Investigation of Air-Oil-Thermal Distribution in Floating Bush Bearing

2017 ◽  
Author(s):  
Yan Wang ◽  
Xiaodong Ren
Keyword(s):  
Thermal Effect ◽  
Thermal Effects ◽  
High Speed ◽  
Low Cost ◽  
Prediction Method ◽  
Cfd Modeling ◽  
Speed Ratio ◽  
Shaft Speed ◽  
Two Phase ◽  
Oil Film

Owing to their low cost and reduced power losses, floating bush bearings are extensively used in high-speed rotors. The advantages are mainly the result of the rotation of the bush. When shaft speed is within a low speed range, bush rotation speed increases linearly with shaft speed. However, the bush-to-shaft speed ratio decreases sharply when the shaft speed reaches a certain range. The mechanism of this phenomenon is not completely clear yet, and a precise prediction method has not been established. The traditional theoretical model predicts that the speed ratio remains constant even when the shaft speed reaches the certain range. Some researchers have attempted to improve the prediction model by considering thermal effect on the assumption that a temperature increase decreases the viscosity of the inner oil film and consequently reduces the speed ratio. However, temperature rise alone is insufficient to induce that much drop of speed ratio. This paper focuses on the effect of air invasion flow in the inner oil film from the axial ends and evaluates the importance of air invasion and thermal effects. Computational fluid dynamics (CFD) modeling is adopted in this study because of its capacity to handle complicated calculation domain and calculate air-oil two-phase flow. Three series of CFD simulations with different models are conducted. These models consider the thermal effect (thermal model), the air invasion effect (air model), and the combination of the thermal and air invasion effects (hybrid model). CFD results of the different models are compared to weigh the importance of each effect. The CFD calculation indicates that a substantial amount of air invades the inner oil film when the shaft speed reaches a certain range. Speed ratio drop is not caused by a single factor, but it is the result of the combination of the air invasion and thermal effects. Air invasion, which researchers previously ignored, plays a greater role than the thermal effect.

A Theoretical Analysis of Floating Bush Journal Bearing With Axial Oil Film Rupture Being Considered

2002 ◽  
Vol 124 (3) ◽  
pp. 494-505 ◽  
Author(s):  
Kiyoshi Hatakenaka ◽  
Masato Tanaka ◽  
Kenji Suzuki
Keyword(s):  
Steady State ◽  
Reynolds Equation ◽  
Speed Ratio ◽  
Shaft Speed ◽  
Film Rupture ◽  
State Behavior ◽  
Oil Film ◽  
Rotordynamic Coefficients ◽  
The Stability ◽  
Very High

A new modified Reynolds equation is derived with centrifugal force acting on the hydrodynamic oil film being considered. This equation, together with a cavitation model, is used to obtain the steady-state equilibrium and calculate the rotordynamic coefficients of lightly loaded floating bush journal bearings operating at very high shaft speeds. The bush-to-shaft speed ratio and the linear cross-coupling spring coefficients of the inner oil film is found to decrease with the increase in shaft speed as the axial oil film rupture develops in the inner oil film. The present model can give reasonable explanation to the steady-state behavior and the stability behavior of the bearing observed in actual machines.

Effect of Mechanical Preloads on the Dynamic Performance of Gas Foil Bearings

2008 ◽  
Author(s):  
Tae Ho Kim ◽  
Luis San Andre´s
Keyword(s):  
Large Amplitude ◽  
High Speed ◽  
Low Cost ◽  
Dynamic Performance ◽  
Cycle Performance ◽  
High Power Density ◽  
Shaft Speed ◽  
Foil Bearings ◽  
Bearing Force ◽  
Good Agreement

Gas foil bearings (GFBs) enable efficient, reliable and maintenance free operation of high-power-density microturbomachinery (< 200 kW). High speed rotors supported on bump-type GFBs, however, are prone to show large-amplitude subsynchronous motions albeit reaching limit cycle performance. Presently, commercial GFBs are simply modified to introduce a mechanical preload that induces a hydrodynamic wedge to generate more load support and direct stiffnesses. Three metal shims inserted under the bump strip layers and in contact with the bearing housing create a multiple lobe clearance profile at a very low cost. Shaft speed coastdown measurements reveal the rotordynamic performance of a rotor supported on original GBFs and (modified) shimmed GFBs. The later GFBs determine a raise in the rotor-bearing system natural frequency, as expected, and also act to delay the onset speed of large-amplitude subsynchronous motions. Predictions of imbalance response implementing linearized bearing force coefficients are in good agreement with measured amplitudes of synchronous response for both GFB configurations, original and modified.

