scholarly journals Chaotic Behaviour Investigation of a Front Opposed-Hemispherical Spiral-Grooved Air Bearing System

2017 ◽  
Vol 2017 ◽  
pp. 1-18
Author(s):  
Cheng-Chi Wang
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Large Scale ◽  
Air Bearing ◽  
Severe Damage ◽  
Design Problems ◽  
Irregular Motion ◽  
Transformation Methods ◽  
Bearing Number ◽  
Bearing System

In recent years, spiral-grooved air bearing systems have attracted much attention and are especially useful in precision instruments and machines with spindles that rotate at high speed. Load support can be multidirectional and this type of bearing can also be very rigid. Studies show that some of the design problems encountered are dynamic and include critical speed, nonlinearity, gas film pressure, unbalanced rotors, and even poor design, all of which can result in the generation of chaotic aperiodic motion and instability under certain conditions. Such irregular motion on a large scale can cause severe damage to a machine or instrument. Therefore, understanding the conditions under which aperiodic behaviour and vibration arise is crucial for prevention. In this study, numerical analysis, including the Finite Difference and Differential Transformation Methods, is used to study these effects in detail in a front opposed-hemispherical spiral-grooved air bearing system. It was found that different rotor masses and bearing number could cause undesirable behaviour including periodic, subperiodic, quasi-periodic, and chaotic motion. The results obtained in this study can be used as a basis for future bearing system design and the prevention of instability.

The Role of High Performance Foil Bearings in an Advanced, Oil-Free, Integral Permanent Magnet Motor Driven, High-Speed Turbo-Compressor Operating Above the First Bending Critical Speed

2002 ◽  
Author(s):  
E. E. Swanson ◽  
H. Heshmat ◽  
J. S. Shin
Keyword(s):  
Permanent Magnet ◽  
High Speed ◽  
High Performance ◽  
Critical Speed ◽  
Elevated Temperatures ◽  
Development Program ◽  
Permanent Magnet Motor ◽  
Foil Bearings ◽  
Turbo Compressor ◽  
Bearing System

The demand for high power density, reliable, low maintenance, oil-free turbomachinery imposes significant demands on the bearing system. The full benefits of high speed, permanent magnet driven machines, for example are realized at speeds exceeding the capabilities of rolling element bearings. The high speeds, and a desire for oil-free operation also make conventional liquid lubricated bearings an undesirable alternative. The modern, oil-free foil bearing provides an excellent alternative, providing low power loss, adequate damping for supercritical operation, tolerance of elevated temperatures and long life. In this paper, the application of modern foil bearings to a high speed, oil-free turbo-compressor is discussed. In this demanding application, foil bearings support a 24 pound, multi-component rotor operating at 70,000 RPM with a bending critical speed of approximately 43,000 RPM. Stable and reliable operation over the full speed range has been demonstrated. This application also required low bearing start-up torque for compatibility with the constant torque characteristic of the integral permanent magnet motor. This work discusses the rotor bearing system design, the development program approach, and the results of testing to date. Data for both a turbine driven configuration, as well as a high speed integral motor driven configuration are presented.

An Externally Pressurized Air Bearing System, Journals and Thrust, for Application to Small Turbomachinery

1992 ◽  
Author(s):  
A. B. Turner ◽  
S. J. Davies ◽  
Y. L. Nimir ◽  
J. D. Richardson
Keyword(s):  
High Speed ◽  
Dynamic Test ◽  
Maximum Temperature ◽  
Air Bearing ◽  
Axial Thrust ◽  
Turbine Wheel ◽  
Air Supply ◽  
Gauge Pressure ◽  
Compressor Impeller ◽  
Bearing System

An aerostatic (externally pressurized) air bearing system for application to small high speed, low temperature turbomachinery has been designed and successfully tested at over 100,000 rpm using an air supply at a gauge pressure of 3.4 bar (50 psig). The test rig used a Holset turbocharger centrifugal compressor impeller and radial turbine wheel mounted at either end of a 150 mm long 40 mm diameter shaft with two 23 mm long inboard journal bearings mounted on either side of an integral 100 mm diameter tapered thrust collar. The turbine was driven by an independent air supply with a maximum temperature of 200°C, and the unit was operated with the shaft vertical. A static axial thrust capability of over 1000 N (225 lbf) has been demonstrated using a novel plenum chamber arrangement to overcome pneumatic instability (air hammer) problems. The paper presents details of the design, some static rig tests and the dynamic test conditions and results.

