Prevention of Nozzle Wear in Abrasive Water Suspension Jets (AWSJ) Using Porous Lubricated Nozzles

2002 ◽  
Vol 125 (1) ◽  
pp. 168-180 ◽  
Author(s):  
Umang Anand ◽  
Joseph Katz
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Abrasive Particle ◽  
High Viscosity ◽  
Oil Viscosity ◽  
Axisymmetric Nozzle ◽  
Oil Film ◽  
Nozzle Wear ◽  
Dimensional Facility ◽  
The Impact

This paper introduces a novel method for preventing nozzle wear in abrasive water jets. It consists of using a porous nozzle, surrounded by a reservoir containing high-viscosity lubricant, which is exposed to the same driving pressure as the flow in the nozzle. The pressure difference across the porous medium, generated due to the high-speed flow in the nozzle, continuously forces lubricant through it. The resulting thin oil film forming on the walls of the nozzle protects the walls from the impact and shear caused by the abrasive particles. The porous nozzles were manufactured using Electric Discharge Machining and examined with Scanning Electron Microscopy. Two test facilities were used for evaluating the porous lubricated nozzles. The first was a two-dimensional facility, supporting a 145 μm wide nozzle with windows on both sides, which enabled visualization of the oil film and measurements of the liquid and abrasive-particle velocities using Particle Image Velocimetry. The measured slip velocities were also compared to computed values from a simple numerical model involving one-way coupling. The second facility used a 200 μm axisymmetric nozzle to determine the extent of nozzle wear under different conditions. We found that the presence of an oil film substantially reduced the extent of nozzle wear, from 111 percent of the diameter, when the nozzle was not lubricated, to 4 percent, when the oil viscosity was 1800 mm2/s and its flow rate was 2.4 percent of the water flow (over the same period). The wear increased as the lubricant flow rate and viscosity decreased. The presence of the oil film also improved the coherence of the jet.

scholarly journals Viscosity Effect on Stiffness of Non-conventional (Five Tilted Pads) Journal Bearing

2018 ◽  
Vol 25 (3) ◽  
pp. 53-57
Author(s):  
Mohammed Oawed Atteaa Alhassany ◽  
Ali Khalid Aldulaimy
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Cross Coupling ◽  
High Viscosity ◽  
Lubricating Oil ◽  
Coupling Coefficients ◽  
Oil Viscosity ◽  
Viscosity Change ◽  
Oil Film ◽  
Stiffness Coefficients

In this tribological study, we highlight the effect of lubricating oil viscosity in the Multi-pads hydrodynamic journal bearings generate important improvement in characteristics of stiffness and stability in the high speed turbomachines. Depending on viscosity of oil film (three values) variation for five tilted pads bearing, each pad is pivoted and is facilitated to be tilted with small angles, by using Matlab program, we calculate the oil film thickness for convergence layer. We applied Reynold’s equation and solved it’s numerically by using finite difference method with 5 nodes technique to find the pressure distributed on each node in the mesh of tilted pad, then calculate stiffness coefficients. Results show that there is clear effect on stiffens with viscosity change. The increase in value of Krr (for n = 0.3) between viscosity (0.04 Pas. s) and viscosity (0.058 Pas. s) is14.33 MN/m, while the increase in Krr value between viscosity (0.058 Pas. s) and viscosity (0.087 Pas. s) is 11.37 MN/m. the increase in value the of Kss (for n = 0.3) between viscosity (0.04 Pas. s) and viscosity (0.058 Pas. s) is5.921 MN/m, while increase in Kss value between viscosity (0.058 Pas. s) and viscosity (0.087 Pas. s) is9.55 MN/m respectively. the increase in value of Ksr (for n = 0.3) between viscosity (0.04 Pas. s) and viscosity (0.058 Pas. s) is 8.95 MN/m, while the increase in Ksr value between viscosity (0.058 Pas. s) and viscosity (0.087 Pas. s) is 14.41 MN/m respectively. the increase in value of Krs (for n = 0.3) between viscosity (0.04 Pas. s) and viscosity (0.058 Pas. s) are 5.08 MN/m, while the increase in Krs value between viscosity (0.058 Pas. s) and viscosity (0.087 Pas. s) is8.19 MN/m respectively. The values of the dominate principal coefficients Krr is greater than that of Ksr, also The values of the principal coefficients Kss is greater than that of cross coupling Krs for all values of viscosity that studied. From this result, we can conclude the side effect of cross coupling coefficients (Ksr ,Krs) can be overcome by great values for principal coefficient (Krr, Kss) respectively, so we can get good improvement instability for this bearing by variation the viscosity. After that, we regarded to use high viscosity lubricant in multi-pad journal bearing to improve the performance and stability by controlling the stiffness coefficients.

