Rotordynamic and Bearing Upgrade of a High-Speed Turbocharger

2002 ◽  
Vol 125 (1) ◽  
pp. 95-101 ◽  
Author(s):  
B. C. Pettinato ◽  
P. DeChoudhury
Keyword(s):  
High Speed ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Journal Bearings ◽  
Experimental Results ◽  
Thrust Bearings ◽  
Vibration Data ◽  
Oil Leakage ◽  
Bearing Life ◽  
Thrust Load

The paper discusses the redesign of a high-speed turbocharger for improved bearing life and mechanical operation. The bearings were changed from a pair of combination journal/thrust bearings to a pair of redesigned journal bearings with double acting thrust bearing at the center of the unit. Internal oil passages, drain cavities, and seals were also revised. These modifications resulted in reduced oil leakage across end seals, reduced coke buildup at the turbine, increased thrust load capacity, and improved rotordynamics. Both the analytical and experimental results, which consisted of bearing performance and vibration data of original and modified systems are presented.

Rotordynamic and Bearing Upgrade of a High-Speed Turbocharger

2001 ◽  
Author(s):  
Brian C. Pettinato ◽  
Pranabesh DeChoudhury
Keyword(s):  
High Speed ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Flow Distribution ◽  
Journal Bearings ◽  
Original Design ◽  
Thrust Bearings ◽  
Vibration Data ◽  
Bearing Life ◽  
Oil Flow

The paper discusses the redesign of a high-speed turbocharger for improved bearing life and mechanical operation. The modifications resulted in reduced oil leakage across the end seal, reduced coke buildup at the turbine, increased thrust load capacity, and improved rotordynamics. In particular, rotordynamic stability was improved by eliminating subsynchronous vibration at the operating speed. The redesign consisted of changing the bearings from a pair of combination journal/thrust bearings to a pair of journal bearings and a double acting thrust bearing at the center of the unit. The active thrust bearing was moved away from the hot turbine end of the machine. The thrust bearing geometry was modified for increased minimum film thickness, reduced metal temperature, and increased load capacity. Inlet and drain passages were revised for better oil flow distribution. Unit rotordynamics were improved by upgrading the journal bearings from three-axial-groove to three-lobe design. The upgraded unit kept the same footprint as the original design with only piping modifications required. Extensive analysis and testing were conducted. Testing of the original and revised turbochargers showed improvements in the redesign with reduced bearing metal temperatures and improved rotordynamic stability. Theoretical results along with test data consisting of bearing performance and vibration data of the original and modified system are presented in this paper.

The Influence of Ambient Pressure on the Measured Load Capacity of Bump-Foil and Spiral-Groove Gas Thrust Bearings at Ambient Pressures up to 69 Bar on a Novel High-Pressure Gas Bearing Test Rig

2019 ◽  
Author(s):  
Jason Wilkes ◽  
Ryan Cater ◽  
Erik Swanson ◽  
Kevin Passmore ◽  
Jerry Brady
Keyword(s):  
Power Loss ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Ambient Pressure ◽  
Spiral Groove ◽  
Test Rig ◽  
Thrust Bearings ◽  
Order Of Magnitude ◽  
Foil Thrust Bearing ◽  
Thrust Load

Abstract This paper will show the influence of ambient pressure on the thrust capacity of bump-foil and spiral-groove gas thrust bearings. The bearings were operating in nitrogen at various pressures up to 69 bar, and were tested to failure. Failure was detected at various pressures by incrementally increasing the thrust load applied to the thrust bearing until the bearing was no longer thermally stable, or until contact was observed by a temperature spike measured by thermocouples within the bearing. These tests were performed on a novel thrust bearing test rig that was developed to allow thrust testing at pressures up to 207 bar cavity pressure at 260°C while rotating at speeds up to 120,000 rpm. The test rig floats on hydrostatic air bearings to allow for the direct measurement of applied thrust load through linkages that connect the stationary thrust loader to the rotor housing. Test results on a 65 mm (2.56 in) bump-foil thrust bearing at 100 krpm show a marked increase in load capacity with gas density, which has not previously been shown experimentally. Results also show that the load capacity of a similarly sized spiral-groove thrust bearing are relatively insensitive to pressure, and supported an order-of-magnitude less load than that observed for the bump-foil thrust bearing. These results are compared with analytical predictions, which agree reasonably with the experimental results. Predicted power loss is also presented for the bump-foil bearing; however, measured power loss was substantially higher.

Development of Foil Thrust Bearings with Simple Structure for Micro Turbines

2011 ◽  
Vol 368-373 ◽  
pp. 1392-1395 ◽  
Author(s):  
Quan Zhou ◽  
Yu Hou ◽  
Ru Gang Chen
Keyword(s):  
High Speed ◽  
Simple Structure ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Complicated Structure ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Rotational Systems ◽  
Micro Turbine ◽  
Foil Thrust Bearing

Because of the low power loss and high stability, foil bearings are suitable lubrication components for high speed rotational systems. At present, the foil bearings used in actual applications almost have complicated structure and are hard to manufacture. In this paper, two kinds of foil thrust bearings with simple structure are presented. Configurations of these two foil thrust bearings are introduced; meanwhile, the load capacity and running stability are also tested in a high speed micro turbine. It is shown that viscoelastic supported foil thrust bearing has higher load capacity and hemisphere convex dots supported foil thrust bearing is more stable in high speed operational condition.

