scholarly journals An Investigation on the Dynamics of High-Speed Systems Using Nonlinear Analytical Floating Ring Bearing Models

2016 ◽  
Vol 2016 ◽  
pp. 1-22 ◽  
Author(s):  
Athanasios Chasalevris
Keyword(s):  
Dynamic Response ◽  
High Speed ◽  
Exact Analytical Solution ◽  
System Of Nonlinear Equations ◽  
Approximation Model ◽  
Rotating Speed ◽  
Time Frequency ◽  
Wide Range ◽  
Transient Dynamic Response ◽  
Bearing System

The scope of this paper is to investigate the dynamics of a rotor-bearing system of high-speed under recently developed analytical bearing models. The development of a theory that can yield the dynamic response of a high-speed system without short/long bearing approximation and without time-consuming numerical methods for the finite-length bearing model is the outcome of this work. The rotor system is introduced as a rigid body so that the dynamics of the system are influenced only from the nonlinear bearing forces which are introduced with closed form expressions. The outcome is a system of nonlinear equations and its solution produces the dynamic response of the high-speed system using exact analytical solution for the bearing forces. The transient dynamic response of the system is evaluated through the wide range of rotating speed and under different bearing solutions including short bearing approximation, presenting the subsynchronous components that are developed when instabilities occur. Time-frequency analysis of the resulting response time-series is presented and the outcome is compared with that obtained from numerical solution of the bearing lubrication and with the short bearing approximation model.

Quasi-Static Thermal Modeling of Multiscale Sliding Contact for Unlubricated Brush Seal Materials

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Qingfeng Xia ◽  
David R. H. Gillespie ◽  
Andrew K. Owen ◽  
Gervas Franceschini
Keyword(s):  
Thermal Conductivity ◽  
High Speed ◽  
Rotating Disk ◽  
Contact Temperature ◽  
Infinite Length ◽  
Rotating Speed ◽  
Thermal Anisotropy ◽  
Heat Partition ◽  
Anisotropic Thermal Conductivity ◽  
Wide Range

Prediction of contact temperature between two materials in high-speed rubbing contact is essential to model wear during unlubricated contact. Conventionally, assumptions of either a steady or an annular heat source are used for slow and high speed rotation, respectively. In this paper, a rotating heating source is solved using an in-house finite element method code. This captures the full geometry and rotating speed of the rubbing bodies. Transient heat transfer is modeled quasi-statically, eliminating the need for a transient 3D simulation. This model is shown to be suitable for contact temperature prediction over a wide range of rotating speeds, anisotropic thermal conductivity, and nonuniform thermal boundary conditions. The model calculates heat partition accurately for a thin rotating disk and short pin combination, which cannot be predicted using the existing analytical solutions. The method is validated against ansys mechanical and experimental infrared thermography. Results demonstrate that the annular source assumption significantly underpredicts contact temperature, especially at the rubbing interface. Explicit modeling of a thin disk results in higher heat partition coefficients compared with the commonplace semi-infinite length assumption on both static and rotating components. The thermal anisotropy of tuft-on-disk configurations is evaluated and compared to a uniform pin-on-disk configuration. Despite the effective thermal conductivity (ETC) in the bristle tuft being approximately 1 order of magnitude lower than along the bristle length (treating the bristle pack as a porous medium), its impact on heat partition and contact temperature is shown to be limited.

Foil Bearings Makes Oil-Free Turbocharger Possible

2005 ◽  
Author(s):  
Crystal A. Heshmat ◽  
Hooshang Heshmat ◽  
Mark J. Valco ◽  
Kevin C. Radil ◽  
Christopher Della Corte
Keyword(s):  
High Speed ◽  
Solid Lubricant ◽  
Load Capacity ◽  
Maximum Load ◽  
Solid Lubricant Coating ◽  
Foil Bearings ◽  
Wide Range ◽  
Rotor Bearing ◽  
Component Development ◽  
Bearing System

