The Effect of Surface Defect on EHL Point Contact

2013 ◽  
Vol 765-767 ◽  
pp. 67-70
Author(s):  
Yu Jin Fan ◽  
Zhe Kun Li ◽  
Wei Da Wang ◽  
Teng Han
Keyword(s):  
Surface Defect ◽  
Negative Impact ◽  
Three Dimensional ◽  
Great Influence ◽  
Point Contact ◽  
Film Pressure ◽  
Lubrication Film ◽  
Pressure Peak ◽  
Effect Of Surface ◽  
Ehl Lubrication

In this paper, the lubrication of three-dimensional EHL point contact with surface defect was solved, the lubrication film shape and film pressure distribution were presented and the characteristics of EHL point contact with defect were analyzed, the effect of surface defect on EHL point contact was studied. The results were presented that convex defect could lead to film pressure peak increasing, there was obvious micro-EHL effect, concave defect could lead to film pressure hollow and peak, film pressure peak was also increasing. The results also shown that convex and concave defects would have negative impact on EHL lubrication, there was great influence of surface defect on EHL lubrication pressure, the significant fluctuation of local film pressure was caused by surface defect, and generating greater pressure peak, maximum film pressure was rapid growth with the defect size increasing, so any kind defect should be to avoid in EHL lubrication.

Effect of Surface Roughness on Performance of Spiral Groove Gas Film Face Seal

2012 ◽  
Vol 184-185 ◽  
pp. 180-183 ◽  
Author(s):  
Gang Ma ◽  
Wei Zhao ◽  
Xin Min Shen
Keyword(s):  
Surface Roughness ◽  
Three Dimensional ◽  
Great Influence ◽  
Face Seal ◽  
Dimensional Model ◽  
Spiral Groove ◽  
Three Dimensional Model ◽  
Three Dimensional Flow ◽  
Gas Face Seal ◽  
Effect Of Surface

The three dimensional model was established for studying performance of spiral groove gas face seal. According to machining features of different surface area, the seal face can be divided into three parts, rotor ring grooved area, rotor ring non-grooved area and static ring area. The effect of roughness on seal performance was analyzed based on calculation of three dimensional flow field. The analysis results show that the surface roughness of rotor ring grooved area has great influence on the seal performance, but the influence is little when roughness on non-grooved rotor ring surface and static ring surface. The influence must be considered when surface roughness of rotor ring grooved area bigger than 0.2μm. Roughness of rotor ring surface can increase the loading force while it also can cause the increase of leakage. It is important to select rational roughness when designing gas face seal.

Point Contact EHL Based on Optically Measured Three-Dimensional Rough Surfaces

1997 ◽  
Vol 119 (3) ◽  
pp. 375-384 ◽  
Author(s):  
Dong Zhu ◽  
Xiaolan Ai
Keyword(s):  
Rough Surface ◽  
Rough Surfaces ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Peak Height ◽  
Machining Process ◽  
Maximum Pressure ◽  
Pressure Peak ◽  
Surface Profiles

This paper presents a numerical solution for the elastohydrodynamic lubrication in point contacts, using optically measured three-dimensional rough surface profiles as input data. The multi-grid computer program originally developed by Ai and Cheng (1993, 1994) is modified, so that both contacting surfaces can be three-dimensional measured rough surfaces moving at different velocities. Many different engineering surfaces are measured and analyzed in the present study, demonstrating that the numerical analysis is practical for real surfaces of bearings, cams, gears and other components, as long as a significant EHL film still exists. In addition, discussions are given in this paper for the effects of three-dimensional rough surface topography, which is related to machining process. It appears that, for the circular contact cases analyzed, surface roughness texture and orientation do not have a significant effect on the average film thickness, but they do affect the maximum pressure peak height and asperity deformation in the contact zone considerably.

