Influence of temperature – viscosity effect on ring-journal speed ratio and stability for a hydrodynamic floating ring bearing

2019 ◽  
Vol 71 (4) ◽  
pp. 540-547 ◽  
Author(s):  
Hong Guo ◽  
Shuai Yang ◽  
Shaolin Zhang ◽  
Zebin Zhang
Keyword(s):  
Computational Models ◽  
Reynolds Equation ◽  
Rotor System ◽  
Speed Ratio ◽  
Outlet Temperature ◽  
Content Type ◽  
Influence Of Temperature ◽  
Viscosity Effect ◽  
Single Mass ◽  
The Stability

Purpose The purpose of this paper is to study the influence of lubricant temperature-viscosity on the performance for a hydrodynamic journal floating ring bearing (FRB), including ring-journal speed ratio and stability. Design/methodology/approach The finite difference method was used to solve computational models of Reynolds equation, energy equation and temperature–viscosity equation. Dynamic coefficients were obtained based on the floating ring balance. The dynamic model of journal and floating ring was established to deduce the stability criterion of single mass symmetrical rigid FRB rotor system by the Routh–Hurwitz method. The outlet temperature and ring-journal speed ratio under different journal speeds were compared to experimental data. Findings The temperature–viscosity effect reduces the ring-journal speed ratio and stability of rotor system. According to theoretical and experimental results, the outlet temperature rises and ring-journal ratio drops when the journal speed rises. Originality/value The temperature–viscosity effect is combined with dynamic characteristics to analyze the stability of the rotor system and lubrication mechanism for an FRB. Influence of temperature–viscosity on the ring-journal ratio and multi-stable regions of system are studied.

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.

Influence of rotational speed of a heavy-duty hydrostatic turret on bearing performance under tilt

2019 ◽  
Vol 72 (5) ◽  
pp. 575-579
Author(s):  
Zhifeng Liu ◽  
Junyuan Guo ◽  
Yumo Wang ◽  
Dong Xiangmin ◽  
Yue Wu ◽  
...  
Keyword(s):  
Bearing Capacity ◽  
Rotational Speed ◽  
Design Methodology ◽  
Reynolds Equation ◽  
Heavy Duty ◽  
Film Stability ◽  
Content Type ◽  
Oil Film ◽  
Tilt Stability ◽  
The Stability

Purpose This paper aims to propose a method for finding the maximum rotational speed of an inclined turntable at which the stability of the bearing oil film is maintained. Design/methodology/approach The finite difference method was used to solve the Reynolds equation. Variation of bearing capacity of a tilted hydrostatic turret over time was determined. The combined effect of tilt and rotational speed of the turret on the oil film stability was also analyzed. Findings When the turntable is operated at low speeds with only small angle of tilt, stability of the oil film is maintained. At lower rotational speeds, a smaller angle of tilt improves the bearing capacity and ensures stability of the oil film. Whereas, higher rotational speeds can have a considerable influence on the bearing capacity. Originality/value The results demonstrate that the inclination or tilt of the turntable significantly affects the stability of the oil film.

Numerical and experimental study on dynamic characteristics of tilting-pad journal bearings considering pivot stiffness in a vertical rotor system

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Fan Zhang ◽  
Peng Yin ◽  
Yuyang Liu ◽  
Jianmei Wang
Keyword(s):  
Dynamic Characteristics ◽  
Journal Bearings ◽  
Rotor System ◽  
Obvious Effect ◽  
Content Type ◽  
Vertical Rotor ◽  
Tilting Pad ◽  
Rotor Bearing ◽  
The Stability ◽  
Tilting Pad Journal Bearings

Purpose The purpose of this paper is to study the influence of pivot stiffness on the dynamic characteristics of tilting-pad journal bearings (TPJBs) and the stability of the bearing-rotor system. Design/methodology/approach A theoretical numerical model is established, and the influences of pivot stiffness on TPJBs and a bearing-rotor system are analyzed. Then, two kinds of pivot structures with different stiffness are designed and the vibration characteristics are tested on the vertical rotor bearing test bench. Findings The pivot stiffness has an obvious effect on the dynamic characteristics of the TPJBs and the stability of the bearing-rotor system. As a result of appropriate pivot stiffness, the critical speed and the vibration amplification factor can be reduced, the logarithmic decay rate and the stability of the rotor system can be effectively increased. While the journal whirl orbit is smoother and the rubbing is obviously reduced when the bearings have flexible pivots. Originality/value The influence of pivot stiffness on TPJBs and a vertical rotor-bearing system is studied by theoretical and experimental methods.

