scholarly journals Analysis of Oil Droplet Deposition Characteristics and Determination of Impact State Criterion in Aero-Engine Bearing Chamber

Processes ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 741
Author(s):  
Fei Wang ◽  
Lin Wang ◽  
Guoding Chen
Keyword(s):  
Impact Velocity ◽  
Incident Angle ◽  
Droplet Diameter ◽  
Oil Droplets ◽  
Oil Droplet ◽  
Spreading Width ◽  
The Impact ◽  
State Criterion ◽  
Maximum Spreading

The research of oil/air two-phase flow and heat transfer is the fundamental work of the design of lubrication and heat transfer in aero-engine bearing chamber. The determination of impact state criterion of the moving oil droplets with the wall and the analysis of oil droplet deposition characteristics are important components. In this paper, the numerical analysis model of the impact between the moving oil droplet and the wall is established by using the finite volume method, and the simulation of oil droplet impingement on the wall is carried out. Then the effects of oil droplet diameter, impact velocity, and incident angle on the characteristic parameters of impact state are discussed. The characteristic parameters include the maximum spreading length, the maximum spreading width, and the number of splashing oil droplets. Lastly the calculation results are verified through comparing with the experimental results in the literature. The results show as follows: (1) The maximum spreading width of oil droplet firstly increases and then slows down with the incident angle and the oil droplet diameter increasing; (2) when the oil droplet diameter becomes small, the influence of the incident angle on the maximum spreading length of oil droplet is obvious and vice versa; (3) with the impact velocity and diameter of oil droplet increasing, the maximum spreading width of oil droplet increases firstly and then slows down, and the maximum spreading length increased gradually; (4) the number of splashing oil droplets increases with the incident angle and impact velocity increasing; and (5) compared with the experimental data in literature, the critical dimensionless splashing coefficient K c proposed in this paper can better distinguish the impact state of oil droplet.

scholarly journals Impact of rockfalls on protection measures: an experimental approach

2015 ◽  
Vol 15 (4) ◽  
pp. 885-893 ◽  
Author(s):  
J. K. Yuan ◽  
Y. R. Li ◽  
R. Q. Huang ◽  
X. J. Pei
Keyword(s):  
Impact Velocity ◽  
Impact Force ◽  
Incident Angle ◽  
Drop Height ◽  
Current Standard ◽  
Protection Measures ◽  
Buffer Material ◽  
Cushion Layer ◽  
Study Laboratory ◽  
The Impact

Abstract. The determination of rockfall impact force is crucial in designing protection measures. In the present study, laboratory tests are carried out by testing the weight and shape of the falling rock fragments, drop height, incident angle, platform on the slideway, and cushion layer on the protection measures to investigate their influences on the impact force. The test results indicate that the impact force is positively exponential to the weight of rockfall and the instantaneous impact velocity of the rockfall approaching the protection measures. The impact velocity is found to be dominated not only by the drop height but also by the shape of rockfall and the length of the platform on the slideway. A great drop height and/or a short platform produces a fast impact velocity. Spherical rockfalls experience a greater impact velocity than cubes and elongated cuboids. A layer of cushion on the protection measures may reduce the impact force to a greater extent. The reduction effects are dominated by the cushion material and the thickness of the cushion layer. The thicker the cushion layer, the greater the reduction effect and the less the impact force. The stiffer the buffer material, the lower the buffering effect and the greater the impact force. The present study indicates that the current standard in China for designing protection measures may overestimate the impact force by not taking into consideration the rockfall shape, platform, and cushion layer.