The Effects of Surface Texture on EHL Point Contacts

1996 ◽  
Vol 118 (1) ◽  
pp. 59-66 ◽  
Author(s):  
Xiaolan Ai ◽  
Herbert S. Cheng
Keyword(s):  
Surface Texture ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Point Contact ◽  
Maximum Pressure ◽  
Point Contacts ◽  
Random Roughness ◽  
Minimum Film Thickness ◽  
Transverse Roughness ◽  
Effect Of Surface

The effect of surface texture on EHL point contact is studied numerically by using the multigrid method. Numerical simulations have been performed for waviness and random roughness with three different orientations, transverse, oblique and longitudinal. Results reveal a strong domination of unidirectional Couette flow in the EHL conjunction. The geometrical variations at inlet of the contact are transported downstream throughout the EHL conjunction. As a consequence, the oblique surface roughness striations are largely distorted, forming nearly longitudinal wavy passages. Results show that the oblique roughness induces local three dimensional EHL pressure fluctuations. The maximum pressure is higher than that of the transverse roughness. For sinusoidal waviness, oblique orientation gives the smallest minimum film thickness as compared with those of longitudinal and transverse waviness.

Advances in coupled axial turbine and nonaxisymmetric exhaust volute aerodynamics for turbomachinery

2020 ◽  
pp. 095441002096645
Author(s):  
Jie Gao ◽  
Chunde Tao ◽  
Dongchen Huo ◽  
Guojie Wang
Keyword(s):  
Performance Improvement ◽  
High Efficiency ◽  
Three Dimensional ◽  
Great Influence ◽  
Aerodynamic Characteristics ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Axial Turbine ◽  
Flow Interactions ◽  
And Performance

Marine, industrial, turboprop and turboshaft gas turbine engines use nonaxisymmetric exhaust volutes for flow diffusion and pressure recovery. These processes result in a three-dimensional complex turbulent flow in the exhaust volute. The flows in the axial turbine and nonaxisymmetric exhaust volute are closely coupled and inherently unsteady, and they have a great influence on the turbine and exhaust aerodynamic characteristics. Therefore, it is very necessary to carry out research on coupled axial turbine and nonaxisymmetric exhaust volute aerodynamics, so as to provide reference for the high-efficiency turbine-volute designs. This paper summarizes and analyzes the recent advances in the field of coupled axial turbine and nonaxisymmetric exhaust volute aerodynamics for turbomachinery. This review covers the following topics that are important for turbine and volute coupled designs: (1) flow and loss characteristics of nonaxisymmetric exhaust volutes, (2) flow interactions between axial turbine and nonaxisymmetric exhaust volute, (3) improvement of turbine and volute performance within spatial limitations and (4) research methods of coupled turbine and exhaust volute aerodynamics. The emphasis is placed on the turbine-volute interactions and performance improvement. We also present our own insights regarding the current research trends and the prospects for future developments.

Experimental investigation on the three-dimensional flow field from a meltblowing slot die

e-Polymers ◽  
2020 ◽  
Vol 20 (1) ◽  
pp. 724-732
Author(s):  
Changchun Ji ◽  
Yudong Wang
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Great Influence ◽  
Distribution Characteristics ◽  
Air Velocity ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Airflow Distribution ◽  
Slot Die ◽  
Center Area

AbstractTo investigate the distribution characteristics of the three-dimensional flow field under the slot die, an online measurement of the airflow velocity was performed using a hot wire anemometer. The experimental results show that the air-slot end faces have a great influence on the airflow distribution in its vicinity. Compared with the air velocity in the center area, the velocity below the slot end face is much lower. The distribution characteristics of the three-dimensional flow field under the slot die would cause the fibers at different positions to bear inconsistent air force. The air velocity of the spinning centerline is higher than that around it, which is more conducive to fiber diameter attenuation. The violent fluctuation of the instantaneous velocity of the airflow could easily cause the meltblowing fiber to whip in the area close to the die.

