Classification and Modeling of Fluid Dynamic Loss in Aeroengine Transmission Gears

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Hidenori Arisawa ◽  
Yuji Shinoda ◽  
Mitsuaki Tanaka ◽  
Tatsuhiko Goi ◽  
Hirofumi Akahori ◽  
...  
Keyword(s):  
Conservation Law ◽  
High Speed ◽  
Fluid Dynamic ◽  
Aircraft Engine ◽  
Management Technique ◽  
Proposed Model ◽  
Loss Prediction ◽  
Dynamic Loss ◽  
Oil Jet ◽  
Experimental Fluid

Reducing the fluid dynamic power loss for increasing speed is critical for the development of highly efficient high-speed aircraft engine gearing. In this study, the fluid dynamic loss was experimentally performed using a precise friction loss management technique along a vacuum being drawn on the gearbox. The experimental fluid dynamic loss could be classified as either “oil jet acceleration loss and oil reacceleration loss based on the conservation law of momentum for a point mass” or “oil churning loss and windage loss based on the conservation law of momentum for an incompressible continuum.” Windage loss and oil dynamic loss (i.e., the summation of oil jet acceleration loss, oil reacceleration loss, and oil churning loss) were modeled to develop equations for a loss prediction. The equations of the windage loss are pressure loss of flow passing through the side clearance of the gears and energy loss caused by the vortex generation in the cavity between tooth valleys. Oil dynamic loss was determined by multiplying the oil jet acceleration loss by an empirical coefficient. The results of the loss prediction equations agree with the experimental results, demonstrating the validity of the proposed model of the fluid dynamic loss.

Classification of Fluid Dynamic Loss in Aeroengine Transmission Gears: Experimental Analysis and CFD Validation

2017 ◽  
Author(s):  
Hidenori Arisawa ◽  
Yuji Shinoda ◽  
Mitsuaki Tanaka ◽  
Tatsuhiko Goi ◽  
Hirofumi Akahori ◽  
...  
Keyword(s):  
High Speed ◽  
Fluid Dynamic ◽  
Aircraft Engine ◽  
Momentum Conservation ◽  
Cfd Modeling ◽  
Management Technique ◽  
Cfd Validation ◽  
Computational Fluid Dynamics Cfd ◽  
Dynamic Loss ◽  
Oil Jet

Reducing fluid dynamic power loss as speed increases is crucial to developing highly efficient high-speed aircraft engine gearing. Therefore, in this study, experiments were conducted using a precise friction-loss management technique and a vacuum pump in the gearbox for experimentally classifying fluid dynamic loss. Consequently, it was found that fluid dynamic loss could be classified into “oil-jet acceleration loss and oil reacceleration loss based on the momentum conservation of point mass” and “oil churning loss and windage loss based on the momentum conservation of an incompressible continuum”. Furthermore, the simulation results obtained via appropriate computational fluid dynamics (CFD) modeling of the resultant mechanisms agreed with the experimental results. The results of the present study are expected to improve the efficiency of mechanical systems, e.g., the fan drive gear system of Geared Turbofan™ and the accessory gearbox.

scholarly journals Numerical Simulation of Oil Jet Lubrication for High Speed Gears

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Tommaso Fondelli ◽  
Antonio Andreini ◽  
Riccardo Da Soghe ◽  
Bruno Facchini ◽  
Lorenzo Cipolla
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Low Pressure ◽  
Adaptive Meshing ◽  
Viscous Effects ◽  
Cfd Simulations ◽  
Oil Jet ◽  
Oil Injection ◽  
Bypass Ratio

The Geared Turbofan technology is one of the most promising engine configurations to significantly reduce the specific fuel consumption. In this architecture, a power epicyclical gearbox is interposed between the fan and the low pressure spool. Thanks to the gearbox, fan and low pressure spool can turn at different speed, leading to higher engine bypass ratio. Therefore the gearbox efficiency becomes a key parameter for such technology. Further improvement of efficiency can be achieved developing a physical understanding of fluid dynamic losses within the transmission system. These losses are mainly related to viscous effects and they are directly connected to the lubrication method. In this work, the oil injection losses have been studied by means of CFD simulations. A numerical study of a single oil jet impinging on a single high speed gear has been carried out using the VOF method. The aim of this analysis is to evaluate the resistant torque due to the oil jet lubrication, correlating the torque data with the oil-gear interaction phases. URANS calculations have been performed using an adaptive meshing approach, as a way of significantly reducing the simulation costs. A global sensitivity analysis of adopted models has been carried out and a numerical setup has been defined.

