A Finite Element Approach to Pad Flexibility Effects in Tilt Pad Journal Bearings: Part II—Assembled Bearing and System Analysis

1990 ◽  
Vol 112 (2) ◽  
pp. 178-182 ◽  
Author(s):  
L. L. Earles ◽  
A. B. Palazzolo ◽  
R. W. Armentrout
Keyword(s):  
Finite Element ◽  
System Analysis ◽  
Journal Bearings ◽  
Complex Eigenvalue ◽  
Finite Element Approach ◽  
Rotor Bearing ◽  
Element Approach ◽  
Bearing System

Pad flexibility effects are studied in an actual bearing. This flexibility is shown to decrease the predicted instability onset speed of the rotor bearing system. The use of complex eigenvalue dependent bearing coefficients as compared with using synchronously reduced coefficients is seen to produce a more significant decrease in the instability onset speed. Further reductions in the instability onset speed are obtained by including pivot stiffness in the complex eigenvalue dependent bearing coefficients.

Modeling and Simulation of Transverse Cracks for Rotor-Bearing Systems

1996 ◽  
Author(s):  
Tachung Yang ◽  
Shi-An Chen
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Strain Energy ◽  
Catastrophic Failure ◽  
Transverse Cracks ◽  
Finite Element Approach ◽  
Rotor Bearing ◽  
Element Approach ◽  
Rotating Shafts ◽  
Bearing System

Undetected cracking of rotating shafts can lead to catastrophic failure of turbomachinery. This paper investigated the dynamic response of rotor-bearing systems containing transverse cracks with a finite element approach. The breathing effect of cracks was analyzed based on the whirling conditions of the rotor, and different crack models were posed for different rotating speeds. The strain energy released due to the cracks was calculated. Then, the finite element for the shaft portion containing cracks was formulated and incorporated into the system matrices of the rotor-bearing system.

A Finite Element Approach to the Transient Dynamics of Rolling Tires with Emphasis on Rolling Noise Simulation4

2007 ◽  
Vol 35 (3) ◽  
pp. 165-182 ◽  
Author(s):  
Maik Brinkmeier ◽  
Udo Nackenhorst ◽  
Heiner Volk
Keyword(s):  
Finite Element ◽  
Traffic Noise ◽  
Complex Eigenvalue ◽  
Arbitrary Lagrangian Eulerian ◽  
Finite Element Approach ◽  
Road Systems ◽  
Element Approach ◽  
Road Surface Roughness ◽  
Complex Eigenvalue Analysis ◽  
Rolling Noise

Abstract The sound radiating from rolling tires is the most important source of traffic noise in urban regions. In this contribution a detailed finite element approach for the dynamics of tire/road systems is presented with emphasis on rolling noise prediction. The analysis is split into sequential steps, namely, the nonlinear analysis of the stationary rolling problem within an arbitrary Lagrangian Eulerian framework, and a subsequent analysis of the transient dynamic response due to the excitation caused by road surface roughness. Here, a modal superposition approach is employed using complex eigenvalue analysis. Finally, the sound radiation analysis of the rolling tire/road system is performed.

Turbomachinery Dual Rotor-Bearing System Analysis

2002 ◽  
Author(s):  
Hsiao-Wei D. Chiang ◽  
Chih-Neng Hsu ◽  
Wes Jeng ◽  
Shun-Hsu Tu ◽  
Wei-Chen Li
Keyword(s):  
Finite Element ◽  
Transfer Matrix ◽  
Critical Speed ◽  
System Analysis ◽  
Design Parameters ◽  
Critical Speeds ◽  
Rotor Design ◽  
Rotor Bearing ◽  
Bearing Stiffness ◽  
Bearing System

It is very common for aircraft engines to have dual rotor or even triple rotor designs. Due to the complexity of having multiple rotor design, the transfer matrix methods have used in the past to deal with multiple rotor-bearing systems. However, due to transfer matrix method’s assumptions, sometimes resulted in numerical stability problems or root-missing problems. The purpose of this paper is to develop a systematic theoretical analysis of the dynamic characteristics of turbomachinery dual rotor-bearing systems. This dual rotor-bearing system analysis will start with a finite element (FEM) rotor-bearing system dynamic model, then using different methods to verify the analysis results including critical speed map and bearing stiffness. In an inertia coordinate system, a general model of continuous dual rotor-bearing systems is established based on a lagrangian formulation. Gyroscopic moment, rotary inertia, bending and shear deformations have been included in the model. From a point of view of the systematic approach, a solution of the finite element method is used to calculate the critical speeds by several different methods, which in turn can help to verify this dual rotor-bearing system approach. The effects of the speed ratio of dual rotors on the critical speed will be studied, which in turn can be used as one of the dual rotor design parameters. Also, both critical speeds are in effect functions of dual rotor speeds. Finally, the bearing stiffness between high speed and low speed shafts not only affect the critical speeds of the dual rotor system, but also affect the mode shapes of the system. Therefore, the bearing stiffness in between is of even greater importance in turbomachinery dual rotor or multiple rotor design.

A Microturbine Rotor-Bearing System Analysis

2002 ◽  
Author(s):  
Hsiao-Wei D. Chiang ◽  
Chih-Neng Hsu ◽  
Wes Jeng ◽  
Shun-Hsu Tu ◽  
Wei-Chen Li
Keyword(s):  
Finite Element ◽  
Critical Speed ◽  
System Analysis ◽  
Modal Testing ◽  
System Dynamic Model ◽  
Fem Model ◽  
Rotor Bearing ◽  
Bearing Stiffness ◽  
Bearing System ◽  
Engine Life

A microturbine of 12-pound thrust was developed for the Unmanned Aerial Vehicle (UAV) applications. Recent tests of the microturbines reveal problems associated with rear ball bearing integrity after extended run times. The microturbine rotor design originally calls for a critical speed margin of at least 15∼20% to prevent excessive vibrations. However, the microturbine was using an existing turbocharger rotor component with unknown margins. Therefore, the purpose of this paper is to perform both theoretical and experimental analyses of the dynamic characteristics of the 12-pound thrust microturbine rotor-bearing system. This rotor-bearing system analyses will start with a finite element (FEM) rotor-bearing system dynamic model, then using modal testing and dynamic engine test to verify the analysis results including critical speed map and bearing stiffness. In this paper, the rotor-bearing system dynamic model will be established under an inertia coordinate system. Through finite element method, this model can be used to predict natural frequencies, critical speed map, and bearing stiffness. Also, under free-free condition, a modal testing will be performed, and its results are used to compare with the FEM model. Then the gyroscopic moment effects are included in the FEM model to calculate the critical speed map. Finally the critical speed map is used to compare with the results of the dynamic experiments of the 12-pound thrust microturbine engine and the bearing stiffness is estimated through an optimization approach. Examination of the microturbine engine and recent product developments indicate that thrust performance and engine life goals can be improved to upgrade the present design. With the rotor-bearing system analysis, the goal of increasing the current engine life and improved performance is sought as a practical goal for the microturbine design.

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