Feasibility study of a turbocharger rotor supported by air foil bearings with diameter of 17 mm focusing on rotordynamic performance

2018 ◽  
Vol 233 (5) ◽  
pp. 1331-1344
Author(s):  
Jiajia Yan ◽  
Zhansheng Liu ◽  
Guanghui Zhang ◽  
Xiangyu Yu ◽  
Liang Xu
Keyword(s):  
Feasibility Study ◽  
Journal Bearing ◽  
Negative Influence ◽  
Journal Bearings ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Damping Coefficients ◽  
Stable Operating ◽  
Lift Off ◽  
Stiffness And Damping

This paper presents the feasibility study of an oil-free turbocharger with journal bearing diameter of 17 mm. Rotordynamic performance of a turbocharger rotor, supported by two identical bump-type foil journal bearings and a pair of foil thrust bearings, is predicted and tested. High-pressure cold nitrogen is adopted to drive the turbocharger rotor. In rotordynamic analysis, the critical speeds and logarithmic decrement of the turbocharger rotor are predicted by employing the finite element method, in which the stiffness and damping coefficients of foil journal bearings and aerodynamic cross-coupled stiffness of the turbine are taken into account. Compared with experimental results, the accuracy of the prediction for rotordynamic analysis is verified for 7.82% marginal error of the critical speed. During the experiment, three foil journal bearings with different nominal clearances are manufactured and tested. The maximum stable operating speed reaches 105,000 r/min for this 17-mm-diameter oil-free turbocharger rotor system. Test results indicate the nominal clearance has a negative influence on threshold speed of sub-synchronous motions. When the nominal clearance is relatively small, the foil journal bearing could not lift off due to a large starting torque, while sub-synchronous motions would emerge under a large nominal clearance because of the reduced stiffness and damping coefficients of foil journal bearings.

Steady-State and Dynamic Behaviour of Multi-Recess Hybrid Oil Journal Bearings

1979 ◽  
Vol 21 (5) ◽  
pp. 345-351 ◽  
Author(s):  
M. K. Ghosh ◽  
B. C. Majumdar ◽  
J. S. Rao
Keyword(s):  
Perturbation Theory ◽  
Steady State ◽  
Theoretical Analysis ◽  
Dynamic Behaviour ◽  
Journal Bearing ◽  
Load Capacity ◽  
Journal Bearings ◽  
Time Dependent ◽  
Damping Coefficients ◽  
Stiffness And Damping

A theoretical analysis of the steady-state and dynamic characteristics of multi-recess hybrid oil journal bearings is presented. A perturbation theory for small vibrations is used to solve an incompressible, finite journal bearing with a time-dependent term. Load capacity, attitude angle, friction parameter, stiffness and damping coefficients are evaluated for a capillary-compensated bearing.

Dynamic Stiffness and Damping Coefficients of Aerostatic, Porous, Journal Bearings

1978 ◽  
Vol 20 (5) ◽  
pp. 291-296 ◽  
Author(s):  
N. S. Rao ◽  
B. C. Majumdar
Keyword(s):  
Continuity Equation ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Dynamic Pressure ◽  
Dynamic Stiffness ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Damping Coefficients ◽  
Design Charts ◽  
Stiffness And Damping

A periodic (displacement) disturbance is imposed on an aerostatic, porous, journal bearing of finite length under steady-state conditions. The dynamic pressure distribution is obtained by a pressure perturbation analysis of Reynolds equation and a modified flow continuity equation in a porous medium. Dynamic stiffness and damping coefficients for different operating conditions are calculated numerically, using a digital computer, and presented in the form of design charts.

Analysis of the Dynamic Characteristics of the Aerostatic Journal Bearings

2014 ◽  
Vol 607 ◽  
pp. 600-603
Author(s):  
Chun Dong Xu ◽  
Hui Hui Feng ◽  
Feng Feng Wang
Keyword(s):  
Finite Difference ◽  
Finite Difference Method ◽  
Dynamic Characteristics ◽  
Difference Method ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Damping Coefficients ◽  
Rotation Center ◽  
The Finite Difference Method ◽  
Stiffness And Damping

This paper investigates the dynamic characteristics of the aerostatic journal bearing, the rotation center of which is not the center of the journal length. The Finite Difference Method (FDM) and the perturbation method are employed to calculate the stiffness and damping coefficients. Results show that the coupled stiffness and damping coefficients cannot be neglected due to the rotation center being not the center of the journal length. Furthermore, with the increase of the distance between the rotation center and the center of the journal length, the coupled stiffness and damping coefficients increase.