scholarly journals Transmissibility Analysis of a Regenerated Rotor System

2021 ◽  
Vol 9 (8) ◽  
pp. 1102-1107
Author(s):  
Akanksha Dhurvey
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Rotor System ◽  
Jet Engines ◽  
Simply Supported ◽  
Rotor Bearing ◽  
Unbalance Force ◽  
Force Transmissibility ◽  
Very High ◽  
Bearing System

Abstract: The aim of this paper is to represents a dynamic behavior of rotor bearing system wirth simply supported beam for three different position disc. rotating machinery such as compressors, turbines, pumps, jet engines, turtobo chargers, etc. are subject to vibrations. rotating machines are operated in very high speed and they are subjected to some unbalance force due to vibration from that machine pass to the foundation of machine.so the analysis of the dynamics parameter of rotor it is important to determine force transmissibility, natural frequency, critical speed and amplitudes of rotor system. Keywords: force transmissibility, vibration, critical speed, rotor bearing system etc.

The Dynamic Analysis of High-Speed Energy Storage Flywheel Rotor System

2013 ◽  
Vol 770 ◽  
pp. 78-83
Author(s):  
Xiu Hua Zhang ◽  
Guang Xi Li ◽  
Long Nie
Keyword(s):  
Steady State ◽  
Energy Storage ◽  
High Speed ◽  
Transient Analysis ◽  
Critical Speed ◽  
Large Scale ◽  
Simulation Analysis ◽  
Rotor System ◽  
Analysis Method ◽  
Flywheel Rotor

This article aims at large-scale energy storage flywheel rotor system, obtaining the dynamic characteristics. Through theoretical analysis, and after doing a simulation analysis for a given flywheel rotor on the 0-20000 RPM, getting the flywheel rotor critical speed, the transient analysis and imbalance response. The system is in steady state at runtime according to the analysis results. Providing also certain theory basis for study of flywheel rotor system according to the analysis method .

AN ANALYSIS OF THE ELECTRIC SPINDLE'S DYNAMIC CHARACTERISTICS OF HIGH-SPEED GRINDER

2011 ◽  
Vol 10 (01) ◽  
pp. 159-166 ◽  
Author(s):  
C. H. LI ◽  
Y. L. HOU ◽  
C. DU ◽  
Y. C. DING
Keyword(s):  
Dynamic Characteristics ◽  
Performance Optimization ◽  
High Speed ◽  
Critical Speed ◽  
Structural Parameters ◽  
Influential Factors ◽  
Variable Cross ◽  
Tightening Force ◽  
Rotor Bearing ◽  
Bearing System

Structural parameters are important factors that affect the dynamic performance of the electrical spindle of high-speed grinder. In this study, the influences of the electric spindle's major structural parameters on its dynamic characteristics are investigated. Based on the transfer-matrix method and taking into consideration the gyroscopic couple, the shear, the variable cross-section, and other influential factors, a dynamic model is established for the multidisk rotor of the rotor-bearing system of the electric spindle. The critical speeds of first three orders, the modes of variation, and other dynamic characteristic parameters of the electric spindle are programmed and calculated. The influences of the axial pre-tightening force of the bearing, the span of the fulcrum bearing as well as the changes in the front and rear overhangs on the critical speed of the rotor-bearing system on the electric spindle and their pattern of changes are analyzed. The results show that the span of the fulcrum bearing and the overhang have significant influences on the critical speed within a certain range, and the study provide the basis and guidance for the structural design and performance optimization of the electric spindle.

Investigation on Critical Speed and Vibration Mode of High Speed Grinder

2011 ◽  
Vol 42 (10) ◽  
pp. 47-54 ◽  
Author(s):  
C. H. Li ◽  
Z. R. Liu ◽  
Y. Zhou ◽  
Y. C. Ding
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Vibration Mode ◽  
Structural Parameters ◽  
Variable Cross Section ◽  
Influential Factors ◽  
Variable Cross ◽  
Tightening Force ◽  
Rotor Bearing ◽  
Bearing System

The influences of the grinder spindle's major structural parameters on its vibration mode were investigated. Based on the transfer-matrix method and taking into consideration the gyroscopic couple, the shear, the variable cross-section and other influential factors, a dynamic model was established for the multi-disk rotor of the rotor-bearing system of the grinder spindle. The critical speeds of first three orders, the modes of variation and other dynamic characteristic parameters of the grinder spindle were programmed and calculated. The influences of the axial pre-tightening force of the bearing, the span of the fulcrum bearing as well as the changes in the front and rear overhangs on the critical speed of the rotor-bearing system on the grinder spindle and their pattern of changes were analyzed. The results showed that the working speed of the spindle system is much lower than the primary critical speed and can therefore stay away the resonance range effectively.

