Thermal Effects in Cryogenic Liquid Annular Seals—Part II: Numerical Solution and Results

1993 ◽  
Vol 115 (2) ◽  
pp. 277-284 ◽  
Author(s):  
Luis San Andres ◽  
Zhou Yang ◽  
Dara W. Childs
Keyword(s):  
High Speed ◽  
Nonlinear Differential Equations ◽  
Cryogenic Liquid ◽  
Performance Characteristics ◽  
Liquid Oxygen ◽  
Dynamic Force ◽  
Two Phase ◽  
Numerical Predictions ◽  
Annular Seal ◽  
Static Performance

A numerical thermohydrodynamic model for solution of the nonlinear differential equations describing the turbulent flow of a single-phase, cryogenic liquid annular seal is presented. A perturbation method is used for calculation of the zeroth and first-order flow solutions to determine the seal steady-state response and dynamic force coefficients. Numerical predictions for a high speed liquid oxygen seal with a roughened stator surface show that, relative to an isothermal-barotropic fluidmodel, the adiabatic THD solution presents a significant temperature-rise with a profound effect on the liquid material properties and seal performance characteristics. The calculations show the onset of two-phase flow conditions at moderate eccentricities despite the large pressure differential across the seal. Comparisons of the static performance characteristics for the reference seal show excellent agreement between the approximate analytical solution developed in Part I and the full numerical results.

Turbulent Flow Foil Bearings for Cryogenic Applications

1995 ◽  
Vol 117 (1) ◽  
pp. 185-195 ◽  
Author(s):  
Luis San Andres
Keyword(s):  
High Speed ◽  
Excitation Frequency ◽  
Liquid Oxygen ◽  
Dynamic Force ◽  
Foil Bearings ◽  
Rotordynamic Coefficients ◽  
Numerical Predictions ◽  
Foil Bearing ◽  
Rotor Support ◽  
System Life

Fluid film foil bearings are an innovative bearing technology proposed for rotor support in cryogenic turbomachinery. These bearings offer system life and rotor speeds currently unachievable with rolling element bearings alone. An isothermal analysis for the turbulent bulk-flow of a variable properties liquid in a foil bearing with a simple elastic matrix is introduced. Numerical predictions compare the static and dynamic force performance of a three pad foil bearing with a rigid surface bearing for a high speed application in liquid oxygen. The major advantages of the foil bearing are immediately apparent, namely linearity in the load versus eccentricity curve, uniform rotordynamic coefficients, and overall unsurpassed stability conditions. The effects of excitation frequency and the foil structural damping on the dynamic force coefficients are discussed.

scholarly journals Analysis of the effect of oil inlet size on the static performance characteristics of non-Newtonian lubricated hole-entry hybrid journal bearings

2021 ◽  
Vol 37 ◽  
pp. 522-531
Author(s):  
Haiyin Cao ◽  
Yu Huang ◽  
Youmin Rong ◽  
Hao Wu ◽  
Minghui Guo
Keyword(s):  
Finite Element Method ◽  
High Speed ◽  
Reynolds Equation ◽  
Journal Bearings ◽  
Performance Characteristics ◽  
Power Law Model ◽  
The Finite Element Method ◽  
Solution Strategy ◽  
Nonuniform Mesh ◽  
Static Performance

Abstract In this study, the influence of inlet pocket size on the static performance of non-Newtonian lubricated hole-entry hybrid journal bearings is theoretically analyzed. The oil film of the bearing is discretized into a nonuniform mesh containing the geometric characteristics of the oil inlet pocket, and the inlet pocket is treated as a micro-oil recess. The Reynolds equation is solved by the finite element method based on Galerkin's techniques, and a new solution strategy to solve the recess/pocket pressure is proposed. The power-law model is used to introduce the non-Newtonian effect. The results show that the static performance characteristics of this type of bearing are greatly affected by the pocket size at both zero speed and high speed.

Angled Injection—Hydrostatic Bearings Analysis and Comparison to Test Results

1997 ◽  
Vol 119 (1) ◽  
pp. 179-187 ◽  
Author(s):  
Luis San Andres ◽  
Dara Childs
Keyword(s):  
High Speed ◽  
Pressure Rise ◽  
Liquid Oxygen ◽  
Momentum Exchange ◽  
Force Coefficients ◽  
Rotordynamic Coefficients ◽  
Rotating Systems ◽  
Static Performance ◽  
Stiffness And Damping ◽  
Frequency Ratios