Theoretical Condition for the Cxy=Cyx Relation in Fluid Film Journal Bearings

1989 ◽  
Vol 111 (3) ◽  
pp. 426-429 ◽  
Author(s):  
T. Kato ◽  
Y. Hori
Keyword(s):  
Reynolds Equation ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Fluid Film ◽  
Finite Width ◽  
Damping Coefficients ◽  
Dynamic Coefficients ◽  
Cross Terms ◽  
Linear Damping ◽  
Theoretical Condition

A computer program for calculating dynamic coefficients of journal bearings is necessary in designing fluid film journal bearings and an accuracy of the program is sometimes checked by the relation that the cross terms of linear damping coefficients of journal bearings are equal to each other, namely “Cxy = Cyx”. However, the condition for this relation has not been clear. This paper shows that the relation “Cxy = Cyx” holds in any type of finite width journal bearing when these are calculated under the following condition: (I) The governing Reynolds equation is linear in pressure or regarded as linear in numerical calculations; (II) Film thickness is given by h = c (1 + κcosθ); and (III) Boundary condition is homogeneous such as p=0 or dp/dn=0, where n denotes a normal to the boundary.

Tilting Pad Journal Bearings: A Discussion on Stability Calculation, Frequency Dependence, and Pad and Pivot Flexibility

2012 ◽  
Author(s):  
Jason C. Wilkes ◽  
Dara W. Childs
Keyword(s):  
Degrees Of Freedom ◽  
Journal Bearing ◽  
Operating Temperature ◽  
Excitation Frequency ◽  
Full Model ◽  
Stability Calculation ◽  
Damping Coefficients ◽  
Tilting Pad ◽  
Stiffness And Damping ◽  
Tilting Pad Journal Bearing

For several years, researchers have presented predictions showing that using a full tilting-pad journal bearing (TPJB) model (retaining all of the pad degrees of freedom) is necessary to accurately perform stability calculations for a shaft operating on TPJBs. This paper will discuss this issue, discuss the importance of pad and pivot flexibility in predicting impedance coefficients for the tilting-pad journal bearing, present measured changes in bearing clearance with operating temperature, and summarize the differences between measured and predicted frequency dependence of dynamic impedance coefficients. The current work presents recent test data for a 100 mm (4 in) five-pad TPJB tested in load on pad (LOP) configuration. Measured results include bearing clearance as a function of operating temperature, pad clearance and radial displacement of the loaded pad (the pad having the static load vector directed through its pivot), and frequency dependent stiffness and damping. Measured hot bearing clearances are approximately 30% smaller than measured cold bearing clearances and are inversely proportional to pad surface temperature; predicting bearing impedances with a rigid pad and pivot model using these reduced clearances results in overpredicted stiffness and damping coefficients that are several times larger than previous comparisons. The effect of employing a full bearing model versus a reduced bearing model (where only journal degrees of freedom are retained) in a stability calculation for a realistic rotor-bearing system is assessed. For the bearing tested, the bearing coefficients reduced at the frequency of the unstable eigenvalue (subsynchronously reduced) predicted a destabilizing cross-coupled stiffness coefficient at the onset of instability within 1% of the full model, while synchronously reduced coefficients for the lightly loaded bearing required 25% more destabilizing cross-coupled stiffness than the full model to cause system instability. The same stability calculation was performed using measured stiffness and damping coefficients at synchronous and subsynchronous frequencies. These predictions showed that both the synchronously measured stiffness and damping and predictions using the full bearing model were more conservative than the model using subsynchronously measured stiffness and damping, an outcome that is completely opposite from conclusions reached by comparing different prediction models. This contrasting outcome results from a predicted increase in damping with increasing excitation frequency at all speeds and loads; however, this increase in damping with increasing excitation frequency was only measured at the most heavily loaded conditions.

