scholarly journals STUDY OF HERMETIC ABILITY OF A COMBINED FERROFLUIDIC SEALED OF BEARING ASSEMBLIES

2021 ◽  
Vol 6 (1) ◽  
pp. 25-31
Author(s):  
Vladimir Terentyev ◽  
Aleksei Bausov ◽  
Mihail Toropov
Keyword(s):  
Pressure Difference ◽  
Critical Pressure ◽  
Magnetic Particles ◽  
Theoretical Data ◽  
Ferromagnetic Phase ◽  
Dynamic Mode ◽  
Static Test ◽  
Lip Seal ◽  
Bearing Assembly ◽  
Starting Torque

The purpose of the research is to increase the efficiency of hermetic ability of bearing assemblies by using com-bined ferrofluidic sealed. The research objective is theoretic justification of the maximum concentration of ferro-magnetic particles in fluid, investigation of hermatic ability of a combined ferrofluidic seal under conditions of tem-perature changing and speed of a shaft rotation of packing bearing assembly. The study of hermetic ability of lip and ferro-fluidic sealed was carried out on a test bench, allowing to determine the packing ability of seals both in static and dynamic mode. On the basis of theoretical data, formulas were determined to find the maximum concen-tration of hard and magnetic phases in a ferrofluid, and its composition based on a polyethylsiloxane liquid PES-5 with a 40 kA/m saturation magnetization and a 1.2 Pas dynamic viscosity coefficient was developed. A mixture of magnetite with powdered iron was used as the ferromagnetic phase. Oleic acid was used as a surfactant. Studies to determine hermetic capacity have shown a higher efficiency of the combined ferrofluidic seal compared to the lip one. During static test within the temperature range between 20 to 600C, the critical pressure difference of the com-bined seal was 4-16% higher than that of the lip seal. Temperature increase of the bearing assembly from 20 to 1200C causes a decrease in critical pressure difference of up to 50%. This is due to a decrease in the sedimentative stability of the magnetic fluid as a result of an increase in temperature. Studies show that the combined ferrofluidic seal has a higher hermetic tightness at the starting torque than the standard lip seal. In contrast to the lip seal (which tends to lose its tightness at the starting torque), no leakage of pressure fluid from the sealed unit was observed of the com-bined ferrofluidic one with a pressure drop of 0.094 MPa. The results obtained allow reasonably select the concen-tration of magnetic particles in the ferrofluid, and also prove the prospects of replacing standard lip seals with com-bined ferrofluidic ones.

The Analysis on the Starting Friction Torque Increase of Magnetic Fluid Revolving Sealing

2013 ◽  
Vol 275-277 ◽  
pp. 429-432 ◽  
Author(s):  
Yu Qiang Cai ◽  
Na Xing
Keyword(s):  
Magnetic Fluid ◽  
Magnetic Particles ◽  
Influence Factor ◽  
Magnetic Field Gradient ◽  
Friction Torque ◽  
Key Factor ◽  
Lower Temperature ◽  
Change Of Microstructure ◽  
Starting Torque ◽  
Main Influence

Abstract. Magnetic fluid revolving sealing is widely used in modern industry. In the process of application, it is founded that the starting friction torque is very large, particularly at lower temperature. This problem has become a key factor restricting the application of magnetic fluid rotation sealing. In this paper, the mechanism of starting torque increase is analyzed, based on the change of microstructure and its viscosity. After analysis , such conclusion is obtained , which can be described: to a certain sealing structure, the type of magnetic fluid, size distribution of magnetic particles as well as the working condition concluding temperature, magnetic field gradient and the revolving velocity of shaft is the main influence factor of starting friction torque . It is very useful to reduce the starting friction torque.

