A Study of the Effect of Various Recess Shapes on Hybrid Journal Bearing Performance Using Computational Fluid Dynamics and Response Surface Method

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Gen Fu ◽  
Alexandrina Untaroiu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Response Surface ◽  
Equilibrium Position ◽  
Journal Bearing ◽  
Response Surface Model ◽  
Dominant Factor ◽  
Surface Model ◽  
Cfd Model ◽  
Geometrical Shapes

Hybrid bearings are mostly used in high-speed and load situations due to their better stability and loading capacity. They are typically designed with recess grooves to enhance both static and dynamic performance of the bearing. Previous theoretical studies on the influence of the recess geometrical shapes often utilize the Reynolds equation method. The aim of this paper is to analytically study the influence of various recess geometrical shapes on hybrid journal bearings. A three-dimensional (3D) computational fluid dynamics (CFD) model of a hybrid journal bearing is built, and a new method of response surface model is employed to determine the equilibrium position of the rotor. Based on the response surface model, an optimization scheme is used to search around the equilibrium position to get an accurate solution. The current analysis includes the geometries of rectangular, circular, triangular, elliptical, and annular shaped recesses. All these different shapes are studied assuming the same operating conditions, and static properties are used as the indices of the bearing performance. This study proposes a new design process using a CFD method with the ability of calculating the equilibrium position. The flow rate, fluid film thickness, and recess flow pattern are analyzed for various recess shapes. The CFD model is validated by published experimental data. The results show that the response surface model method is fast and robust in determining the rotor equilibrium position, even though a 3D-CFD model is utilized. The results suggest that recess shape is a dominant factor in hybrid bearing design.

A Study of the Effect of Various Recess Shapes on Hybrid Journal Bearing Using CFD and Response Surface Method

2016 ◽  
Author(s):  
Gen Fu ◽  
Alexandrina Untaroiu
Keyword(s):  
Response Surface ◽  
Equilibrium Position ◽  
High Speed ◽  
Journal Bearing ◽  
Accurate Solution ◽  
Response Surface Model ◽  
Dominant Factor ◽  
Surface Model ◽  
Cfd Model ◽  
Geometrical Shapes

Hybrid bearings are mostly used in high speed and load situations due to their better stability and loading capacity. They are typically designed with recess grooves to enhance both static and dynamic performance of the bearing. Previous theoretical studies on the influence of the recess geometrical shapes often utilize the Reynolds equation method and most of the research focuses on thrust bearings. The aims of this paper is to analytically study the influence of various recess geometrical shapes on hybrid journal bearings. A 3-D CFD model of a hybrid journal bearing is built and a new method of response surface model is employed to determine the equilibrium position of the rotor. Based the response surface model, an optimization scheme is used to search around the equilibrium position to get a more accurate solution. The current analysis includes the recess geometry of rectangular, circular, triangular, elliptical and annular shapes. All these different shapes are studied assuming the same operating and loading conditions and bearing static properties are used as the indices of the bearing performance. The flow rate, fluid film thickness and recess flow pattern are analyzed for various recess shapes. The CFD model for the baseline bearing is validated against experimental data. The results show that the response surface model method is fast and robust in determining the rotor equilibrium position even though a 3-D CFD model is utilized. The results suggest that recess shape is a dominant factor in hybrid bearing design. This study proposed a new design process for a 3-D CFD bearing model with the ability of calculating equilibrium position and is expected to be useful to bearing designers.

scholarly journals Journal Bearing: An Integrated CFD-Analytical Approach for the Estimation of the Trajectory and Equilibrium Position

2020 ◽  
Vol 10 (23) ◽  
pp. 8573
Author(s):  
Franco Concli
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Distribution ◽  
Equilibrium Position ◽  
Analytical Approach ◽  
Journal Bearing ◽  
Cfd Model ◽  
Cavitation Model ◽  
Computational Fluid Dynamics Cfd ◽  
The Mathematical Model

For decades, journal bearings have been designed based on the half-Sommerfeld equations. The semi-analytical solution of the conservation equations for mass and momentum leads to the pressure distribution along the journal. However, this approach admits negative values for the pressure, phenomenon without experimental evidence. To overcome this, negative values of the pressure are artificially substituted with the vaporization pressure. This hypothesis leads to reasonable results, even if for a deeper understanding of the physics behind the lubrication and the supporting effects, cavitation should be considered and included in the mathematical model. In a previous paper, the author has already shown the capability of computational fluid dynamics to accurately reproduce the experimental evidences including the Kunz cavitation model in the calculations. The computational fluid dynamics (CFD) results were compared in terms of pressure distribution with experimental data coming from different configurations. The CFD model was coupled with an analytical approach in order to calculate the equilibrium position and the trajectory of the journal. Specifically, the approach was used to study a bearing that was designed to operate within tight tolerances and speeds up to almost 30,000 rpm for operation in a gearbox.