Hydrostatic/hydrodynamic (hybrid) journal bearings handling process liquids have limited dynamic stability characteristics and their application as support elements to high speed flexible rotating systems is severely restricted. Measurements on water hybrid bearings with angled orifice injection have demonstrated improved rotordynamic performance with virtual elimination of cross-coupled stiffness coefficients and null or negative whirl frequency ratios. A bulk-flow model for prediction of the static performance and force coefficients of hybrid bearings with angled orifice injection is advanced. The analysis reveals that the fluid momentum exchange at the orifice discharge produces a pressure rise in the hydrostatic recess which retards the shear flow induced by journal rotation, and thus, reduces cross-coupling forces. The predictions from the model are compared with experimental measurements for a 45 deg angled orifice injection, 5 recess, water hydrostatic bearing operating at 10.2, 17.4, and 24.6 krpm and with supply pressures of 4, 5.5 and 7 MPa. The correlations include recess pressures, flow rates, and rotordynamic force coefficients at the journal centered position. An application example for a liquid oxygen hybrid bearing also demonstrates the advantages of tangential orifice injection on the rotordynamic coefficients and stability indicator for forward whirl motions, and without performance degradation on direct stiffness and damping coefficients.

Turbulent Flow, Flexure-Pivot Hybrid Bearings for Cryogenic Applications

1996 ◽  
Vol 118 (1) ◽  
pp. 190-200 ◽  
Author(s):  
Luis San Andres
Keyword(s):  
High Speed ◽  
Energy Transport ◽  
Load Capacity ◽  
Equations Of Motion ◽  
Liquid Oxygen ◽  
Hydrodynamic Bearings ◽  
Numerical Predictions ◽  
Tilting Pad ◽  
Direct Stiffness ◽  
Stiffness And Damping

The thermal analysis of flexure-pivot tilting-pad hybrid (combination hydrostatic-hydrodynamic) bearings for cryogenic turbopumps is presented. The advantages of this type of bearing for high speed operation are discussed. Turbulent bulk-flow, variable properties, momentum and energy transport equations of motion govern the flow in the bearing pads. Zeroth-order equations for the flow field at a journal equilibrium position render the bearing flow rate, load capacity, drag torque, and temperature rise. First-order equations for perturbed flow fields due to small amplitude journal motions provide rotordynamic force coefficients. A method to determine the tilting-pad moment coefficients from the force displacement coefficients is outlined. Numerical predictions correlate well with experimental measurements for tilting-pad hydrodynamic bearings. The design of a liquid oxygen, flexure-pad hybrid bearing shows a reduced whirl frequency ratio and without loss in load capacity or reduction in direct stiffness and damping coefficients.

Dynamic Characteristics of the Combined Smart Bearing

2011 ◽  
Author(s):  
Yong Bok Lee ◽  
Kyung Min Lee ◽  
Jin-Taek Chung ◽  
Seung Jong Kim ◽  
Se Na Jeong
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Magnetic Bearing ◽  
Dynamic Force ◽  
Rotating Speed ◽  
Numerical Predictions ◽  
Efficient Performance ◽  
Speed Change ◽  
Hybrid Bearing ◽  
The Stability

The stability, reliability, efficient performance of high speed turbo machinery is very important, and accordingly has increased the demand for advanced bearings. In order to meet the advanced bearing needs, Heshmat proposed a hybrid foil-magnetic bearing [1]. The hybrid bearing combining the two bearings takes advantage of the strengths of each while compensating for each other’s weaknesses. This paper presents dynamic characteristics of the combined smart bearing (CSB) of different structure from Heshmat’s bearing. The CSB and test rig were designed, fabricated and carried out the test. Numerical predictions of Air foil bearing (AFB) and CSB were compared the dynamic force performance, and analysis of bearings are performed by finite element method (FEM). Experiments were conducted to determine the structural static and dynamic characteristics of AFB. The dynamic characteristics of AFB and CSB compared depending on the rotating speed change. The experimental results were obtained the dynamic characteristics of the CSB 50% higher than value of the stiffness effect. In addition to, the CSB 100% higher than value of the damping effect.

Two-Phase Short Circuit in the Power Grid Powered by a Transformer with a Y/Δ-11 Winding Connection

2020 ◽  
pp. 25-30
Author(s):  
Aleksandr S. Serebryakov ◽  
Vladimir L. Osokin ◽  
Sergey A. Kapustkin
Keyword(s):  
High Speed ◽  
Short Circuit ◽  
Relay Protection ◽  
Electric Circuit ◽  
Operational Reliability ◽  
Research Purpose ◽  
Industrial Complex ◽  
Two Phase ◽  
Short Circuit Currents ◽  
Secondary Winding

