Stability Analysis of Turbomachinery From the Viewpoint of Seal

1991 ◽  
Author(s):  
T. Iwatsubo ◽  
B. C. Sheng
Keyword(s):  
Stability Analysis ◽  
Working Conditions ◽  
Single Stage ◽  
Fluid Element ◽  
Individual Contribution ◽  
Rotating Fluid ◽  
Dynamic Interactions ◽  
Multi Stage ◽  
The Stability ◽  
The Individual

Abstract The stability of the typical rotating fluid machineries such as the single-stage and multi-stage pumps which consist of impellers, bearings and noncontacting seals is evaluated from the viewpoint of seals. The individual contribution of the impeller, bearing as well as seal to the stability, and the dynamic interactions of these fluid elements are investigated. In the investigation, some types of bearings, and seals such as annular smooth seals, parallel grooved seals and damper seals are compared to seek the better ones for the rotor stability. The effect of working conditions on the stability is also investigated. The results show that the rotor stability is strongly affected by the characteristics of these fluid elements, and the stability can be improved by changing the unstable fluid element.

scholarly journals Evaluation of Seal Effects on the Stability of Rotating Fluid Machinery

1995 ◽  
Vol 2 (2) ◽  
pp. 85-92
Author(s):  
T. Iwatsubo ◽  
B. C. Sheng
Keyword(s):  
Finite Element Method ◽  
Operating Conditions ◽  
Individual Contribution ◽  
Rotating Fluid ◽  
The Finite Element Method ◽  
Fluid Machinery ◽  
Dynamic Interactions ◽  
Multi Stage ◽  
The Stability ◽  
The Individual

The stability of typical rotating fluid machinery such as single and multi-stage pumps is evaluated by using the finite element method. The individual contribution of the impellers, bearings and seals to the stability and the dynamic interactions of these fluid elements are examined. Various types of bearings and seals, such as annular smooth, parallel grooved and damper seals, are compared for better rotor stability. The effect of the operating conditions on the stability is also investigated. The results show that rotor stability can be easily improved by replacing the unstable fluid elements.

scholarly journals Evaluation of Seal Effects on the Stability of Rotating Fluid Machinery

1995 ◽  
Vol 1 (2) ◽  
pp. 145-152 ◽  
Author(s):  
T. Iwatsubo ◽  
B. C. Sheng
Keyword(s):  
Finite Element Method ◽  
Operating Conditions ◽  
Individual Contribution ◽  
Rotating Fluid ◽  
The Finite Element Method ◽  
Fluid Machinery ◽  
Dynamic Interactions ◽  
Multi Stage ◽  
The Stability ◽  
The Individual

The stability of typical rotating fluid machinery such as single ahd multi-stage pumps is evaluated by using the finite element method. The individual contribution of the impellers, bearings and seals to the stability and the dynamic interactions of these fluid elements are examined. Various types of bearings and seals, such as annular smooth, parallel grooved and damper seals, are compared for better rotor stability. The effect of the operating conditions on the stability is also investigated. The results show that rotor stability can be easily improved by replacing the unstable fluid elements.

The Stability Analysis of Slope of Shegang Protecting Dyke

2011 ◽  
Vol 261-263 ◽  
pp. 1841-1845
Author(s):  
Hui Qin Yao
Keyword(s):  
Stability Analysis ◽  
Working Conditions ◽  
Saturation Line ◽  
Dam Safety ◽  
Design Code ◽  
Embankment Dam ◽  
Safe Operation ◽  
Calculation Results ◽  
The Stability ◽  
Reinforcement Design

Appraisal of dam slope safety is essential for security and stability of the dyke that has been constructed for many years. According to the requirements of the appraisal of dam safety, the stability analysis of slope of Shegang dyke has been carried out by using Sweden circular-arc method, Bishop method, Engineer Corps method and Lowe method four methods under many kinds of working conditions and some conditions when the saturation line raising. Combined with the design code form embankment dam, the calculation results can be analyzed. The analysis can show that the security indexes of anti-slide under four kinds of working conditions and some conditions when the saturation line raising meet the requirements of the design code. This can provide basis for the reinforcement design of the dam, which also has a certain directive significance for the safe operation and observation of the dam in the future.

scholarly journals Stability Analysis of a Single-Ball Automatic Balancer

2005 ◽  
Vol 128 (1) ◽  
pp. 122-125 ◽  
Author(s):  
Chung-Jen Lu
Keyword(s):  
Stability Analysis ◽  
Theoretical Model ◽  
Working Conditions ◽  
Rotating Disk ◽  
Disk Drive ◽  
Optical Disk ◽  
Equilibrium States ◽  
Relevant Parameter ◽  
Optical Disk Drive ◽  
The Stability

Under proper working conditions, a ball-type automatic balancer can effectively reduce the imbalance vibrations of an optical disk drive. The proper working conditions can be determined by a stability analysis of the equilibrium states of the nonlinear system formed by the rotating disk, balancer, and suspension system. Several attempts have been made to study the stability of the equilibrium states numerically in some finite regions of the relevant parameter space. This paper in contrast analytically investigates the stability characteristics of the equilibrium states. A theoretical model of an optical disk drive packed with an automatic balancer is constructed first. The governing equations of the theoretical model are derived using Lagrange’s equations and closed-form formulas for the equilibrium positions are presented. Finally, general guidelines on the stability of the equilibrium states are proposed.