Windage Losses of a Meshing Gear Pair Measured at Different Working Conditions

2018 ◽  
Author(s):  
D. Massini ◽  
T. Fondelli ◽  
B. Facchini ◽  
L. Tarchi ◽  
F. Leonardi
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Volume Flow Rate ◽  
Fluid Dynamic ◽  
Lubrication System ◽  
Test Rig ◽  
Rotating Speed ◽  
Aero Engine ◽  
Speed Up ◽  
Oil Jet

In recent years the aero-engine community is looking towards the reduction of specific fuel consumption by increasing the efficiency of gearing systems. Considering their weight contribution, internal power losses and lubrication requirements, they have indeed a direct impact on the engine overall efficiency. Even though nowadays gears have reached very high efficiencies, over 99%, all the power dissipated through losses is converted into heat that must be removed by the lubrication system. Heat reduction is hence beneficial for minimizing lubrication system dimensions that is crucial in aero engine applications where it is mandatory to limit the weight of every component. Among the sources of loss, two main categories may be distinguished: load dependent and load independent losses. The first ones are due to the transmission of torque and have been deeply studied in the last years, the latter are related to fluid-dynamic interaction between gears and the surrounding environment, they are negligible at low pitch line velocities, but become very important in high speed applications, typical of turbomachinery. This work deals with an experimental investigation of the load independent losses due to a couple of spur meshing gears working at different conditions in presence of an oil-jet lubrication system. The test rig allows the gears to rotate, at different velocities up to 15000 rpm, in a controlled environment contained in a sealed box. Test rig pressure can be imposed (0.3–1.0 bar) and monitored as well as the oil jet conditions, in terms of mass flow rate (jet volume flow rate up to 1.65 litres per minute), temperature (80–140 °C) and inclination angle. A high precision bearing-less torque meter, equipped with a speedometer, was exploited to measure at the same time the torque losses and rotating speed. Results of the experimental survey allowed a better understanding of load independent losses at pitch line speed up to 100 m/s and in different environmental conditions.

scholarly journals Modeling the Excess Velocity of Low-Viscous Taylor Droplets in Square Microchannels

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 162 ◽  
Author(s):  
Thorben Helmers ◽  
Philip Kemper ◽  
Jorg Thöming ◽  
Ulrich Mießner
Keyword(s):  
High Speed ◽  
Process Intensification ◽  
Continuous Phase ◽  
Channel Cross Section ◽  
Optimization Approach ◽  
Mean Flow ◽  
Bypass Flow ◽  
Wall Film ◽  
Proposed Model ◽  
The Mean

Microscopic multiphase flows have gained broad interest due to their capability to transfer processes into new operational windows and achieving significant process intensification. However, the hydrodynamic behavior of Taylor droplets is not yet entirely understood. In this work, we introduce a model to determine the excess velocity of Taylor droplets in square microchannels. This velocity difference between the droplet and the total superficial velocity of the flow has a direct influence on the droplet residence time and is linked to the pressure drop. Since the droplet does not occupy the entire channel cross-section, it enables the continuous phase to bypass the droplet through the corners. A consideration of the continuity equation generally relates the excess velocity to the mean flow velocity. We base the quantification of the bypass flow on a correlation for the droplet cap deformation from its static shape. The cap deformation reveals the forces of the flowing liquids exerted onto the interface and allows estimating the local driving pressure gradient for the bypass flow. The characterizing parameters are identified as the bypass length, the wall film thickness, the viscosity ratio between both phases and the C a number. The proposed model is adapted with a stochastic, metaheuristic optimization approach based on genetic algorithms. In addition, our model was successfully verified with high-speed camera measurements and published empirical data.

A fully automated method of human identification based on dental panoramic radiographs using a convolutional neural network

2021 ◽  
Author(s):  
Young Hyun Kim ◽  
Eun-Gyu Ha ◽  
Kug Jin Jeon ◽  
Chena Lee ◽  
Sang-Sun Han
Keyword(s):  
Neural Network ◽  
Convolutional Neural Network ◽  
High Speed ◽  
Large Scale ◽  
Oral Surgery ◽  
Human Identification ◽  
Running Time ◽  
Automated Method ◽  
Image Characteristics ◽  
Proposed Model