Modeling and Experimental Investigation of Micro-hydrostatic Gas Thrust Bearings for Micro-turbomachines

2005 ◽  
Vol 128 (4) ◽  
pp. 597-605 ◽  
Author(s):  
C. J. Teo ◽  
Z. S. Spakovszky
Keyword(s):  
High Speed ◽  
Scaling Laws ◽  
Thrust Bearing ◽  
Journal Bearings ◽  
Axial Stiffness ◽  
Stable Operation ◽  
Successful Operation ◽  
Element Analysis ◽  
Essential Information ◽  
Thrust Bearings

One major challenge for the successful operation of high-power-density micro-devices lies in the stable operation of the bearings supporting the high-speed rotating turbomachinery. Previous modeling efforts by Piekos (2000, “Numerical Simulation of Gas-Lubricated Journal Bearings for Microfabricated Machines,” Ph.D. thesis, Department of Aeronautics and Astronautics, MIT), Liu et al. (2005, “Hydrostatic Gas Journal Bearings for Micro-Turbo Machinery,” ASME J. Vib. Acoust., 127, pp. 157–164), and Spakovszky and Liu (2005, “Scaling Laws for Ultra-Short Hydrostatic Gas Journal Bearings,” ASME J. Vib. Acoust. 127, pp. 254–261) have focused on the operation and stability of journal bearings. Thrust bearings play a vital role in providing axial support and stiffness, and there is a need to improve the understanding of their dynamic behavior. In this work, a rigorous theory is presented to analyze the effects of compressibility in micro-flows (characterized by low Reynolds numbers and high Mach numbers) through hydrostatic thrust bearings for application to micro-turbomachines. The analytical model, which combines a one-dimensional compressible flow model with finite-element analysis, serves as a useful tool for establishing operating protocols and assessing the stability characteristics of hydrostatic thrust bearings. The model is capable of predicting key steady-state performance indicators, such as bearing mass flow, axial stiffness, and natural frequency as a function of the hydrostatic supply pressure and thrust-bearing geometry. The model has been applied to investigate the static stability of hydrostatic thrust bearings in micro-turbine generators, where the electrostatic attraction between the stator and rotor gives rise to a negative axial stiffness contribution and may lead to device failure. Thrust-bearing operating protocols have been established for a micro-turbopump, where the bearings also serve as an annular seal preventing the leakage of pressurized liquid from the pump to the gaseous flow in the turbine. The dual role of the annular pad poses challenges in the operation of both the device and the thrust bearing. The operating protocols provide essential information on the required thrust-bearing supply pressures and axial gaps required to prevent the leakage of water into the thrust bearings. Good agreement is observed between the model predictions and experimental results. A dynamic stability analysis has been conducted, which indicates the occurrence of instabilities due to flow choking effects in both forward and aft thrust bearings. A simple criterion for the onset of axial rotor oscillations has been established and subsequently verified in a micro-turbocharger experiment. The predicted frequencies of the unstable axial oscillations compare well with the experimental measurements.

A Rotordynamic, Thermal, and Thrust Load Performance Gas Bearing Test Rig and Test Results for Tilting Pad Journal Bearings and Spiral Groove Thrust Bearings

2016 ◽  
Author(s):  
Aaron M. Rimpel ◽  
Giuseppe Vannini ◽  
Jongsoo Kim
Keyword(s):  
Thrust Bearing ◽  
Journal Bearings ◽  
Temperature Gradients ◽  
Spiral Groove ◽  
Test Rig ◽  
Thrust Bearings ◽  
Tilting Pad ◽  
Gas Bearing ◽  
Thrust Load ◽  
Tilting Pad Journal Bearings

A high speed gas bearing test rig was developed to characterize rotordynamic, thermal, and thrust load performance of gas bearings being developed for an oil-free turboexpander. The radial bearings tested in this paper were tilting pad journal bearings with radial compliance features that allow the bearing bore to increase to accommodate shaft growth, and the thrust bearings were a spiral groove type with axial compliance features. The thrust bearing accounts for over 90% of the combined bearing power consumption, which has a cubic relationship with speed and increases with case pressure. Radial bearing circumferential pad temperature gradients increased approximately with speed to the fourth or fifth power, with slightly higher temperature rise for lower case pressure. Maximum steady state bearing pad temperatures increase with increasing speed for similar cooling mass flow rates; however, only the thrust bearing showed a significant increase in temperature with higher case pressure. The thrust bearings were stable at all speeds, but the load capacity was found to be lower than anticipated, apparently due to pad deformations caused by radial temperature gradients in the stator. More advanced modeling approaches have been proposed to better understand the thrust bearing thermal behavior and to improve the thrust bearing design. Finally, the radial bearings tested were demonstrated to be stable up to the design speed of 130 krpm, which represents the highest surface speed for tilting pad gas bearings tested in the literature.

