Test Evolution and Oil-Free Engine Experience of a High Temperature Foil Air Bearing Coating

2006 ◽  
Author(s):  
Daniel Lubell ◽  
Christopher DellaCorte ◽  
Malcolm Stanford
Keyword(s):  
High Temperature ◽  
Gas Turbines ◽  
Solid Lubricants ◽  
Deposition Process ◽  
Air Bearing ◽  
Free Gas ◽  
Foil Bearings ◽  
Start Up ◽  
High Temperature Operation

During the start-up and shut-down of a turbomachine supported on compliant foil bearings, before the bearings have full development of the hydrodynamic gas film, sliding occurs between the rotor and the bearing foils. Traditional solid lubricants (e.g., graphite, Teflon®) readily solve this problem at low temperature. High temperature operation, however, has been a key obstacle. Without a suitable high temperature coating, foil air bearing use is limited to about 300°C (570°F). In oil-free gas turbines, a hot section bearing presents a very aggressive environment for these coatings. A NASA developed coating, PS304, represents one tribological approach to this challenge. In this paper, the use of PS304 as a rotor coating operating against a hot foil gas bearing is reviewed and discussed. During the course of several long term, high cycle, engine tests, which included two coating related failures, the PS304 technology evolved and improved. For instance, a post deposition thermal treatment to improve dimensional stability, and improvements to the deposition process to enhance strength resulted from the engine evaluations. Largely because of this work, the bearing/coating combination has been successfully demonstrated at over 500°C (930°F) in an oil-free gas turbine for over 2500 hours and 2900 start-stop cycles without damage or loss of performance when properly applied. Ongoing testing at Glenn Research Center as part of a long term program is over 3500 hours and 150 cycles.

On the Integration of Hot Foil Bearings Into Gas Turbine Engines: Theoretical Treatment

2019 ◽  
Author(s):  
Hooshang Heshmat ◽  
James F. Walton
Keyword(s):  
High Temperature ◽  
System Dynamics ◽  
High Performance ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Structural Stiffness ◽  
Foil Bearings ◽  
Foil Bearing ◽  
High Temperature Operation ◽  
Bearing System

Abstract To achieve high power density Gas Turbine Engines (GTEs), R&D efforts have strived to develop machines that spin faster and run hotter. One method to achieve that goal is to use high temperature capable foil bearings. In order to successfully integrate these advanced foil bearings into GTE systems, a theoretical understanding of both bearing and rotor system integration is essential. Without a fundamental understanding and sound theoretical modeling of the foil bearing coupled with the rotating system such an approach would prove application efforts fruitless. It is hoped that the information provided in this paper will open up opportunistic doors to designs presently thought to be impossible. In this paper an attempt is made to describe how an advanced foil bearing is modeled for extreme high temperature operation in high performance turbomachinery including GTEs, Supercritical CO2 turbine generators and others. The authors present the advances in foil bearing capabilities that were crucial to achieving high temperature operation. Achieving high performance in a compliant foil bearing under the wide extremes of operating temperatures, pressures and speeds, requires a bearing system design approach that accounts for the highly interrelated compliant surface foil bearing elements such as: the structural stiffness and frictional characteristics of the underlying compliant support structure across the operating temperature and pressure spectrum; and the coupled interaction of the structural elements with the hydrodynamic pressure generation. This coupled elasto-hydrodynamic-Finite Element highly non-linear iterative methodology will be used by the authors to present a series of foil bearing design evaluations analyzing and modeling the foil bearing under extreme conditions. The complexity of the problem of achieving foil bearing system operation beyond 870°C (1600°F) requires as a prerequisite the attention to the tribological details of the foil bearing. For example, it is necessary to establish how both the frictional and viscous damping coefficient elements as well as the structural and hydrodynamic stiffness are to be combined. By combining these characteristics the influence of frictional coefficients of the elastic and an-elastic materials on bearing structural stiffness and hence the bearing effective coupled elasto-hydrodynamic stiffness coefficients will be shown. Given that the bearing dynamic parameters — stiffness and damping coefficients — play a major role in the control of system dynamics, the design approach to successfully integrate compliant foil bearings into complex rotating machinery systems operating in extreme environments is explored by investigating the effects of these types of conditions on rotor-bearing system dynamics. The proposed rotor/bearing model is presented to describe how system dynamics and bearing structural properties and operating characteristics are inextricably linked together in a manner that results in a series separate but intertwined iterative solutions. Finally, the advanced foil bearing modeling and formulation in connection with resulting rotor dynamics of the system will be carried out for an experimental GTE simulator test rig. The analytical results will be compared with the experiments as presented previously to demonstrate the effectiveness of the developed method in a real world application [1].

