Fluid Dynamic Excitation of Centrifugal Compressor Rotor Vibrations

1978 ◽  
Vol 100 (1) ◽  
pp. 73-78
Author(s):  
W. E. Thompson
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Operating Experience ◽  
Orbital Stability ◽  
Dynamic Force ◽  
Force Coefficient ◽  
Streamline Curvature ◽  
Compressor Rotor ◽  
Pressure Distributions ◽  
The Stability

A mechanism by which compressor rotor lateral vibration perturbs the mass flow-rate, the velocity and the pressure distributions within impeller passages is postulated. Such a perturbation will develop an unbalanced force on the rotor which, if it enhances the rotor vibration, is termed self-exciting. The concepts of rotor orbital velocity, the virtual center of shaft rotation, the reduction of unsteady flow to quasi-steady flow, the fluid dynamic force coefficient, mechanical orbital stability and the stability increment are introduced. The ideas are imposed on the streamline curvature method of quasi-three dimensional analysis of passage flow and a computer program has been assembled to carry out computation. No generalized guidelines have been found as yet but rather individual passage calculations are needed to determine the potentially exciting or damping character of the induced fluid dynamic forces. The average stability increment per stage for nine industrial multistage centrifugal compressors has been determined and compared with known operating experience. Important engineering characteristics of two of the compressors are shown in an example of the analysis. A provisional limit of the stability increment per stage ⩽ 1.85 lbf-s/in. (323.9N-s/m) is suggested, below which unstable nonsynchronous vibration of the compressor rotor can be expected.

Development of an Improved Streamline Curvature Approach for Transonic Axial Compressor

2016 ◽  
Author(s):  
Wu Xiaoxiong ◽  
Bo Liu ◽  
Shi Lei ◽  
Zhang Guochen ◽  
Mao Xiaochen
Keyword(s):  
Incidence Angle ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Internal Flow ◽  
Field Analysis ◽  
Design Stage ◽  
Axial Compressors ◽  
Transonic Compressor ◽  
Streamline Curvature

In this paper, an improved streamline curvature (SLC) approach is presented to obtain the internal flow fields and evaluate the performance of transonic axial compressors. The approach includes some semi-empirical correlations established based on previous literatures, such as minimum loss incidence angle model, deviation model and total pressure loss model. Several developments have been made in this paper for the purpose of considering the influences of three-dimensional (3D) flow in high-loaded multistage compressors with high accuracy. A revised deviation model is applied to predict the cascade with large deflection range. The method for predicting the shock loss is also discussed in detail. In order to validate the reliability of the approach, two test cases including a two-stage transonic fan and a three-stage transonic compressor are conducted. The overall performance and distribution of spanwise aerodynamic parameters are illustrated in this paper. Compared with both the experimental and computational fluid dynamic (CFD) data at design and a number of different off-design condition, the SLC results give reasonable characteristic curves. The validation demonstrates that this improved approach can serve as a fast and reliable tool for flow field analysis and performance prediction in preliminary design stage of axial compressors.

Axial Compressor Performance Prediction Using Improved Streamline Curvature Approach

2018 ◽  
Author(s):  
Tao Li ◽  
Yadong Wu ◽  
Hua Ouyang ◽  
Xiaoqing Qiang
Keyword(s):  
Performance Prediction ◽  
Incidence Angle ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Internal Flow ◽  
Field Calculation ◽  
Axial Compressors ◽  
Streamline Curvature ◽  
Loss Models

This paper presents in detail the improved streamline curvature approach (SLC) to the performance evaluation and internal flow field calculation of subsonic and transonic axial compressors. Based on previous research, the diverse incidence, deviation and total pressure loss models, generally existing in the form of fitting curves and semi-empirical correlations, are discussed respectively. Typically, transonic flow in axial compressor results in the variation of several flow parameters and particularly the appearance of shock waves compared with subsonic flow. In this paper, the revision and improvement of loss models are applied to reach higher accuracy, especially considering the loss component due to actual incidence angle. Several modifications have been made as well considering the influence of three-dimensional flow. For the purpose of validating this approach, two test cases, including a single-stage transonic axial compressor NASA Stage37 and a 3-stage subsonic axial compressor P&W 3S1, are calculated. The overall characteristics and spanwise aerodynamic parameters for blade rows are demonstrated at both design and off-design conditions. Furthermore, the results agree well with both experimental data and computational fluid dynamic (CFD) results. This throughflow method is verified as an applicable and convenient tool for aerodynamic analysis and performance prediction of subsonic and transonic axial compressors.

