Two-way coupled shooting analysis of fluid force in the annular plain seal and vibration of the rotor system

2020 ◽  
pp. 1-20
Author(s):  
Yudai Kunori ◽  
Tsuyoshi Inoue ◽  
Kenjiro Miyake
Keyword(s):  
Transition Region ◽  
Spectral Radius ◽  
Mutual Influence ◽  
Dynamical Behavior ◽  
Great Influence ◽  
Coupled System ◽  
Rotor System ◽  
Experimental Results ◽  
Coupled Analysis ◽  
Fluid Force

Abstract In turbomachinery, the rotor dynamic (RD) fluid force generated in a fluid element, by the interaction between the shaft behavior and the fluid flow, is one of the causes of the shaft behavior and has a great influence on the stability of the turbomachinery. In order to improve the reliability of turbomachinery, it is important to analyze the dynamical behavior considering the mutual influence of the RD fluid force and shaft motion. In this paper, the two-way coupled analysis between the fluid force in the annular plain seal and the vibration of the rotor system was expanded by introducing the shooting method in it. The frequency response was obtained, and onset speed of instability (OSI) was predicted effectively. The influence of parameters on the OSI was investigated and discussed. Then, the numerical results obtained by this two-way coupled shooting analysis was compared with the experimental results and the validity of the analysis was confirmed. The influence of disturbance on the error of predicted OSI was also discussed. The transition region to instability was introduced for the predicted OSI using the spectral radius, and the error between the numerical and experimental results of the OSI was explained. As a result, the two-way coupled shooting analysis can predict the OSI values in various situation of two-way coupled system more effectively than the direct numerical simulation. Also, the robustness of stability for the predicted OSI can be evaluated simultaneously by investigating the spectral radius and defining the transition region to instability appropriately.

Two Way Coupled Analysis of Fluid Force in the Annular Plain Seal and Vibration of the Rotor System Using Shooting Method

2019 ◽  
Author(s):  
Yudai Kunori ◽  
Tsuyoshi Inoue ◽  
Kenjiro Miyake
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Shooting Method ◽  
Coupled System ◽  
Coupled Analysis ◽  
Fluid Element ◽  
Fluid Force ◽  
Precise Prediction ◽  
Shaft Vibration ◽  
Rotor Dynamic

Abstract In turbomachinery, the rotor dynamic (RD) fluid force generated in a fluid element is one of the causes of shaft vibration. RD fluid force is caused by the interaction between shaft vibration and fluid force, and its precise prediction for various rotor’s orbit is difficult. This study performs a two-way coupled analysis of the fluid flow in the annular plain seal and shaft vibration using the shooting method. The frequency response is obtained and compared with that obtained from a direct numerical simulation of the coupled system, and the validity of the analysis is confirmed. The onset speed of instability is effectively and accurately obtained using the two-way coupled analysis with the shooting method, and the effects of the parameters on it are investigated.

Coupled Analysis of the Rotor-Dynamic Fluid Forces in the Annular Plain Seal and the Shaft Vibration

2018 ◽  
Author(s):  
K. Miyake ◽  
A. Ikemoto ◽  
M. Uchiumi ◽  
T. Inoue
Keyword(s):  
Poisson Equation ◽  
Constant Load ◽  
Rotor System ◽  
Bulk Flow ◽  
Coupled Analysis ◽  
Fluid Force ◽  
The Poisson Equation ◽  
Shaft Vibration ◽  
The Stability ◽  
Rotor Dynamic

In recent years, along with demands for higher rotational speed and higher efficiency in the rotating machinery, shaft vibration has been a serious problem. One of the causes of this shaft vibration problem is the rotor-dynamic fluid force (RD fluid force) generated by working fluid at turbo machinery parts. It is important in the design stage of rotating machines to estimate the RD fluid force and predict the stability of the rotor system accurately. Therefore, many researches have been conducted to clarify the characteristics of RD fluid force. One of the traditional methods for analyzing the RD fluid force is the bulk flow theory. However, in conventional bulk flow analysis, it is assumed that the amplitude of the shaft displacement is sufficiently smaller than the clearance. Therefore, influence of nonlinearity in the large amplitude whirl may not be included in this analysis. Accordingly, this paper focuses on constructing a coupled analysis of the fluid force and the shaft vibration that describes each behavior of fluid and shaft at the same time. By using this coupled analysis, the interaction between fluid and shaft systems can be taken into consideration more accurately. Regarding the fluid region, finite difference method is used for bulk flow continuity and momentum transport equations. Incompressible fluid is assumed, and the pressure field is calculated by solving the Poisson equation of pressure. In solving the Poisson equation of pressure, a specific problem for this coupled analysis relating unknown shaft acceleration arises. In this paper, this problem is solved by obtaining the approximated acceleration based on Newmark-beta technique. This coupled analysis is conducted for a simple flexible rotor system with annular plain seal, and the frequency response is obtained. First, the case with isotropic support stiffness and with no gravitational force is considered. Then, the case with the constant load and the case with anisotropic support stiffness are analyzed. These analytical results show that both the constant load and structural anisotropy may affect the stability of the rotor system. As a result, the usefulness of the proposed coupled analysis procedure of the fluid force and the shaft vibration is validated.

