Numerical and Experimental Investigations on Preload Effects in Air Foil Journal Bearings

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Marcel Mahner ◽  
Pu Li ◽  
Andreas Lehn ◽  
Bernhard Schweizer
Keyword(s):  
Friction Torque ◽  
Fluid Film ◽  
Radial Clearance ◽  
Experimental Investigations ◽  
Hysteresis Curves ◽  
Numerical Predictions ◽  
Wide Range ◽  
Reaction Forces ◽  
Bearing Stiffness ◽  
Definition Of

A detailed elastogasdynamic model of a preloaded three-pad air foil journal bearing is presented. Bump and top foil deflections are herein calculated with a nonlinear beamshell theory according to Reissner. The two-dimensional pressure distribution in each bearing pad is described by the Reynolds equation for compressible fluids. The assembly preload is calculated by simulating the assembly process of top foil, bump foil, and shaft. Most advantageously, there is no need for the definition of an initial radial clearance in the presented model. With this model, the influence of the assembly preload on the static bearing hysteresis as well as on the aerodynamic bearing performance is investigated. For the purpose of model validation, the predicted hysteresis curves are compared with measured curves. The numerically predicted and the measured hysteresis curves show a good agreement. The numerical predictions exhibit that the assembly preload increases the elastic foil structural stiffness (in particular for moderate shaft displacements) and the bearing damping. It is observed that the effect of the fluid film on the overall bearing stiffness depends on the assembly preload: For lightly preloaded bearings, the fluid film affects the overall bearing stiffness considerably, while for heavily preloaded bearings the effect is rather small for a wide range of reaction forces. Furthermore, it is shown that the assembly preload increases the friction torque significantly.

Numerical and Experimental Investigations on Preload Effects in Air Foil Journal Bearings

2017 ◽  
Author(s):  
Marcel Mahner ◽  
Pu Li ◽  
Andreas Lehn ◽  
Bernhard Schweizer
Keyword(s):  
Reynolds Equation ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Compressible Fluids ◽  
Experimental Investigations ◽  
Hysteresis Curves ◽  
Numerical Predictions ◽  
Bearing Stiffness ◽  
Gasdynamic Model ◽  
Good Agreement

A detailed elasto-gasdynamic model of a preloaded three-pad air foil journal bearing is presented. Bump and top foil deflections are herein calculated with a nonlinear beamshell theory according to Reissner. The 2D pressure distribution in each bearing pad is described by the Reynolds equation for compressible fluids. With this model, the influence of the assembly preload on the static bearing hysteresis as well as on the aerodynamic bearing performance is investigated. For the purpose of model validation, the predicted hysteresis curves are compared with measured curves. The numerically predicted and the measured hysteresis curves show a good agreement. The numerical predictions exhibit that the assembly preload increases the bearing stiffness (in particular for moderate shaft displacements) and the bearing damping.

Numerical Characterization of Hot Gas Ingestion Through Turbine Rim Seals

2016 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Cosimo Bianchini ◽  
Carl M. Sangan ◽  
James A. Scobie ◽  
Gary D. Lock
Keyword(s):  
Flow Rate ◽  
Numerical Study ◽  
Axial Flow ◽  
Radial Clearance ◽  
Buffering Effect ◽  
Hot Gas ◽  
Numerical Predictions ◽  
Wide Range ◽  
Thermal Buffering

This paper deals with a numerical study aimed at the characterization of hot gas ingestion through turbine rim seals. The numerical campaign focused on an experimental facility which models ingress through the rim seal into the upstream wheel-space of an axial-turbine stage. Single-clearance arrangements were considered in the form of axial- and radial-seal gap configurations. With the radial-seal clearance configuration, CFD steady-state solutions were able to predict the system sealing effectiveness over a wide range of coolant mass flow rates reasonably well. The greater insight of flow field provided by the computations illustrates the thermal buffering effect when ingress occurs: for a given sealing flow rate, the effectiveness on the rotor was significantly higher than that on the stator due to the axial flow of hot gases from stator to rotor caused by pumping effects. The predicted effectiveness on the rotor was compared with a theoretical model for the thermal buffering effect showing good agreement. When the axial-seal clearance arrangement is considered, the agreement between CFD and experiments worsens; the variation of sealing effectiveness with coolant flow rate calculated by means of the simulations display a distinct kink. It was found that the “kink phenomenon” can be ascribed to an over-estimation of the egress spoiling effects due to turbulence modelling limitations. Despite some weaknesses in the numerical predictions, the paper shows that CFD can be used to characterize the sealing performance of axial- and radial-clearance turbine rim seals.