Magnetic Pulse Welding by Electromagnetic Compression: Determination of the Impact Velocity

2014 ◽  
Vol 966-967 ◽  
pp. 489-499 ◽  
Author(s):  
Joern Lueg-Althoff ◽  
Amanda Lorenz ◽  
Soeren Gies ◽  
Christian Weddeling ◽  
Gunther Goebel ◽  
...  
Keyword(s):  
Impact Velocity ◽  
Measurement Data ◽  
Analytical Determination ◽  
Geometrical Parameters ◽  
Magnetic Pulse ◽  
Engineering Structures ◽  
Magnetic Pulse Welding ◽  
Pulse Welding ◽  
The Impact

The implementation of multi-material concepts and the manufacturing of modern lightweight structures, for example in automotive engineering, require appropriate joining technologies. The ability to join dissimilar materials without additional mechanical elements, chemical binders, or adverse influences of heat on the joining partners is key in reaching the desired weight reduction in engineering structures. The Magnetic Pulse Welding (MPW) process meets these demands, making it a viable alternative to conventional thermal welding and mechanical joining processes. The present paper focuses on the analytical determination of the impact velocity as one of the key parameters of MPW processes. On the basis of experimentally recorded data concerning the course of the discharge current and geometrical parameters of the welding setup, the respective velocity is determined. A comparison with measurement data gained by Photon Doppler Velocimetry is performed.

scholarly journals Numerical Simulation of the Oil Droplet Size Distribution Considering Coalescence and Breakup in Aero-Engine Bearing Chamber

2020 ◽  
Vol 10 (16) ◽  
pp. 5648
Author(s):  
Fei Wang ◽  
Lin Wang ◽  
Guoding Chen ◽  
Donglei Zhu
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Mass Flow ◽  
Droplet Diameter ◽  
Droplet Size Distribution ◽  
Oil Droplets ◽  
Oil Droplet ◽  
Aero Engine ◽  
Oil Droplet Size ◽  
Engine Bearing

In order to improve the inadequacy of the current research on oil droplet size distribution in aero-engine bearing chamber, the influence of oil droplet size distribution with the oil droplets coalescence and breakup is analyzed by using the computational fluid dynamics-population balance model (CFD-PBM). The Euler–Euler equation and population balance equation are solved in Fluent software. The distribution of the gas phase velocity field and the volume fraction of different oil droplet diameter at different time are obtained in the bearing chamber. Then, the influence of different initial oil droplet diameter, air, and oil mass flow on oil droplet size distribution is discussed. The result of numerical analysis is compared with the experiment in the literature to verify the feasibility and validity. The main results provide the following conclusions. At the initial stage, the coalescence of oil droplets plays a dominant role. Then, the breakup of larger diameter oil droplet appears. Finally, the oil droplet size distribution tends to be stable. The coalescence and breakup of oil droplet increases with the initial diameter of oil droplet and the air mass flow increasing, and the oil droplet size distribution changes significantly. With the oil mass flow increasing, the coalescence and breakup of oil droplet has little change and the variation of oil droplet size distribution is not obvious.

scholarly journals Study of the effect of surface wettability on droplet impact on spherical surfaces

2020 ◽  
Vol 15 (3) ◽  
pp. 414-420 ◽  
Author(s):  
Xiaohua Liu ◽  
Kaimin Wang ◽  
Yaqin Fang ◽  
R J Goldstein ◽  
Shengqiang Shen
Keyword(s):  
Contact Angle ◽  
Impact Velocity ◽  
Droplet Impact ◽  
Surface Wettability ◽  
Spreading Factor ◽  
Curvature Ratio ◽  
Spherical Surfaces ◽  
The Impact ◽  
Maximum Spreading ◽  
Effect Of Surface

Abstract The effect of surface wettability on droplet impact on spherical surfaces is studied with the CLSVOF method. When the impact velocity is constant, with the increase in the contact angle (CA), the maximum spreading factor and time needed to reach the maximum spreading factor (tmax) both decrease; the liquid film is more prone to breakup and rebound. When CA is constant, with the impact velocity increasing, the maximum spreading factor increases while tmax decreases. With the curvature ratio increasing, the maximum spreading factor increases when CA is between 30 and 150°, while it decreases when CA ranges from 0 to 30°.