Fluid Dynamic Study in a Femoral Artery Branch Casting of Man With Upstream Main Lumen Curvature for Steady Flow

1985 ◽  
Vol 107 (3) ◽  
pp. 240-248 ◽  
Author(s):  
M. R. Back ◽  
Y. I. Cho ◽  
L. H. Back
Keyword(s):  
Steady Flow ◽  
Fluid Transport ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Pressure Distributions ◽  
Flow Investigation ◽  
Measured Pressure

An in-vitro, steady flow investigation was conducted in a hollow, transparent vascular replica of the profunda femoris branch of man for a range of physiological flow conditions. The replica casting tested was obtained from a human cadaver and indicated some plaque formation along the main lumen and branch. The flow visualization observations and measured pressure distributions indicated the highly three-dimensional flow characteristics with arterial curvature and branching, and the important role of centrifugal effects in fluid transport mechanisms.

scholarly journals A Three-Dimensional Navier-Stokes Calculation Applied to an Axial Compressor Rotor and Stator

1993 ◽  
Author(s):  
Robert P. Dring ◽  
Ricky J. VanSeters ◽  
Robert M. Zacharias
Keyword(s):  
Total Pressure ◽  
Large Scale ◽  
State Of The Art ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Measured Data ◽  
Navier Stokes ◽  
Second Stage ◽  
Compressor Rotor ◽  
Pressure Distributions

The objective of this paper is to apply a three-dimensional Navier-Stokes calculation to the second stage rotor and stator of a large scale compressor and to compare the computed results with measured data. The comparisons include: (1) airfoil and endwall surface streamlines, (2) radial-circumferential distributions of exit total pressure, (3) spanwise distributions of circumferentially averaged inlet and exit flow quantities, and (4) fullspan airfoil pressure distributions. This assessment demonstrates that the computational state-of-the-art has advanced to a point where calculations such as this can be applied with reasonable confidence in both design and analysis situations.

Dynamic Stability of a Flexible Spinning Cylinder Partially Filled With Liquid

2002 ◽  
Vol 69 (5) ◽  
pp. 708-710 ◽  
Author(s):  
M. Tao ◽  
W. Zhang
Keyword(s):  
Dynamic Stability ◽  
Three Dimensional ◽  
Dynamic Force ◽  
Two Dimensional ◽  
Euler Beam ◽  
Dimensional Flow ◽  
Analytical Stability ◽  
Two Dimensional Flow ◽  
Spinning Cylinder ◽  
The Stability

Dynamic stability of a flexible spinning cavity cylinder partially filled with liquid is discussed in the paper. The cylinder is assumed to be slender. Choosing characteristic quantities and estimating the orders of magnitude of all terms in the governing equations and boundary conditions, the three-dimensional flow in the slender cylinder is reduced to a quasi-two-dimensional flow. Using the known formulas of a two-dimensional dynamic force acting on the rotor and regarding the slender cylinder as a Bernoulli-Euler beam, the perturbed equations of the liquid-filled beam-wise cylinder are derived. The analytical stability criteria as well as the stability boundaries are obtained. The results further the study of this problem.

Rotordynamic Performance of the Interlocking Labyrinth Seal With a Tilting Rotor

2021 ◽  
Vol 143 (1) ◽  
Author(s):  
Wanfu Zhang ◽  
Yingfei Wang ◽  
Qianlei Gu ◽  
Lu Yin ◽  
Jiangang Yang
Keyword(s):  
Flow Rate ◽  
Labyrinth Seal ◽  
System Stability ◽  
Dynamic Force ◽  
Misalignment Angle ◽  
Analysis Model ◽  
Force Coefficient ◽  
Leakage Flow Rate ◽  
The Stability ◽  
Positive Effect

Abstract Numerical analysis model of an interlocking labyrinth seal (ILS) is established for studying the effect of tilting rotor on its rotordynamic characteristics. The dynamic characteristic identification method based on infinitesimal theory is applied to solve the dynamic force coefficient of the seal with arbitrary elliptical orbits and eccentric positions under field conditions. The paper investigated the dynamic characteristics of the interlocking labyrinth seal with various misalignment angles (θ = 0, 0.1 deg, 0.2 deg, 0.3 deg, 0.4 deg, 0.5 deg, 0.6 deg), different pressure ratios (Pin = 6.9 bar, PR = 0.5, 0.8), locations of misalignment center (Loc = 0, L/2, L). Results show that the tilting rotor could minimize the leakage flow rate of the ILS. When the misalignment angle θ = 0.6 deg, the mass flow rate can be reduced about 2.5%. The effect of each cavity in the ILS on the stability of the system is different. The cavity with the inlet close to the rotor and the outlet away from the rotor helps to improve the system stability due to its locally antirotational flow. The effective damping of the entire ILS increases as the misalignment angle increases. The system shows the best stability when the misalignment center is close to the seal inlet. The tilting rotor has a positive effect on the stability of the ILS only except for high whirling frequency (>100 Hz) under Loc = L.