Performance Analysis of a Nonrecessed Hybrid Conical Journal Bearing Compensated With Capillary Restrictors

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Prashant G. Khakse ◽  
Vikas M. Phalle ◽  
S. S. Mantha
Keyword(s):  
Performance Analysis ◽  
Film Thickness ◽  
Journal Bearing ◽  
Fluid Film ◽  
Load Parameter ◽  
Radial Load ◽  
Wide Range ◽  
Bearing Stiffness ◽  
Fluid Film Thickness ◽  
Film Stiffness

The present paper deals with the performance analysis of a nonrecessed hole-entry hydrostatic/hybrid conical journal bearing with capillary restrictors. Finite element method has been used for solving the modified Reynolds equation governing the flow of lubricant in the clearance space of journal and bearing. The hole-entry hybrid conical journal bearing performance characteristics have been depicted for a wide range of radial load parameter (W¯r  = 0.25–1.5) with uniform distribution of holes at an angle of 30 deg in the circumferential direction. The numerically simulated results have been presented in terms of maximum fluid film pressure, minimum fluid film thickness, lubricant flow rate, direct fluid film stiffness coefficients, direct fluid film damping coefficients, and stability threshold speed. However, the proposed investigation of nonrecess hole-entry hybrid conical journal bearing shows important performance for bearing stiffness and minimum fluid film thickness at variable radial load and at given operating speed.

Numerical Characterization of Hot-Gas Ingestion Through Turbine Rim Seals

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Riccardo Da Soghe ◽  
Cosimo Bianchini ◽  
Carl M. Sangan ◽  
James A. Scobie ◽  
Gary D. Lock
Keyword(s):  
Flow Rate ◽  
Numerical Study ◽  
Axial Flow ◽  
Radial Clearance ◽  
Buffering Effect ◽  
Hot Gas ◽  
Numerical Predictions ◽  
Wide Range ◽  
Thermal Buffering

This paper deals with a numerical study aimed at the characterization of hot-gas ingestion through turbine rim seals. The numerical campaign focused on an experimental facility which models ingress through the rim seal into the upstream wheel-space of an axial-turbine stage. Single-clearance arrangements were considered in the form of axial- and radial-seal gap configurations. With the radial-seal clearance configuration, computational fluid dynamics (CFD) steady-state solutions were able to predict the system sealing effectiveness over a wide range of coolant mass flow rates reasonably well. The greater insight of flow field provided by the computations illustrates the thermal buffering effect when ingress occurs: For a given sealing flow rate, the effectiveness on the rotor was significantly higher than that on the stator due to the axial flow of hot gases from stator to rotor caused by pumping effects. The predicted effectiveness on the rotor was compared with a theoretical model for the thermal buffering effect showing good agreement. When the axial-seal clearance arrangement is considered, the agreement between CFD and experiments worsens; the variation of sealing effectiveness with coolant flow rate calculated by means of the simulations displays a distinct kink. It was found that the “kink phenomenon” can be ascribed to an overestimation of the egress spoiling effects due to turbulence modeling limitations. Despite some weaknesses in the numerical predictions, the paper shows that CFD can be used to characterize the sealing performance of axial- and radial-clearance turbine rim seals.