Influence of Creep on Low-Cycle Fatigue Life Assessment of Ultra-Supercritical Steam Turbine Rotor

2014 ◽  
Author(s):  
W. Z. Wang ◽  
J. H. Zhang ◽  
H. F. Liu ◽  
Y. Z. Liu
Keyword(s):  
High Temperature ◽  
Steam Turbine ◽  
Fatigue Damage ◽  
Low Cycle Fatigue ◽  
Turbine Rotor ◽  
High Temperature Creep ◽  
Cycle Fatigue ◽  
Term Operation ◽  
Start Up

Linear damage method is widely used to calculate low-cycle fatigue damage of turbine rotor in the long-term operation without fully considering the interaction between creep and low cycle fatigue. However, with the increase of steam turbine pressure and temperature, the influence of high-temperature creep on the strain distribution of turbine rotor becomes significant. Accordingly, the strain for each start-up or shut-down process is different. In the present study, the stress and strain during 21 iterations of continuous start-up, running and shut-down processes was numerically investigated by using the finite element analysis. The influence of high-temperature creep on low cycle fatigue was analyzed in terms of equivalent strain, Mises stress and low cycle fatigue damage. The results demonstrated that the life consumption of turbine rotor due to low cycle fatigue in the long-term operation of startup, running and shutdown should be determined from the full-time coverage of the load of turbine rotor.

Identification and Correction of Rotor Instability in an Oil-Free Gas Turbine

2008 ◽  
Author(s):  
Daniel R. Lubell ◽  
Jonathan L. Wade ◽  
Navjot S. Chauhan ◽  
John G. Nourse
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Early Stage ◽  
Turbine Wheel ◽  
Free Gas ◽  
Foil Bearings ◽  
Root Cause ◽  
Final Design ◽  
Acceptance Tests ◽  
Conventional Oil

The direction of advanced gas turbines and other turbomachinery has been towards oil-free designs, enabled by the significant improvements of high temperature foil bearings. The advantages of oil-free gas turbines have been studied and shown to be realistic. However, the oil-free technology is still at an early stage in its development relative to conventional oil lubricated turbomachinery systems which have been studied and manufactured for about 100 years, and the bearings even longer. Oil-free gas turbines are most successful as a system design initiated with oil-free bearings. Making these successful designs requires knowledge of the strengths and weaknesses of integrating oil-free bearings. A common example is foil bearings, the type typically considered for oil-free gas turbines. These bearings are lower in damping than their oil lubricated counterparts. Therefore special considerations are made by the experienced oil-free gas turbine designer early in the design process. Knowledge of the opportunities for instability that are not as common in conventional turbomachinery provides value to the final design. This paper presents the identification and correction of rotor instability in an oil-free microturbine of a 65 kW system. The manufacturer put significant effort into identifying the root cause of the seemingly random occurrences of rotor instability, in order to improve yield for acceptance tests. Through the application of conventional rotordynamics theory and techniques, combined with 3-D imaging of complex cast parts, the root cause was identified as an Alford’s-type force at the turbine driven by critical machined and cast features of the turbine wheel that would not have been important in a conventional oil lubricated turbomachine. A successful corrective process has been put in place, providing final confirmation of the root cause.

scholarly journals Evaluation of printed-circuit boards materials for high temperature operation

2017 ◽  
Vol 2017 (HiTEN) ◽  
pp. 000057-000062
Author(s):  
Oriol Aviño-Salvado ◽  
Wissam Sabbah ◽  
Cyril Buttay ◽  
Hervé Morel ◽  
Pascal Bevilacqua
Keyword(s):  
High Temperature ◽  
Printed Circuit Boards ◽  
Printed Circuit Board ◽  
Circuit Board ◽  
Circuit Boards ◽  
Printed Circuit ◽  
Physical Measurements ◽  
Epoxy Material ◽  
High Temperature Operation

ABSTRACT This article presents the long term (1000 h) behaviour of two printed-circuit board materials (Panasonic R1755V, a high-TG glass-epoxy composite and Arlon 85N, a polyimide-based laminate) stored at high temperature (190 °C). Tests are performed in air and in nitrogen atmospheres. Electrical and physical measurements are performed regularly (once per week). Almost no degradation is observed for both materials, when stored in nitrogen. On the contrary, the board stored in air show the consequences of ageing. This is especially true for the glass-epoxy material, which becomes unusable after 2 weeks, because of large swelling.

Long-term reliability of Al-free InGaAsP/GaAs (λ=808 nm) lasers at high-power high-temperature operation

1997 ◽  
Vol 71 (21) ◽  
pp. 3042-3044 ◽  
Author(s):  
J. Diaz ◽  
H. J. Yi ◽  
M. Razeghi ◽  
G. T. Burnham
Keyword(s):  
High Temperature ◽  
High Power ◽  
High Temperature Operation

An Ultra-Low Noise Instrumentation Amplifer Designed for High Temperature Applications

2012 ◽  
Vol 2012 (HITEC) ◽  
pp. 000082-000086
Author(s):  
Jeff Watson ◽  
Gustavo Castro
Keyword(s):  
High Temperature ◽  
High Performance ◽  
Low Noise ◽  
Silicon On Insulator ◽  
Instrumentation Amplifier ◽  
Leakage Currents ◽  
Comprehensive Reliability ◽  
High Temperature Operation ◽  
Temperature Applications

This paper discusses a very low noise instrumentation amplifier designed specifically for high temperature applications. The device uses a proprietary silicon-on-insulator process that minimizes parasitic leakage currents at elevated temperature. Variance in device parameters are managed to maintain high performance over a wide temperature range. Layout and packaging considerations that would affect long term reliability are addressed. The amplifier is well characterized above 200°C and attains much higher performance than amplifiers not optimized for high temperature operation. Comprehensive reliability testing over temperature has been completed.

