A Model for Oil Flow and Fluid Temperature Inlet Mixing in Hydrodynamic Journal Bearings

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Thomas Hagemann ◽  
Hubert Schwarze
Keyword(s):  
Boundary Conditions ◽  
High Speed ◽  
Hydrodynamic Lubrication ◽  
Three Dimensional ◽  
Journal Bearings ◽  
Conductive Heat ◽  
Fluid Temperature ◽  
Inlet Region ◽  
Oil Flow ◽  
The Impact

The quality of predictions for the operating behavior of high-speed journal bearings strongly depends on realistic boundary conditions within the inlet region supplying a mixture of hot oil from the upstream pad and fresh lubricant from the inlet device to the downstream located pad. Therefore, an appropriate modeling of fundamental phenomena within the inlet region is essential for a reliable simulation of fluid and heat flow in the entire bearing. A theoretical model including hydraulic, mechanical, and energetic effects and the procedure of its numerical implementation in typical bearing codes for thermo-hydrodynamic lubrication is described and validated. Convective and conductive heat transfer as well as dissipation due to internal friction in the lubricant is considered for the space between pads or the pocket where the inlet is located. In contrast to most other models, the region between the physical inlet and the lubricant film is part of the solution domain and not only represented by boundary conditions. The model provides flow rate and temperature boundary conditions for extended Reynolds equation and a three-dimensional (3D) energy equation of film and inlet region, respectively. The impact of backflow from the inlet region to the outer supply channel possibly occurring in sealed pockets is taken into account. Moreover, the model considers the influence of turbulent flow in the inlet region.

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.

The Impact of Oil and Sealing Air Flow, Chamber Pressure, Rotor Speed, and Axial Load on the Power Consumption in an Aeroengine Bearing Chamber

2005 ◽  
Vol 127 (1) ◽  
pp. 182-186 ◽  
Author(s):  
Michael Flouros
Keyword(s):  
Power Consumption ◽  
High Speed ◽  
Air Flow ◽  
Flow Chamber ◽  
Chamber Pressure ◽  
Power Losses ◽  
Rolling Element ◽  
Oil Flow ◽  
The Impact ◽  
Circle Diameter

Trends in aircraft engines have dictated high speed rolling element bearings up to 3 million DN or more with the consequence of having high amounts of heat rejection in the bearing chambers and high oil scavenge temperatures. A parametric study on the bearing power consumption has been performed with a 124 mm pitch circle diameter (PCD) ball bearing in a bearing chamber that has been adapted from the RB199 turbofan engine DN∼2×106. The operating parameters such as oil flow, oil temperature, sealing air flow, bearing chamber pressure, and shaft speed have been varied in order to assess the impact on the power consumption. This work is the first part of a survey aiming to reduce power losses in bearing chambers. In the first part, the parameters affecting the power losses are identified and evaluated.

Influence of geometric parameters and operating conditions on the thermohydrodynamic behaviour of plain journal bearings

2000 ◽  
Vol 214 (5) ◽  
pp. 445-457 ◽  
Author(s):  
I Pierre ◽  
M Fillon
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Three Dimensional ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Thermal Dissipation ◽  
Radial Clearance ◽  
Geometric Factors ◽  
Essential Components ◽  
Mass Flowrate

Hydrodynamic journal bearings are essential components of high-speed machinery. In severe operating conditions, the thermal dissipation is not a negligible phenomenon. Therefore, a three-dimensional thermohydrodynamic (THD) analysis has been developed that includes lubricant rupture and re-formation phenomena by conserving the mass flowrate. Then, the predictions obtained with the proposed numerical model are validated by comparison with the measurements reported in the literature. The effects of various geometric factors (length, diameter and radial clearance) and operating conditions (rotational speed, applied load and lubricant) on the journal bearing behaviour are analysed and discussed in order to inform bearing designers. Thus, it can be predicted that the bearing performance obtained highly depends on operating conditions and geometric configuration.