This paper describes an oil-free, 150 Hp turbocharger that was successfully operated with compliant foil bearings in a range of pitch and roll angles, including vertical operation, thereby demonstrating its viability for aircraft applications. On a gas test stand the turbocharger was operated to 120,000 rpm, under extreme conditions. In addition, the compliant foil bearing-supported turbocharger successfully tolerated shock and vibration of 40 g. Advanced technologies have been applied to the second generation of this turbocharger, shown in Figure 1, including self acting, compliant foil hydrodynamic air bearings with advanced coatings capable, of operation above 815 °C (1500°F). Journal foil bearings with maximum load capacity up to 670 kPa (97 psi) were used in conjunction with thrust foil bearings capable of maximum loads to 570 kPa (83 psi). Bearing component development tests demonstrated 30,000 start stop cycles at 815 °C (1500°F) with a newly developed, solid lubricant coating, KOROLON™. KOROLON™ exhibits a coefficient of friction of less than 0.1 at a wide range of temperatures. Current-designed foil bearings with KOROLON™ have immensely decreased turbolag, allowing acceleration from rest to over 100,000 rpm in less than 2 seconds. Advanced bearing stiffness maintained rotor total axial end-to-end motion within 100 microns (0.004 inch). Total radial static and dynamic motion was controlled within 25 microns (0.001 inch). Development of this high speed turbomachine included bearing and solid lubricant component development tests, rotor-bearing dynamic simulator qualification and gas stand tests of the assembled turbocharger. Gas stand and simulator test results revealed stable bearing temperatures, low rotor vibrations, good shock tolerance and the ability of the rotor bearing system to sustain overspeed conditions beyond 120,000 rpm. This combination of component and integrated rotor-bearing system technology addresses many of the issues associated with application of compliant foil bearings to industrial compressors, blowers, and gas turbine engines, overcoming many of the inherently show-stopping and debilitating features of rolling element bearings, i.e., speed and temperature limitations.

scholarly journals Theoretical and Experimental Study on the Transient Time-Frequency Characteristics of the Bending-Torsional Coupling Motions of a Rub-Impact Dual-Rotor System

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Tian Gao ◽  
Shuqian Cao ◽  
Tiancheng Zhang
Keyword(s):  
Friction Coefficient ◽  
Fault Detection ◽  
High Speed ◽  
Rotor System ◽  
Bending Vibration ◽  
Transient Time ◽  
Rotating Speed ◽  
Time Frequency ◽  
Runge Kutta Method ◽  
Torsional Coupling

This paper focuses on the fault characteristics of the bending and torsional motions of a rub-impact dual-rotor system caused by aircraft flight maneuvers. The equations of the bending-torsional coupling motion of a dual-rotor system are established considering a low-pressure rotor rub-impact fault and the transient barrel roll flight of an aircraft. The 4th Runge-Kutta method with varied steps is used to obtain the bending and torsional responses. Then, the influences of the system parameters, including the rub-impact stiffness, friction coefficient, and rotating speed, on the bending and torsional motions of the dual-rotor system are investigated in detail. At last, a rotor rubbing experiment is carried out, verifying the validity of the simulation results. The results show that the rub-impact stiffness affects bending vibration significantly and the torsional motion is sensitive to the friction coefficient. Correspondingly, the torsional responses show apparent fractional fault frequencies and rotating fault frequencies within the whole region of the rub-impact stiffness. The bending responses can only display fault frequencies at certain rub-impact stiffness. As for the rotating speed, the torsional responses are also more effective than the bending responses for the rub-impact fault detection at the low- and high-speed regions. The results will contribute to a comprehensive basis for the rub-impact fault detection.

Numerical and Experimental Investigation on Centrifugal Cooling Fan in a Traction Motor

2018 ◽  
Author(s):  
Xiaoyun Qu ◽  
Jie Tian ◽  
Tong Wang
Keyword(s):  
High Speed ◽  
Aerodynamic Performance ◽  
Aerodynamic Noise ◽  
Centrifugal Fan ◽  
High Speed Train ◽  
Traction Motor ◽  
Rotating Speed ◽  
Cooling Fan ◽  
Wide Range ◽  
Cfd Method

