scholarly journals Effect of random roundness error on the stability of a hydrodynamic journal bearing system part I: Theoretical study

2019 ◽  
Vol 11 (4) ◽  
pp. 168781401984625 ◽  
Author(s):  
Bing Li ◽  
Dejian Zhou ◽  
Wubin Xu ◽  
Yilei Zhang
Keyword(s):  
Theoretical Study ◽  
Journal Bearing ◽  
Roundness Error ◽  
System Part ◽  
Hydrodynamic Journal Bearing ◽  
The Stability ◽  
Bearing System

Effect of journal cylindricity error with saddle or drum distribution on the performance of hydrodynamic journal bearing systems

2019 ◽  
Vol 234 (7) ◽  
pp. 1092-1105
Author(s):  
Bing Li ◽  
Dejian Zhou ◽  
Peter Ogrodnik ◽  
Wubin Xu
Keyword(s):  
Journal Bearing ◽  
System Stability ◽  
Analysis Method ◽  
Shape Distribution ◽  
Hydrodynamic Journal Bearing ◽  
The Stability ◽  
Cylindricity Error ◽  
Saddle Shape ◽  
Fourier Model ◽  
Bearing System

The present study investigates the effect of cylindricity error on the performance of hydrodynamic journal bearing systems. Two types of cylindricity errors of the journal, namely the drum shape distribution cylindricity error (DCE) and the saddle shape distribution cylindricity error (SCE), are considered. The Legendre–Fourier model is used to characterize the profile of each journal. Based on the nonlinear analysis method, the dynamic characteristics and stability of hydrodynamic journal bearing systems are analyzed. The results indicate that cylindricity error affects the system stability, and the effect is related to the type and level of the error. DCE used with a certain range of operating speed and load is not harmful and is even beneficial to the stability of hydrodynamic journal bearing systems; conversely, SCE decreases the system stability. When the Sommerfeld number is between 0.02 and 0.05, cylindricity errors have a minimal effect on the system stability. Additionally, the results indicate that the effect of cylindricity error on the bearing system is more significant than that of roundness error.

The effect of active control on stability characteristics of hydrodynamic journal bearings with an axial groove

2002 ◽  
Vol 216 (9) ◽  
pp. 939-946 ◽  
Author(s):  
B-H Rho ◽  
K-W Kim
Keyword(s):  
Active Control ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Linear Dynamic ◽  
Conventional Analysis ◽  
Theoretical Investigations ◽  
Rotor Bearing ◽  
Hydrodynamic Journal Bearing ◽  
The Stability ◽  
Bearing System

Results of theoretical investigations on stability characteristics of an actively controlled hydrodynamic journal bearing are presented. Proportional, derivative and integral controls are adopted for a hydrodynamic journal bearing with an axial groove. Furthermore, a cavitation algorithm, implementing the Jakobsson-Floberg-Olsson boundary condition, is adopted to predict cavitation regions in a fluid film more accurately than the conventional analysis, which uses the Reynolds condition. Using the bearing's linear dynamic coefficients, which are evaluated from the perturbation method, the stability characteristics of a rotor-bearing system are investigated using the Routh-Hurwitz criteria. It is shown that the instability threshold speed of a rotor-bearing system can be greatly increased and the unbalanced responses of the system can be markedly decreased by both proportional and derivative control of the bearing. Results show that active control of a hydrodynamic journal bearing can be adopted for stability improvement and reduction of the unbalanced whirl amplitude of a rotor-bearing system.