Objectives: This study aimed to develop a fully automated human identification method based on a convolutional neural network (CNN) with a large-scale dental panoramic radiograph (DPR) dataset. Methods: In total, 2,760 DPRs from 746 subjects who had 2 to 17 DPRs with various changes in image characteristics due to various dental treatments (tooth extraction, oral surgery, prosthetics, orthodontics, or tooth development) were collected. The test dataset included the latest DPR of each subject (746 images) and the other DPRs (2,014 images) were used for model training. A modified VGG16 model with two fully connected layers was applied for human identification. The proposed model was evaluated with rank-1, –3, and −5 accuracies, running time, and gradient-weighted class activation mapping (Grad-CAM)–applied images. Results: This model had rank-1,–3, and −5 accuracies of 82.84%, 89.14%, and 92.23%, respectively. All rank-1 accuracy values of the proposed model were above 80% regardless of changes in image characteristics. The average running time to train the proposed model was 60.9 sec per epoch, and the prediction time for 746 test DPRs was short (3.2 sec/image). The Grad-CAM technique verified that the model automatically identified humans by focusing on identifiable dental information. Conclusion: The proposed model showed good performance in fully automatic human identification despite differing image characteristics of DPRs acquired from the same patients. Our model is expected to assist in the fast and accurate identification by experts by comparing large amounts of images and proposing identification candidates at high speed.

Thermo-Fluid-Dynamic Design of Reciprocating Compressor Cylinders by Fluid Structure Interaction (FSI)

2011 ◽  
Author(s):  
Riccardo Traversari ◽  
Alessandro Rossi ◽  
Marco Faretra
Keyword(s):  
High Speed ◽  
Fluid Dynamic ◽  
Fluid Structure Interaction ◽  
Classical Equation ◽  
Flow Coefficient ◽  
Reciprocating Compressor ◽  
Complex Situation ◽  
Fluid Structure ◽  
Associated Gas ◽  
Structure Interaction

Pressure losses at the cylinder valves of reciprocating compressors are generally calculated by the classical equation of the flow through an orifice, with flow coefficient determined in steady conditions. Rotational speed has increased in the last decade to reduce compressor physical dimensions, weight and cost. Cylinder valves and associated gas passages became then more and more critical, as they determine specific consumption and throughput. An advanced approach, based on the new Fluid Structure Interaction (FSI) software, which allows to deal simultaneously with thermodynamic, motion and deformation phenomena, was utilized to simulate the complex situation that occurs in a reciprocating compressor cylinder during the motion of the piston. In particular, the pressure loss through valves, ducts and manifolds was investigated. A 3D CFD Model, simulating a cylinder with suction and discharge valves, was developed and experimentally validated. The analysis was performed in transient and turbulent condition, with compressible fluid, utilizing a deformable mesh. The 3D domain simulating the compression chamber was considered variable with the law of motion of the piston and the valve rings mobile according to the fluid dynamic forces acting on them. This procedure is particularly useful for an accurate valve loss evaluation in case of high speed compressors and heavy gases. Also very high pressure cylinders, including LDPE applications, where the ducts are very small and MW close to the water one, can benefit from the new method.

scholarly journals Dynamic loss and magnetization loss of HTS coated conductors, stacks, and coils for high-speed synchronous machines

2020 ◽  
Vol 33 (8) ◽  
pp. 084008
Author(s):  
Hongye Zhang ◽  
Philip Machura ◽  
Kevin Kails ◽  
Hongyi Chen ◽  
Markus Mueller
Keyword(s):  
High Speed ◽  
Coated Conductors ◽  
Synchronous Machines ◽  
Magnetization Loss ◽  
Dynamic Loss

Oil Pumping in High Speed and High Loaded Ball Bearings

2004 ◽  
Author(s):  
Michael Flouros
Keyword(s):  
High Speed ◽  
Ball Bearing ◽  
Research Programme ◽  
Aircraft Engine ◽  
Ball Bearings ◽  
European Research ◽  
Rolling Bearings ◽  
Engine Design ◽  
Oil Flow ◽  
Total Oil

Trends in aircraft engine design cause increased mechanical stress requirements for rolling bearings. Consequently high amounts of heat are rejected which results in high oil scavenge temperatures. The direction of oil flow in the bearing can considerably affect the heat transported by the oil. An RB199 turbofan bearing and its associated chamber were modified to carry out the survey. The test bearing was a 124mm PCD ball bearing. The bearing has a split inner-ring employing under-race lubrication by two individual jets. The total oil flow could be devided to any ratio through the jets. This had an impact on the oil scavenge temperatures and the scavenge flows on both sides of the bearing. Significant reduction in the ‘heat to oil’ was achieved when oil was fed at certain proportions (ratio). This work is part of the European Research programme Brite Euram ATOS (Advanced Transmission and Oil Systems).

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