A non-central feeding hydrostatic thrust bearing

1975 ◽  
Vol 72 (1) ◽  
pp. 113-120 ◽  
Author(s):  
Chuen-Yen Chow
Keyword(s):  
High Speed ◽  
Thrust Bearing ◽  
Flow Direction ◽  
Load Capacity ◽  
Angular Speed ◽  
Feeding System ◽  
Rotor Speed ◽  
Thrust Bearings ◽  
Bearing Analysis

In a conventional hydrostatic thrust bearing, the lubricant is supplied from the centre and flows radially outwards. It has been found that the load capacity of such a bearing decreases with increasing angular speed of the rotor. The bearing fails when a critical rotor speed is reached at which the load capacity becomes zero. In this paper a modified feeding system is suggested in which the lubricant is supplied from a ring-shaped groove situated between the exits at the centre and the edge of the bearing. Analysis shows that, by reversing the flow direction near the centre, the load capacity of a bearing of proper geometry can be made to decrease at a much slower rate than that of a conventional bearing as the rotor speed increases. The non-central feeding system might be considered for use in high-speed thrust bearings.

Static and Dynamic Characteristics of Oil Lubricated Beveled-Step Herringbone-Grooved Journal Bearings

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
M. M. Nemat-Alla ◽  
A. M. Gad ◽  
A. A. Khalil ◽  
A. M. Nasr
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Hydrodynamic Lubrication ◽  
Journal Bearings ◽  
Friction Torque ◽  
Experimental Results ◽  
Static And Dynamic Characteristics ◽  
Thrust Bearings ◽  
Rectangular Profile ◽  
The Stability

Recently, herringbone-grooved journal bearings (HGJBs) have important applications in high-speed rotating machinery. The groove action in pumping the lubricating fluid inward generates supporting stiffness and improves the stability of the bearing when operating concentrically. Several researchers have investigated the static and dynamic characteristics of HGJBs and grooved thrust bearings. Most of these investigations were theoretical and concentrated on HGJBs with rectangular-profile grooves. In the present work, the static and dynamic characteristics of the beveled-step HGJBs are experimentally investigated. The bearing attitude angle, pressure distribution, and bearing friction torque were measured on a hydrodynamic lubrication unit, and then the static and dynamic characteristics were determined. The obtained experimental results are compared to the obtained experimental results for plain journal bearing. The merits as well as the demerits of the groove profile were discussed through comparisons with plain journal bearings.

Numerical and experimental studies on the thermal and static characteristics of multi-leaf foil thrust bearing

2021 ◽  
pp. 135065012110110
Author(s):  
Yu Guo ◽  
Yu Hou ◽  
Qi Zhao ◽  
Xionghao Ren ◽  
Shuangtao Chen ◽  
...  
Keyword(s):  
High Speed ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Failure Process ◽  
Experimental Studies ◽  
Elastic Model ◽  
Static Characteristics ◽  
Bearing Load ◽  
Foil Thrust Bearing ◽  
Cooling Air

Foil bearing is considered to be a promising supporting technology in high-speed centrifugal machinery. Due to the high-speed shearing effect in the viscous lubricant film, heat generation could not be ignored. In this paper, a thermo-elastic model of the multi-leaf foil thrust bearing is proposed to predict its thermal and static characteristics. In the model, modified Reynolds equation, energy equation, and Kirchhoff equation are solved in a coupling way. The contact area between the foil and welding plate is taken into account. Besides, the effect of cooling air on the bearing temperature is investigated. The ultimate load capacity and transient overload failure process of the bearing is analyzed and discussed. The effect of rotation speed on the bearing temperature is more obvious than that of the bearing load. The bearing temperature drops obviously by introducing the cooling air, and the cooling effect is improved with the supply pressure. The transient overload failure of the bearing occurs when the bearing load exceeds the ultimate value.

An Accurate Solution of the Gas Lubricated, Flat Sector Thrust Bearing

1977 ◽  
Vol 99 (1) ◽  
pp. 82-88 ◽  
Author(s):  
I. Etsion ◽  
D. P. Fleming
Keyword(s):  
Film Thickness ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Thickness Distribution ◽  
Maximum Load ◽  
Accurate Solution ◽  
Operating Conditions ◽  
Thrust Bearings ◽  
Practical Design ◽  
Minimum Film Thickness

A flat sector shaped pad geometry for gas lubricated thrust bearings is analyzed considering both pitch and roll angles of the pad and the true film thickness distribution. Maximum load capacity is achieved when the pad is tilted so as to create a uniform minimum film thickness along the pad trailing edge. Performance characteristics for various geometries and operating conditions of gas thrust bearings are presented in the form of design curves. A comparison is made with the rectangular slider approximation. It is found that this approximation is unsafe for practical design, since it always overestimates load capacity.

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.

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