High-speed train is developing popular in China, which provides the convenient and fast transportation way, comparable to plane. The moving direction and speed of high-speed train is decided by the traction motor. Generally, a coaxial centrifugal fan is used to cool the motor and assemble in the motor casing. To ensure the reliability of the traction motor, more and more attention is paid to improve the performance of cooling fans in a wide range of rotating speed. As the train is designed to move in both directions, the traction motor is designed to rotate in both directions, so does the coaxial motor cooling fan. Symmetrical and straight blade structure is adopted to get the same performance of the fan in both forward and reverse moving directions. Therefore, the aerodynamic performance of the cooling fan is relatively not good enough, which results in relatively high aerodynamic noise. In order to analyze the cooling fan aerodynamic performance and aerodynamic noise, CFD method was performed on the full 3D model with the impeller-casing clearance. The acoustic analogy method was used to analyze the noise of the centrifugal cooling fan. In addition, the aerodynamic noise of the motor with the cooling fan was tested at different rotating speed in the semi-anechoic lab. The CFD method is verified and the results are in good agreement with the experimental results. The results show that it is necessary to consider the effects of impeller-casing leakage and the vacuum inlet condition in the simulated model to get its more accurate performance. Modified CFD model of the cooling fan was proposed here. It is suggested that the modified structure of the casing can be used to improve the performance of the cooling fan and reduce the corresponding aerodynamic noise.

Comparative Studies on the Dynamic Performances of High Speed Turbocharger Rotor Supported on Oil-Free Bearings Versus Conventional Floating Ring Systems

2017 ◽  
Author(s):  
Rajasekhara Reddy Mutra ◽  
J. Srinivas
Keyword(s):  
Dynamic Response ◽  
High Speed ◽  
Equations Of Motion ◽  
Dynamic Modelling ◽  
Dynamic Responses ◽  
Effect Of Temperature ◽  
Time Step ◽  
Foil Bearing ◽  
Dynamic Performances ◽  
Bearing System

Present work focuses on the dynamic modelling of the dual-disc rotor supported on oil-free bearings idealizing a turbocharger rotor bearing system. The equations of motion of the rotor system are formulated and solved by finite element method to obtain the dynamic response of the system. The gas-foil bearing forces obtained from finite-difference approach at each time-step of solution. The same rotor model is used with the conventional floating ring bearing system where, the bearing forces are provided as displacement dependent time-varying oil and floating ring forces. As a practical environmental condition, the effect of temperature on the viscosity is studied using Dowson equation. The dynamic responses are illustrated both for rotor supported on both gas-foil and floating-ring type bearings. The effects of changes in bearing clearances on the overall dynamic characteristics of the rotor are reported. In order to utilize the gas foil bearing model, an identification study is performed to predict the operating clearance and air viscosity using dynamic response data.

scholarly journals Effect of preload on the dynamic characteristics of ceramic bearings based on a dynamic thermal coupling model

2020 ◽  
Vol 12 (1) ◽  
pp. 168781402090385
Author(s):  
Ke Zhang ◽  
Zinan Wang ◽  
Xiaotian Bai ◽  
Huaitao Shi ◽  
Qi Wang
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Thermal Deformation ◽  
Coupling Model ◽  
Transfer Model ◽  
Thermal Coupling ◽  
Motorized Spindle ◽  
Rotating Speed ◽  
Spindle Bearing ◽  
Bearing System

Ceramic bearings have a good dynamic output performance under an ultra-high, ultra-low temperature due to their small deformation property. Based on the Harris and Palmgren empirical equation, this article establishes the thermal transfer model of a ceramic motorized spindle. The thermal deformation of a ceramic angular contact ball bearing is calculated. A dynamic and thermal coupling model of the ceramic motorized spindle is built using the Hertz contact theory, which can determine the optimal preload force under different rotating speed conditions. The influence of different temperatures, preload, and rotation speeds on the bearing vibration characteristics was studied. The accuracy of the dynamic and thermal coupling model was verified by the motorized spindle experimental platform. The results show that the thermal deformation of the bearing is an important influencing factor for the output of the dynamic characteristics. Considering the thermal displacement of the bearing, the simulation accuracy of the ceramic motorized spindle-bearing system is in good agreement with the experimental results. By adjusting the bearing preload, the parameters of the rotating speed can effectively reduce the temperature rise and suppress the vibration. The spindle-bearing system model provides a theoretical basis for the dynamic development of a high-speed ceramic bearing.