An Energy Analysis of Amplitude Death of a Pair of Oscillators With Delayed Coupling

2005 ◽  
Author(s):  
Zaihua Wang ◽  
Haiyan Hu
Keyword(s):  
Stability Analysis ◽  
Coupled Oscillators ◽  
Present Method ◽  
Special Function ◽  
Energy Analysis ◽  
Arbitrary Solution ◽  
Amplitude Death ◽  
Delayed Coupling ◽  
The Stability ◽  
The Individual

This paper presents an energy analysis of the amplitude death, a phenomenon that the individual oscillators cease to oscillate when coupled and go to an equilibrium motion instead, of a pair of coupled oscillators with time delay that are slightly perturbed from two undamped oscillators and with delayed coupling. The energy analysis reveals that amplitude death, as well as the stability of the phase-locked periodic solutions, can be justified by the sign of the averaged total powers along a special function with harmonic entries, rather than along arbitrary solution of the coupled oscillators as in the application of the method of Lyapunov’s function for stability analysis. An illustrative example is given to show the effectiveness of the present method.

Measurements of the Four-Quadrant Characteristics on a Multi-Stage Turbine

1980 ◽  
Vol 102 (2) ◽  
pp. 316-321 ◽  
Author(s):  
K. Bammert ◽  
P. Zehner
Keyword(s):  
Gas Turbines ◽  
Single Stage ◽  
Operation Conditions ◽  
Multi Stage ◽  
Performance Curves ◽  
Stage Performance ◽  
The Individual ◽  
Four Quadrant ◽  
Operating Points ◽  
Energy Plants

With turbines, operation conditions far from the design range are possible. With gas turbines, in nuclear and solar energy plants in the case of a fault, flow in reverse directions may even occur. For extreme operations insufficient knowledge was available, so measurements were carried out at first on a single-stage turbine and then on a seven-stage turbine, with both the mass flow and the rotor speed systematically varied in the positive (normal direction) and negative ranges (four-quadrant characteristics). The measurement on the seven-stage turbine basically tally with the single-stage measurements. Stage performance curves can be approximately calculated also for four quadrants from the cascade characteristics of the middle section. The calculated curves are compared to the results of the single-stage measurements. During operation far from the design point, the individual stages of a multi-stage turbine work at a wide variety of operating points, so the characteristics of such a turbine have to be determined by the superimposition of the corresponding stage performance curves on each other.

Vehicle-Foundation Stability Systems with a Single Point of Contact

1994 ◽  
Vol 13 (3) ◽  
pp. 103-109
Author(s):  
J.B. Da Silva ◽  
L. Jezequel
Keyword(s):  
Stability Analysis ◽  
Linear System ◽  
Complex Systems ◽  
Critical Frequency ◽  
Single Point ◽  
Winkler Foundation ◽  
Dynamic Interactions ◽  
Infinite Beam ◽  
Moving Vehicle ◽  
The Stability

A method allowing the calculation at low numerical cost is used to study the dynamic interactions between two simple vehicle models and a guideway consisting of an Euler-Bernoulli infinite beam resting on a Winkler foundation. The study includes an evaluation of the effects of variations of the critical speeds of a moving vehicle as a function of its mass and of its critical frequency. The stability analysis for linear system is performed by investigating the roots of the resulting characteristic equation. The results obtained by comparatively simple models are believed to remain valid also for more complex systems.

Implications of Person Fluctuation for the Stability and Validity of Test Scores

Methodology ◽  
2006 ◽  
Vol 2 (4) ◽  
pp. 142-148 ◽  
Author(s):  
Pere J. Ferrando
Keyword(s):  
Item Response ◽  
Test Scores ◽  
Temporal Stability ◽  
Person Fit ◽  
Item Parameters ◽  
Individual Trait ◽  
The Stability ◽  
The Individual ◽  
Different Levels ◽  
Fluctuation Model

In the IRT person-fluctuation model, the individual trait levels fluctuate within a single test administration whereas the items have fixed locations. This article studies the relations between the person and item parameters of this model and two central properties of item and test scores: temporal stability and external validity. For temporal stability, formulas are derived for predicting and interpreting item response changes in a test-retest situation on the basis of the individual fluctuations. As for validity, formulas are derived for obtaining disattenuated estimates and for predicting changes in validity in groups with different levels of fluctuation. These latter formulas are related to previous research in the person-fit domain. The results obtained and the relations discussed are illustrated with an empirical example.

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