Material Considerations for High Temperature Tilting Pad Gas Bearings

1968 ◽  
Vol 90 (4) ◽  
pp. 818-828 ◽  
Author(s):  
S. F. Murray ◽  
M. B. Peterson
Keyword(s):  
High Temperature ◽  
Contact Area ◽  
High Speed ◽  
Contact Problems ◽  
Sliding Contact ◽  
Gas Bearings ◽  
Hydrodynamic Bearing ◽  
Tilting Pad ◽  
Short Time

This paper is concerned with the sliding contact problems encountered in tilting pad gas bearings operating at temperatures up to 1400 deg F. Both the pivots and the bearing surfaces are considered. Short time experimental evaluations of pivot damage are summarized. The results of start-stop and high-speed rub tests on a single tilting pad hydrodynamic bearing are also described. Based on the results obtained to date, damage-resistant coatings are available for use on the bearing surfaces at high temperature. There are also suitable pivot materials, but the pivot must be properly designed to minimize slip in the contact area.

Analysis on Dynamic Performance of Hydrodynamic Tilting-Pad Gas Bearings Using Partial Derivative Method

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Yang Lihua ◽  
Qi Shemiao ◽  
Yu Lie
Keyword(s):  
Analytical Method ◽  
Gas Turbines ◽  
High Speed ◽  
Dynamic Performance ◽  
Gas Bearings ◽  
Dynamic Coefficients ◽  
Tilting Pad ◽  
Dynamic Performances ◽  
Perturbation Frequency ◽  
San Andres

Tilting-pad gas bearings are widely used in high-speed rotating machines due to their inherent stability characteristics. This paper advances the analytical method for prediction of the dynamic performances of tilting-pad gas bearings. The main advantage of the analytical method is that the complete set of dynamic coefficients of tilting-pad gas bearings can be obtained. The predictions show that the perturbation frequency has the strong effects on the dynamic coefficients of gas bearings. In general, at lower perturbation frequency, the equivalent direct stiffness coefficients increase with frequency, whereas equivalent direct damping coefficients dramatically reduce. For higher perturbation frequency, the dynamic coefficients are nearly independent of the frequency. Moreover, the equivalent dynamic coefficients of four-pad tilting-pad gas bearing obtained by the method in this paper are in good agreement with those obtained by Zhu and San Andres [(2007), “Rotordynamic Performance of Flexure Pivot Hydrostatic Gas Bearings for Oil-Free Turbomachinery,” ASME J. Eng. Gas Turbines Power, 129(4), pp. 1020–1027] in the published paper. The results validate the feasibility of the method presented in this paper in calculating the dynamic coefficients of gas-lubricated tilting-pad bearings.

Experimental Studies on Flexure Pivot Tilting Pad Gas Bearings With Pad Radial Compliance

2007 ◽  
Author(s):  
Kyuho Sim ◽  
Aaron Rimpel ◽  
Daejong Kim
Keyword(s):  
High Speed ◽  
Experimental Studies ◽  
Experimental Results ◽  
Frequency Dependent ◽  
Gas Bearings ◽  
Force Coefficients ◽  
Tilting Pad ◽  
Operation Frequency ◽  
Large Rotor ◽  
Good Agreement

This paper presents experimental studies on imbalance responses of a rotor supported by two flexure pivot tilting pad gas bearings with radial compliance. The radial compliance was aimed to accommodate large rotor centrifugal growth inherent with high speed operation. Frequency-dependent rotordynamic force coefficients calculated from developed software were used to predict critical speeds and onset speed of instability and compared with experimental results. Two results show very good agreement.

Centrifugal Internal Grinding by Assembled Wheel with Radially Mobile Segments

2016 ◽  
Vol 874 ◽  
pp. 85-90 ◽  
Author(s):  
David Blurtsyan
Keyword(s):  
High Temperature ◽  
Heat Generation ◽  
Contact Area ◽  
High Speed ◽  
Air Flow ◽  
Grinding Wheel ◽  
Generation Zone ◽  
Internal Grinding ◽  
Turbulent Air Flow ◽  
Evacuation System

Productivity of internal grinding processes is limited by wheel-workpiece contact area and high temperature generated during grinding. Existing internal grinding methods do not guarantee presence of coolant liquid in the heat generation zone. Usually coolant liquid from external nozzles could not penetrate turbulent air flow around grinding wheel. Assembled wheel with radially mobile segments allows increasing contact area but needs to be supported by more efficient heat evacuation system. New grinding wheel and method of internal grinding are developed and evaluated. New tool generates high speed hydrodynamic circular flow and dynamic wedges of coolant liquid in the cutting zones.