Exploring the overall behaviour of solutions of recursive computational models

2005 ◽  
Vol 24 (1) ◽  
pp. 167-178
Author(s):  
J.S. Hämäläinen ◽  
M. Aunola ◽  
S.R. Malm
Keyword(s):  
Case Studies ◽  
Parameter Space ◽  
Design Methodology ◽  
Computational Models ◽  
Simulation Models ◽  
Good Choice ◽  
Systematic Analysis ◽  
Content Type ◽  
The Stability

PurposeTo determine and/or examine overall behaviour of simulation models with large input using as few parameters as possible. To introduce a methodology describing stability of the partitioning of simulation results and the corresponding parameter space.Design/methodology/approachPartitionings of the parameter space are performed using real‐valued mappings called measures of merit. Tools for examining evolution of partitionings and correlations between different partitionings are developed. These tools are applied in two case studies within the field of electrical engineering.FindingsThe presented approach provides tools for systematic analysis of parametrised models. Since the classification of results is based on measures of merit, a good choice both simplifies the analysis and improves the stability of partitioning. Included case studies highlight these conclusions.Research limitations/implicationsThe present form of the methodology is targeted at recursive simulations. Use of more complex partitioning procedures could be the topic of further research.Originality/valueSolid framework for handling and analysing complex parametrised simulations.

Numerical Method and Bifurcation Analysis of Jeffcott Rotor System Supported in Gas Journal Bearings

2008 ◽  
Vol 4 (1) ◽  
Author(s):  
Jiazhong Zhang ◽  
Wei Kang ◽  
Yan Liu
Keyword(s):  
Dynamical System ◽  
Numerical Method ◽  
Bifurcation Analysis ◽  
Reynolds Equation ◽  
Rotor System ◽  
Nonlinear Phenomena ◽  
Direct Integral ◽  
Stability And Bifurcation ◽  
Jeffcott Rotor ◽  
The Stability

From the viewpoint of nonlinear dynamics, the stability and bifurcation of the rotor dynamical system supported in gas bearings are investigated. First, the dynamical model of gas bearing-Jeffcott rotor system is given, and the finite element method is used to approach the unsteady Reynolds equation in order to obtain gas film forces. Then, the method for stability analysis of the unbalance response of the rotor system is developed in combination with the Newmark-based direct integral method and Floquet theory. Finally, a numerical example is presented, and the complex behaviors of the nonlinear dynamical system are simulated numerically, including the trajectory of the journal and phase portrait. In particular, the stabilities of the system’s equilibrium position and unbalance responses are studied via the orbit diagram, phase space, Poincaré mapping, bifurcation diagram, and power spectrum. The results show that the numerical method for solving the unsteady Reynolds equation is efficient, and there exist a rich variety of nonlinear phenomena in the system. The half-speed whirl encountered in practice is the result from Hopf bifurcation of equilibrium, and the numerical method presented is available for the stability and bifurcation analysis of the complicated gas film-rotor dynamic system.

The influence of temperature on the corrosion inhibition of API 5L X42 pipeline steel in HCl medium by gum arabic

2017 ◽  
Vol 64 (4) ◽  
pp. 409-417 ◽  
Author(s):  
Hamza Bentrah ◽  
Abdelouahad Chala ◽  
Mounir Djellab ◽  
Youssouf Rahali ◽  
Hicham Taoui
Keyword(s):  
Inhibition Efficiency ◽  
Electrochemical Impedance ◽  
Pipeline Steel ◽  
Physical Adsorption ◽  
Gum Arabic ◽  
Corrosion Mechanism ◽  
Content Type ◽  
Influence Of Temperature ◽  
Temperature Range ◽  
The Stability