Disintegration of Oil Films Emerging From Radial Holes in a Rotating Cylinder

2003 ◽  
Vol 125 (4) ◽  
pp. 1011-1020 ◽  
Author(s):  
A. Glahn ◽  
M. F. Blair ◽  
K. L. Allard ◽  
S. Busam ◽  
O. Scha¨fer ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Droplet Diameter ◽  
Rotating Disk ◽  
Operating Conditions ◽  
Droplet Generation ◽  
Diameter Distribution ◽  
Oil Droplets ◽  
Flow Angle ◽  
Oil Films

A fundamental study has been performed to examine the disintegration of oil films emerging from radial holes in a rotating hollow cylinder. The configuration investigated is an abstraction of one of the droplet generation sources in an aeroengine bearing compartment; similar configurations may also occur inside gearboxes. The paper aims to contribute to both the determination of directly applicable droplet characteristics and the establishment of a database that can be used for the development of droplet generation models. Similar to a prior paper on droplet generation processes at the rim of a rotating disk (Glahn, A. et al., 2000, “Droplet Generation by Disintegration of Oil Films at the Rim of a Rotating Disk,” ASME Paper No. 2000-GT-0279.) the near-term objectives of the study are (i) to determine droplet sizes under relevant aeroengine bearing compartment operating conditions, and (ii) to measure individual droplet diameter/velocity relationships. The long-term objective is to incorporate this information into advanced CFD-based design tools. Therefore, special emphasis has been directed towards a correlation of test results that enables determination of boundary conditions for a two-phase (oil droplets/air) simulation of lubrication system components. Based on the results of the present paper, droplet flow boundary conditions in terms of mean diameter, standard deviation of the diameter distribution, starting velocity, and flow angle are available for oil droplets generated by disintegration of oil films emerging from rotating radial holes and rotating disks.

Bioaccessibility of oil-soluble vitamins (A, D, E) in plant-based emulsions: impact of oil droplet size

2021 ◽  
Author(s):  
Yunbing Tan ◽  
Hualu Zhou ◽  
Zhiyun Zhang ◽  
David Julian McClements
Keyword(s):  
Vitamin D ◽  
Vitamin E ◽  
Vitamin A ◽  
Droplet Size ◽  
Droplet Diameter ◽  
Oil Droplet ◽  
Vitamin E Acetate ◽  
The Impact ◽  
Oil Droplet Size

We systematically investigated the impact of oil droplet diameter (≈0.15, 1.6, and 11 μm) on the bioaccessibility of three oil-soluble vitamins (vitamin A palmitate, vitamin D, and vitamin E acetate) encapsulated within plant-based emulsions.

scholarly journals Numerical Simulation of Single-Droplet Dynamics, Vaporization, and Heat Transfer from Impingement onto Static and Vibrating Surfaces

Fluids ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 188
Author(s):  
J. Thalackottore Jose ◽  
J. F. Dunne
Keyword(s):  
Heat Transfer ◽  
Impact Velocity ◽  
Liquid Droplet ◽  
Droplet Diameter ◽  
Droplet Evaporation ◽  
Time Interval ◽  
Initial Contact ◽  
Droplet Impingement ◽  
The Impact ◽  
Minimum Impact

A numerical study is presented to examine the behavior of a single liquid droplet initially passing through air or steam, followed by impingement onto a static or vibrating surface. The fluid dynamic equations are solved using the Volume of Fluid method, which includes both viscous and surface tension effects, and the possibility of droplet evaporation when the impact surface is hot. Initially, dynamic behavior is examined for isothermal impingement of a droplet moving through air, first without and then with boundary vibration. Isothermal simulations are used to establish how droplet rebound conditions and the time interval between initial contact to detachment vary with droplet diameter for droplet impingement onto a stationary boundary. Heat transfer is then assessed for a liquid droplet initially at saturation temperature passing through steam, followed by contact with a hot vibrating boundary, in which droplet evaporation commences. The paper shows that, for droplet impingement onto a static boundary, the minimum impact velocity for rebound reduces linearly with droplet diameter, whereas the time interval between initial contact and detachment appears to increase linearly with droplet diameter. With the introduction of a vibrating surface, the minimum relative impact velocity for isothermal rebound is found to be higher than the minimum impact velocity for static boundary droplet rebound. For impingement onto a hot surface, in which droplet evaporation commences, it is shown that large-amplitude surface vibration reduces heat transfer, whereas low-amplitude high-frequency vibration appears to increase heat transfer.