Optimization of an Oil Film Journal Bearing for Temperature Reduction

2021 ◽  
Author(s):  
Steven Chatterton ◽  
Paolo Pennacchi ◽  
Andrea Vania ◽  
Phuoc Vinh Dang
Keyword(s):  
High Speed ◽  
Maximum Temperature ◽  
Shear Stresses ◽  
Oil Viscosity ◽  
Minimum Thickness ◽  
White Metal ◽  
Oil Film ◽  
Lubricating Film ◽  
Bearing Stiffness ◽  
Dynamic Performances

Abstract Rotating machines are generally equipped with tilting-pad journal bearings. In general, during the design phase, the aspects that are most taken into account are the dynamic performances in terms of stiffness and damping and the minimum thickness of the oil film to avoid mixed lubrication conditions that can lead to white metal wear phenomena. The thermal aspect, on the other hand, is often underestimated and can be critical for machines operating at high speed and high load. Thermal heating is caused by shear stresses in the lubricating film. In general, an increase in lubricant temperature corresponds to a reduction in oil viscosity followed by a reduction in lubricant film thickness. This has a beneficial effect on bearing stiffness. On the contrary, a high temperature in the oil film is detrimental to the mechanical characteristics of the white metal which is characterized by a low melting temperature and subject to thermal creep phenomena. The article analyzes, by means of numerical simulations, the influence of the bearing geometry on the thermal behavior of the bearing. The bearing geometry will then be optimized to reduce the maximum temperature in the bearing.

Deformation, heating and melting of solids in high-speed friction

1961 ◽  
Vol 260 (1303) ◽  
pp. 433-458 ◽  
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Frictional Heating ◽  
Vertical Axis ◽  
High Viscosity ◽  
Molten Material ◽  
General Behaviour ◽  
Low Viscosity ◽  
Heavy Loads ◽  
The Impact

An experimental study has been made of the effects of frictional heating on the deformation of solids rubbing at very high speeds and at reasonably heavy loads. A new method for measuring the friction under these conditions is described. A steel ball, rapidly spinning round its vertical axis, is allowed to fall a short distance and to bounce off an inclined flat solid surface. The friction of steel on various solids in a vacuum of ca . 10 -4 mm Hg, at sliding speeds up to 700 m/s, is determined from the measured direction of the ball’s horizontal velocity after the impact. In addition, separate piezo-electric measurements are made of the load and the friction force. Again the coefficient of friction is found to decrease with increasing sliding speed. The general behaviour is similar to that observed at light loads but there are important differences. With heavy loads the deformation of the solids appears to be primarily plastic. Within a very short time after being brought into contact with a fast-moving surface, solids with a sufficiently low melting point melt on a large scale so that a continuous film of molten material is developed over the area of contact. The resistance to motion is determined primarily by this liquid film so that it may now increase as the speed rises. The heating due to the shearing of this film causes the solid to melt away rapidly, and as a result the wear rate of such solids usually becomes great at high sliding speeds. Certain polymers, however, exhibit a greater wear resistance than metals and other solids which possess a low viscosity in the molten state. Calculations indicate that in these polymers, owing to their high viscosity, the temperature of the sheared film may be considerably higher than the melting temperature. As a consequence, a larger proportion of the heat developed by the shearing may be absorbed in the already molten material, and less heat will be available for further melting. Gas liberated by thermal decomposition may also reduce the friction and wear.

scholarly journals Study of Fluid Flow to a Horizontal Well

2021 ◽  
Vol 21 (2) ◽  
pp. 64-70
Author(s):  
Oksana N. Shevchenko ◽  
Keyword(s):  
Flow Rate ◽  
Horizontal Well ◽  
Initial Pressure ◽  
Horizontal Wells ◽  
Surface Friction ◽  
Economic Assessment ◽  
High Viscosity ◽  
Geological Structure ◽  
Oil Viscosity ◽  
Fluid Filtration

