Squeeze Film Dynamics of Two-Phase Seals

1992 ◽  
Vol 114 (2) ◽  
pp. 236-246 ◽  
Author(s):  
J. A. Yasuna ◽  
W. F. Hughes
Keyword(s):  
Steady State ◽  
Dynamic Analysis ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Transient Responses ◽  
Two Phase ◽  
Thermal Transients ◽  
Face Seals

A dynamic analysis of two-phase face seals including squeeze film effects and thermal transients is presented. Axial responses to perturbations from equilibrium for various sets of typical seal operating conditions are examined, and the sensitivity of these responses to certain parameters is discussed. Sample calculations indicate damped transient responses which often decay as steady state is approached asymptotically. In some cases, however, stable and unstable oscillations are observed.

Squeeze Film Dynamics of Two-Phase Seals: Part II—Turbulent Flow

1994 ◽  
Vol 116 (3) ◽  
pp. 479-487 ◽  
Author(s):  
J. A. Yasuna ◽  
W. F. Hughes
Keyword(s):  
Turbulent Flow ◽  
Dynamic Model ◽  
Entire Range ◽  
Squeeze Film ◽  
Turbulent Regime ◽  
Two Phase ◽  
Thermal Transients ◽  
Face Seals ◽  
Laminar And Turbulent Flow

A previously developed dynamic model for two-phase face seals is extended to include turbulent flow. Thermal transients over the entire range of laminar and turbulent flow are considered for both parallel and tapered geometries. Inlet losses and choking are accounted for in the turbulent regime. Axial responses to perturbations from equilibrium are examined, and general criteria are discussed for predicting stable, unstable and bistable seal operation.

A new model to predict the behaviour of cavitated squeeze-film bearings

1987 ◽  
Vol 411 (1841) ◽  
pp. 445-466
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Lift Force ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Successful Operation ◽  
New Model ◽  
Damping Coefficients ◽  
Stiffness Coefficients ◽  
Linear Damping

Squeeze-film bearings are used extensively to control vibration in rotor-bearing systems. No closed-form mathematical model exists to represent the stiffness and dam ping characteristics of a cavitated squeeze-film bearing when it is describing a non-circular, non-concentric orbit. In this paper nonlinear expressions are developed for the oil-film forces from which are derived two direct linear stiffness and two direct linear damping coefficients with all the cross stiffness and dam ping coefficients zero. The linearized stiffness coefficients and the damping coefficients are functions of the amplitude of the journal orbit. The dynamic lift-force which is fundamental to the successful operation of a cavitated squeeze-film bearing when designed without centralizing springs has not previously been predicted analytically. An expression is derived for this lift force. Its magnitude is shown to be dependent upon the amplitude of the steady-state orbit, that is, it is dependent upon the dynamic load. A numerical experiment is performed to assess the validity of the new model over a range of operating conditions.

First Paper: An Investigation into the Steady-State Characteristics of Plain Slideways

1969 ◽  
Vol 184 (1) ◽  
pp. 1075-1087 ◽  
Author(s):  
R. Bell ◽  
M. Burdekin
Keyword(s):  
Cast Iron ◽  
Steady State ◽  
Hydrodynamic Lubrication ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Sliding Velocity ◽  
Experimental Conditions ◽  
Friction Characteristics ◽  
Feed Drive ◽  
Lubricant Viscosity

This paper describes steady-state friction tests on a scraped-cup ground combination of cast iron surfaces. The experimental conditions were representative of the operating conditions on a machine tool feed drive employing plain slideways. The range of the relative sliding velocity investigated was 0 → 1 in s-1, and the influence of lubricant viscosity of both polar and non-polar additive lubricants is shown. An investigation into the effect of oil grooves is also reported. Data obtained from squeeze film measurements enabled the characteristics, normal to the sliding plane, to be specified. These characteristics, together with measurements of the separation of the surfaces, enabled the steady-state friction characteristics to be predicted over the range of mixed and hydrodynamic lubrication covered by the tests. This work formed a basis for the investigation into the mechanism of the friction characteristics under dynamic conditions.

