scholarly journals Simulation of a Simplified Aeroengine Bearing Chamber Using a Fully Coupled Two-way Eulerian Thin Film/Discrete Phase Approach Part II: Droplet Behaviour in the Chamber

2021 ◽  
Author(s):  
Andrew Nicoli ◽  
Kathy Johnson ◽  
Richard J Jefferson-Loveday
Keyword(s):  
Thin Film ◽  
Film Surface ◽  
Research Centre ◽  
Operational Parameters ◽  
Axial Loads ◽  
Two Phase ◽  
Oil Flow ◽  
Discrete Phase ◽  
Edge Separation ◽  
Fully Coupled

Abstract Within aeroengines, bearing chambers exhibit a highly complex two-phase environment as a result of the complex air/oil interactions. The desire to operate at higher temperatures and shaft speeds requires sufficient understanding of these systems for design optimisation. Typically, bearings are used to support the radial and axial loads transmitted by the shafts, requiring oil for lubrication and cooling. These bearings are housed in bearing chambers sealed using airblown seals. Efficient scavenging systems ensure the oil is collected and returned to tank avoiding any unnecessary working of the oil. Previous work at the Gas Turbine and Transmissions Research Centre (G2TRC) has highlighted the need for an adequate computational model that can appropriately model the oil shedding behaviour from such bearings. Oil can breakup forming droplets and ligaments, subsequently forming thin and thick films driven by both gravity and shear. The objective of this paper is to explore the modelling capability of fully two-way coupled Eulerian thin film/discrete phase models (ETFM-DPM) applied to our simplified bearing chamber configuration. The models are created using OpenFOAM and two-way coupling is employed, enabling Lagrangian droplets to either impinge on the film surface or be removed through effects such as film stripping, splashing or edge separation. This paper focuses on the droplets, presenting statistics relating to size, velocity, impingement and residence time providing insight into solution sensitivity to operational parameters including shaft speed and oil flow rate. This extends upon our previously published work and improves bearing chamber modelling capability.

scholarly journals Simulation of a Simplified Aeroengine Bearing Chamber Using a Fully Coupled Two-Way Eulerian Thin Film/Discrete Phase Approach Part I: Film Behaviour Near The Bearing

2021 ◽  
Author(s):  
Andrew Nicoli ◽  
Kathy Johnson ◽  
Richard J Jefferson-Loveday
Keyword(s):  
Thin Film ◽  
Experimental Data ◽  
Film Thickness ◽  
Gas Turbine ◽  
Residence Time ◽  
Research Centre ◽  
Shaft Speed ◽  
Oil Flow ◽  
Discrete Phase ◽  
Fully Coupled

Abstract Previous work at the Gas Turbine and Transmissions Research Centre (G2TRC) has highlighted the need for an adequate computational model that can appropriately model the oil shedding behaviour from bearings. Oil can breakup forming droplets and ligaments, subsequently forming thin and thick films driven by both gravity and shear. Our previously published work using OpenFOAM successfully coupled the Eulerian thin film model (ETFM) with the discrete phase model (DPM) [1]. In this paper, the previously developed ETFM-DPM capability is, for the first time, extended to an aeroengine representative bearing chamber configuration. The configuration matches that of a simplified aeroengine bearing chamber that has been investigated by researchers at the Gas Turbine and Transmissions Research Centre (G2TRC). Numerical investigations are conducted for three different shaft speeds: 5,000, 7,000 and 12,000 rp; at two oil flow rates: 7.3 l/min and 5.2 l/min. CFD results are validated against existing experimental data for the two lower shaft speeds. Evaluation of computed mean film thickness shows excellent agreement with the experimental data. Results show that there is a diminishing reduction of film thickness with an increasing shaft speed. The computational study allows investigation of oil residence time in the annulus near the bearing. Residence time is seen to reduce with increasing shaft speed and with increasing oil flow rate. This CFD investigation represents the first successful fully coupled two-way ETFM-DPM investigation for bearing chamber applications, establishing a firm foundation for future aeroengine bearing chamber modelling.