Design and Hydrodynamic Performance of Hybrid Flexural Pivot Gas Bearings for High Speed Oil-Free Micro Turbomachinery

2005 ◽  
Author(s):  
Kyuho Sim ◽  
Daejong Kim
Keyword(s):  
High Speed ◽  
Hydrodynamic Performance ◽  
Bending Vibrations ◽  
Hydrodynamic Mode ◽  
Critical Speeds ◽  
Gas Bearings ◽  
Radial Stiffness ◽  
Tilting Pad ◽  
Rotor Bearing ◽  
Final Design

This paper introduces new flexural pivot tilting pad gas bearings for high speed oil-free micro turbomachinery. The new flexural pivot tilting pad gas bearings have a special web geometry that provides a radial stiffness to accommodate rotor growths and high vibrations at critical speed, a pitching stiffness to accommodate rotor-bearing misalignments or rotor bending vibrations, and a very small tilting stiffness for rotor stability. Comprehensive numerical simulations involving orbit simulations and coast-down simulations were performed to investigate the effects of preloads and pivot offsets on the critical speeds and onset speeds of instability. Higher preload and pivot offset increased both critical speeds of the rotor-bearing system and onset speeds of instability due to the increased wedge effect. Design procedures of radial stiffness were presented considering both rotor centrifugal and thermal growths. From simple adiabatic solution of temperature distribution of gas film under pure hydrodynamic mode, enough bearing clearance at pivot was found to be a very important design aspect for high speed hydrodynamic gas bearings. Asymmetric radial stiffness was chosen as a final design to meet the target design speed of 180 krpm for bearing diameter of 28.52mm. Suggested tilting pad gas bearing with asymmetric radial stiffness was predicted to be very stable even under high external destabilizing forces.

Flexure Pivot Tilting Pad Hybrid Gas Bearings: Operation With Worn Clearances and Two Load-Pad Configurations

2007 ◽  
Author(s):  
Luis San Andre´s ◽  
Keun Ryu
Keyword(s):  
High Speed ◽  
High Performance ◽  
Test System ◽  
Viscous Drag ◽  
Widespread Application ◽  
Critical Speeds ◽  
Gas Bearings ◽  
Foil Bearings ◽  
Modal Damping ◽  
Tilting Pad

Gas film bearings enable the successful deployment of high-speed micro-turbomachinery. Foil bearings are in use; however, cost and lack of calibrated predictive tools prevent their widespread application. Other types of bearing configurations, simpler to manufacture and fully engineered, are favored by commercial turbomachinery manufacturers. Externally pressurized tilting pad bearings offer a sound solution for stable rotor support. This paper reports measurements of the rotordynamic response of a rigid rotor, 0.825 kg and 28.6 mm in diameter, supported on flexure pivot tilting pad hybrid gas bearings. The tests are performed for various imbalances, increasing supply pressures, and under load-on-pad (LOP) and load-between-pad (LBP) configurations. Presently, the initial condition of the test bearings shows sustained wear and dissimilar pad clearances after extensive testing reported earlier, see Ref. [1]. In the current measurements, there are no noticeable differences in rotor responses for both LOP and LBP configurations due to the light-weight rotor, i.e. small static load acting on each bearing. External pressurization into the bearings increases their direct stiffnesses and reduces their damping, while raising the system critical speeds with a notable reduction in modal damping ratios. The rotor supported on the worn bearings shows a ∼10% drop in first critical speeds and roughly similar modal damping than when tested with pristine bearings. Pressurization into the bearings leads to large times for rotor deceleration, thus demonstrating the little viscous drag typical of gas bearings. Rotor deceleration tests with manually controlled supply pressures eliminate the passage through critical speeds, thus paving a path for rotordynamic performance without large amplitude motions over extended regions of shaft speed. The rotordynamic analysis shows critical speeds and peak amplitudes of motion agreeing very well with the measurements. The synchronous rotor responses for increasing imbalances demonstrate the test system linearity. Superior stability and predictable performance of pressurized flexure pivot gas bearings can further their implementation in high performance oil-free microturbomachinery. More importantly, the measurements show the reliable performance of the worn bearings even when operating with enlarged and uneven clearances.