Non-linear stability analysis of micropolar fluid lubricated journal bearings with turbulent effect

2019 ◽  
Vol 71 (1) ◽  
pp. 31-39
Author(s):  
Subrata Das ◽  
Sisir Kumar Guha
Keyword(s):  
Stability Analysis ◽  
Linear Stability ◽  
Micropolar Fluid ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Turbulent Regime ◽  
Content Type ◽  
Non Linear ◽  
The Stability ◽  
Bearing System

Purpose The purpose of this paper is to investigate the effect of turbulence on the stability characteristics of finite hydrodynamic journal bearing lubricated with micropolar fluid. Design/methodology/approach The non-dimensional transient Reynolds equation has been solved to obtain the non-dimensional pressure field which in turn used to obtain the load carrying capacity of the bearing. The second-order equations of motion applicable for journal bearing system have been solved using fourth-order Runge–Kutta method to obtain the stability characteristics. Findings It has been observed that turbulence has adverse effect on stability and the whirl ratio at laminar flow condition has the lowest value. Practical implications The paper provides the stability characteristics of the finite journal bearing lubricated with micropolar fluid operating in turbulent regime which is very common in practical applications. Originality/value Non-linear stability analysis of micropolar fluid lubricated journal bearing operating in turbulent regime has not been reported in literatures so far. This paper is an effort to address the problem of non-linear stability of journal bearings under micropolar lubrication with turbulent effect. The results obtained provide useful information for designing the journal bearing system for high speed applications.

Stability Analysis of a Hydrodynamic Journal Bearing With Rotating Herringbone Grooves

2003 ◽  
Vol 125 (2) ◽  
pp. 291-300 ◽  
Author(s):  
G. H. Jang ◽  
J. W. Yoon
Keyword(s):  
Journal Bearing ◽  
Equations Of Motion ◽  
Fourier Series Expansion ◽  
Algebraic Equations ◽  
High Rotational Speed ◽  
Dynamic Coefficients ◽  
Stiffness Coefficients ◽  
Hydrodynamic Journal Bearing ◽  
The Stability ◽  
Herringbone Grooves

This paper presents an analytical method to investigate the stability of a hydrodynamic journal bearing with rotating herringbone grooves. The dynamic coefficients of the hydrodynamic journal bearing are calculated using the FEM and the perturbation method. The linear equations of motion can be represented as a parametrically excited system because the dynamic coefficients have time-varying components due to the rotating grooves, even in the steady state. Their solution can be assumed as a Fourier series expansion so that the equations of motion can be rewritten as simultaneous algebraic equations with respect to the Fourier coefficients. Then, stability can be determined by solving Hill’s infinite determinant of these algebraic equations. The validity of this research is proved by the comparison of the stability chart with the time response of the whirl radius obtained from the equations of motion. This research shows that the instability of the hydrodynamic journal bearing with rotating herringbone grooves increases with increasing eccentricity and with decreasing groove number, which play the major roles in increasing the average and variation of stiffness coefficients, respectively. It also shows that a high rotational speed is another source of instability by increasing the stiffness coefficients without changing the damping coefficients.

Linear stability analysis of finite hydrodynamic journal bearing under turbulent lubrication with coupled-stress fluid

2016 ◽  
Vol 68 (3) ◽  
pp. 386-391 ◽  
Author(s):  
Abhishek Ghosh ◽  
Sisir Kumar Guha
Keyword(s):  
Stability Analysis ◽  
Newtonian Fluid ◽  
High Speed ◽  
Journal Bearing ◽  
Slenderness Ratio ◽  
Linear Perturbation ◽  
Content Type ◽  
Hydrodynamic Journal Bearing ◽  
The Stability ◽  
Coupled Stress