scholarly journals Numerical Simulation of Solid-Fluid 2-Phase-Flow of Cutting System for Cutter Suction Dredgers

2018 ◽  
Vol 25 (s2) ◽  
pp. 117-124 ◽  
Author(s):  
Min Zhang ◽  
Shidong Fan ◽  
Hanhua Zhua ◽  
Sen Han
Keyword(s):  
Flow Characteristics ◽  
Continuous Phase ◽  
Parameters Optimization ◽  
Phase Flow ◽  
Operational Parameters ◽  
Two Phase ◽  
Rotating Speed ◽  
Discrete Phase ◽  
Different Characteristics ◽  
Cutting System

Abstract The study of the flow characteristics of the solid-fluid two phase flow in the cutter suction dredger is very important for exploring the slurry formation mechanism and optimizing the operational parameters. In this study, standard k-ε model and Multiple Reference Frame are applied to numerically simulate flow field in and around the cutting system, then with the steady convergent result of the simulation as the initial condition, Discrete Phase Mode is used to solve the particle motion equation by fully coupling the continuous phase and the particles. The influence of suction flow velocity and cutter’s rotating speed on particles suction are analyzed, and effectively suctioned particles numbers are also quantitatively studied. The simulation result shows that the DPM model is able to simulate the movement of particles in and around the cutter suction dredger’s cutting system, in the fluid flow filed velocity vector and pressure distribution on different planes show different characteristics, and under higher suction velocity and lower cutter rotating speed more particles are suctioned into the suction inlet. The results can help better understand flow characteristics of solid-fluid 2-phase-flow of cutter suction dredger’s cutting system, and provide theoretical support for relative system design and operational parameters optimization.

A New OpenFOAM Solver Capable of Modelling Oil Jet-Breakup and Subsequent Film Formation for Bearing Chamber Applications

2019 ◽  
Author(s):  
Andrew Nicoli ◽  
Richard Jefferson-Loveday ◽  
Kathy Simmons
Keyword(s):  
Experimental Data ◽  
Film Thickness ◽  
High Speed ◽  
Surface Film ◽  
Thin Liquid Film ◽  
Research Centre ◽  
Source Terms ◽  
Thickness Measurements ◽  
Edge Separation ◽  
Fully Coupled

Abstract To create an adequate computational model of oil behaviour in an aeroengine bearing chamber previous work at the Gas Turbine and Transmissions Research Centre (G2TRC) suggests it is necessary to be able to model oil shedding from bearings, breaking up into droplets/ligaments and forming thin and thick films driven by gravity and shear. Our previously published work using Fluent successfully coupled volume of fluid with the Eulerian thin film model (ETFM) and identified the challenges coupling the ETFM with the discrete phase modelling (DPM). For this latter work comparison was made to published experimental and modelling data in which a jet is injected into a duct breaking up into droplets before forming a wall film. In this paper the use of the open-source CFD code OpenFOAM is investigated for this application recognising that such an approach eliminates some of the restrictions in a commercial product. A transient solver for spray particle cloud modelling and thin liquid film transport (sprayParcelFilmFoam) has been developed and incorporated within OpenFOAM. Fully coupled DPM-ETFM is presented, capable of modelling both primary atomization and secondary breakup. In addition two new film sub-models have been implemented for film stripping and edge separation. In order to achieve accurate statistical representation of droplets, modifications to the DPM particle injector code were implemented. CFD results are validated against published high speed imaging and phase Doppler experimental data and in addition there is a comparison to computational results obtained using ANSYS Fluent. The fidelity of both the solver and the novel surface film sub-models are evaluated against average film thickness measurements along the duct centreline. With the inclusion of both film stripping and edge separation, a normalized root mean squared deviation of 5.1 % was achieved when compared to film thickness measurements, improving significantly on the results obtained with Fluent. A comparison with experimental data of particle diameters and velocities downstream of the expansion edge gives good qualitative agreement. Future work is recommended to provide a better formulation for the edge-separated droplet diameters. Analysis of film momentum source terms highlights the necessity for including both the gas and hydrostatic pressure source terms within the film momentum transport equation. This CFD investigation has successfully established a fully coupled two-way DPM-ETFM approach. This work illustrates an advance in bearing chamber modelling capability and has established a necessary foundation for future aeroengine bearing chamber film modelling.

