Numerical Investigation of Two Phase Flow in a Dual Drive Booster (DDB)

2019 ◽  
Author(s):  
Arun Prabhakar ◽  
Stephen Ambrose ◽  
Herve Morvan
Keyword(s):  
Power Systems ◽  
Flow Behavior ◽  
Operating Conditions ◽  
Multiphase Model ◽  
Computational Domain ◽  
Two Phase ◽  
Ansys Fluent ◽  
Oil Flow ◽  
Gear Box ◽  
Polyhedral Grid

Abstract Recent efforts have been devoted in developing cutting edge methods and technologies to overcome the complications involved in extracting power from the spools in turbofan engines to drive the power systems in aircraft. In a contemporary turbofan engine design, a Dual Drive Booster turbofan (DDBTF) summation gear box is employed to derive power from the low pressure (LP) and high pressure (HP) spools. This paper aims to investigate the scavenging of lubrication oil from the Dual Drive Booster gearbox. It is essential that that the scavenging of oil from the gearbox is efficient to eradicate risks that may arise when oil resides in the gear box for prolonged durations. Longer residence times of oil in the gearbox can lead to rapid oil degradation. Simulations were conducted on a previously optimized geometry and the work in this paper will focus on investigating the effect of different operating conditions on the scavenging performance of the scavenge chamber. The effect of attitude, altitude and the inlet flow rate of oil have been simulated to understand their influence on the oil flow behavior. Emphasis is given on the predicting potential oil churning, recirculation and pooling behaviors in the scavenge chamber that encloses the gear box. Numerical Investigations are carried out using ANSYS Fluent. The Volume of Fluid (VOF) multiphase model is employed to model the multiphase flow arising between air and oil in the system and the effects of turbulence are modelled using the standard k-ϵ model. The computational domain is discretized using a polyhedral grid comprising of 4 million cells which was adopted based on grid independency tests that were conducted prior to the main simulations. Validation against published experimental data for similar flow regimes was also carried out. Results indicate that the scavenging performance is not affected significantly under the various operating conditions and scenarios that were investigated. This is because the effects of the windage outweigh the effects caused by the different operating conditions that are imposed to the scavenge chamber. The windage in the system drives the oil efficiently out from the chamber with the aid of the tangential sump (shown in Figure 4). Oil is distributed in an axially central section of the chamber and the total residence mass of oil is compared and under 0.5 kg for all the cases presented in this paper.

scholarly journals Multiphase CFD Modeling of External Oil Flow From a Journal Bearing

2018 ◽  
Author(s):  
Martin Berthold ◽  
Hervé Morvan ◽  
Richard Jefferson-Loveday ◽  
Benjamin C. Rothwell ◽  
Colin Young
Keyword(s):  
Boundary Conditions ◽  
Journal Bearing ◽  
Flow Behavior ◽  
Phase Interface ◽  
Numerical Schemes ◽  
Ansys Fluent ◽  
Oil Film ◽  
Reconstruction Scheme ◽  
Geometric Reconstruction ◽  
Oil Flow

High loads and bearing life requirements make journal bearings a potential choice for use in high power, epicyclic gearboxes in jet engines. Particularly in a planetary configuration the kinematic conditions are complex. With the planet gears rotating about their own axis and orbiting around the sun gear, centrifugal forces generated by both motions interact with each other and affect the external flow behavior of the oil exiting the journal bearing. Computational Fluid Dynamics (CFD) simulations using the Volume of Fluid (VoF) method are carried out in ANSYS Fluent [1] to numerically model the two-phase flow behavior of the oil exiting the bearing and merging into the air surrounding the bearing. This paper presents an investigation of two numerical schemes that are available in ANSYS Fluent to track or capture the air-oil phase interface: the geometric reconstruction scheme and the compressive scheme. Both numerical schemes are used to model the oil outflow behavior in the most simplistic approximation of a journal bearing: a representation, rotating about its own axis, with a circumferentially constant, i.e. concentric, lubricating gap. Based on these simplifications, a three dimensional (3D) CFD sector model with rotationally periodic boundaries is considered. A comparison of the geometric reconstruction scheme and the compressive scheme is presented with regards to the accuracy of the phase interface reconstruction and the time required to reach steady state flow field conditions. The CFD predictions are validated against existing literature data with respect to the flow regime, the direction of the predicted oil flow path and the oil film thickness. Based on the findings and considerations of industrial requirements, a recommendation is made for the most suitable scheme to be used. With a robust and partially validated CFD model in place, the model fidelity can be enhanced to include journal bearing eccentricity. Due to the convergent-divergent gap and the resultant pressure field within the lubricating oil film, the outflow behavior can be expected to be very different compared to that of a concentric journal bearing. Naturally, the inlet boundary conditions for the oil emerging from the journal bearing into the external environment must be consistent with the outlet conditions from the bearing. The second part of this paper therefore focuses on providing a method to generate appropriate inlet boundary conditions for external oil flow from an eccentric journal bearing.