The Stability of Pumping Systems—The 1980 Freeman Scholar Lecture

1981 ◽  
Vol 103 (2) ◽  
pp. 193-242 ◽  
Author(s):  
E. M. Greitzer
Keyword(s):  
Steady State ◽  
Dynamic Instability ◽  
Transient Behavior ◽  
Operating Conditions ◽  
System Stability ◽  
Hydraulic Systems ◽  
Two Phase ◽  
Pumping System ◽  
Basic Concepts ◽  
Steady State Performance

A review is presented of the types of instabilities which are encountered in pumping systems of technological interest. These include axial and centrifugal compression systems, pumping systems involving cavitation, systems with two-phase flow, systems with combustion, hydraulic systems, and systems which have two or more pumping elements in parallel. All of the above will be seen to exhibit instabilities under certain operating conditions, although the mechanism of instability, as well as the particular system element that is responsible for the instability, will be quite different in the different systems. However, several basic concepts, such as the idea of negative damping which is associated with dynamic instability, will be seen to be common to the different systems. The review is organized around the different types of systems that are discussed, and includes descriptions of the steady-state performance, the regimes in which one would expect instability, and the mechanisms of instability. An idealized pumping system is first examined to illustrate some of the basic concepts. More realistic systems are then treated in the same manner of showing steady-state performance, regimes of instability and mechanisms. In the review attention is given mainly to those areas in which there is high current engineering interest, and an attempt is made to describe those areas of research which can be most fruitfully pursued. In general, it is suggested that efforts should be directed toward obtaining an improved understanding of the transient behavior of the active (instability causing) elements within the system, since it is lack of knowledge of this aspect that currently limits the accuracy of system stability predictions.

Analysis of Face Seals With Shrouded Pockets

1982 ◽  
Vol 104 (2) ◽  
pp. 262-270 ◽  
Author(s):  
Jed A. Walowit ◽  
Oscar Pinkus
Keyword(s):  
Dynamic Capabilities ◽  
Incompressible Fluids ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Face Seal ◽  
Design And Optimization ◽  
Face Seals ◽  
Quantitative Basis ◽  
Geometric Permutations ◽  
Hydrostatic Component

The paper offers an analysis of face seals, using incompressible fluids, aimed at arriving at a quantitative basis for the design and optimization of seals. To improve its hydrodynamic and dynamic capabilities, the parallel face seal is provided with pockets pressurized by the sealed fluid, and shrouded at both the inner and outer peripheries. The relevant Poisson equation is solved for its hydrodynamic, hydrostatic, and squeeze-film components. A parametric study of various geometric permutations and operating conditions is then obtained from the computerized solutions. The results show that the contribution of the hydrostatic forces to stiffness is insignificant, and that both K3 and W3 can be ignored in the optimization of seal dimensions. For high seal pressures, the dominant force and leakage are geared to the hydrostatic component, whereas for low seal pressures, both the hydrodynamic and squeeze-film effects are important.

Dynamic Analysis of Rupture in Thin Fluid Films. I—A Noninertial Theory

1983 ◽  
Vol 105 (1) ◽  
pp. 96-104 ◽  
Author(s):  
C. H. T. Pan
Keyword(s):  
Steady State ◽  
Theoretical Model ◽  
Dynamic Analysis ◽  
Squeeze Film ◽  
Transient Condition ◽  
Film Rupture ◽  
Fluid Films ◽  
Film Pressure ◽  
Sliding Surfaces ◽  
Thin Fluid

A noninertial theoretical model for the dynamics of film rupture has been formulated. Under the transient condition, movement of the rupture boundary is governed by the condition of flow continuity between the film flux and adhered film transport in the cavitation domain. The traditional Swift-Stieber condition for film breakup is shown to be valid upon reaching steady-state. Generalization is extended to allow consideration of two sliding surfaces and the pure squeeze-film. The possibility of subcavitation film pressure is shown to result in dry regions in the cavitation domain.

A tensometric method to determine the hold-up of liquid in packed bed apparatures

1982 ◽  
Vol 47 (8) ◽  
pp. 2190-2200 ◽  
Author(s):  
Vladimír Jiřičný ◽  
Vladimír Staněk ◽  
Jiří Šmíd ◽  
Vladimír Jelínek
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Pressure Drop ◽  
Packed Bed ◽  
Gas Pressure ◽  
Operating Conditions ◽  
Dynamic State ◽  
Phase Flow ◽  
Two Phase ◽  
Packed Bed Columns

Results have been presented in the paper of the tests and calibration of a tensometric scale developed for weighing packed bed columns under operating conditions. The results have shown the tensometric method to be suitable weighing packed bed columns under the two-phase flow of gas and liquid in the dynamic state. Experimental results have been presented of the steady state liquid hold-up and gas pressure drop obtained by the developed tensometric method in an experimental column 190 mm in diameter. The experimental data have been compared with those of other authors obtained by different experimental techniques.

