Spectral Analysis of Gas Bearing Systems for Stability Studies

Pan, C. H. T.

doi:10.21236/ad0610872

Cited by 13 publications

(16 citation statements)

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“…Licht et al [19] proposed stable criteria theorem for single concentric circle thrust air bearing with air pocket. Pan [20] investigated the stability of air bearing through spectral analysis. The pneumatic hammer phenomenon always induces not only vibration but also noise.…”

Section: Conceptmentioning

confidence: 99%

Magneto-aerostatic bearing for miniature air turbine

Huang¹,

Chang²

2014

Mechanics & Industry

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-Under the circumstance of pursuing high speed and miniaturization, mini-type air turbines have been widely applied to high-speed dental handpieces in recent years. Among all the components of a mini-type air turbine, bearing is the most important part which significantly affects its efficiency. Friction, collision, and wear are the main causes to make the ball bearing unable to reach higher efficiency. Though very small sliding friction can be realized by the aerostatic bearing, its poor bearing capacity limits the application. This research combines the magnetic and aerostatic levitation principle to develop a magnetoaerostatic hybrid bearing for miniature air turbine. The aerostatic bearing undertakes the main function of the radial and the axial bearings. However, the air bearing also possesses a drawback, which is pneumatic hammer effect induced by the air compressibility. In order to eliminate the pneumatic instability, an axial passive magnetic bearing is integrated into the aerostatic bearing. With the magnetic bearing, not only the bearing capacity can be improved, but also the pneumatic hammer effect can be significantly damped. Both theoretical calculation and finite element method (FEM) are used to study the cause and elimination solution of the pneumatic instability. Through experimental testing, the performance of our developed magneto-aerostatic bearing is also verified. The magneto-aerostatic bearing suppresses the axial vibration over 57%, and also enhances its axial bearing capacity by 50%.

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Section: Conceptmentioning

confidence: 99%

Magneto-aerostatic bearing for miniature air turbine

Huang¹,

Chang²

2014

Mechanics & Industry

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“…The bearing model is coupled with a linear, rigid body rotordynamic model, implementing an extension of the spectral analysis approach by Pan [9,10]. The technical approach is based on an integrated rotordynamic model for rotors supported on gaslubricated bearings.…”

Section: Goals and Objectivesmentioning

confidence: 99%

“…The approach here is based on Pan's spectral analysis method [9] extended by Schiffmann and Favrat [7,8]. An important feature of gas-lubricated bearings is that the bearing properties are not only a function of rotor speed but also depend on excitation frequency.…”

Section: Whirl Speed and Stabilitymentioning

confidence: 99%

“…This needs to be taken into account in the stability assessment. It is common practice to measure rotor stability using the logarithmic decrement defined as r = - (9) Stable operation requires F > 0. The rigid-body rotordynamic system is shown in Fig.…”

Section: Whirl Speed and Stabilitymentioning

confidence: 99%

“…The rigid-body rotordynamic system is shown in Fig. A compact description of stability was proposed by Pan [9,10] and Lund [15] by characterizing the stability threshold for cylindrical rotor motion through a nondimensional critical mass parameter. Equation (7) yields an eigenvalue problem with eigenvalues (8) where the imaginary part cu, = fi/CORot represents the damped natural frequency of the whirl motion and A, is the corresponding damping coefficient.…”

Section: Whirl Speed and Stabilitymentioning

confidence: 99%

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Enhanced Groove Geometry for Herringbone Grooved Journal Bearings

Schiffmann

2013

Journal of Engineering for Gas Turbines and Power

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Although gas-lubricated herringbone grooved journal bearings (HGJB) are known for high rotordynamic stability thresholds, small clearance to diameter ratios are required for stable rotor operation. Tight clearances not only increase bearing losses but also yield challenging manufacturing and assembly tolerances, which ultimately translate into cost. Traditionally, the grooves of HGJB are of helical nature with constant cross section and pitch. The current paper aims at increasing the clearance to diameter ratio and the stability threshold of grooved bearings by introducing enhanced groove geometries. The axial evolution of groove width, depth, and local pitch are described by individual third order polynomials with four interpolation points. The expression for the smooth pressure distribution resulting from the narrow groove theory is modified to enable the calculation of bearing properties with modified groove patterns. The reduced order bearing model is coupled to a linear rigid body rotordynamic model for predicting the whirl speed map and the corresponding stability. By introducing a critical mass parameter as a measure for stability, a criterion for the instability onset is proposed. The optimum groove geometry is found by coupling the gas bearing supported rotor model with a multiobjective optimizer. By maximizing both the clearance to diameter ratio and the rotordynamic stability it is shown that with optimal groove geometry, which deviates from helicoids with constant pitch and cross section, the critical mass parameter can be improved by more than one order of magnitude compared to traditional HGJB geometries. The clearance to diameter ratio can be increased by up to 80% while keeping the same stability margin, thus reducing both losses and manufacturing constraints. The optimum groove pattern distributions (width ratio, angle, and depth) are summarized for a variety of LID ratios and for different compressibility numbers in a first attempt to set up general design guidelines for enhanced gas-lubricated HGJB.Nature of the Issues. Gas bearing technology falls into two categories: externally pressurized or dynamic. In the latter case the relative shear motion between rotor and sleeve combined with Journal of Engineering for Gas Turbines and Power

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Tilting Pad Air Bearings

2021

Air Bearings

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Spectral Analysis of Gas Bearing Systems for Stability Studies

Cited by 13 publications

References 1 publication

Magneto-aerostatic bearing for miniature air turbine

Magneto-aerostatic bearing for miniature air turbine

Enhanced Groove Geometry for Herringbone Grooved Journal Bearings

Tilting Pad Air Bearings

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