The Critical Pressure Difference Prediction of Sand Production in Deepwater Sandstone Gas Reservoirs

2013 ◽  
Vol 31 (19) ◽  
pp. 1925-1932
Author(s):  
J. Deng ◽  
L. Wang ◽  
P. Li ◽  
W. Zhao
Keyword(s):  
Pressure Difference ◽  
Critical Pressure ◽  
Sand Production ◽  
Gas Reservoirs

A single cell model for pretreatment of wood by microwave explosion

Holzforschung ◽  
2010 ◽  
Vol 64 (5) ◽  
Author(s):  
Xianjun Li ◽  
Yongdong Zhou ◽  
Yonglin Yan ◽  
Zhiyong Cai ◽  
Fu Feng
Keyword(s):  
Pressure Difference ◽  
Critical Pressure ◽  
Cell Model ◽  
Circumferential Stress ◽  
Longitudinal Direction ◽  
Critical Conditions ◽  
Maximum Pressure ◽  
Parenchyma Cells ◽  
Ray Parenchyma ◽  
Ray Parenchyma Cells

Abstract A theoretical model was developed to better understand the process of microwave explosion treatment of wood cells. The cell expansion and critical conditions concerning pressure and temperature of ray parenchyma cells in Eucalyptus urophylla were simulated during microwave pretreatment. The results indicate that longitudinal and circumferential stresses were generated in the cell walls owing to the internal steam pressure during extensive microwave treatment. The circumferential stress is twice as high as the longitudinal stress. The pressure difference reaches its maximum value of 0.84 MPa when the extension ratio is 1.20 for the longitudinal direction and 1.62 for the circumferential direction. The maximum pressure difference at the theoretical yielding point is the critical pressure difference that can eventually rupture the ray cell. The critical pressure difference decreases with increasing cell radius and decreasing shear modulus in the cell wall. This simulated result provides useful information to modify wood at the level of ray parenchyma cells.

Numerical Analysis of Smoke Confinement by Means of Air Curtains in High-Rise Buildings

2016 ◽  
Vol 858 ◽  
pp. 287-293 ◽  
Author(s):  
Xiao Tao Zhang ◽  
Chong Tan ◽  
Yu Shi Lu
Keyword(s):  
Pressure Difference ◽  
Critical Pressure ◽  
Discharge Coefficient ◽  
Wind Effect ◽  
Cfd Simulations ◽  
Air Curtain ◽  
High Rise ◽  
Discharge Velocity ◽  
Fire Effect ◽  
Computational Fluid Dynamics Cfd

As an effective approach to confine fire-induced smoke transportation, the application of air curtains is introduced in high-rise buildings during fire. A series of computational fluid dynamics (CFD) simulations were carried out for a full scale corridor in high-rise building, in which different factors such as air curtain discharge velocity (ACDV), human evacuation and pressure difference are considered. The results show that with the ACDV increasing, the smoke flowing resistance of air curtain is greater. The factor of evacuation cause significant impact on the efficiency of air curtain. Compared with the pressure difference caused by wind effect, the fire effect would lead to higher critical pressure difference and discharge coefficient.

Propagation of an Air Finger Into a Fluid Filled Bifurcation

2010 ◽  
Author(s):  
Benjamin L. Vaughan ◽  
James B. Grotberg
Keyword(s):  
Numerical Model ◽  
Viscous Fluid ◽  
Pressure Difference ◽  
Respiratory Diseases ◽  
Critical Pressure ◽  
Distress Syndrome ◽  
The Other ◽  
Liquid Plug ◽  
Pulmonary Airways ◽  
Single Branch

The occlusion of pulmonary airways can be caused by many respiratory diseases such as respiratory distress syndrome. It is believed that these occluded airways are reopened by the propagation of an air finger. The mechanics of airway reopening have been studied in-depth for an individual airway [1,2] without considering the frequent branching of pulmonary airways. The presence of a bifurcation leads to the question of whether the propagating air finger will clear both branches of the airway or will propagate through a single branch, leaving the other branch occluded. The propagation of a finite length liquid plug through a fixed bifurcation has been studied experimentally [3, 4]. We wish to develop a numerical model for the propagation of an air finger through bifurcating channel filled with a viscous fluid. In this model, the air finger is driven by a pressure difference between the parent channel and the two daughter branches. The presence of an additional pressure difference between the two branches can cause unsymmetrical splitting of the air finger and, above a critical pressure difference, prevent the clearance of both branches.