Plate Fin Regenerators for Industrial Gas Turbines

1978 ◽  
Vol 100 (4) ◽  
pp. 576-585 ◽  
Author(s):  
K. W. Cuffe ◽  
P. K. Beatenbough ◽  
M. J. Daskavitz ◽  
R. J. Flower
Keyword(s):  
High Temperature ◽  
Gas Turbine ◽  
Gas Turbines ◽  
The Past ◽  
Mode Of Operation ◽  
Industrial Gas Turbines ◽  
Industrial Gas Turbine ◽  
High Temperature Operation ◽  
Surface Changes

This paper reviews Harrison Radiator’s various designs and improvements in the Industrial Gas Turbine Regenerator that it has been supplying over the past 20 years, and describes a new design regenerator intended for high cyclic and/or high temperature operation. Design improvements and surface changes have occurred to keep pace with the changing consumer’s requirements and application. These changes have been effective in improving the cyclic ability of the regenerator and in reducing the field maintenance required on the earlier models due to the changing mode of operation. The new regenerator design has been created to meet the changing requirements of the applications.

scholarly journals Current and Future Materials in Advanced Gas Turbine Engines

1994 ◽  
Author(s):  
G. A. Kool
Keyword(s):  
High Temperature ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Metallic Materials ◽  
Temperature Capability ◽  
Higher Temperature ◽  
Strength And Stiffness

Gas turbine engines are constructed of components with excellent strength and stiffness, a minimum density, a high temperature capability for long times, and at affordable cost. Metallic materials are the centrepiece in fulfilling these requirements. Future gas turbine engines will have to have higher thrust-to-weight ratios, better fuel efficiencies and still lower costs. This will require new and advanced lightweight materials with higher temperature capabilities. This paper discusses some of the presently applied materials in the fan, compressor and turbine sections of gas turbines, and reviews the material developments that are occurring and will be necessary for the near and long term futures.

scholarly journals Evaluation of Printed-Circuit Board Materials for High-Temperature Operation

2017 ◽  
Vol 14 (4) ◽  
pp. 166-171
Author(s):  
Oriol Aviño-Salvado ◽  
Wissam Sabbah ◽  
Cyril Buttay ◽  
Hervé Morel ◽  
Pascal Bevilacqua
Keyword(s):  
High Temperature ◽  
Printed Circuit Board ◽  
Epoxy Composite ◽  
Circuit Board ◽  
Printed Circuit ◽  
Physical Measurements ◽  
Epoxy Material ◽  
High Temperature Operation

This article presents the long-term (1,000 h) behavior of two printed-circuit board materials (Panasonic R1755V, a high-TG glass-epoxy composite and Arlon 85N, a polyimide-based laminate) stored at high temperature (190°C). Tests are performed in air and in nitrogen atmospheres. Electrical and physical measurements are performed regularly (once per week). Almost no degradation is observed for both materials when stored in nitrogen. On the contrary, the board stored in air shows the consequences of ageing. This is especially true for the glass-epoxy material, which becomes unusable after 2 w, because of large swelling.

scholarly journals Characterization of Fatigue Mechanisms of Thermal Barrier Coatings by a Novel Laser-Based Test

1998 ◽  
Author(s):  
Uwe Rettig ◽  
Ulrich Bast ◽  
Dinorah Steiner ◽  
Matthias Oechsner
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Fatigue Behavior ◽  
Temperature Gradients ◽  
Stress Fields ◽  
Thermal Barrier ◽  
Data Set ◽  
Barrier Coatings

The use of high performance ceramic thermal barrier coatings in stationary gas turbines requires fundamental knowledge of their fatigue behavior under high temperature gradients and thermal cycling. An experimental method based on rapid laser heating complemented with finite-element calculations was developed in order to identify the major damage mechanisms and to obtain a data set for reliability assessment of thermal barrier coatings for temperature and stress fields similar to gas turbine conditions. The observed failures are strongly related to the pretreatment procedures such as annealing under high temperature gradients and isothermal long-term oxidation. The vertical crack patterns observed close to the top surface of the Zirconia coating are generated at the moment of rapid cooling. These cracks are induced by high biaxial tensile stresses caused by the temperature gradient and the stress reversion after relaxation of compressive stresses at high temperatures. The long-term fatigue behavior is decisively determined by two processes: (i) The porous Zirconia loses its damage tolerant properties by densification. (ii) The growth of an oxide layer at the bond coat degrades adhesion and produces localized stress fields at the interface. Cyclic loads increase the length of existing in-plane cracks and delaminations rather than enlarging their number. Misfit of the crack flanks and wedge effects are the driving forces for continued crack propagation. These experimental results are discussed in terms of fracture mechanics.

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