scholarly journals Verification and Validation of a Methodology to Numerically Generate Waves Using Transient Discrete Data as Prescribed Velocity Boundary Condition

2021 ◽  
Vol 9 (8) ◽  
pp. 896
Author(s):  
Rafael P. Maciel ◽  
Cristiano Fragassa ◽  
Bianca N. Machado ◽  
Luiz A. O. Rocha ◽  
Elizaldo D. dos Santos ◽  
...  
Keyword(s):  
Boundary Condition ◽  
Numerical Analysis ◽  
Laboratory Experiment ◽  
Ocean Waves ◽  
Discrete Data ◽  
Multiphase Model ◽  
Computational Domain ◽  
Regular Waves ◽  
Ansys Fluent ◽  
Wave Channel

This work presents a two-dimensional numerical analysis of a wave channel and a oscillating water column (OWC) device. The main goal is to validate a methodology which uses transient velocity data as a means to impose velocity boundary condition for the generation of numerical waves. To achieve this, a numerical wave channel was simulated using regular waves with the same parameters as those used in a laboratory experiment. First, these waves were imposed as prescribed velocity boundary condition and compared with the analytical solution; then, the OWC device was inserted into the computational domain, aiming to validate this methodology. For the numerical analysis, computational fluid dynamics ANSYS Fluent software was employed, and to tackle with water–air interaction, the nonlinear multiphase model volume of fluid (VOF) was applied. Although the results obtained through the use of discrete data as velocity boundary condition presented a little disparity; in general, they showed a good agreement with laboratory experiment results. Since many studies use regular waves, there is a lack of analysis with ocean waves realistic data; thus, the proposed methodology stands out for its capacity of using realistic sea state data in numerical simulations regarding wave energy converters (WECs).

Numerical Research of the Effect of the Outlet Diameter of Diffuser on the Performance and the Radial Force in a Single-Stage Centrifugal Pump

2014 ◽  
Author(s):  
Jiang Wei ◽  
Li Guojun ◽  
Liu Pengfei ◽  
Zhang Lisheng ◽  
Qing Hongyang
Keyword(s):  
Centrifugal Pump ◽  
Radial Force ◽  
Numerical Results ◽  
Operating Conditions ◽  
Single Stage ◽  
Navier Stokes ◽  
Computational Domain ◽  
Ansys Fluent ◽  
Vaned Diffuser ◽  
Unsteady Numerical Simulation

In this paper, a single-stage pump with diffuser vanes of different outlet diameters has been investigated both numerically and experimentally. The influence of the diffuser vane outlet diameter on pump hydraulic performance and on the radial force of the impeller is explored. Pumps equipped with three different diffusers but with impellers and volutes of the same parameters were simulated by 3D Navier-Stokes solver ANSYS-FLUENT in order to study the effect of the outlet diameter of vaned diffuser on performance of the centrifugal pump. Structured grids of high quality were applied on the whole computational domain. Experimental results were acquired by prototype experiments and were then compared with the numerical results. Both experimental and numerical results show that the performance of a pump with a diffuser of smaller outlet diameter is better than of bigger outlet diameter under all operating conditions. The radial force imposed on the impeller obtained by unsteady numerical simulation was analyzed. The results also indicated that an appropriate decrease in the outlet diameter of the diffuser vane could increase the radial force.