Two-Phase Air/Oil Flow in Aero Engine Bearing Chambers: Characterization of Oil Film Flows

1996 ◽  
Vol 118 (3) ◽  
pp. 578-583 ◽  
Author(s):  
A. Glahn ◽  
S. Wittig
Keyword(s):  
High Speed ◽  
Force Balance ◽  
Two Phase ◽  
Oil Film ◽  
Theoretical Approaches ◽  
Geometric Conditions ◽  
Oil Flow ◽  
Secondary Air ◽  
Film Flows

For the design of secondary air and lubrication oil systems, a sufficient knowledge of two-phase flow and heat transfer phenomena under bearing chamber flow conditions is required. The characterization of oil film flows at the bearing chamber walls is one of the major tasks for a better understanding of these processes and, therefore, a necessity for improvements of the efficiency of aero engines. The present paper gives a contribution to this subject. Utilizing a fiber-optic LDV setup, measurements of oil film velocity profiles have been performed in our high-speed bearing chamber rig simulating real engine conditions. All data have been compared with different theoretical approaches, which have been derived from a force balance at a liquid film element, including geometric conditions and temperature dependent fluid properties, and by approaches for the eddy viscosity available in the literature.

Effect of the inlet oil temperature on vibration characteristics of the high-speed turbocharger rotor system

2021 ◽  
pp. 135065012098703
Author(s):  
Xinli Zhong ◽  
Yuan Huang ◽  
Guangfu Bin ◽  
Anhua Chen
Keyword(s):  
Finite Element ◽  
Power Consumption ◽  
Finite Element Model ◽  
Temperature Rise ◽  
High Speed ◽  
Element Model ◽  
Rotor System ◽  
Speed Ratio ◽  
Oil Film ◽  
Light Load

The inlet oil temperature of the rotor system with high-speed and light-load turbocharger will change during operation, which will change the vibration characteristics of the rotor system and even cause vibration accidents. Taking a certain type of high-speed and light-load turbocharger rotor system as the research object, the changes in oil film viscosity, friction power consumption, oil film temperature rise, and ring speed ratio with the inlet oil temperature of floating ring bearings are analyzed. A dynamic finite-element model of the turbocharger rotor–floating-ring-bearing system is constructed, and the finite-element model is verified through the critical speed and colormap spectrogram. The Newmark integral method is used to analyze the nonlinear transient response of the rotor system, and the influence of the inlet oil temperature on the vibration response characteristics of the rotor system is studied. The results show that an increase in the inlet oil temperature leads to a decrease in the internal and external oil film viscosities, frictional power consumption, temperature rise, and an increase in the ring speed ratio. When the inlet oil temperature increases from 50 °C to 130 °C, the amplitude of the inner oil film oscillation will gradually decrease, but the amplitude of the outer oil film vortex will gradually increase, and the journal speed point where the inner oil film oscillation and the outer oil film vortex will appear about 30% in advance. In summary, the rotor vibration is better when the inlet oil temperature is about 90 °C. The conclusion of this paper can provide a theoretical reference for selecting the operating parameters of the rotor system with the least vibration for high-speed light-load turbochargers.

scholarly journals An SVM-Based NAND Flash Endurance Prediction Method

Micromachines ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 746
Author(s):  
Haichun Zhang ◽  
Jie Wang ◽  
Zhuo Chen ◽  
Yuqian Pan ◽  
Zhaojun Lu ◽  
...  
Keyword(s):  
Flash Memory ◽  
High Speed ◽  
Low Cost ◽  
Prediction Method ◽  
Machine Learning Algorithms ◽  
Nand Flash ◽  
Transient Faults ◽  
Nand Flash Memory ◽  
Process Improvements ◽  
Noise Interference