The article describes main provisions and relations for calculating short-circuit currents and phase currents in a three-phase traction transformer with a star-triangle-11 connection of windings, which feeds two single-phase loads in AC traction networks with a nominal voltage of 25 kilovolts. These transformers provide power to the enterprises of the agro-industrial complex located along the railway line. (Research purpose) The research purpose is in substantiating theoretical equations for digital intelligent relay protection in two-phase short circuits. (Materials and methods) It was found that since the sum of instantaneous currents in each phase is zero, each phase of the transformer works independently. We found that this significantly simplifies the task of analyzing processes with a two-phase short circuit. In this case, the problem of calculating short-circuit currents in the traction network can be simplified by reducing it to the calculation of an ordinary electric circuit with three unknown currents. (Results and discussion) The article describes equations for calculating short-circuit resistances for one phase of the transformer when connecting the secondary winding as a star or a triangle. The currents in the phases of the transformer winding at short circuit for the star-triangle-11 and star-star-with-ground schemes are compared. It was found that when calculating short-circuit currents, there is no need to convert the secondary winding of the traction transformer from a triangle to a star. (Conclusions) It was found that the results of the research can be used in the transition of relay protection systems from electromagnetic relays to modern high-speed digital devices, which will increase the operational reliability of power supply systems for traction and non-traction power consumers.

Development and Validation of a Three-Dimensional Multiphase Flow CFD Analysis for Journal Bearings in Steam and Heavy Duty Gas Turbines

2012 ◽  
Author(s):  
Stephan Uhkoetter ◽  
Stefan aus der Wiesche ◽  
Michael Kursch ◽  
Christian Beck
Keyword(s):  
Experimental Data ◽  
Multiphase Flow ◽  
Gas Turbines ◽  
High Speed ◽  
Three Dimensional ◽  
Air Entrainment ◽  
Journal Bearings ◽  
Heavy Duty ◽  
Present Contribution ◽  
Two Phase

The traditional method for hydrodynamic journal bearing analysis usually applies the lubrication theory based on the Reynolds equation and suitable empirical modifications to cover turbulence, heat transfer, and cavitation. In cases of complex bearing geometries for steam and heavy-duty gas turbines this approach has its obvious restrictions in regard to detail flow recirculation, mixing, mass balance, and filling level phenomena. These limitations could be circumvented by applying a computational fluid dynamics (CFD) approach resting closer to the fundamental physical laws. The present contribution reports about the state of the art of such a fully three-dimensional multiphase-flow CFD approach including cavitation and air entrainment for high-speed turbo-machinery journal bearings. It has been developed and validated using experimental data. Due to the high ambient shear rates in bearings, the multiphase-flow model for journal bearings requires substantial modifications in comparison to common two-phase flow simulations. Based on experimental data, it is found, that particular cavitation phenomena are essential for the understanding of steam and heavy-duty type gas turbine journal bearings.

Experimental Characterization of a Modified Airlift Pump

2014 ◽  
Author(s):  
Afshin Goharzadeh ◽  
Keegan Fernandes
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
High Speed ◽  
Water Flow Rate ◽  
High Speed Photography ◽  
Two Phase ◽  
Inner Diameter ◽  
Airlift Pump ◽  
Flow Map ◽  
Churn Flow

This paper presents an experimental investigation on a modified airlift pump. Experiments were undertaken as a function of air-water flow rate for two submergence ratios (ε=0.58 and 0.74), and two different riser geometries (i) straight pipe with a constant inner diameter of 19 mm and (ii) enlarged pipe with a sudden expanded diameter of 19 to 32 mm. These transparent vertical pipes, of 1 m length, were submerged in a transparent rectangular tank (0.45×0.45×1.1 m3). The compressed air was injected into the vertical pipe to lift the water from the reservoir. The flow map regime is established for both configurations and compared with previous studies. The two phase air-water flow structure at the expansion region is experimentally characterized. Pipeline geometry is found to have a significant influence on the output water flow rate. Using high speed photography and electrical conductivity probes, new flow regimes, such as “slug to churn” and “annular to churn” flow, are observed and their influence on the output water flow rate and efficiency are discussed. These experimental results provide fundamental insights into the physics of modified airlift pump.

Dynamic Force and Torque Analysis of Spherical Four Link Mechanisms

1983 ◽  
Vol 105 (3) ◽  
pp. 492-497 ◽  
Author(s):  
A. T. Yang ◽  
Sun Zhishang
Keyword(s):  
Dynamic Analysis ◽  
Optimum Design ◽  
Mass Distribution ◽  
High Speed ◽  
Dynamic Force ◽  
Arbitrary Mass ◽  
Link Mechanism ◽  
Torque Analysis ◽  
Analytical Expressions

In this paper we present a dynamic analysis of a general spherical four-link mechanism whose links have arbitrary mass distribution. Results, which are in explicit analytical expressions in terms of inertia-induced forces and moments in links, are useful for optimum design of the mechanism under high-speed operation.

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