Optimized Gun Barrel Based on Numerical Simulation to Produced Oil With Low BSW Content

2020 ◽  
Author(s):  
Silvia Araujo Daza ◽  
Urbano Montañez Villamizar
Keyword(s):  
Flow Rate ◽  
Operating Conditions ◽  
Water Mixture ◽  
Two Phase ◽  
Ansys Fluent ◽  
Inlet Flow ◽  
Gun Barrel ◽  
Vof Model ◽  
Inlet Flow Rate ◽  
Computational Fluid Dynamics Cfd

Abstract This work presents the methodology and results of the optimization of the internals (Inlet distributor, oil and water collectors) of a 20,000 BPD (0.037 m3/s) gun-barrel tank starting from an existing design. Computational fluid dynamics (CFD) was applied to simulate and evaluate the performance of various internal configurations. These simulations were performed to determine the best configuration to ensure efficient separation of the oil-water mixture and oil with a low BSW content < 2% at the outlet. The simulations were carried out using the commercial software ANSYS Fluent under the two-phase flow VOF model and k-ε realizable turbulence model. Further CFD simulations were performed to evaluate the behavior of the gun barrel tank under different operating conditions (Different inlet flow rate) and to determine the maximum operation flow which allows obtaining the crude-oil with a maximum BSW content of 0.5%. From the simulation results, an operating curve (operating flow vs retention time) was constructed. This information allows, in practice, to identify the inlet flow rate based on the desired content of BSW in the separated oil.

Numerical Analysis of Mass Flow Leakage Through Orifices for Supercritical CO2: Two-Phase Flow Effects

2020 ◽  
Author(s):  
Ladislav Vesely ◽  
Akshay Khadse ◽  
Andres Curbelo ◽  
Jayanta S. Kapat ◽  
Luca Petrungaro
Keyword(s):  
Mass Flow ◽  
Thermodynamic Equilibrium ◽  
Supercritical Co2 ◽  
Two Phase Flow ◽  
Operating Conditions ◽  
Working Fluid ◽  
Great Promise ◽  
Phase Flow ◽  
Computational Domain ◽  
Two Phase

Abstract Supercritical CO2 (sCO2) holds a great promise as a future working fluid for power generating Brayton cycles. One of the challenging research areas in sCO2 power cycles is flow leakage and the design of seals on the compressor side of the cycle. Given the compact nature of sCO2 turbomachinery, even a minimal amount of leakage can lead to a significant power efficiency loss. Hence accurate prediction of mass flow leakage rate becomes important. However, on the compressor side of the cycle, operating conditions across the seal lead to two-phase flow. This makes flow modeling very challenging because conventional one-phase flow CFD models cannot be used. This paper is an attempt to understand the behavior of two-phase sCO2 flow going through circular and annular orifices. The focus is to utilize commercially available CFD scheme for modeling phase change and two-phase flow through constrictions. Since the pressure loss across constrictions is also accompanied with reduction in temperature, the flow becomes two-phase by entering the saturation dome. CFD simulation is performed using commercially available software STAR CCM+. 2D axisymmetric geometry is considered as the computational domain. Eulerian Multi-phase Mixture model is used in conjunction with the Two-Phase Thermodynamic Equilibrium implementation. This model is intended for applications that involve two phases of the same substance that are in thermodynamic equilibrium. Fluid properties are defined over a large range of temperatures and pressures, including both the liquid and vapor phases.

scholarly journals Meander-Like Shape Optimization of the Stator-Rotor Platform Cavity

2018 ◽  
Author(s):  
Paht Juangphanich ◽  
Guillermo Paniagua
Keyword(s):  
Geometry Optimization ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Practical Implementation ◽  
Computational Domain ◽  
Optimization Strategy ◽  
Minimum Thickness ◽  
Ansys Fluent ◽  
Driving Mechanisms ◽  
Wide Range

Recent progress in additive manufacturing has enabled opportunities to explore novel stator rim geometries which can be implemented to improve cooling strategies in turbomachinery. This paper presents a simplified stationary geometry optimization strategy to produce enhanced stator-rotor cavity sealing and highlights main driving mechanisms. The stator and rotor rims were designed using a design strategy based on inspiration from the meandering of rivers. A minimum thickness of 2mm was maintained throughout the cavity to ensure a practical implementation. The computational domain comprised of the stator outlet, hub disk leakage cavity, and rotor platform was meshed using NUMECA Int. package, Hexpress. The numerical analysis required 3D Unsteady Reynolds Average Navier-Stokes to replicate vorticial structures using Ansys Fluent. The operating conditions were representative of engine-like conditions, exploring a wide range of massflow ratios from 1 to 3%. The optimization yielded designs that provide 30% reduction in rear platform temperature while minimizing coolant massflow. The applicability of the design was compared against 3D sector in both stationary and in rotation.

