests of the assembled turbocharger. Gas stand and simulator test results revealed stable bearing temperatures, low rotor vibrations, good shock tolerance and the ability of the rotor bearing system to sustain overspeed conditions beyond 120,000 rpm. This combination of component and integrated rotor-bearing system technology addresses many of the issues associated with application of compliant foil bearings to industrial compressors, blowers, and gas turbine engines, overcoming many of the inherently show-stopping and debilitating features of rolling element bearings, i.e., speed and temperature limitations.

Optimum Design of Fluid Film Bearing for HDD Spindle Considering the Tolerances

2010 ◽  
Author(s):  
Yuta Sunami ◽  
Masayuki Ochiai ◽  
Hiromu Hashimoto
Keyword(s):  
Optimum Design ◽  
High Speed ◽  
Low Noise ◽  
Production Costs ◽  
Fluid Film ◽  
Rotating Shaft ◽  
Fluid Film Bearings ◽  
Support Element ◽  
Characteristic Values ◽  
Bearing Characteristic

Fluid film bearings are widely used for high speed rotating machineries acting as rotating shaft support element. Especially, the bearings are widely applied to the OA equipments and IT devices. Optimization of bearing parameters is effective to improve the performance of the fluid film bearings since low noise and impact-proof characteristics are essential requirements for these equipments. On the other hand, bearings for miniaturized spindles are generally made by mass production process which will eventually requires reduction of production costs. In this paper, therefore small size HDD spindle using fluid film bearings is treated. Sensitivity analysis and optimum design that considered dimensional tolerances using the probabilistic techniques are conducted. As a result, the influence of bearing characteristic values on the occurrence of dimensional tolerances was clarified.

Dynamic Forced Response of a Rotor-Hybrid Gas Bearing System Due to Intermittent Shocks

2009 ◽  
Author(s):  
Luis San Andre´s ◽  
Keun Ryu
Keyword(s):  
Natural Frequency ◽  
Fuel Efficiency ◽  
Forced Response ◽  
System Level ◽  
Jet Engines ◽  
Test Rig ◽  
Gas Bearings ◽  
Business Jet ◽  
Gas Bearing ◽  
Bearing System

Gas bearings in microturbomachinery (MTM) offer significant system level benefits, such as improved fuel efficiency, reduction in weight and number of components, extending life cycle and maintenance intervals, and reducing NOX emissions with a lower CO2 footprint. Emerging opportunities for gas bearings applications range from automotive turbochargers to engines for business jet aircraft, for example. Gas bearings, because of the inherently low gas viscosity, have low damping relative to oil-lubricated bearings and are prone to wear during rotor start-up and shut down procedures. The lack of damping brings concerns about rotor-gas bearing system robustness and endurance to tolerate shock induced loads, sudden while landing in jet engines, or intermittent in vehicles while moving across a rough terrain, for example. The paper demonstrates the reliability of a hybrid gas bearing system from rotor vibration measurements induced by sporadic shock loads acting on the base of a test rig and while the rotor is coasting down from a top speed of 60 krpm (1000 Hz). In the tests, (1) an electromagnetic pusher delivers impacts to the rig base, or (2) the whole rig is manually tilted and dropped. The test rig consists of a rigid rotor, 0.825 kg and 28.6 mm in diameter, supported on two flexure pivot tilting pad type, hybrid gas bearings, each with four pads and 60% pivot offset and 0.6 mm feeding holes. The bearings are supplied with feed pressures of 2.36, 3.72, and 5.08 bar (ab). Intermittent shocks, up to 30 g pk-pk and exciting a broad frequency range to 400 Hz, produce a remarkable momentary increase of the overall rotor response amplitude, up to 50 μm (pk-pk). The shocks readily excite the fundamental natural frequency of the rotor-bearing system (150–200 Hz), and on occasion the natural frequency (40 Hz) of the whole test rig. For operation at rotor speeds above the system critical speed, the rotor synchronous response is isolated; with transient motions induced by a shock, subsynchronous in whirl frequency, quickly disappearing. Full recovery takes place in ∼0.10 second. The measurements demonstrate that the hybrid gas bearings have enough damping to rapidly attenuate rotor transient motions and to dissipate the energy induced from intermittent shocks. Note that the shocks acted while the rotor traversed its critical speeds. The reliability of engineered gas bearings to forced transient events is no longer in question.

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