Recently, it is necessary to note the presence of negative dynamics in the deterioration of the reserves structure for newly discovered fields, and most of the them are classified as hard-to-recover, confined to deposits with a complex geological structure, low permeability, high oil viscosity, complicated by the presence of faults, active bottom waters and gas caps. Hard-to-recover reserves are drilled with horizontal wells. This is primarily because horizontal wells make it possible to multiply the area of fluid filtration due to the increase in the drainage area, due to the extensive contact of the horizontal well section with the rock, allowing to increase the well flow rate many times over. Summarizing the above, horizontal wells are used to develop fields with the following parameters: fields with a thin oilsaturated rim (up to 15 m), with a gas cap and bottom water; fields of heavy oil, with a viscosity of more than 30 mPa·s; fields with low reservoir permeability (less than 0.002 μm2). Under these conditions, linear Darcy’s law cannot describe fluid filtration. Under the conditions of high-viscosity oil and lowpermeability reservoir existence, a certain initial pressure gradient is determined, due to the rheological properties of the filtering fluid and high values of the surface friction coefficient. Under conditions of a thin oil rim and an increased gas factor, the limiting filtration rates due to the dissolved gas regime are observed, and a nonlinear law describes the fluid inflow. One of the main parameters in the preparation of the technical and economic assessment of the reservoir is the flow rate of each individual horizontal well. Analytical methods for calculating the horizontal well flow rate show a high error. It is proposed to take a fresh look at the problem of determining the predicted flow rate of a horizontal well, using well-known approaches for solving this issue. It is rather difficult to reliably predict the parameters of reservoir operation: the horizontal wells productivity obtained with the help of modern hydrodynamic stimulators turns out to be unreliable, which leads to the formation of an insufficiently rational development system. And the arising complications during operation in field conditions have to be eliminated due to significant volumes of material and labor resources. Thus, the development of methods that contribute to obtaining a reliable calculation of production is an urgent task for the oil industry.

The Role of Emulsification and Interfacial Tension Ift For the Enhanced Oil Recovery Eor in Surfactant Flooding

2021 ◽  
Author(s):  
Xiaoxiao Li ◽  
Xiang'an Yue ◽  
Jirui Zou ◽  
Lijuan Zhang ◽  
Kang Tang
Keyword(s):  
Interfacial Tension ◽  
Crude Oil ◽  
Flow Rate ◽  
Oil Recovery ◽  
Surfactant Flooding ◽  
Displacement Efficiency ◽  
Oil Viscosity ◽  
Oil Film ◽  
Oil Flow ◽  
Emulsifying Capacity

Abstract In this study, a visualized physical model of artificial oil film was firstly designed to investigate the oil film displacement mechanisms. Numerous comparative experiments were conducted to explore the detachment mechanisms of oil film and oil recovery performances in different fluid mediums with flow rate. In addition, the of influencing factors of oil film were comprehensively evaluated, which mainly includes: flow rate, surfactant behaviors, and crude oil viscosity. The results show that, (1) regardless of the viscosity of crude oil, flow rate presents a limited contribution to the detachment of oil film and the maximum of ultimate oil film displacement efficiency is only approximately 10%; (2) surfactant flooding has a synergistic effect on the oil film displacement on two aspects of interfacial tension (ITF) reduction and emulsifying capacity. Giving the most outstanding performance for two oil samples in all runs, IFT reduction of ultra-low value is not the only decisive factor affecting oil film displacement efficiency, but the emulsifying capability plays the key role to the detachment of oil film due to effect of emulsifying and dispersing on oil film; (3) the increasing flow rate of surfactant flooding is able to enhance the detachment of oil film but has an objective effect on the final oil film displacement efficiency; (4) flow rate have the much influence on the detachment of oil film, but the most easily controlled factor is the surfactant property. The finding provides basis for oil film detachment and surfactant selection EOR application.

Impact of a Lubricated Surface by a Sphere

1975 ◽  
Vol 97 (4) ◽  
pp. 613-615 ◽  
Author(s):  
H. D. Conway ◽  
H. C. Lee
Keyword(s):  
Flat Surface ◽  
Oil Viscosity ◽  
Film Pressure ◽  
Oil Film ◽  
Pressure Distributions ◽  
The Impact ◽  
Oil Film Pressure

This paper presents an analysis of the impact between a sphere and a flat surface covered by an oil film. Pressure distributions are found as functions of time for oils whose viscosities are either constant or pressure-dependent. It is believed that the increase of oil viscosity with pressure is a main cause of the deep conical dents observed experimentally.