Multiphase Computational Fluid Dynamics Modeling of External Oil Flow From a Journal Bearing

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Martin Berthold ◽  
Hervé Morvan ◽  
Richard Jefferson-Loveday ◽  
Colin Young ◽  
Benjamin C. Rothwell ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Boundary Conditions ◽  
Journal Bearing ◽  
Flow Behavior ◽  
Phase Interface ◽  
Ansys Fluent ◽  
Reconstruction Scheme ◽  
Geometric Reconstruction ◽  
Oil Flow

High loads and bearing life requirements make journal bearings a potential choice for use in high power, epicyclic gearboxes in jet engines. Particularly, in a planetary configuration, the kinematic conditions are complex. With the planet gears rotating about their own axes and orbiting around the sun gear, centrifugal forces generated by both motions interact with each other and affect the external flow behavior of the oil exiting the journal bearing. Computational fluid dynamics (CFD) simulations using the volume of fluid (VoF) method are carried out in ANSYS fluent (ANSYS, 2013, “ANSYS Fluent User's Guide,” ANSYS Inc., Canonsburg, PA) to numerically model the two-phase flow behavior of the oil exiting the bearing and merging into the air surrounding the bearing. This paper presents an investigation of two numerical schemes that are available in ansysfluent to track or capture the air–oil phase interface: the geometric reconstruction scheme and the compressive scheme. Both numerical schemes are used to model the oil outflow behavior in the most simplistic approximation of a journal bearing: a representation, rotating about its own axis, with a circumferentially constant, i.e., concentric, lubricating gap. Based on these simplifications, a three-dimensional (3D) CFD sector model with rotationally periodic boundaries is considered. A comparison of the geometric reconstruction scheme and the compressive scheme is presented with regard to the accuracy of the phase interface reconstruction and the time required to reach steady-state flow-field conditions. The CFD predictions are validated against existing literature data with respect to the flow regime, the direction of the predicted oil flow path, and the oil film thickness. Based on the findings and considerations of industrial requirements, a recommendation is made for the most suitable scheme to be used. With a robust and partially validated CFD model in place, the model fidelity can be enhanced to include journal bearing eccentricity. Due to the convergent-divergent gap and the resultant pressure field within the lubricating oil film, the outflow behavior can be expected to be very different compared to that of a concentric journal bearing. Naturally, the inlet boundary conditions for the oil emerging from the journal bearing into the external environment must be consistent with the outlet conditions from the bearing. The second part of this paper therefore focuses on providing a method to generate appropriate inlet boundary conditions for external oil flow from an eccentric journal bearing.

A Novel Approach to Model Thermo-Fluids of Gearbox Systems

2013 ◽  
Author(s):  
Miad Yazdani ◽  
Marios Soteriou ◽  
Barbara Botros ◽  
Hailing Wu ◽  
Joe Liou ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fluid Mechanics ◽  
Automobile Industry ◽  
Driving Forces ◽  
Fluid Model ◽  
Phase Interface ◽  
Computational Cost ◽  
Operating Conditions ◽  
Two Phase ◽  
Ansys Fluent