Investigation of rotor–gas foil bearing system and its application for an ultra-high-speed permanent magnet synchronous motor

2021 ◽  
pp. 135065012110317
Author(s):  
Jiale Tian ◽  
Baisong Yang ◽  
Sheng Feng ◽  
Lie Yu ◽  
Jian Zhou
Keyword(s):  
Permanent Magnet ◽  
High Speed ◽  
Dynamic Performance ◽  
Permanent Magnet Synchronous Motor ◽  
Synchronous Motor ◽  
Rotating Speed ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Ultra High Speed ◽  
Bearing System

In this study, an ultra-high-speed rotor–gas foil-bearing system is designed and applied to a permanent magnet synchronous motor. Gas foil journal bearings and gas foil thrust bearings are used to provide journal and axial support to the rotor, respectively. The bearings are analyzed theoretically considering the nonlinear deflection of the top foil, and the static and dynamic characteristics are obtained with which the rotor dynamic performances of the tested rotor are calculated using the finite element method. During the experiment, the permanent magnet synchronous motor can operate stably at 94,000 r/min, which demonstrates a great dynamic performance of the gas foil bearings and the stability that it provides to the entire system. The sub-synchronous vibration also occurs when the rotating speed reaches 60,000 r/min and as the speed keeps rising, the amplitude of such vibration increases, which will contribute to the destabilization of the rotor–gas foil-bearing system. Finally, the axial force of the rotor is calculated theoretically as well as measured directly by four micro force sensors mounted in the thrust end cover of the permanent magnet synchronous motor. The experimental results presented in this article are expected to provide a useful guide to the design and analysis of the rotor–gas foil-bearing system and high-speed permanent magnet synchronous motor.

Impact of Rail Fastener Looseness on Vertical Dynamic Responses of High-Speed Vehicle and Ballastless Track

2021 ◽  
Author(s):  
Jianbo Li ◽  
Hongmei Shi
Keyword(s):  
Dynamic Response ◽  
Detailed Analysis ◽  
Frequency Domain ◽  
High Speed ◽  
Vibration Response ◽  
Dynamic Responses ◽  
Time Frequency ◽  
Ballastless Track ◽  
Track System ◽  
Track Irregularity

The fastener system is an essential component of the high-speed ballastless track system. A detailed analysis for the effect of fastener looseness on the vertical dynamic response of the vehicle–track coupling system is conducted from the time domain, frequency domain and time–frequency domain in this paper. A fine fastener system model is employed, which includes two spring rods and one rail pad. The preloaded force is proposed to simulate the defect of the fastener, and a looseness coefficient is defined to represent the loose degree of the fastener. First, three fastener system models are introduced into the model, respectively, and the difference in the vehicle–track dynamic is analyzed and compared. The results show that the proposed model is more consistent with the real situation and more suitable to simulate fastener defects. Then, the detailed analysis of vehicle and track dynamic responses is explored in the case of different degrees of loose fasteners and the case of completely loose fasteners. According to the simulation results, there is little impact on the dynamic response of the vehicle–track system when the looseness coefficient is less than 0.9. When the fasteners are completely loosened, the dynamic response of the wheelset and the rail significantly increases. The vibration responses of rail and wheelset enhance with the increase of the number of the completely loose fastener. The loose fasteners affect the low-frequency part of the wheelset vibration response and the high-frequency part of the rail vibration response. Finally, a time–frequency analysis method is used to analyze the system vibration response under the combined effect of the completely loose fastener and the track irregularity. The track irregularity still dominates the excitation of the system, and the vibration response of the wheelset and the rail is more sensitive to the fastener defect at low speed.

Dynamic Response and Stability of a Spur Gear Pair

1999 ◽  
Author(s):  
C. Nataraj ◽  
N. K. Arakere
Keyword(s):  
Dynamic Response ◽  
High Speed ◽  
Dynamic Stiffness ◽  
Periodic Variation ◽  
Spur Gear ◽  
Approximation Technique ◽  
Gear Pair ◽  
Wide Range ◽  
Minimum Number ◽  
Six Degree Of Freedom

Abstract This paper deals with the linearized dynamics of a high-speed spur-gear pair supported on linear orthotropic bearings. The mating teeth are modeled accurately and the effect of the dynamic stiffness variation on the dynamic response is taken into account and, in fact, forms the essence of this work. The resulting six degree of freedom system is nondimensionalized in order to reduce the model to a minimum number of independent parameters and to make the results valid for a wide range of practical situations. The equations are solved using a recently developed approximation technique using Chebyshev polynomials. It is shown that not accounting for the periodic variation of the stiffness can lead to drastic differences in dynamic response and stability.

Sign in / Sign up

Export Citation Format

Share Document