Unbalance Response of a Dual Rotor System: Theory and Experiment

1993 ◽  
Vol 115 (4) ◽  
pp. 427-435 ◽  
Author(s):  
K. Gupta ◽  
K. D. Gupta ◽  
K. Athre
Keyword(s):  
System Theory ◽  
Transfer Matrix ◽  
Mode Shape ◽  
Reasonable Agreement ◽  
Complex Variables ◽  
Rotor System ◽  
Experimental Results ◽  
Unbalance Response ◽  
Theoretical Results ◽  
Theory And Experiment

A dual rotor rig is developed and is briefly discussed. The rig is capable of simulating dynamically the two spool aeroengine, though it does not physically resemble the actual aeroengine configuration. Critical speeds, mode shape, and unbalance response are determined experimentally. An extended transfer matrix procedure in complex variables is developed for obtaining unbalance response of dual rotor system. Experimental results obtained are compared with theoretical results and are found to be in reasonable agreement.

Fluid-Coupled Vibrations of Immersed Spent Nuclear Racks: A Nonlinear Model Accounting for Squeeze-Film and Dissipative Phenomena

2004 ◽  
Author(s):  
Miguel Moreira ◽  
Jose´ Antunes
Keyword(s):  
Dynamical Behavior ◽  
Coupled System ◽  
Differential Algebraic Equations ◽  
Nonlinear Flow ◽  
Squeeze Film ◽  
Algebraic Equations ◽  
Spent Fuel ◽  
Coupled Modes ◽  
Small Water ◽  
Flow Effects

Fluid-coupling effects lead to a complex dynamical behavior of immersed spent fuel assembly storage racks. Predicting their responses under strong earthquakes is of prime importance for the safety of nuclear plant facilities. In the near-past we introduced a simplified linearized model for the vibrations of such systems, in which gap-averaged velocity and pressure fields were described analytically in terms of a single space-coordinate for each fluid inter-rack channel. Using such approach it was possible to generate and assemble a complete set of differential-algebraic equations describing the multi-rack fluid coupled system dynamics. Because of the linearization assumptions, we achieved computation of the flow-structure coupled modes, but also time-domain simulations of the system responses. However, nonlinear squeeze-film and dissipative flow effects, connected with very large amplitude responses and/or relatively small water gaps, cannot be properly accounted unless the linearization assumption is relaxed. Such is the aim of the present paper. Here, using a similar approach, we generalize our theoretical model to deal with nonlinear flow effects. Besides that the proposed methodology can be automatically implemented in a symbolic computational environment, it is much less computer-intensive than finite element formulations. Using the proposed technique, computations of basic flow-coupled rack configurations subjected to impulse excitations are presented, in order to highlight the essential features of such systems as well as the relevance of squeeze-film and dissipative effects. Finally, more realistic simulations of complex system responses to strong seismic excitations are presented and discussed.

A Simplified Method for Determining Acoustic and Tube Eigenfrequencies in Heat Exchangers

1982 ◽  
Vol 104 (3) ◽  
pp. 175-179 ◽  
Author(s):  
J. Planchard ◽  
F. N. Remy ◽  
P. Sonneville
Keyword(s):  
Eigenvalue Problem ◽  
Sound Velocity ◽  
Heat Exchangers ◽  
Fluid Structure Interaction ◽  
Coupled System ◽  
Experimental Results ◽  
Structure Interaction ◽  
Experimental Apparatus ◽  
Tube Arrays ◽  
Simplified Method