scholarly journals Simulation of the Gas Filling and Evacuation Processes in an Inertial Confinement Fusion (ICF) Hohlraum

Processes ◽  
2019 ◽  
Vol 7 (5) ◽  
pp. 269
Author(s):  
Liangyu Wu ◽  
Hua Zhou ◽  
Cheng Yu ◽  
Feng Yao
Keyword(s):  
Mass Flow ◽  
Pressure Difference ◽  
Inertial Confinement Fusion ◽  
Critical Pressure ◽  
Flow Simulation ◽  
Pressure Variation ◽  
Inertial Confinement ◽  
Confinement Fusion ◽  
Variation Rate ◽  
Hole Number

In indirect inertial confinement fusion (ICF), the prediction of gas pressures and mass flow rates in the hohlraum is critical for fielding the hohlraum film and the support tent. To this end, it is desirable to understand the gas filling and evacuation process through the microcapillary fill tube and the support tent. In this work, a unified flow simulation of the filling and evacuation processes through the microcapillary fill tube and the support tent in an ICF hohlraum was conducted to study the gas pressure and mass flow rate in the hohlraum. The effects of the support tent size and the microcapillary fill tube size on the critical pressure variation and pressure difference across the hole on the support tent are examined. The results indicate that an increase in the diameter of the hole and the hole number leads to a smaller pressure difference across the hole on the support tent. If the diameter of the hole on the support tent is larger than 0.06 mm, the critical pressure variation rate is nearly independent of the diameter and the hole number. Increases in the diameter and decreases in the length of the microcapillary fill tube induce a larger critical pressure variation rate and pressure difference across the hole, which is conductive to fielding the hohlraum film.

scholarly journals Simulating the Effects of Structural Parameters on the Hydraulic Performances of Venturi Tube

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Yanqi Sun ◽  
Wenquan Niu
Keyword(s):  
Pressure Difference ◽  
Critical Pressure ◽  
Structural Parameters ◽  
Pressure Coefficient ◽  
Head Loss ◽  
Hydraulic Performance ◽  
Outlet Section ◽  
Minimum Pressure ◽  
Absorption Ratio ◽  
Contraction Ratio

The effects of Venturi structural parameters on its hydraulic performance were studied, which provided theoretical basis for the design of Venturi injector. With an inlet diameter of 50 mm, based on the method of computational fluid dynamics (CFD), the effects of the structural parameters (such as throat taper, throat contraction ratio, and throat length) on their hydraulic performance (such as outlet faceted average velocity, minimum pressure, and critical pressure) were studied under different inlet pressures and pressure differences between inlet and outlet. A power function relationship existed between the mean velocity in outlet section and pressure difference, with an approximate flow stance index of 0.53. Minimum pressure occurred in the throat inlet wall and there was a linear relationship between the minimum pressure and the pressure difference at the inlet and outlet. The throat contraction ratio was the main factor on the effect of Venturi injector performance, which was positively correlated with outlet velocity, negatively to critical pressure, the minimal in-tube pressure, coefficient of local head loss, and fertilizer absorption ratio. For designing Venturi injector, contraction ratio should be reasonably selected according to the coefficient of local head loss and fertilizer absorption ratio.

scholarly journals Virtual Instrumentation Programming and Psoc Embedded Design for Bearing Fault Detection: Uses Impulse Excitation Technique

2018 ◽  
Vol 7 (3.27) ◽  
pp. 170
Author(s):  
J J. Jayakanth ◽  
M Chandrasekaran
Keyword(s):  
Power Spectrum ◽  
Virtual Instrument ◽  
Vibration Signal ◽  
Test Method ◽  
Dynamic Mode ◽  
Static Mode ◽  
Vibration Signals ◽  
Static Test ◽  
Impulse Excitation ◽  
On Chip