Computationally Efficient Modelling of Oil Jet-Breakup and Film Formation for Bearing Chamber Applications

2018 ◽  
Author(s):  
Jee Loong Hee ◽  
Kathy Simmons ◽  
Bruce Kakimpa ◽  
David Hann
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
Film Formation ◽  
Viscous Sublayer ◽  
Current Data ◽  
Turbulent Dispersion ◽  
Research Centre ◽  
Shear Stresses ◽  
Two Phase ◽  
Injection Point

In previously published experimental work completed at the Gas Turbine and Transmissions Research Centre (G2TRC), oil fed to an aeroengine location bearing via underrace feed was seen to shed from the cage, forming a film on static surfaces near the bearing and subsequently shedding into the bearing chamber. A high-fidelity computational model of the two-phase flow in an aeroengine bearing chamber must adequately reproduce such behaviour but there are significant challenges in modelling both the oil breakup after shedding and the subsequent film formation. It is very computationally costly to resolve an oil film interface using the Volume of Fluid (VOF) approach at regions of thin film and it is unacceptably inaccurate to resolve thick film using an explicit thin film modelling technique such as the Eulerian Thin Film Model (ETFM). A proposed solution is to couple together VOF, ETFM and discrete phase modelling (DPM). Previously published G2TRC work shows how VOF and ETFM can be successfully coupled. This paper investigates the coupling of ETFM and DPM. The evaluation of film momentum transport and air-particle momentum transfer/Lagrangian particle tracking are studied using a low Reynolds number turbulence model. Validation is required to ensure that these models work together as intended. To this end a preliminary CFD study was carried out on a published case investigated experimentally and computationally in which a jet is injected into a duct via a nozzle, breaking up into droplets before forming a wall film. The droplets are produced by primary atomization due to liquid instabilities at the injection point. Secondary breakup occurs due to surface instabilities prompted by the high-velocity cross-flow. Small droplets are transported downstream whereas larger droplets deflect minimally hitting the wall and forming a thin film. In the work presented here quantitative film thickness data from experiments and prior simulations are compared to current data. The success of the simulation is found to depend on shear-transportation, turbulent dispersion of the particles, particle grouping, mass transportation as well as accurate prediction of interfacial shear-stresses. With suitable modelling parameters it was possible to predict film thickness to within 28.9% of those seen experimentally. The present ETFM-DPM modelling showed improvements over previously published models in prediction of shear-stresses and film transportation as the ω-equation could be integrated through the viscous sublayer. The developed approach is now mature enough to be applied to the bearing chamber geometry investigated experimentally at G2TRC and this is proposed for future work.

Numerical DPM Model for Two-Phase Flow in Aero-Engine Bearing Chamber

2011 ◽  
Vol 201-203 ◽  
pp. 2267-2270 ◽  
Author(s):  
Rang Shu Xu ◽  
Juan Juan Wang ◽  
Wei Xu ◽  
Li Bo Liu
Keyword(s):  
Two Phase Flow ◽  
Lubricating Oil ◽  
Phase Flow ◽  
Lubrication System ◽  
Discrete Phase Model ◽  
Main Bearing ◽  
Two Phase ◽  
Aero Engine ◽  
Oil Flow ◽  
Discrete Phase

The main bearing chamber is a major part of the lubrication system in aero-engine, it is important to know the influence of operation parameters on air/oil two-phase flow, so as to optimize the design of aero-engine lubrication system. The air/oil two-phase flow in a simplified bearing chamber model in an aero-engine is simulated by means of discrete phase model (DPM) and wall-film model with CFD approach. The simulation results coincide with the existing experimental data. The oil film thickness and concentration of droplets in bearing chamber are presented at different rotational speeds and different lubricating oil flow rates.