Dynamic Design of a High-Speed Motorized Spindle-Bearing System

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Shuyun Jiang ◽  
Shufei Zheng
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Dynamic Stiffness ◽  
Processing Condition ◽  
Rolling Bearing ◽  
Design Sensitivity ◽  
Structure Parameters ◽  
Motorized Spindle ◽  
Spindle Bearing ◽  
Bearing System

This technical brief presents a dynamic model based on the traditional transfer matrix method (TMM) and Jones–Harris nonlinear rolling bearing model to study the effects of the extended structure parameters on the vibration behavior of a high-speed motorized spindle-bearing system. The first critical speed and the dynamic stiffness of the high-speed motorized spindle-bearing system are systematically studied. A design sensitivity analysis of the structure parameters is then conducted to identify the main factor to affect the first critical speed of the spindle-bearing system. The results show that the processing condition, the shaft shoulder, the dimension of motor, and the bearing arrangement are sensitive to the spindle dynamic behavior. The TMM model of the spindle-bearing system is verified by measuring the high-speed motorized spindle overall dynamic stiffness.

Formation of Standing Waves in Radial Tires

1984 ◽  
Vol 12 (1) ◽  
pp. 44-63 ◽  
Author(s):  
Y. D. Kwon ◽  
D. C. Prevorsek
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Unit Length ◽  
Standing Waves ◽  
Rolling Resistance ◽  
Damping Coefficient ◽  
Circular Membrane ◽  
Critical Speeds ◽  
Steel Cord ◽  
The Individual

Abstract Radial tires for automobiles were subjected to high speed rolling under load on a testing wheel to determine the critical speeds at which standing waves started to form. Tires of different makes had significantly different critical speeds. The damping coefficient and mass per unit length of the tire wall were measured and a correlation between these properties and the observed critical speed of standing wave formation was sought through use of a circular membrane model. As expected from the model, desirably high critical speed calls for a high damping coefficient and a low mass per unit length of the tire wall. The damping coefficient is particularly important. Surprisingly, those tire walls that were reinforced with steel cord had higher damping coefficients than did those reinforced with polymeric cord. Although the individual steel filaments are elastic, the interfilament friction is higher in the steel cords than in the polymeric cords. A steel-reinforced tire wall also has a higher density per unit length. The damping coefficient is directly related to the mechanical loss in cyclic deformation and, hence, to the rolling resistance of a tire. The study shows that, in principle, it is more difficult to design a tire that is both fuel-efficient and free from standing waves when steel cord is used than when polymeric cords are used.

Do elite soccer players cover longer distance when losing? Differences between attackers and defenders

2020 ◽  
pp. 174795412098227
Author(s):  
Carlos Lago-Peñas ◽  
Anton Kalén ◽  
Miguel Lorenzo-Martinez ◽  
Roberto López-Del Campo ◽  
Ricardo Resta ◽  
...  
Keyword(s):  
New York ◽  
High Speed ◽  
Large Scale ◽  
Tracking System ◽  
Soccer Players ◽  
Running Performance ◽  
Situational Variables ◽  
Total Distance ◽  
Professional Soccer ◽  
Score Line

This study aimed to evaluate the effects playing position, match location (home or away), quality of opposition (strong or weak), effective playing time (total time minus stoppages), and score-line on physical match performance in professional soccer players using a large-scale analysis. A total of 10,739 individual match observations of outfield players competing in the Spanish La Liga during the 2018–2019 season were recorded using a computerized tracking system (TRACAB, Chyronhego, New York, USA). The players were classified into five positions (central defenders, players = 94; external defenders, players = 82; central midfielders, players = 101; external midfielders, players = 72; and forwards, players = 67) and the following match running performance categories were considered: total distance covered, low-speed running (LSR) distance (0–14 km · h−1), medium-speed running (MSR) distance (14–21 km · h−1), high-speed running (HSR) distance (>21 km · h−1), very HSR (VHSR) distance (21–24 km · h−1), sprint distance (>24 km · h−1) Overall, match running performance was highly dependent on situational variables, especially the score-line condition (winning, drawing, losing). Moreover, the score-line affected players running performance differently depending on their playing position. Losing status increased the total distance and the distance covered at MSR, HSR, VHSR and Sprint by defenders, while attacking players showed the opposite trend. These findings may help coaches and managers to better understand the effects of situational variables on physical performance in La Liga and could be used to develop a model for predicting the physical activity profile in competition.

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