Purpose Several researchers have observed that to satisfy modern day’s need, it is essential to enhance the characteristics of journal bearing, which is used in numerous applications. Moreover, the use of Newtonian fluid as a lubricant is diminishing day by day, and the use of Non-Newtonian fluids is coming more into picture. Furthermore, if turbo-machinery applications are taken into account, then it can be seen that journal bearings are used for high speed applications as well. Thus, neglecting turbulent conditions may lead to erroneous results. Hence, this paper aims to present focuses on studying the stability characteristics of finite hydrodynamic journal bearing under turbulent coupled-stress lubrication. Design/methodology/approach First, the governing equation relevant to the problem is generated. Then, the dynamic analysis is carried out by linear perturbation technique, leading to three perturbed equations, which are again discretized by finite difference method. Finally, these discretized equations are solved with the help of Gauss-Seidel Iteration technique with successive over relaxation scheme. Consequently, the film response coefficients and the stability parameters are evaluated at different parametric conditions. Findings It has been concluded from the study that with increase in value of the coupled-stress parameter, the stability of the journal may increase. Whereas, with increase in Reynolds number, the stability of the journal decreases. On the other hand, stability increases with increasing values of slenderness ratio. Originality/value Researches have been performed to study the dynamic characteristics of journal bearing with non-Newtonian fluid as the lubricant. But in the class of non-Newtonian lubricants, the use of coupled-stress fluid has not yet been properly investigated. So, an attempt has been made to perform the stability analysis of bearings with coupled-stress fluid as the advanced lubricant.

Morton Effect Induced Synchronous Instability in Mid-Span Rotor–Bearing Systems, Part 2: Models and Simulations

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Zenglin Guo ◽  
Gordon Kirk
Keyword(s):  
Journal Bearing ◽  
Negative Impact ◽  
System Stability ◽  
Stability Performance ◽  
Fluid Film Bearings ◽  
Morton Effect ◽  
Thermal Bending ◽  
Hydrodynamic Journal Bearing ◽  
The Stability ◽  
Thermal Imbalance

The mechanism of the Morton Effect induced synchronous instability has been discussed in Part 1, using an assumption of isotropic linear bearings. The second part of the current study will now focus on the more realistic systems, mid-span rotors supported by the hydrodynamic journal bearings. First, the models to calculate the thermal bending of the shaft and the temperature distribution across the journal surface are established. This can be used to calculate the equivalent thermal imbalance. The calculations of the temperature difference and its equivalent thermal imbalance using hydrodynamic plain journal bearing models are conducted and discussed with the comparison to the analytical results obtained in Part 1. It shows that the thermal imbalance induced by the Morton Effect may increase to the level of the mechanical imbalance and then its influence on the system stability should be included. The suggested thermal bending model also partially explains that the mid-span rotors are less liable to be influenced by the Morton Effect induced instability than are the overhung configurations, because of the restraining effect between two supports. Finally, a symmetric mid-span rotor - hydrodynamic journal bearing system is calculated to show its stability performance. The results show the inclusion of the Morton Effect may lead to an unstable operation of the system. Considering the existence of the oil film self-induced vibration due to the dynamic characteristics of fluid film bearings, the Morton Effect may make a further negative impact on the stability of the system. The simulation results of the unbalance response show that the Morton Effect changes the shapes of the whirling orbits and makes them no longer the standard elliptical orbits around the static equilibriums.

Comparison of Effects of Dimensional Manufacturing Tolerances and Journal Out-of-Roundness on Stability of Hydrodynamic Journal Bearing System

2011 ◽  
Vol 121-126 ◽  
pp. 1966-1971
Author(s):  
Wu Bin Xu ◽  
De Jian Zhou ◽  
Peter Ogrodnik ◽  
Mike Goodwin
Keyword(s):  
Theoretical Analysis ◽  
Taguchi Method ◽  
Journal Bearing ◽  
Journal Bearings ◽  
System Stability ◽  
Design Stage ◽  
Analysis Method ◽  
Manufacturing Tolerances ◽  
Hydrodynamic Journal Bearing ◽  
Bearing System

The manufacturing tolerances of a hydrodynamic journal bearing system are inevitable in manufacturing process. To examine and understand the effect of manufacturing tolerances on the system stability can help engineers to confidently choose reasonable tolerances at design stage. This study presented a theoretical analysis method to determine and compare the effects of dimensional manufacturing tolerances and journal out-of-roundness on system stability by Taguchi method. The results show that the journal out-of-roundness has the most significant effect on the system stability and the journal out-of-roundness appears to stabilize the system. The authors suggest that both dimensional manufacturing tolerances and journal roundness should be taken into account in the design of cylindrical journal bearings.

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