Stoichiometric composition of thin-film surface structures and its influence on the functional characteristics as regards gyroscopic devices

2020 ◽  
pp. 78-90
Author(s):  
M. A. Tit ◽  
S. N. Belyaev
Keyword(s):  
Thin Film ◽  
Titanium Nitride ◽  
Niobium Carbide ◽  
Structural Phase ◽  
Stoichiometric Composition ◽  
Film Surface ◽  
Surface Structures ◽  
Functional Surface ◽  
Base Surface ◽  
Thin Film Surface

This article considers the research results of the effect of stoichiometry on the properties of titanium nitride thin-film coatings of the float and electrostatic gyroscopes. It presents the results of tests of such mechanical and optical characteristics of titanium nitride thin-film structures as microhardness, resistance to wear and friction, and image contrast determined by the reflection coefficients of a titanium nitride base surface and a raster pattern formed by local laser oxidation. When making a rotor of a cryogenic gyroscope, the prospects of use and technological methods for the formation of functional surface structures of niobium carbide and nitride are considered. It is shown that during the formation of coatings of the required composition, the most important is the thermodynamic estimation of possible interactions. These interactions allow us to accomplish the structural-phase modification of the material, which is determined by the complex of possible topochemical reactions leading to the formation of compounds, including non-stoichiometric composition.

Atomic Layer Deposition of Chalcogenides for Next-Generation Phase Change Memory

2021 ◽  
Author(s):  
Yoon Kyeung Lee ◽  
Chanyoung Yoo ◽  
Woohyun Kim ◽  
Jeongwoo Jeon ◽  
Cheol Seong Hwang
Keyword(s):  
Thin Film ◽  
Atomic Layer Deposition ◽  
Film Growth ◽  
Phase Change Memory ◽  
Film Surface ◽  
Atomic Layer ◽  
Thin Film Growth ◽  
Growth Technique ◽  
Layer Deposition ◽  
Change Memory

Atomic layer deposition (ALD) is a thin film growth technique that uses self-limiting, sequential reactions localized at the growing film surface. It guarantees exceptional conformality on high-aspect-ratio structures and controllability...

Exotic Doping for Zno Thin Films: Possibility of Monolithic Optical Integrated Circuit

1999 ◽  
Vol 574 ◽  
Author(s):  
Norifumi Fujimura ◽  
Tamaki Shimura ◽  
Toshifumi Wakano ◽  
Atsushi Ashida ◽  
Taichiro Ito
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Nonlinear Optic ◽  
Integrated Circuit ◽  
Film Surface ◽  
Zno Thin Films ◽  
Process Window ◽  
Electro Optic ◽  
Film Substrate ◽  
Optical Integrated Circuit

AbstractWe propose the application of ZnO:X (X = Li, Mg, N, In, Al, Mn, Gd, Yb etc.) films for a monolithic Optical Integrated Circuit (OIC). Since ZnO exhibits excellent piezoelectric effect and has also electro-optic and nonlinear optic effects and the thin films are easily obtained, it has been studied as one of the important thin film wave guide materials especially for an acoustooptic device[1]. In terms of electro-optic and nonlinear optic effects, however, LiNbO3 or LiTaO3 is superior to ZnO. The most important issue of thin film waveguide using such ferroelectrics is optical losses at the film/substrate interface and the film surface, because the process window to control the surface morphology is very narrow due to their high deposition temperature. Since ZnO can be grown at extremely low temperature, the roughness at the surface and the interface is expected to be minimized. This is the absolute requirement especially for waveguide using a blue or ultraviolet laser. Recently, lasing at the wavelength of ultraviolet, ferroelectric and antiferromagnetic behaviors of ZnO doped with various exotic elements (exotic doping) have been reported. This paper discusses the OIC application of ZnO thin films doped with exotic elements.

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