Simulation of Temperature Field of Oil Film in Super-High Speed Hybrid Journal Bearing Based on FLUENT

2009 ◽  
Vol 69-70 ◽  
pp. 296-300 ◽  
Author(s):  
Shi Chao Xiu ◽  
Peng Bo Xiu ◽  
Shi Qiang Gao
Keyword(s):  
Temperature Field ◽  
High Speed ◽  
Journal Bearing ◽  
Flow State ◽  
Oil Viscosity ◽  
Oil Film ◽  
High Speed Grinding ◽  
Higher Temperature ◽  
Grinding Machine ◽  
Geometrical Field

The hybrid journal bearing with the high rigidity and rotation accuracy has been used in super-high speed grinding machine in some cases. But the main shortcoming of hybrid journal bearing is the higher temperature rise in the oil film when bearing works, which can lower the bearing capacity and cause the bearing failure due to the drop of oil viscosity and the larger thermal deformation. Fluent is a special CFD soft to simulate and analyze the flow and the heat exchange of liquid in the complex geometrical field. In this paper, the simulations of the temperature field of the oil film in the super-high speed hybrid journal bearing were performed by Fluent based on the mathematical models. The simulation results can not only forecast the flow state and the thermal properties of the bearing oil, but also find the design limitation of the bearing for the more improvement of the bearing design.

scholarly journals Mustafa Ozsipahi, Sertac Cadirci, Hasan Gunes, Husnu Kerpicci, Kemal Sarioglu

2020 ◽  
Vol 7 ◽  
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Internal Surface ◽  
Suction Side ◽  
Oil Viscosity ◽  
Two Phase ◽  
Oil Film ◽  
Lubricant Oil ◽  
Immiscible Mixture

The aim of this study is to numerically investigate theeffects of various parameters on the lubricant (oil)-coolant two phaseflow in the lubrication system of hermetic compressors commonlyused on household refrigerators. Lubrication oil is pumped from thesump through an asymmetrically opened hole on the bottom of thecrankshaft (suction side or inlet) by its rotational motion and climbsas an oil film on the internal surface of the helical channel carved onthe crankshaft surface. This oil film is directed to crankshaft upperexit discharging into the coolant refrigerant and it is used tolubricate the moving components of the compressor including thecylinder piston. The oil forms an immiscible mixture with coolant,thus a two phase flow model using Volume of Fluid (VOF) method isused. Specifically, the mass flow-rate of oil is determined as afunction of the rotational speed, oil viscosity and the submersiondepth of the crankshaft in the oil-sump. With increasing rotationalspeed and submersion depth, the mass flow-rate through thecrankshaft upper exit also increases. With increasing oil viscosity themass flow-rate through the crankshaft upper exit decreases due to theincreased friction.

A gear rattle model accounting for oil squeeze between the meshing gear teeth

2005 ◽  
Vol 219 (9) ◽  
pp. 1075-1083 ◽  
Author(s):  
R Brancati ◽  
E Rocca ◽  
R Russo
Keyword(s):  
High Frequency ◽  
Oil Viscosity ◽  
Damping Force ◽  
Oil Film ◽  
One Dimensional ◽  
Gear Teeth ◽  
High Frequency Vibrations ◽  
The Impact ◽  
Gear Rattle ◽  
Lubrication Conditions

In this paper a non-linear one-degree-of-freedom model for analysis of gear rattle vibrations in automotive manual transmissions is presented. In order to take into account the damping effects owing to the oil in the gap between two teeth of a meshing gear, a simple one-dimensional model for the oil-film squeeze effects is proposed. The squeeze model assumes that the damping force is proportional to the oil viscosity and to the extension of the oil film in the plane of curvature of the teeth, which may depend on the lubrication conditions (dry sump, splash, bath). The results provided from several numerical simulations, carried out with reference to helical involute tooth pairs, confirm the capability of oil in reducing the high-frequency vibrations subsequent to the impact between the teeth. In particular, the influence exerted by oil viscosity and gap extension on the rattle characteristics is investigated through the analysis of the transient response of the driven gear by imposing a harmonic motion to the driving gear.

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