NAND flash memory is widely used in communications, commercial servers, and cloud storage devices with a series of advantages such as high density, low cost, high speed, anti-magnetic, and anti-vibration. However, the reliability is increasingly getting worse while process improvements and technological advancements have brought higher storage densities to NAND flash memory. The degradation of reliability not only reduces the lifetime of the NAND flash memory but also causes the devices to be replaced prematurely based on the nominal value far below the minimum actual value, resulting in a great waste of lifetime. Using machine learning algorithms to accurately predict endurance levels can optimize wear-leveling strategies and warn bad memory blocks, which is of great significance for effectively extending the lifetime of NAND flash memory devices and avoiding serious losses caused by sudden failures. In this work, a multi-class endurance prediction scheme based on the SVM algorithm is proposed, which can predict the remaining P-E cycle level and the raw bit error level after various P-E cycles. Feature analysis based on endurance data is used to determine the basic elements of the model. Based on the error features, we present a variety of targeted optimization strategies, such as extracting the numerical features closely related to the endurance, and reducing the noise interference of transient faults through short-term repeated operations. Besides a high-parallel flash test platform supporting multiple protocols, a feature preprocessing module is constructed based on the ZYNQ-7030 chip. The pipelined module of SVM decision model can complete a single prediction within 37 us.

Floating Ring Balance Analysis of Journal Floating Ring Hybrid Bearing in Turbulent Regime

2014 ◽  
Vol 672-674 ◽  
pp. 1637-1641
Author(s):  
Hong Guo ◽  
Shao Lin Zhang
Keyword(s):  
High Speed ◽  
Dynamic Performance ◽  
Flow Equation ◽  
Radial Clearance ◽  
Speed Ratio ◽  
Turbulent Regime ◽  
Shaft Speed ◽  
Eccentricity Ratio ◽  
Pressure Boundary Condition ◽  
Balance Analysis

An externally pressurized deep/shallow pockets hybrid journal floating ring bearing compensated by flat capillary restrictor which can meet the need of high speed rotating machinery is presented in this paper. Bases on turbulent flow theory, the equations governing the flow of inner and outer fluid film in the journal floating ring bearing are established. The control equations together with the pressure boundary condition and the restrictor flow equation are solved by using the Finite Element Method. The balance of floating ring is achieved by adjusting ring-to-shaft speed ratio, inner film radial clearance and inner film eccentricity ratio. It can be seen from simulation results that the ring-to-shaft speed ratio and inner film clearance vary slightly and the floating ring can keep balance under different speed and eccentricity ratio. The variation of static and dynamic performance with eccentricity and rotational speed are calculated and analyzed based on floating ring balance.

Investigation of Air-Oil Distribution of Low Oil-Supplied Pressure Grooved Ring Floating Ring Bearing

2018 ◽  
Author(s):  
Wang Yan ◽  
Li Yuhong
Keyword(s):  
Thermal Effect ◽  
Fluid Dynamic ◽  
Great Influence ◽  
Air Entrainment ◽  
Simulation Method ◽  
Speed Ratio ◽  
Good Prediction ◽  
Shaft Speed ◽  
Entrainment Effect ◽  
Cfd Method

Oil lubricated floating ring bearings (FRBs) are popular among the passenger vehicle turbochargers. Air entrainment occurs in the inner film of the FRB under low oil-supplied pressure. Air entrainment has great impact on the bearing performance. Experiments reported that FRB with a circumferential groove on the ring shows lower ring-to-shaft speed and improved stabilizing capacity at high shaft speed. This study aims to construct the numerical simulation method to predict the multiphase flow in the grooved ring (GR) FRB. Computational fluid dynamic (CFD) method is adopted to obtain the bearing performance considering air entrainment. CFD calculation can obtain detailed air entrainment results that experiment cannot provide. Calculation results are compared with the experimental results to validate the proposed CFD method. Analysis shows the great influence of grooved ring on the air entrainment. Air entrainment contributes to the decrease of the ring-to-shaft speed ratio in the GR FRB. The proposed CFD calculation considering air entrainment can give good prediction of the ring rotation speed under different shaft speed. Besides, detailed analysis of the effective viscosity indicates that outer film is mainly affected by thermal effect. Inner film is affected by both thermal effect and air entrainment effect, where latter is more predominant.