Performance Evaluation of Magnetohydrodynamic Bearing

2005 ◽  
Author(s):  
H. Hirani ◽  
P. Samanta
Keyword(s):  
High Speed ◽  
Permanent Magnets ◽  
Magnetic Levitation ◽  
Hydrodynamic Lubrication ◽  
Low Cost ◽  
Low Friction ◽  
Oil Flow ◽  
Hybrid Bearing ◽  
Commercial Applications ◽  
Structural Simplicity

The present paper introduces a concept of hydrodynamic-permanent-magnetic hybrid bearing. The hybrid bearing uses repulsive force between permanent magnets and fluid force developed due to relative speed in a single assembly arrangement. Repulsive type passive magnetic levitation has advantage of minimum starting torque. Hydrodynamic lubrication mechanism has advantage of low friction at medium and high speed. This hybridization will be an attractive choice in commercial applications for its low cost, structural-simplicity and no metal-to-metal contact. An experimental setup is designed and developed to investigate the performance characteristics of proposed concept of hybrid bearing. Minimum film thickness, oil flow rate, and temperature rise are recorded at various speed- and load- conditions. Results are plotted to demonstrate the behavior of hybrid bearing arrangement.

Investigation of Dynamic Photoelasticity Based on a Three-Dimensional Model

2011 ◽  
Vol 83 ◽  
pp. 261-266
Author(s):  
Bin Li ◽  
Guo Biao Yang ◽  
Fan Ni ◽  
Qi Rong Zhu
Keyword(s):  
Boundary Conditions ◽  
High Speed ◽  
Three Dimensional ◽  
Green Laser ◽  
Structure Design ◽  
Dynamic Photoelasticity ◽  
Three Dimensional Model ◽  
Design And Optimization ◽  
True Value ◽  
Dimensional Models

Dynamic photoelasticity has been widely utilized to investigate the phenomena generated by impact loading. The dynamic parameters of structures, such as propagation of stress wave and stress concentration, are obtained through this method, which provide guidelines for structure design and optimization. In the previous studies, two-dimensional models are wildly used by researchers. In these models, the inaccuracy of the boundary conditions leads to error amplification during the conversion of the tested results into real ones. In this study of dynamic photoelasticity, three-dimensional models are used. An improved digital dynamic photoelastic system is also adopted to calculate elastic wave propagation in the medium, where the diode-pumped solid-state green laser and high-speed CCD are used as light source luminaries and recording system respectively. Based on these models, where the boundary conditions approach to true value, the resulting data are higher in resolution than is possible with other experimental techniques. This method has been adopted and tested successfully by generating better results with less amplification of errors.

The effect analysis of an engine jet on an aircraft blast deflector

2018 ◽  
Vol 41 (4) ◽  
pp. 990-1001
Author(s):  
Song Ma ◽  
Jianguo Tan ◽  
Xiankai Li ◽  
Jiang Hao
Keyword(s):  
High Temperature ◽  
Flow Field ◽  
High Speed ◽  
Deflection Angle ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Aircraft Engine ◽  
Experimental Results ◽  
Exhaust Gases ◽  
The Impact

This paper establishes a novel mathematical model for computing the plume flow field of a carrier-based aircraft engine. Its objective is to study the impact of jet exhaust gases with high temperature, high speed and high pressure on the jet blast deflector. The working condition of the nozzle of a fully powered on engine is first determined. The flow field of the exhaust jet is then numerically simulated at different deflection angle using the three-dimensional Reynolds averaged Navier–Stokes equations and the standard [Formula: see text]-[Formula: see text] turbulence method. Moreover, infra-red temperature tests are further carried out to test the temperature field when the jet blast deflector is at the [Formula: see text] deflection angle. The comparison between the simulation results and the experimental results show that the proposed computation model can perfectly describe the system. There is only 8–10% variation between them. A good verification is achieved. Moreover, the experimental results show that the jet blast deflector plays an outstanding role in driving the high-temperature exhaust gases. It is found that [Formula: see text] may be the best deflection angle to protect the deck and the surrounding equipment effectively. These data results provide a valuable basis for the design and layout optimization of the jet blast deflector and deck.