Hybrid Flexure Pivot-Tilting Pad Gas Bearings: Analysis and Experimental Validation

2006 ◽  
Vol 128 (3) ◽  
pp. 551-558 ◽  
Author(s):  
Luis San Andrés
Keyword(s):  
High Speed ◽  
Experimental Validation ◽  
Operating Speed ◽  
Dynamic Force ◽  
Low Friction ◽  
Gas Bearings ◽  
Rotordynamic Coefficients ◽  
Damping Coefficients ◽  
Tilting Pad ◽  
System Time

Gas film bearings offer unique advantages enabling successful deployment of high-speed microturbomachinery. Current applications encompass micro power generators, air cycle machines, and turbo expanders. Mechanically complex gas foil bearings are in use; however, their excessive cost and lack of calibrated predictive tools deter their application to mass-produced oil-free turbochargers, for example. The present investigation advances the analysis and experimental validation of hybrid gas bearings with static and dynamic force characteristics desirable in high-speed turbomachinery. These characteristics are adequate load support, good stiffness and damping coefficients, low friction and wear during rotor startup and shutdown, and most importantly, enhanced rotordynamic stability at the operating speed. Hybrid (hydrostatic/hydrodynamic) flexure pivot-tilting pad bearings demonstrate superior static and dynamic forced performance than other geometries as evidenced in a high-speed rotor-bearing test rig. A computational model including the effects of external pressurization predicts the rotordynamic coefficients of the test bearings and shows good correlation with measured force coefficients, thus lending credence to the predictive model. In general, direct stiffnesses increase with operating speed and external pressurization, whereas damping coefficients show an opposite behavior. Predicted mass flow rates validate the inherent restrictor-type orifice flow model for external pressurization. Measured coast-down rotor speeds demonstrate very low-friction operation with large system time constants. Estimated drag torques from the gas bearings indirectly validate the recorded system time constant.

ALX ALLOY

Alloy Digest ◽  
1963 ◽  
Vol 12 (1) ◽  
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
High Speed ◽  
Heat Treating ◽  
Temperature Performance ◽  
Cobalt Base

Abstract ALX is a composition of nonferrous materials with a cobalt base containing chromium, tungsten and carbon. This alloy is commonly supplied in the cast-to-shape form, having an as-cast hardness of Rockwell C60-62 and requiring no further heat treatment. ALX is also supplied as cast tool bit material and is useful where conventional high-speed steels or carbides do not function effectively. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as casting, forming, heat treating, and machining. Filing Code: Co-35. Producer or source: Allegheny Ludlum Corporation.

Ti-679

Alloy Digest ◽  
1966 ◽  
Vol 15 (11) ◽  
Keyword(s):  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Creep Strength ◽  
Heat Treating ◽  
High Temperature Alloy ◽  
Temperature Performance ◽  
Time Strength ◽  
Short Time

Abstract Ti-679 is a titanium high temperature alloy having an excellent combination of short-time strength, creep strength and stability to 900 F. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance as well as forming, heat treating, machining, and joining. Filing Code: Ti-48. Producer or source: Titanium Metals Corporation of America.

CYCLOPS M4

Alloy Digest ◽  
1978 ◽  
Vol 27 (7) ◽  
Keyword(s):  
High Temperature ◽  
Physical Properties ◽  
Abrasion Resistance ◽  
High Speed ◽  
Heat Treating ◽  
Heavy Duty ◽  
Maximum Hardness ◽  
Temperature Performance ◽  
Sharp Edges ◽  
Normal Carbon

Abstract CYCLOPS M4 is a deep-hardening steel that was developed to utilize the excellent abrasion resistance that results from higher-than-normal carbon and vanadium contents in the molybdenum-tungsten family of high-speed steels. It is recommended for heavy-duty cutting operations and for sharp edges for fine cuts. Cyclops M4 should always be used at or near maximum hardness. This datasheet provides information on composition, physical properties, hardness, and elasticity. It also includes information on high temperature performance as well as forming, heat treating, machining, and joining. Filing Code: TS-335. Producer or source: Cyclops Corporation.

Sign in / Sign up

Export Citation Format

Share Document