A method of computation of eigenfrequencies of large tube arrays is presented, which is based on homogenization techniques. It is supposed that the fluid is compressible, at rest and contained in a cavity; the bundle geometry is assumed to be repetitive; an equivalent sound velocity through the tubes can then be calculated, and the fluid-structure interaction is taken into account. A new eigenvalue problem is so obtained, defined over a simpler domain, i.e., the region occupied by both fluid and tubes; it is then easy to solve it for computing the eigenfrequencies of the coupled system. Numerical and experimental results are presented and some details of the experimental apparatus are given.

scholarly journals Study on the Dynamic Problems of Double-Disk Rotor System Supported by Deep Groove Ball Bearing

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Yang Liu ◽  
Jiyuan Han ◽  
Siyao Zhao ◽  
Qingyu Meng ◽  
Tuo Shi ◽  
...  
Keyword(s):  
Ball Bearing ◽  
Structural Characteristics ◽  
Great Influence ◽  
Vibration Characteristics ◽  
Rotor System ◽  
Ball Bearings ◽  
Bearing Clearance ◽  
Deep Groove ◽  
Deep Groove Ball Bearing ◽  
System Nodes

Aiming at the analysis of the dynamic characteristics of the rotor system supported by deep groove ball bearings, the dynamic model of the double-disk rotor system supported by deep groove ball bearings was established. In this paper, the nonlinear finite element method is used combined with the structural characteristics of deep groove ball bearings. Based on the nonlinear Hertz contact theory, the mechanical model of deep groove ball bearings is obtained. The excitation response results of the rotor system nodes are solved by using the Newmark-β numerical solution method combined with the Newton–Raphson iterative method. The vibration characteristics of the rotor system supported by deep groove ball bearings are studied deeply. In addition, the effect of varying compliance vibration (VC vibration) caused by the change in bearing support stiffness on the dynamics of the system is considered. The time domain and frequency domain characteristics of the rotor system at different speeds, as well as the influence of bearing clearance and bearing inner ring’s acceleration on the dynamics of the rotor system are analyzed. The research shows that the VC vibration of the bearing has a great influence on the motion of the rotor system when the rotational speed is low. Moreover, reasonable control of bearing clearance can reduce the mutual impact between the bearing rolling element and the inner or outer rings of the bearing and reduce the influence of unstable bearing motion on the vibration characteristics of the rotor system. The results can provide theoretical basis for the subsequent study of the nonlinear vibration characteristics of the deep groove ball bearing rotor system.

Numerical and Experimental Tools for Offshore DP Operations

2011 ◽  
Author(s):  
Fabiano P. Rampazzo ◽  
Joa˜o Luis B. Silva ◽  
Daniel P. Vieira ◽  
Antonio L. Pacifico ◽  
Lazaro Moratelli Junior ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Experimental Tests ◽  
Coupled System ◽  
Coupled Analysis ◽  
Cfd Analysis ◽  
Maximum Condition ◽  
Commercial Code ◽  
Close Proximity ◽  
Fully Coupled ◽  
Two Bodies

DP crane vessel operation can be analyzed based on the uncoupled system or considering the fully coupled system. Parameters such as top-crane acceleration, thruster capability and vessel motions are evaluated for several environmental conditions. Numerical and experimental tools are used and the important result of this analysis is the maximum condition in such that the operation can be safely executed. Those operations are critical, since the vessel is kept in close proximity with other unit and large loads are transported in a pendulum configuration. A precise positioning of the crane-vessel is required, in order to avoid unsafe relative motions, as well as keep the load being transported on a stable position. The uncoupled analysis approach does not consider the influence of the other unit in the crane vessel. This paper presents a methodology for evaluating a DP crane vessel in the offshore operations (DP crane vessel, load being transported, mooring and assistance lines, platform) considering the fully coupled method based on integration of the in house codes with the commercial code WAMIT® system. The methodology is based on the integration of numerical and experimental tools. The dimensions of the transported modules and the proximity of the vessels change the behavior of the vessel motions and line tensions. So, a full nonlinear time domain simulator (TPN – Numerical Offshore Tank) is used to perform the coupled analysis of the system subjected to several environmental conditions, considering also the dynamics of the suspended load and the hydrodynamic interference between the bodies. In order to calibrate the numerical model, several experimental tests are performed such as wind tests with some positions of the crane, tests in towing tanks to evaluated the current effects, thrusters tests to calibrate DP algorithm and wave test with the two bodies. In some cases a complementary CFD analysis is requested in order to evaluate the current and wind shadow effect. Several alternative relative positions between the vessels can be evaluated. This methodology results a more accurate estimative of the system performance.