scholarly journals Engineering Comprehensive Model of Complex Wind Fields for Flight Simulation

Aerospace ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 145
Author(s):  
Jianwei Chen ◽  
Liangming Wang ◽  
Jian Fu ◽  
Zhiwei Yang
Keyword(s):  
Wind Field ◽  
Three Dimensional ◽  
Great Influence ◽  
Spatial Location ◽  
Flight Simulation ◽  
Comprehensive Model ◽  
Flight Trajectory ◽  
Wind Fields ◽  
Wind Field Simulation ◽  
Low Level Jet

A complex wind field refers to the typical atmospheric disturbance phenomena existing in nature that have a great influence on the flight of aircrafts. Aimed at the issues involving large volume of data, complex computations and a single model in the current wind field simulation approaches for flight environments, based on the essential principles of fluid mechanics, in this paper, wind field models for two kinds of wind shear such as micro-downburst and low-level jet plus three-dimensional atmospheric turbulence are established. The validity of the models is verified by comparing the simulation results from existing wind field models and the measured data. Based on the principle of vector superposition, three wind field models are combined in the ground coordinate system, and a comprehensive model of complex wind fields is established with spatial location as the input and wind velocity as the output. The model is applied to the simulated flight of a rocket projectile, and the change in the rocket projectile’s flight attitude and flight trajectory under different wind fields is analyzed. The results indicate that the comprehensive model established herein can reasonably and efficiently reflect the influence of various complex wind field environments on the flight process of aircrafts, and that the model is simple, extensible, and convenient to use.

scholarly journals Analysis of Turn-to-Turn Fault on Split-Winding Transformer Using Coupled Field-Circuit Approach

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1314
Author(s):  
Cunxiang Yang ◽  
Yiwei Ding ◽  
Hongbo Qiu ◽  
Bin Xiong
Keyword(s):  
Low Voltage ◽  
Short Circuit ◽  
Three Dimensional ◽  
Great Influence ◽  
Normal Operation ◽  
Transient Field ◽  
Axial Forces ◽  
Leakage Field ◽  
Characteristics Analysis ◽  
Split Winding

The turn-to-turn faults (TTF) are also inevitable in split-winding transformers. The distorted leakage field generated by the TTF current results in large axial forces and end thrusts in the fault windings as well as affecting other branch windings normal operation, so it is of significance to study TTF of split-winding transformers. In this paper, the characteristics analysis of the split-winding transformer under the TTFs of the low voltage winding at different positions are presented. A 3600 KVA four split-windings transformer is taken as an example. Then, a simplified three-dimensional simplified model is established, taking into account the forces of the per-turn coil. The nonlinear-transient field-circuit coupled finite element method is used for the model. The leakage field distribution under the TTFs of the low voltage winding at different positions is studied. The resultant force of the short-circuit winding and the force of the per-turn coil are obtained. Subsequently, the force and current relationship between the branch windings are analyzed. The results show that the TTF at the specific location has a great influence on the axial windings on the same core, and the distorted leakage magnetic field will cause excessive axial force and end thrust of the normal and short-circuit windings. These results can provide a basis for the short-circuit design of split-winding transformer.

Automated Surface Inspection Using 3D Point Cloud Data in Manufacturing: A Case Study

2018 ◽  
Author(s):  
Romina Dastoorian ◽  
Ahmad E. Elhabashy ◽  
Wenmeng Tian ◽  
Lee J. Wells ◽  
Jaime A. Camelio
Keyword(s):  
Point Cloud ◽  
Surface Defect ◽  
Fault Location ◽  
Three Dimensional ◽  
Practical Case ◽  
3D Point Cloud ◽  
Point Cloud Data ◽  
Defect Inspection ◽  
Cloud Data