scholarly journals The Series Hybrid Bearing—A New High Speed Bearing Concept

1972 ◽  
Vol 94 (2) ◽  
pp. 117-122 ◽  
Author(s):  
W. J. Anderson ◽  
D. P. Fleming ◽  
R. J. Parker
Keyword(s):  
Fatigue Life ◽  
High Speed ◽  
Ball Bearing ◽  
Rolling Element Bearing ◽  
Speed Ratio ◽  
Shaft Speed ◽  
Rolling Element ◽  
Element Bearing ◽  
Hybrid Bearing ◽  
Inner Race

The series-hybrid bearing couples a fluid-film bearing with a rolling-element bearing such that the rolling-element bearing inner race runs at a fraction of shaft speed. A series-hybrid bearing was analyzed and experiments were run at thrust loads from 100 to 300 lb and speeds from 4000 to 30,000 rpm. Agreement between theoretical and experimental speed sharing was good. The lowest speed ratio (ratio of ball bearing inner-race speed to shaft speed) obtained was 0.67. This corresponds to an approximate reduction in DN value of 1/3. For a ball bearing in a 3 million DN application, fatigue life would theoretically be improved by a factor as great as 8.

Two-Phase Air/Oil Flow in Aero Engine Bearing Chambers: Characterization of Oil Film Flows

1995 ◽  
Author(s):  
A. Glahn ◽  
S. Wittig
Keyword(s):  
High Speed ◽  
Force Balance ◽  
Two Phase ◽  
Oil Film ◽  
Theoretical Approaches ◽  
Oil Flow ◽  
Secondary Air ◽  
Aero Engines ◽  
Film Flows

For the design of secondary air and lubrication oil systems a sufficient knowledge on two-phase flow and heat transfer phenomena under bearing chamber flow conditions is required. The characterization of oil film flows at the bearing chamber walls is one of the major tasks for a better understanding of these processes and, therefore, a necessity for improvements of the efficiency of aero engines. The present paper gives a contribution to this subject. Utilizing a fibre-optic LDV-setup, measurements of oil film velocity profiles have been performed in our high speed bearing chamber rig simulating real engine conditions. All data have been compared with different theoretical approaches which have been derived from a force balance at a liquid film element, including geometrical conditions and temperature dependent fluid properties, and by approaches for the eddy viscosity available in the literature.

scholarly journals A Performance Prediction Method for Pumps as Turbines (PAT) Using a CFD Modeling Approach

2016 ◽  
Author(s):  
Emma Frosina ◽  
Dario Buono ◽  
Adolfo Senatore
Keyword(s):  
Test Bench ◽  
Low Cost ◽  
Three Dimensional ◽  
Prediction Method ◽  
Cfd Modeling ◽  
Centrifugal Pumps ◽  
Software Model ◽  
Pumping Mode ◽  
Using Data ◽  
The University

Small and micro hydropower represents an attractive solution for electricity generation, with low cost and low environmental impact. The pump-as-turbine (PAT) approach has promise in this application owing to its low purchase and maintenance costs. In this paper, a new method to predict the inverse characteristic of industrial centrifugal pumps is presented. This method is based on results of simulations performed with commercial three-dimensional CFD software. Model results have been first validated in pumping mode using data supplied by pump manufacturers. Then, results have been compared to experimental data for a pump running in reverse condition. Experimentation has been performed on a dedicated test bench installed in the Department of Civil Construction and Environmental Engineering of the University of Naples Federico II. Three different pumps, with different specific speeds, have been analyzed. Using the model results, the inverse characteristic and the best efficiency point have been evaluated. Finally, results of this methodology have been compared to prediction methods available in the literature.

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