Incorporation of THD Boundary Conditions for the Efficient Evaluation of Journal Bearing Performance

2007 ◽  
Author(s):  
P. S. Keogh ◽  
M. M. Khonsari
Keyword(s):  
Boundary Conditions ◽  
High Speed ◽  
Current Practice ◽  
Journal Bearing ◽  
Coefficient Matrix ◽  
Journal Bearings ◽  
Heat Fluxes ◽  
Solid Component ◽  
Influence Coefficient ◽  
Thermal Boundary Conditions

The evaluation of the thermohydrodynamic (THD) performance of journal bearings continues to be an important issue. This is particularly so for high speed or heavily loaded bearing designs. This paper focuses attention on the thermal boundary conditions at the lubricant-bearing interface. The solid component conduction problem is solved in advance of the main THD analysis. Boundary conditions are then imposed on the lubricant THD analysis through use of an appropriate influence coefficient matrix that incorporates the solid component conduction problem. This avoids the current practice of solving the lubricant and solid component problems separately in an iterative loop to achieve continuous temperatures and heat fluxes at the interface. Instead, only the lubricant problem needs to be solved using the boundary conditions imposed by the influence coefficient matrix.

scholarly journals Impact of Inflow Boundary Conditions on the Calculation of CT-Based FFR

Fluids ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 60 ◽  
Author(s):  
Ernest Lo ◽  
Leon Menezes ◽  
Ryo Torii
Keyword(s):  
Boundary Conditions ◽  
Coronary Arteries ◽  
Three Dimensional ◽  
Patient Specific ◽  
Fractional Flow ◽  
Anatomical Models ◽  
Diastolic Phase ◽  
Flow Reserve ◽  
Population Average ◽  
The Impact

Background: Calculation of fractional flow reserve (FFR) using computed tomography (CT)-based 3D anatomical models and computational fluid dynamics (CFD) has become a common method to non-invasively assess the functional severity of atherosclerotic narrowing in coronary arteries. We examined the impact of various inflow boundary conditions on computation of FFR to shed light on the requirements for inflow boundary conditions to ensure model representation. Methods: Three-dimensional anatomical models of coronary arteries for four patients with mild to severe stenosis were reconstructed from CT images. FFR and its commonly-used alternatives were derived using the models and CFD. A combination of four types of inflow boundary conditions (BC) was employed: pulsatile, steady, patient-specific and population average. Results: The maximum difference of FFR between pulsatile and steady inflow conditions was 0.02 (2.4%), approximately at a level similar to a reported uncertainty level of clinical FFR measurement (3–4%). The flow with steady BC appeared to represent well the diastolic phase of pulsatile flow, where FFR is measured. Though the difference between patient-specific and population average BCs affected the flow more, the maximum discrepancy of FFR was 0.07 (8.3%), despite the patient-specific inflow of one patient being nearly twice as the population average. Conclusions: In the patients investigated, the type of inflow boundary condition, especially flow pulsatility, does not have a significant impact on computed FFRs in narrowed coronary arteries.

Experimental investigation of the aerodynamic drag of roof-mounted insulators for trains

2019 ◽  
Vol 234 (8) ◽  
pp. 834-846
Author(s):  
Jonathan Tschepe ◽  
Jörg-Torsten Maaß ◽  
Christian Navid Nayeri ◽  
Christian Oliver Paschereit
Keyword(s):  
Boundary Conditions ◽  
Energy Demand ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Aerodynamic Resistance ◽  
Reynolds Numbers ◽  
Experimental Investigations ◽  
Flexible Material ◽  
High Speed Trains ◽  
The Impact

This paper presents the results of experimental investigations on the aerodynamic drag of roof-mounted insulators for use on low- and high-speed trains. Wind tunnel investigations at different Reynolds numbers in the subcritical, critical, and supercritical flow regime were performed, in addition to investigations using wall-mounted cylinders. Furthermore, the impact of insulator sheds made of flexible material was analyzed. For a better understanding of the aerodynamic behavior of the insulators when mounted on trains, different boundary conditions representing realistic configurations as found on the roof of trains were simulated. From the measured drag, the energy demand to overcome the aerodynamic resistance of different types of insulators was calculated. Depending on the above mentioned boundary conditions, a noticeable contribution of the insulators to the entire train's aerodynamic drag could be observed. With flexible insulator sheds, a further increased air resistance was observed with the onset of fluttering. Similar to the cylinder, the aerodynamic behavior of the insulators depends on the respective Reynolds number.

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