Computational Fluid Dynamics Based Mixing Prediction for Tilt Pad Journal Bearing TEHD Modeling—Part I: TEHD-CFD Model Validation and Improvements

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Jongin Yang ◽  
Alan Palazzolo
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Journal Bearing ◽  
Dynamic Performance ◽  
Three Dimensional ◽  
Prediction Method ◽  
Conventional Approach ◽  
Machine Learning Techniques ◽  
Prediction Errors ◽  
Cfd Model

Abstract The core contributions of Part I (1) present a computational fluid dynamics (CFD)-based approach for tilting pad journal bearing (TPJB) modeling including thermo-elasto hydrodynamic (TEHD) effects with multi-mode pad flexibility, (2) validate the model by comparison with experimental work, and (3) investigate the limitations of the conventional approach by contrasting it with the new approach. The modeling technique is advanced from the author’s previous work by including pad flexibility. The results demonstrate that the conventional approach of disregarding the three-dimensional flow physics between pads (BP) can generate significantly different pressure, temperature, heat flux, dynamic viscosity, and film thickness distributions, relative to the high-fidelity CFD model. The uncertainty of the assumed mixing coefficient (MC) may be a serious weakness when using a conventional, TPJB Reynolds model, leading to prediction errors in static and dynamic performance. The advanced mixing prediction method for “BP” thermal flow developed in Part I will be implemented with machine learning techniques in Part II to provide a means to enhance the accuracy of conventional Reynolds based TPJB models.

Comparison of flight test data with a computational fluid dynamics model of a Scottish Aviation Bulldog aircraft

2013 ◽  
Vol 117 (1198) ◽  
pp. 1273-1291 ◽  
Author(s):  
N. J. Lawson ◽  
N. Salmon ◽  
J. E. Gautrey ◽  
R. Bailey
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Test Data ◽  
Laser Scanner ◽  
Flight Test ◽  
Test Methods ◽  
Surface Model ◽  
Cfd Model ◽  
Ansys Fluent ◽  
Lift And Drag

Abstract The following paper presents detailed aerodynamic data of a Scottish Aviation Bulldog light aircraft. The data is taken from the pre-stall region of the aircraft flight envelope through two flight test methods and from a geometrically accurate computational fluid dynamics (CFD) model of the full scale aircraft, which was meshed in Ansys ICEM CFD and solved in Ansys Fluent. The fidelity of the CFD model was achieved by development of a CATIA solid model with surfaces matching a spatial point cloud of the aircraft taken using a 3D laser scanner. Following a CFD verification process, a 3·4m hybrid mesh with a Spalart-Allmaras (SA) turbulence model was found to give the best overall lift and drag characteristics. Further detailed comparisons with the glide flight test data showed the CFD drag polar to have 63% lower zero lift drag, although this discrepancy was related to the simplification of the original CATIA surface model, which excluded the undercarriage, aerials and other protuberance drags. Inclusion of estimates of these sources of drag resulted in a match in zero lift drag to within 15% and a maximum lift to drag of 10:1 which was within 11% of the glide flight test result. The remaining drag discrepancy is attributed to other effects including trim drag and the surface finish of the actual aircraft.

Three-Dimensional Thermo-Elasto-Hydrodynamic Computational Fluid Dynamics Model of a Tilting Pad Journal Bearing—Part I: Static Response

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Jongin Yang ◽  
Alan Palazzolo
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Boundary Conditions ◽  
Journal Bearing ◽  
Three Dimensional ◽  
Cfd Model ◽  
Flow And Heat Transfer ◽  
Tilting Pad ◽  
Tilting Pad Journal Bearing

This paper presents the first simulation model of a tilting pad journal bearing (TPJB) using three-dimensional (3D) computational fluid dynamics (CFD), including multiphase flow, thermal-fluid, transitional turbulence, and thermal deformation of the shaft and pads employing two-way fluid–structure interaction (FSI). Part I presents a modeling method for the static performance. The model includes flow between pads BP, which eliminates the use of an uncertain, mixing coefficient (MC) in Reynold's equation approaches. The CFD model is benchmarked with Reynold's model with a 3D thermal-film, when the CFD model boundary conditions are consistent with the Reynolds boundary conditions. The Reynolds model employs an oversimplified MC representation of the three-dimensional mixing effect of the BP flow and heat transfer, and it also employs simplifying assumptions for the flow and heat transfer within the thin film between the journal and bearing. This manufactured comparison shows good agreement between the CFD and Reynold's equation models. The CFD model is generalized by removing these fictitious boundary conditions on pad inlets and outlets and instead models the flow and temperature between pads. The results show that Reynold's model MC approach can lead to significant differences with the CFD model including detailed flow and thermal modeling between pads. Thus, the CFD approach provides increased reliability of predictions. The paper provides an instructive methodology including detailed steps for properly applying CFD to tilt pad bearing modeling. Parts I and II focus on predicting static and dynamic response characteristic responses, respectively.

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