Automatic Segmentation of Pores in Weld Images Based on Transition Region Extraction

2012 ◽  
Vol 217-219 ◽  
pp. 1964-1967
Author(s):  
Tong Tong ◽  
Yan Cai ◽  
Da Wei Sun ◽  
Peng Liu
Keyword(s):  
Transition Region ◽  
Automatic Segmentation ◽  
Experimental Results ◽  
Gray Level ◽  
Segmentation Method ◽  
Complex Environment ◽  
Weld Defects ◽  
Contrast Enhanced ◽  
Region Extraction ◽  
Low Pass

In allusion to the complex images of weld defects, weak contrast between the target and the background, a new segmentation method based on gray level difference transition region extraction is proposed. The paper analyzes the characteristic of weld defects, and then low-pass filtering and contrast enhanced are used to enhance the clarity. Finally, we extract the transition region and confirm a threshold for defects segmentation. The experimental results show that the method can extract the transition region more accurate, and segment the image much better in complex environment.

Numerical and Experimental Research on Periodic Solution Stability of Inclined Rotor Journal Bearing System

2011 ◽  
Author(s):  
Dashuai Qian ◽  
Zhansheng Liu ◽  
Jiajia Yan ◽  
Liquan Sun ◽  
Yongliang Wang
Keyword(s):  
Periodic Solution ◽  
Journal Bearing ◽  
Rotor System ◽  
Experimental Results ◽  
System Stability ◽  
Response Analysis ◽  
Solution Stability ◽  
Special Cases ◽  
Rotor Journal ◽  
Bearing System

Rotor bearing systems on ships usually work in inclined states when ships are swaying in wave and wind. The inclined status will affect the lubricant condition of journal bearing and bring about changes of the dynamic characteristics of the rotor system. To study the periodic solution stability of inclined rotor journal bearing system, Capone’s short bearing model is employed to describe the journal bearing support properties. Considering the inclination induced change of bearing radial load, the dynamic equation of inclined rotor system is established by using finite element method. The periodic solution stability is discussed based on bifurcation and response analysis. With the increase of rotating speed, instability of period-1 motion happens and oil whirl occurs. The motion then develops into a kind of quasi-periodic motion. Two special cases of inclined rotor system, the horizontal and the vertical cases, are compared and discussed. Both of the numerical and the experimental results show that the periodic solution unstable threshold decreases with the increase of rotor inclination angle. At last, some experimental results about influences of experiments conditions on rotor system stability are given.

Experimental and finite element study on the single-layer reticulated composite joints

2020 ◽  
Vol 23 (10) ◽  
pp. 2174-2187
Author(s):  
Liang Zheng ◽  
Cheng Qin ◽  
Hong Guo ◽  
Dapeng Zhang ◽  
Mingtan Zhou ◽  
...  
Keyword(s):  
Finite Element ◽  
Bearing Capacity ◽  
Axial Compression ◽  
Wall Thickness ◽  
Great Influence ◽  
Single Layer ◽  
Experimental Results ◽  
Steel Pipe ◽  
Cover Plate ◽  
Element Analysis

In this article, a new type of reticulated joint, named the steel–concrete composite reticulated shell joint, is proposed. The proposed reticulated shell joint consists of an inner circular steel pipe, an outer circular steel pipe, a steel cover plate, and internal concrete. Five test specimens were tested under axial compression. The variable study included the wall thickness of the inner and outer circular steel pipes and the radius of the inner circular steel pipe. The test specimens exhibited a high bearing capacity and good plastic deformation ability under axial compression. The test results show that the wall thickness of the outer circular steel pipe and the radius of the inner circular steel pipe have a great influence on the bearing capacity of the steel–concrete composite reticulated shell joint, while the wall thickness of the inner circular steel pipe has little influence on the bearing capacity of the steel–concrete composite reticulated shell joint. Based on the test of the steel–concrete composite reticulated shell joints under axial load, the three-dimensional nonlinear finite element model was used to analyze the mechanical properties of the steel–concrete composite reticulated shell joints under axial compression. The results of the finite element analysis showed good agreement with the experimental results. The formula for calculating the bearing capacity of the joint is derived. By comparing with the experimental results, the calculated results are basically consistent with the experimental results.

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