Steady State Performance Characteristics of Single Pad Externally Adjustable Fluid Film Bearing in the Laminar and Turbulent Regimes

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
B. S. Shenoy ◽  
R. Pai
Keyword(s):  
Steady State ◽  
Performance Characteristics ◽  
Fluid Film ◽  
Radial Clearance ◽  
Wide Range ◽  
Tilting Pad ◽  
Load Carrying ◽  
Static Performance ◽  
Laminar And Turbulent Regimes ◽  
Steady State Performance

In an externally adjustable fluid film bearing, the hydrodynamic conditions can be changed as required in a controlled manner. The principal feature of the bearing is the facility to adjust its radial clearance and circumferential film thickness gradient. Unlike a tilting pad bearing, this bearing can have radial adjustments. The tilt adjustments are obtained by providing flexibility to the pad at one corner. This paper deals with the effect of turbulence on the steady state performance characteristics of a centrally loaded 120 deg single pad externally adjustable fluid film bearing. The bearing has an aspect ratio of 1 and operates over a wide range of eccentricity ratios with different radial and tilt adjustments. The Reynolds equation is solved numerically using the finite difference method. The linearized turbulence model of Ng and Pan (1965, “A Linearized Turbulent Lubrication Theory,” ASME J. Basic Eng., 87, pp. 675–688) as well as the simplified adiabatic model of Pinkus and Bupara (1979, “Adiabatic Solutions for Finite Journal Bearings,” ASME J. Lubr. Technol., 101, pp. 492–496) are incorporated in the solution scheme. The static performance characteristics calculated are presented in terms of load carrying capacity, attitude angle, friction variable, and Sommerfeld number. A comparative study with the combination of adjustments predicts that the static performance of the bearing is superior with negative radial and tilt adjustments.

The Effect of Cavitation on the Vibration Behaviour of Nonlinear Rotor Bearing Systems

2006 ◽  
Author(s):  
Duc Pham ◽  
Ningsheng Feng ◽  
Eric Hahn
Keyword(s):  
Dynamic Properties ◽  
Fluid Film ◽  
Stable Operation ◽  
Rotor Bearing ◽  
Reaction Forces ◽  
Bearing Stiffness ◽  
Operation Stability ◽  
Bearing Force ◽  
Air Ingress ◽  
Stiffness And Damping

Rotor bearing systems frequently utilise hydrodynamic bearings whose dynamic properties are generally influenced by the bearing reaction forces (which determine the bearing stiffness and damping coefficients). These reaction forces are frequently unknown and are generally determined from the solution of the Reynolds equation using rotor motion measurements as input. Of interest is the attainable accuracy of such bearing force determinations, and for experimental evaluation, a test rig was fabricated, the design specification of which required that the rotor system run stably over its operating speed range. This paper describes the commissioning of this rig for stability purposes with the aid of natural frequency analyses, noting the required design modifications to ensure stable operation. Stability was found to be significantly influenced by the extent of the continuous fluid film in the hydrodynamic circumferentially grooved bearings. It was concluded that the assumption of a 180 degree film extent was totally inappropriate even though the bearing ends were open to the atmosphere, whereas the assumption of fluid film break up at the lubricant saturation vapour pressure proved appropriate for stability predictions provided one ensured that the bearings were flooded. Preliminary bearing force evaluations proved inconclusive, primarily because the self aligning bearings nevertheless experienced angular misalignment; and because there was uncertainty as to how much air was entrained in the bearings, in spite of attempts to prevent air ingress.

scholarly journals Measurement of the crankshaft seals friction losses in a modern passenger car diesel engine

2019 ◽  
Vol 234 (7) ◽  
pp. 1106-1113 ◽  
Author(s):  
Christoph Knauder ◽  
Hannes Allmaier ◽  
David E Sander ◽  
Theodor Sams
Keyword(s):  
Diesel Engine ◽  
Friction Torque ◽  
Experimental Investigations ◽  
Test Bed ◽  
Passenger Car ◽  
Wide Range ◽  
Speed Range ◽  
Lip Seals ◽  
Full Speed ◽  
Strip Test

This paper presents results of experimental investigations on the friction losses of the crankshaft radial lip seals of a modern four-cylinder diesel engine for passenger car applications. A two stage strip-test has been conducted on a motored engine test bed to obtain the friction torque of the radial lip seals. For the experimental investigations with the crankshaft seals removed from the engine, a special sealing apparatus has been designed and built. A wide range of tests have been performed covering the full speed range of the engine at lubricant temperatures of 70 ℃, 90 ℃, and 110 ℃. The results show a dependency on crankshaft speed and engine media supply temperature but also revealed the presence of constant plateaus of friction torque over engine speed.