Rotordynamic Performance of the Interlocking Labyrinth Seal With a Tilting Rotor

2020 ◽  
Author(s):  
Wanfu Zhang ◽  
Yingfei Wang ◽  
Qianlei Gu ◽  
Lu Yin ◽  
Jian-gang Yang
Keyword(s):  
Flow Rate ◽  
Labyrinth Seal ◽  
System Stability ◽  
Radial Clearance ◽  
Dynamic Force ◽  
Misalignment Angle ◽  
Analysis Model ◽  
Force Coefficient ◽  
Annular Seal ◽  
The Stability

Abstract Numerical analysis model of an interlocking labyrinth seal (ILS), including 6 seal cavities and 7 seal teeth (3 teeth on the rotor, 4 teeth on the stator), is established for studying the effect of tilting rotor on its rotordynamic characteristics. The dynamic characteristic identification method based on infinitesimal theory is applied to solve the dynamic force coefficient of the annular seal with arbitrary elliptical orbits and eccentric positions under field conditions. The paper investigated the dynamic characteristics of the interlocking labyrinth seal with various misalignment angles (θ = 0, 0.1°, 0.2°, 0.3°, 0.4°, 0.5°, 0.6°), different pressure ratios (Pin = 6.9 bar, PR = 0.5, 0.8), locations of misalignment center (Loc = 0, L/2, L). Results show that the tilting rotor could minimize the leakage flow rate of the ILS. When the misalignment angle θ = 0.6°, the mass flow rate can be reduced about 2.5%. The tilting rotor will cause the geometric deformation of the ILS cavity and the changes in the radial clearance of the teeth, which results in an increasing pressure drop in the seal cavity. The effect of each cavity in the ILS on the stability of the system is different. The cavity with the inlet close to the rotor and the outlet away from the rotor helps to improve the system stability due to its locally anti-rotational flow. The effective damping of the entire ILS increases as the misalignment angle increases. The system shows the best stability when the misalignment center is close to the seal inlet. The stability of the seal cavity C1 can be improved for any misalignment centers. The stability of the seal cavity C2 decreases when the misalignment center moves toward the seal outlet. For the seal cavities C3∼C6, their stability can be improved for Loc = 0, L/2, and decreases for Loc = L. The tilting rotor has a positive effect on the stability of the ILS only except for high whirling frequency (> 100 Hz) under Loc = L.

Computational Fluid Dynamics Simulation of a Single-Phase Rectangular Thermosiphon

2020 ◽  
Author(s):  
Tri Nguyen ◽  
Elia Merzari
Keyword(s):  
Single Phase ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Heat Removal ◽  
Spectral Element ◽  
Dynamics Simulation ◽  
Velocity Measurements ◽  
Buoyancy Driven Flows ◽  
The Stability ◽  
Flow Reversals

Abstract Buoyancy-driven flows are widespread in diverse engineering applications. Such flows have been studied in great detail theoretically, experimentally, and numerically. However, the fluid-dynamic instabilities and flow reversals of thermosiphon are still actively investigated. The presence of such instabilities limits the effectiveness of such devices for decay heat removal. Traditionally the stability analysis of natural convection loops has been confined to one-dimensional calculations, on the argument that the flow would be mono-dimensional when the ratio between the radius of the loop and the radius of the pipe is much larger than 1. Nevertheless, accurate velocity measurements of the flow in toroidal loops have shown that the flow presents three-dimensional effects. Previous works of the authors have shown that these structures can be seen in thermosiphons. In this paper, we aim to use modern CFD methods to investigate the three-dimensional flow in thermosiphons. This paper focuses on rectangular thermosiphons. In particular, we perform a series of high-fidelity simulations using the spectral element code Nek5000 to investigate the stability behavior of the flow in a rectangular thermosiphon. We compare the results with available existing experimental data from the L2 facility in Genoa. We examine in detail the flow structures generated. Moreover, in the past various authors have demonstrated that the overall behavior of the thermosiphon depends strongly on the boundary conditions (BCs). The simulation campaign was carried out with different BCs to investigate and confirm this effect. In particular, simulations with Dirichlet, Neumann and Robin BCs for heater and sink were performed.

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