An experimental investigation of a microturbine simulated rotor supported on multileaf gas foil bearings with backing bump foils

2017 ◽  
Vol 232 (9) ◽  
pp. 1169-1180 ◽  
Author(s):  
Bo Zhang ◽  
Shemiao Qi ◽  
Sheng Feng ◽  
Haipeng Geng ◽  
Yanhua Sun ◽  
...  
Keyword(s):  
High Speed ◽  
Preliminary Test ◽  
Journal Bearings ◽  
Rotating Machinery ◽  
System Stability ◽  
Test Rig ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Simulated System ◽  
First Time

Two multileaf gas foil journal bearings with backing bump foils and one set of gas foil thrust bearings were designed, fabricated, and used in a 100 kW class microturbine simulated rotor system to ensure stability of the system. Meanwhile, a preliminary test rig had been built to verify the simulated system stability. The rotor synchronous and subsynchronous responses were well controlled by using of the gas foil bearings. It is on the multileaf gas foil bearings with backing bump foils that the test was conducted and verified for the first time in open literatures. The success in the experiments shows that the design and fabrication of the rotor and the gas foil bearings can provide a useful guide to the development of the advanced high speed rotating machinery.

Theoretical Prediction of the Lift-Off Speed in Aerodynamic Compliant Foil Journal Bearings

2010 ◽  
Author(s):  
Shemiao Qi ◽  
Y. S. Ho ◽  
Haipeng Geng ◽  
Lie Yu
Keyword(s):  
Theoretical Prediction ◽  
Generalized Solution ◽  
Journal Bearings ◽  
Numerical Results ◽  
Computational Method ◽  
Radial Clearance ◽  
Eccentricity Ratio ◽  
Foil Bearings ◽  
Lift Off ◽  
Air Film

In aerodynamic bearings, since the supporting air film is generated by rotor motion, there is no support at the start of motion. As in all such bearings, there is dry rubbing until the rotor achieves sufficient speed to lift-off. Thus, the lower the lift-off speed, the less will be the rubbing and so the greater will be the life of the bearing. This paper focuses on the theoretical prediction of lift-off speed in aerodynamic compliant foil journal bearings based on a generalized solution of elasto-aerodynamically coupled lubrication for compliant foil bearings. A computational method is presented which is used to predict the lift-off speed in aerodynamic foil journal bearings with eccentricity ratio greater than or equal to 1.0. Special emphasis is placed on investigating the effects of the load imposed on the bearing, the nominal radial clearance and the bearing radius on the lift-off speed. The numerical results obtained indicate that lift-off speed decreases with the decrease of load and nominal radial clearance, but with an increase in bearing radius. The eccentricity ratios are all greater than 1.0 at the lift-off speed for the aerodynamic compliant foil journal bearings used in this study.

An Analytical Complete Model of Tilting-Pad Journal Bearing Considering Pivot Stiffness and Damping

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Zhiyong Yan ◽  
Yi Lu ◽  
Tiesheng Zheng
Keyword(s):  
Degrees Of Freedom ◽  
Journal Bearing ◽  
Local Coordinate System ◽  
Dynamical Behavior ◽  
Complete Model ◽  
Damping Coefficients ◽  
Tilting Pad ◽  
Generalized Force ◽  
Stiffness And Damping ◽  
Tilting Pad Journal Bearing

Considering the freedom of pad tilting and pad translation along preload orientation, an analytical complete model, as well as mathematical method, which contains 2n+2 degrees of freedom, is presented for calculating the dynamical characteristics of tilting-pad journal bearing. Based on the motion relationship of shaft and pad, the local coordinate system, the generalized displacement, and the generalized force vector are chosen. The concise transformation of generalized displacement, generalized force, and its Jacobian matrix between the local and global coordinate systems are built up in matrix form. A fast algorithm using the Newton–Raphson method for calculating the equilibrium position of journal and pads is proposed. The eight reduced stiffness and damping coefficients can be obtained assuming that the journal and all pads are subject to harmonic vibration. Numerical results show that the reduced damping coefficients and the threshold speed can be effectively enhanced by giving suitable pad pivot stiffness and damping simultaneously, and this analytical method can be applied to analyze dynamical behavior of the tilting-pad journal bearing rotor system.

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