Purpose This paper aims to investigate the influence of temperature (25-65°C) on the adsorption and the inhibition efficiency of gum arabic (GA) for the corrosion of API 5L X42 pipeline steel in 1M HCl. Design/methodology/approach Inhibition behaviour on steel in HCl has been studied in relation to the concentration of the inhibitor and the temperature using potentiodynamic polarization curves and electrochemical impedance spectroscopy. Thermodynamic parameters of adsorption were calculated from the viewpoint of adsorption theory. Findings The results show that at a temperature range from 25 to 65°C, GA was a good inhibitor for API 5L X42 pipeline steel, and its inhibition efficiency was significantly stable. The maximum inhibition efficiency (93 per cent) is obtained at 4 g L−1. In absence and presence of GA, there is almost no change in the corrosion mechanism regardless of the temperature. The adsorption of GA on steel surface is an exothermic process. The adsorption of GA involves physical adsorption. Practical implications The use of GA as an eco-friendly corrosion inhibitor is practical for carbon steel in HCl. Originality/value The stability of inhibition efficiency of GA at a temperature range from 25 to 65°C could find possible applications in acid pickling, industrial acid cleaning and acid descaling.

Stability analysis and control of a flywheel energy storage rotor with rotational damping and nonsynchronous damping

2021 ◽  
pp. 107754632110212
Author(s):  
Huiwei Wang ◽  
Huichun Peng ◽  
Yaxin Zhen
Keyword(s):  
Stability Analysis ◽  
Dynamical Behavior ◽  
Linear Quadratic Regulator ◽  
Rotor System ◽  
Speed Ratio ◽  
Linear Quadratic ◽  
Coupling Effects ◽  
The Stability ◽  
Rotational Damping ◽  
Flywheel Rotor

Based on the principle of Lagrange mechanics, especially considering the effects of rotation damping and nonsynchronous damping, a radial 4-dimensional dynamic model of the flywheel bearing rotor system is proposed. Applying the Laplace eigenvalue method, the stability effects of rotational damping, nonsynchronous damping, and their coupling effects are investigated by means of root locus method. Under the control of the linear quadratic regulator, dynamical characteristics of the flywheel bearing rotor system with varied rotational damping and nonsynchronous damping are also studied. The results show that the rotation damping, nonsynchronous damping, and their coupling effects have vast and complex instability effects on high-speed flywheel bearing rotor system. However, there are three exceptions. The tiny proportional rotational damping, remaining below 12%, and the minuscule proportional co-nonsynchronous damping; the product of the nonsynchronous damping and the speed ratio below 5% both can enhance the stability of the system. Furthermore, in the situation that the counter-nonsynchronous damping is coupled with the large proportion of rotational damping, the stability of the system can also be boosted distinctly. On the other hand, the numerical experimental results show that the rotational damping and nonsynchronous damping have a beneficial effect on the flywheel system controlled by linear quadratic regulator. In addition, under the control of linear quadratic regulator, the transient dynamical behavior of the flywheel rotor system with rotational damping or co-nonsynchronous damping performed better than the flywheel rotor system with the coupled damping. The numerical simulations of the transient response of the flywheel rotor system under active control are consistent with some of the derived stability analysis results. The results about the stability analysis and the performance in vibration control give the suggestions for the instability control and fault detection of the system.

Dynamic characteristics of opposed-conical gas-dynamic bearings

2019 ◽  
Vol 72 (3) ◽  
pp. 415-425 ◽  
Author(s):  
Yan Li ◽  
Desheng Zhang ◽  
Fuhai Duan
Keyword(s):  
Dynamic Characteristics ◽  
Design Methodology ◽  
Reynolds Equation ◽  
Critical Mass ◽  
Degree Of Freedom ◽  
Content Type ◽  
Damping Coefficients ◽  
Gas Dynamic ◽  
The Stability ◽  
Stiffness And Damping

Purpose The purpose of this paper is to investigate dynamic characteristics of opposed-conical gas-dynamic bearings considering five degree-of-freedom motion, including translation and tilt. Design/methodology/approach The steady-state Reynolds equation and perturbed Reynolds equations are solved on the surface of conical bearings, and both stiffness and damping coefficients are calculated. A formula for quickly calculating critical mass is deduced to discriminate the stability of the rotor considering the five degree-of-freedom motion. Findings Results show that the stability of the rotor is mainly determined by translation rather than tilt. The formula of critical mass is validated by comparing the results with traditional Routh–Hurwitz criterion. Originality/value The formula proposed in this paper greatly simplifies the solution of critical mass, which facilitates the rotor stability design. It is applicable for opposed-conical bearings, opposed-hemispherical bearings and spherical bearings. The results provide theoretical guidance for the design of gas-dynamic bearings.