Experimental research on dynamic characteristics of viscous droplets impacting rough solid surfaces at different temperatures

2019 ◽  
Vol 97 (12) ◽  
pp. 1288-1300
Author(s):  
Yuan Zhong ◽  
Haicun Du ◽  
Ying Zhang ◽  
Yue Chen ◽  
Qiang Liu ◽  
...  
Keyword(s):  
Surface Tension ◽  
Impact Velocity ◽  
Wall Temperature ◽  
Experimental Results ◽  
Viscous Force ◽  
Equilibrium Contact Angle ◽  
High Speed Photography ◽  
Spreading Factor ◽  
The Impact ◽  
Maximum Spreading

In view of different factors that influence dynamic behavior of a droplet impacting a solid surface, high-speed photography technology was used to capture oscillation processes and splash forms after changing seven kinds of physical properties, droplets impacting different roughness and temperature walls, and with different velocities and sizes. A physical model was established, and the theoretical value correlation of maximum spreading factor was derived to compare the theoretical analysis with experimental results. The effects of viscosity, surface tension, impact velocity, diameter of droplet, roughness, and temperature of the substrates on movement characteristics during the droplet’s impact on the wall surface were investigated. As the research indicates, the rebound and oscillatory phenomena of the fluid become more obvious with an increase in surface tension, and viscous force restricts the spreading of droplets. The higher the impact velocity, the greater the spreading factor at the same time, and the more pronounced the splashing phenomenon will be. The growth rate of maximum spreading factor (βmax) increases at first and then decreases with increasing initial diameter (d0) of the droplets. The smaller the d0, the more consistent the experimental results with the analytical solutions. The equilibrium contact angle (θe) of the droplet increases with surface roughness (Ra), whereas the surface wettability degrades. θe decreases with rising wall temperature. The increase of Ra promotes the “finger-like edge” and the splash motion of droplets; moreover, the critical velocity of splash declines with Ra. The optimum temperature (Tc) of a droplet impacting the high-temperature wall reduces with a decrease of Re. Furthermore, the greater the difference between wall temperature and Tc, the more significantly βmax changes. Droplet spreading is hindered on the low-temperature wall, and the lower Re is, the smaller the decrease in amplitude of βmax with dropping wall temperature.

scholarly journals Impact of rockfalls on protection measures: an experimental approach

2015 ◽  
Vol 3 (1) ◽  
pp. 337-365
Author(s):  
J. Yuan ◽  
Y. Li ◽  
R. Huang ◽  
X. Pei
Keyword(s):  
Impact Velocity ◽  
Impact Force ◽  
Incident Angle ◽  
Drop Height ◽  
Current Standard ◽  
Protection Measures ◽  
Buffer Material ◽  
Cushion Layer ◽  
Study Laboratory ◽  
The Impact

Abstract. The determination of rockfall impact force is crucial in designing the protection measures. In the present study, laboratory tests are carried out by taking the weight and shape of the falling rock fragments, drop height, incident angle, platform on the slideway and cushion layer on the protection measures as factors to investigate their influences on the impact force. The test results indicate that the impact force is positively exponential to the weight of rockfall and the instantaneous impact velocity of the rockfall approaching the protection measures. The impact velocity is found to be dominated not only by the drop height but also by the shape of rockfall as well as the length of the platform on the slideway. A great drop height and/or a short platform produce a fast impact velocity. Spherical rockfalls experience a reater impact velocity than cubic and cylindrical ones. A layer of cushion on the protection measures may reduce the impact force to a greater extent. The reduction effects are dominated by the cushion material and the thickness of the cushion layer. The thicker the cushion layer, the greater the reduction effect and the less the impact force. The stiffer the buffer material, the less the buffering effect and the greater the impact force. The present study indicates that the current standard in China for designing protection measures may overestimate the impact force by taking no consideration for the rockfall shape, platform and cushion layer.

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