Calculations and Experiments on the Unbalance Response of a Flexible Rotor

1967 ◽  
Vol 89 (4) ◽  
pp. 785-796 ◽  
Author(s):  
J. W. Lund ◽  
F. K. Orcutt
Keyword(s):  
Critical Speed ◽  
Distributed Parameter ◽  
Distributed Parameter System ◽  
Flexible Rotor ◽  
Parameter System ◽  
Damping Coefficients ◽  
The Third ◽  
Tilting Pad ◽  
Speed Range ◽  
Bearing System

The results of a combined analytical and experimental investigation of the unbalance vibrations of a rotor are presented. The analysis applies to a general rotor-bearing system in which the dynamic bearing forces are represented by four spring coefficients and four damping coefficients. The rotor can be represented as either a lumped or a distributed parameter system, and gyroscopic moments are included. In general, the unbalance whirl motion of the rotor will be elliptical. The analysis has been programmed for a digital computer to obtain results for comparison with the experimental data. The test rotor is a uniform, flexible shaft with heavy wheels mounted at the ends and in the middle. The rotor is supported in two silicone fluid-lubricated, tilting-pad bearings. The rotor amplitude caused by an induced unbalance has been measured over a speed range of 3000 to 24,000 rpm for three different rotor configurations, obtained by removing one or both end wheels. This speed range extends to or through the third critical speed for each of the rotor configurations. The results are compared with the theoretical values and, in general, the agreement is found to be good.

Identification method of dynamic characteristics coefficients of tilting pad bearing in critical speed range of large unit

2020 ◽  
pp. 135065012092950
Author(s):  
Runlin Chen ◽  
Xingzhao Wang ◽  
Chen Du ◽  
Kai Liu ◽  
Xiaoyang Yuan
Keyword(s):  
Iterative Method ◽  
Critical Speed ◽  
Direct Method ◽  
Stiffness Coefficient ◽  
Large Unit ◽  
First Order ◽  
Damping Coefficients ◽  
Tilting Pad ◽  
Speed Range ◽  
Stiffness And Damping

For tilting pad bearing of large unit, it is not easy to identify stiffness and damping coefficients in full-size unit test. Because of many limiting factors in large unit test, the stiffness and damping test methods are not fully applicable to large units, which can be easily implemented in laboratory. The nonexcitation methods are proposed in this paper to identify the stiffness and damping coefficients of tilting pad bearing in the critical speed range of large unit, including direct method and iterative method. Firstly, the rotor speed and vibration during the whole period are obtained. The vibration data of the first-order critical speed range in the startup stage are selected, and the stiffness and damping coefficients of tilting pad bearing are identified through the two methods. The results show that the stiffness and damping coefficients identified through the direct method are generally less than the theoretical values. The identification error of stiffness coefficient is within ±9%, and the identification accuracy of stiffness coefficient is significantly higher than that of damping coefficient. The damping coefficient identified by the iterative method agrees well with the theoretical value, and the identification error is about −3%. In conclusion, the stiffness and damping coefficients of tilting pad bearing in the range of first-order critical speed can be obtained by combining the two identification methods. These identification results are relatively reliable and can basically meet the analysis requirements of important vibration problems of bearing-rotor system.

Application of the Mode-Acceleration Technique to the Solution of the Moving Oscillator Problem

1999 ◽  
Author(s):  
Alexander V. Pesterev ◽  
Lawrence A. Bergman
Keyword(s):  
Shear Force ◽  
Series Representation ◽  
Bending Moment ◽  
Static Solution ◽  
Distributed Parameter ◽  
Distributed Parameter System ◽  
Parameter System ◽  
One Dimensional ◽  
Acceleration Technique ◽  
Moving Oscillator

Abstract The problem of calculating the dynamic response of a one-dimensional distributed parameter system excited by an oscillator traversing the system with an arbitrarily varying speed is investigated. An improved series representation for the solution is derived that takes into account the jump in the shear force at the point of the attachment of the oscillator, which makes it possible to efficiently calculate the distributed shear force and, where applicable, bending moment. The improvement is achieved through the introduction of the “quasi-static” solution, an approximation to the desired one, which makes it possible to apply to the moving oscillator problem the “mode-acceleration” technique conventionally used for acceleration of series in problems related to the steady-state vibration of distributed systems. Numerical results illustrating the efficiency of the method are presented.

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