LANDSLIDE RISK MANAGEMENT IN THE COASTAL ZONE OF THE KUIBYSHEV RESERVOIR DUE THE DESIGN OF HIGH-SPEED LINE "MOSCOW-KAZAN"

2017 ◽  
Author(s):  
Nikolai Petrov ◽  
Nikolai Petrov ◽  
Inna Nikonorova ◽  
Inna Nikonorova ◽  
Vladimir Mashin ◽  
...  
Keyword(s):  
High Speed ◽  
Computational Models ◽  
Stable State ◽  
Landslide Risk ◽  
Kuibyshev Reservoir ◽  
Stepped Surface ◽  
The Stability ◽  
Landslide Slope ◽  
The Village

High-speed railway "Moscow-Kazan" by the draft crosses the Volga (Kuibyshev reservoir) in Chuvashia region 500 m below the village of New Kushnikovo. The crossing plot is a right-bank landslide slope with a stepped surface. Its height is 80 m; the slope steepness -15-16o. The authors should assess the risk of landslides and recommend anti-landslide measures to ensure the safety of the future bridge. For this landslide factors have been analyzed, slope stability assessment has been performed and recommendations have been suggested. The role of the following factors have been analyzed: 1) hydrologic - erosion and abrasion reservoir and runoff role; 2) lithologyc (the presence of Urzhum and Northern Dvina horizons of plastically deformable rocks, displacement areas); 3) hydrogeological (the role of perched, ground and interstratal water); 4) geomorphological (presence of the elemental composition of sliding systems and their structure in the relief); 5) exogeodynamic (cycles and stages of landslide systems development, mechanisms and relationship between landslide tiers of different generations and blocks contained in tiers). As a result 6-7 computational models at each of the three engineering-geological sections were made. The stability was evaluated by the method “of the leaning slope”. It is proved that the slope is in a very stable state and requires the following measures: 1) unloading (truncation) of active heads blocks of landslide tiers) and the edge of the plateau, 2) regulation of the surface and groundwater flow, 3) concrete dam, if necessary.

Hybrid Analysis of Gas Annular Seals With Energy Equation

2013 ◽  
Author(s):  
Patrick J. Migliorini ◽  
Alexandrina Untaroiu ◽  
William C. Witt ◽  
Neal R. Morgan ◽  
Houston G. Wood
Keyword(s):  
Experimental Data ◽  
Hybrid Method ◽  
Energy Equation ◽  
Flow Analysis ◽  
Experimental Studies ◽  
Rotor System ◽  
Bulk Flow ◽  
Outlet Temperature ◽  
Cfd Analysis ◽  
Annular Seals

Annular seals are used in turbomachinery to reduce secondary flow between regions of high and low pressure. In a vibrating rotor system, the non-axisymmetric pressure field developed in the small clearance between the rotor and the seal generate reactionary forces that can affect the stability of the entire rotor system. Traditionally, two analyses have been used to study the fluid flow in seals, bulk-flow analysis and computational fluid dynamics (CFD). Bulk-flow methods are computational inexpensive, but solve simplified equations that rely on empirically derived coefficients and are moderately accurate. CFD analyses generally provide more accurate results than bulk-flow codes, but solution time can vary between days and weeks. For gas damper seals, these analyses have been developed with the assumption that the flow can be treated as isothermal. Some experimental studies show that the difference between the inlet and outlet temperature temperatures is less than 5% but initial CFD studies show that there can be a significant temperature change which can have an effect on the density field. Thus, a comprehensive analysis requires the solution of an energy equation. Recently, a new hybrid method that employs a CFD analysis for the base state, unperturbed flow and a bulk-flow analysis for the first order, perturbed flow has been developed. This method has shown to compare well with full CFD analysis and experimental data while being computationally efficient. In this study, the previously developed hybrid method is extended to include the effects of non-isothermal flow. The hybrid method with energy equation is then compared with the isothermal hybrid method and experimental data for several test cases of hole-pattern seals and the importance of the use of energy equation is studied.

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