This paper describes, a novel innovative design for generating vibration signals in a bearing, which is in static mode not in dynamic mode like other usual measurements reported in literatures,  for various types of bearing faults analysis supports users with a technique based on monitoring vibration signals. This paper reports the computed power spectrum from vibration signal clearly identifies the fault signature with its raise in amplitude. Hence, in an impulse excitation technique vibration analysis with computed power spectrum provides an efficient monitoring of fault in axle bearings in a short timing. Programmable System on Chip (PSoC) creator design and Virtual Instrument program written in LabVIEW, a graphical language, provides efficient implementation of impulse excitation technique possible in static test method in a minimal time.   

scholarly journals Tuning of Hidden Order and Superconductivity in URu2Si2 by Applied Pressure and Re Substitution

2006 ◽  
Vol 986 ◽  
Author(s):  
Nicholas P. Butch ◽  
Jason R. Jeffries ◽  
Benjamin T. Yukich ◽  
M. Brian Maple
Keyword(s):  
Single Crystals ◽  
Critical Field ◽  
Electrical Transport ◽  
Critical Pressure ◽  
Applied Pressure ◽  
Ferromagnetic Phase ◽  
Zero Temperature ◽  
Czochralski Technique ◽  
Transport Studies ◽  
Hidden Order

AbstractSingle crystals of URu2-xRexSi2 have been grown via the Czochralski technique. Detailed electrical transport studies under pressure on single crystals of URu2Si2 confirm that the zero-temperature critical field is suppressed smoothly towards an extrapolated critical pressure of 15 kbar, which also corresponds to the accepted critical pressure of the hidden order phase. Improving on previous work on polycrystalline samples, studies of single crystals of URu2-xRexSi2 have provided more precise tracking of the suppression of both the hidden order phase at low doping and the ferromagnetic phase at intermediate Re concentrations.

scholarly journals Nonlinear Flow Characteristics of a System of Two Intersecting Fractures with Different Apertures

Processes ◽  
2018 ◽  
Vol 6 (7) ◽  
pp. 94 ◽  
Author(s):  
Richeng Liu ◽  
Yujing Jiang ◽  
Hongwen Jing ◽  
Liyuan Yu
Keyword(s):  
Numerical Simulation ◽  
Pressure Difference ◽  
Critical Pressure ◽  
Stokes Equations ◽  
Nonlinear Flow ◽  
Fracture Aperture ◽  
Simulation Code ◽  
Hydraulic Aperture ◽  
Mechanical Aperture ◽  
Forchheimer’S Law

The nonlinear flow regimes of a crossed fracture model consisting of two fractures have been investigated, in which the influences of hydraulic gradient, surface roughness, intersecting angle, and scale effect have been taken into account. However, in these attempts, the aperture of the two crossed fractures is the same and effects of aperture ratio have not been considered. This study aims to extend their works, characterizing nonlinear flow through a system of two intersecting fractures with different apertures. First, three experiment models with two fractures having different apertures were established and flow tests were carried out. Then, numerical simulations by solving the Navier-Stokes equations were performed and the results compared with the experiment results. Finally, the effects of fracture aperture on the critical pressure difference and the ratio of hydraulic aperture to mechanical aperture were systematically analyzed. The results show that the numerical simulation results agree well with those of the fluid flow tests, which indicates that the visualization techniques and the numerical simulation code are reliable. With the increment of flow rate, the pressure difference increases first linearly and then nonlinearly, which can be best fitted using Forchheimer’s law. The two coefficients in Forchheimer’s law decrease with the increasing number of outlets. When increasing fracture aperture from 3 mm to 5 mm, the critical pressure difference increases significantly. However, when continuously increasing fracture aperture from 5 mm to 7 mm, the critical pressure difference changes are negligibly small. The ratio of hydraulic aperture to mechanical aperture decreases more significantly for a fracture that has a larger aperture. Increasing fracture aperture from 5 mm to 7 mm, that has a negligibly small effect on the critical pressure difference will however significantly influence the ratio of hydraulic aperture to mechanical aperture.

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