scholarly journals Measurement of the Crankshaft Seals Friction Losses in a Modern Passenger Car Diesel Engine

2020 ◽  
Author(s):  
Christoph Knauder ◽  
Hannes Allmaier ◽  
David E Sander
Keyword(s):  
Diesel Engine ◽  
Friction Torque ◽  
Experimental Investigations ◽  
Test Bed ◽  
Passenger Car ◽  
Wide Range ◽  
Speed Range ◽  
Lip Seals ◽  
Full Speed ◽  
Strip Test

This paper presents results of experimental investigations on the friction losses of the crankshaft radial lip seals of a modern four-cylinder diesel engine for passenger car applications. A two stage strip-test has been conducted on a motored engine test bed to obtain the friction torque of the radial lip seals. For the experimental investigations with the crankshaft seals removed from the engine, a special sealing apparatus has been designed and built. A wide range of tests have been performed covering the full speed range of the engine at lubricant temperatures of 70 ℃, 90 ℃, and 110 ℃. The results show a dependency on crankshaft speed and engine media supply temperature but also revealed the presence of constant plateaus of friction torque over engine speed.

Typologization of security regulation

2020 ◽  
pp. 20-27
Author(s):  
Denis Tikhomirov
Keyword(s):  
Social Relations ◽  
Scientific Literature ◽  
Legal Regulation ◽  
Procedural Understanding ◽  
Limited Ability ◽  
Methodological Basis ◽  
Wide Range ◽  
The Subject ◽  
Definition Of ◽  
Legal Understanding

The purpose of the article is to typologize terminological definitions of security, to find out the general, to identify the originality of their interpretations depending on the subject of legal regulation. The methodological basis of the study is the methods that made it possible to obtain valid conclusions, in particular, the method of comparison, through which it became possible to correlate different interpretations of the term "security"; method of hermeneutics, which allowed to elaborate texts of normative legal acts of Ukraine, method of typologization, which made it possible to create typologization groups of variants of understanding of the term "security". Scientific novelty. The article analyzes the understanding of the term "security" in various regulatory acts in force in Ukraine. Typological groups were understood to understand the term "security". Conclusions. The analysis of the legal material makes it possible to confirm that the issues of security are within the scope of both legislative regulation and various specialized by-laws. However, today there is no single conception on how to interpret security terminology. This is due both to the wide range of social relations that are the subject of legal regulation and to the relativity of the notion of security itself and the lack of coherence of views on its definition in legal acts and in the scientific literature. The multiplicity of definitions is explained by combinations of material and procedural understanding, static - dynamic, and conditioned by the peculiarities of a particular branch of legal regulation, limited ability to use methods of one or another branch, the inter-branch nature of some variations of security, etc. Separation, common and different in the definition of "security" can be used to further standardize, in fact, the regulatory legal understanding of security to more effectively implement the legal regulation of the security direction.

Music after the Fall

2017 ◽  
Author(s):  
Tim Rutherford-Johnson
Keyword(s):  
New Media ◽  
Contemporary Music ◽  
The United States ◽  
Art Music ◽  
Sound Art ◽  
Musical Composition ◽  
Western Art ◽  
Wide Range ◽  
Definition Of ◽  
The Cold War

By the start of the 21st century many of the foundations of postwar culture had disappeared: Europe had been rebuilt and, as the EU, had become one of the world’s largest economies; the United States’ claim to global dominance was threatened; and the postwar social democratic consensus was being replaced by market-led neoliberalism. Most importantly of all, the Cold War was over, and the World Wide Web had been born. Music After The Fall considers contemporary musical composition against this changed backdrop, placing it in the context of globalization, digitization, and new media. Drawing on theories from the other arts, in particular art and architecture, it expands the definition of Western art music to include forms of composition, experimental music, sound art, and crossover work from across the spectrum, inside and beyond the concert hall. Each chapter considers a wide range of composers, performers, works, and institutions are considered critically to build up a broad and rich picture of the new music ecosystem, from North American string quartets to Lebanese improvisers, from South American electroacoustic studios to pianos in the Australian outback. A new approach to the study of contemporary music is developed that relies less on taxonomies of style and technique, and more on the comparison of different responses to common themes, among them permission, fluidity, excess, and loss.

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