Gearboxes are integral machine components that determine the capability and reliability of many aerospace and automobile industry systems. Continuous demand for higher efficiency and reliability, increased load-carrying capacity and endurance life, smaller size, lower weight, lower noise and vibrations, prolonged service intervals and low costs are the main driving forces in the development of gear drives in the future. For many gearboxes, the thermo-fluids of the gas/oil/solid system determine the gearbox performance and its durability and life. However, there is a very limited predictive capability of the thermo-fluid characteristics of gearbox due, in large part, to its excessive complexity. In this paper, we present a coupled thermo-fluid model for the simulation of the two-phase flow along with the heat transfer within gearbox systems in a conjugate fashion. The primary challenge is the enormous separation of fluid-mechanics and heat-transfer time-scales which makes the conventional way of solving the coupled thermo-fluid system of equations computationally prohibitive. In contrast, the approximate approach developed in this study exploits this separation of scales to provide an accurate representation of the long-term, time dependent thermo-fluid state of the gearbox at a modest computational cost. The commercial package ANSYS FLUENT is used to solve URANS equations for fluid mechanics and VOF for the two-phase interface capturing, while the energy equation is modified through user-defined functions to solve for the temperature field inside the fluid and solid components. In addition, the heat generation raised by the meshing of the gears is provided by a separate model based on gear geometry and operating conditions. The approach is verified against a full-fidelity simulation for a simplified and accelerated gear system and is validated against experiments.

scholarly journals Hysteresis in Oil Flow through a Rotating Tube with Twin Exit Branches

1997 ◽  
Vol 3 (4) ◽  
pp. 249-258 ◽  
Author(s):  
Sun-Wen Cheng ◽  
Wen-Jei Yang
Keyword(s):  
Flow Rate ◽  
Transmission Lines ◽  
Rotational Speed ◽  
Flow Behavior ◽  
Piping System ◽  
Air Bubbles ◽  
Two Phase ◽  
Oil Flow ◽  
Flow Through ◽  
Total Oil

Oil enters a horizontal rotating tube through a radially-attached duct at one end. The tube with the other end closed is attached with radial twin exit branches permitting oil to exit into open air. Air begins to enter through one of the two branches into the tube when its rotational speed reaches certain critical values. An experimental study is performed to investigate this air-oil two-phase flow behavior. Both the tube and the branches are transparent to allow illumination and flow visualization during spin-up and spin-down processes. The branch-totube diameter ratio, rotational speed, and oil flow rate are varied. Changes in oil flow rates are measured as a function of rotational speed. A comparison is made between cases of a varying total oil flow rate due to rotation effects and a constant one under control. It is disclosed that cavitation in oil flow is induced by air entering the branches opposite to the ejecting oil flow. Subsequently air bubbles progress in the tube. The origin of this intrusion depends on the hydraulic head loss of the piping system. This study can be applied to oil lubrication analysis of rotating machinery, such as automotive transmission lines.

scholarly journals Design and Optimization of Chemical Mixing System for Vacuum Chambers: Simulation Results

2014 ◽  
Vol 5 ◽  
Author(s):  
Faruk Unker ◽  
Erdar Kaplan ◽  
Olkan Cuvalci
Keyword(s):  
Gas Flow ◽  
Flow Behavior ◽  
Atomic Layer ◽  
Flow Patterns ◽  
Operating Conditions ◽  
Tantalum Nitride ◽  
Ansys Fluent ◽  
Design And Optimization ◽  
Parametric Investigation ◽  
Process Gas

Computational fluid dynamics (CFD) is widely used in device design to determine gas flow patterns and turbulence levels.  CFD is also used to simulate particles and droplets, which are subjected to various forces, turbulence and wall interactions. These studies can now be performed routinely because of the availability of commercial software containing high quality turbulence and particle models. In order to understand how the gas is brought down to wafer, it is necessary to have a knowledge of the gas flow behavior very early in the design spiral of the Tantalum nitride-Atomic layer deposition(TaN-ALD) chamber by undertaking parametric investigation of the interaction effect between gas flow and the funnel structure. This paper presents such a  parametric  investigation on a generic TaN-ALD chamber using CFD. The results presented have been analyzed for a total of 11 different cases by varying neck and nozzle angles for a process gas. The gas flow was mainly investigated for the nozzle angles of  4.5◦,  9◦,  12◦  and  20◦ and the film thickness results were compared with numerical flow patterns. CFD simulations using the turbulence model in ANSYS Fluent v.13 are undertaken. The parametric study has demonstrated that CFD is a powerful tool to study the problem of gas flow-structure interaction on funnel and is capable of providing a means of visualizing the path of the gas under different operating conditions

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