With the latest advancements in three-dimensional (3D) measurement technologies, obtaining 3D point cloud data for inspection purposes in manufacturing is becoming more common. While 3D point cloud data allows for better inspection capabilities, their analysis is typically challenging. Especially with unstructured 3D point cloud data, containing coordinates at random locations, the challenges increase with higher levels of noise and larger volumes of data. Hence, the objective of this paper is to extend the previously developed Adaptive Generalized Likelihood Ratio (AGLR) approach to handle unstructured 3D point cloud data used for automated surface defect inspection in manufacturing. More specifically, the AGLR approach was implemented in a practical case study to inspect twenty-seven samples, each with a unique fault. These faults were designed to cover an array of possible faults having three different sizes, three different magnitudes, and located in three different locations. The results show that the AGLR approach can indeed differentiate between non-faulty and a varying range of faulty surfaces while being able to pinpoint the fault location. This work also serves as a validation for the previously developed AGLR approach in a practical scenario.

scholarly journals Research Progress of Automated Visual Surface Defect Detection for Industrial Metal Planar Materials

Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5136
Author(s):  
Xiaoxin Fang ◽  
Qiwu Luo ◽  
Bingxing Zhou ◽  
Congcong Li ◽  
Lu Tian
Keyword(s):  
Defect Detection ◽  
Surface Defect ◽  
Three Dimensional ◽  
Image Features ◽  
Stereoscopic Vision ◽  
Research Progress ◽  
Inspection System ◽  
Two Dimensional ◽  
Surface Defect Detection ◽  
Planar Materials

The computer-vision-based surface defect detection of metal planar materials is a research hotspot in the field of metallurgical industry. The high standard of planar surface quality in the metal manufacturing industry requires that the performance of an automated visual inspection system and its algorithms are constantly improved. This paper attempts to present a comprehensive survey on both two-dimensional and three-dimensional surface defect detection technologies based on reviewing over 160 publications for some typical metal planar material products of steel, aluminum, copper plates and strips. According to the algorithm properties as well as the image features, the existing two-dimensional methodologies are categorized into four groups: statistical, spectral, model, and machine learning-based methods. On the basis of three-dimensional data acquisition, the three-dimensional technologies are divided into stereoscopic vision, photometric stereo, laser scanner, and structured light measurement methods. These classical algorithms and emerging methods are introduced, analyzed, and compared in this review. Finally, the remaining challenges and future research trends of visual defect detection are discussed and forecasted at an abstract level.

scholarly journals POINT-CONTACT SPECTROSCOPY OF MAGNESIUM DIBORIDE WITH DIFFERENT COUNTER-ELECTRODES

2003 ◽  
Vol 17 (27n28) ◽  
pp. 1405-1416
Author(s):  
A. I. D'YACHENKO ◽  
V. YU. TARENKOV ◽  
M. A. BELOGOLOVSKII ◽  
V. N. VARYUKHIN ◽  
A. V. ABAL'OSHEV ◽  
...  
Keyword(s):  
Andreev Reflection ◽  
Magnesium Diboride ◽  
Three Dimensional ◽  
Point Contact ◽  
Band Model ◽  
Counter Electrodes ◽  
Break Junctions ◽  
Point Contact Spectroscopy ◽  
Dc Current ◽  
Two Band Model

We report on tunneling and Andreev-reflection conductance spectra of 39 K superconducting magnesium diboride, obtained with Pb and Au counter-electrodes. Two distinct steps at close to 2.7 and 7.1 meV appear in a low-resistance metallic-type Au–MgB 2 junction characteristic, whereas a tunneling-like spectrum measured for the same junction, annealed by the application of DC current, exhibits only a rounded contribution of the larger gap. Junctions with a superconducting lead counter-electrode pressed into a bulk MgB 2 sample reveal two conductance peaks that are interpreted as the result of the formation of a highly-transmitting break junctions inside the magnesium diboride ceramic. Our results strongly support the two-band model with two different gap values on quasi-two-dimensional σ (7.1 meV) and three-dimensional π (2.7 meV) Fermi surface sheets of MgB 2.

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