Dynamic analysis of a helical gear reduction by experimental and numerical methods

2020 ◽  
Vol 68 (1) ◽  
pp. 48-58
Author(s):  
Chao Liu ◽  
Zongde Fang ◽  
Fang Guo ◽  
Long Xiang ◽  
Yabin Guan ◽  
...  
Keyword(s):  
Numerical Methods ◽  
Dynamic Analysis ◽  
Dynamic Behavior ◽  
Fourth Order ◽  
Numerical Models ◽  
Helical Gear ◽  
Operating Conditions ◽  
Dynamic Responses ◽  
Lumped Mass ◽  
Gear Mesh

Presented in this study is investigation of dynamic behavior of a helical gear reduction by experimental and numerical methods. A closed-loop test rig is designed to measure vibrations of the example system, and the basic principle as well as relevant signal processing method is introduced. A hybrid user-defined element model is established to predict relative vibration acceleration at the gear mesh in a direction normal to contact surfaces. The other two numerical models are also constructed by lumped mass method and contact FEM to compare with the previous model in terms of dynamic responses of the system. First, the experiment data demonstrate that the loaded transmission error calculated by LTCA method is generally acceptable and that the assumption ignoring the tooth backlash is valid under the conditions of large loads. Second, under the common operating conditions, the system vibrations obtained by the experimental and numerical methods primarily occur at the first fourth-order meshing frequencies and that the maximum vibration amplitude, for each method, appears on the fourth-order meshing frequency. Moreover, root-mean-square (RMS) value of the acceleration increases with the increasing loads. Finally, according to the comparison of the simulation results, the variation tendencies of the RMS value along with input rotational speed agree well and that the frequencies where the resonances occur keep coincident generally. With summaries of merit and demerit, application of each numerical method is suggested for dynamic analysis of cylindrical gear system, which aids designers for desirable dynamic behavior of the system and better solutions to engineering problems.

Validation of On-line Respiration Meter and its Applications by Computer Simulation

1992 ◽  
Vol 26 (5-6) ◽  
pp. 1355-1363 ◽  
Author(s):  
C-W. Kim ◽  
H. Spanjers ◽  
A. Klapwijk
Keyword(s):  
Steady State ◽  
Activated Sludge ◽  
Respiration Rate ◽  
Oxygen Demand ◽  
Operating Conditions ◽  
Mass Balances ◽  
Short Term ◽  
Respiration Rates ◽  
On Line ◽  
Made In

An on-line respiration meter is presented to monitor three types of respiration rates of activated sludge and to calculate effluent and influent short term biochemical oxygen demand (BODst) in the continuous activated sludge process. This work is to verify if the calculated BODst is reliable and the assumptions made in the course of developing the proposed procedure were acceptable. A mathematical model and a dynamic simulation program are written for an activated sludge model plant along with the respiration meter based on mass balances of BODst and DO. The simulation results show that the three types of respiration rate reach steady state within 15 minutes under reasonable operating conditions. As long as the respiration rate reaches steady state the proposed procedure calculates the respiration rate that is equal to the simulated. Under constant and dynamic BODst loading, the proposed procedure is capable of calculating the effluent and influent BODst with reasonable accuracy.

Steady-state Security Assessment Based on K-Means Clustering Algorithm and Phasor Measurement Units

2020 ◽  
Vol 13 (4) ◽  
pp. 559-570
Author(s):  
Bassam A. Hemade ◽  
Hamed A. Ibrahim ◽  
Hossam E.A. Talaat
Keyword(s):  
Steady State ◽  
Clustering Algorithm ◽  
System Security ◽  
Phasor Measurement Units ◽  
Operating Conditions ◽  
Security Assessment ◽  
State Security ◽  
Phasor Measurement ◽  
Measurement Units ◽  
Silhouette Analysis

Background: The security assessment plays a crucial role in the operation of the modern interconnected power system network. Methods: Hence, this paper addresses the application of k-means clustering algorithm equipped with Principal Component Analysis (PCA) and silhouette analysis for the classification of system security states. The proposed technique works on three principal axes; the first stage involves contingency quantification based on developed insecurity indices, the second stage includes dataset preparation to enhance the overall performance of the proposed method using PCA and silhouette analysis, and finally the application of the clustering algorithm over data. Results: The proposed composite insecurity index uses available synchronized measurements from Phasor Measurement Units (PMUs) to assess the development of cascading outages. Considering different operational scenarios and multiple levels of contingencies (up to N-3), Fast Decoupled Power Flow (FDPF) have been used for contingency replications. The developed technique applied to IEEE 14-bus and 57-bus standard test system for steady-state security evaluation. Conclusion: The obtained results ensure the robustness and effectiveness of the established procedure in the assessment of the system security irrespective of the network size or operating conditions.

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