Numerical Simulation of a Cavitating Pulsating Water Jet Used for Removing Contaminants from Metal Surfaces

The paper presents an environmentally friendly method for cleaning metal surfaces from contaminants. In this method, the contaminants are removed from surfaces by a cavitating pulsating water jet generated in the nozzle and directed at the surface. The cavitation-generating effectiveness of three various design nozzles was investigated numerically using the SolidWorks 2015 Flow Simulation software. The volume fraction of the vapour generated in the flow inside the nozzles was determined. Selected nozzle was studied experimentally in respect of efficiency of abrasive particle removal. After having carried out experiments to test the removal efficiency of the method, it was established that the water that has remained on the cleaned surface decreases its effectiveness. To solve this problem, a prototype of a cavitation-generating head with a water removal system was created and studied numerically

Investigation of vibrational behavior of friction pair under starved lubrication conditions

The paper presents results of measurements of radial vibrations of steel friction pair "rotating roller – fixed segment" under starved and amply lubricated boundary lubrication conditions. Experiments were conducted on computerized tribometer, the friction pair was lubricated with mineral motor oil. Vibrations were measured by means of accelerometer attached to the loaded element of friction pair – segment. Results are presented as vertical vibration spectra of segment versus lubrication mode and loa

Investigation of dissipative properties of liquid crystalline lubricant layer

This work aims to investigate vibration behavior of rotating roller - a fixed segment friction pair lubricated with pure motor oil and motor oil containing liquid crystal (cholesteryl oleate) additive. Experiments were performed under boundary friction conditions. Mechanical vibrations were registered through the processing and analysis of radial vibration data of the segment, obtained for each lubricant composition under constant roller speed. It is established that vibration level of the segment is reduced at the presence of liquid crystal additive. Theoretical investigations of load-carrying properties of individual layered liquid crystal in a lubricating gap of the film lubrication bearing show a strong increase in load as compared with the equivalent viscous lubricant

Investigation Into Levitating Polishing Disc Used for Flat Surface Finishing

The paper presents a new type of flat surface polishing device. The polishing disc rotates using the pressure of compressed air. The polishing disc has a special geometry, wherein it has holes for flow turbulence minimisation in the air pressure areas of the boundary. The influence of the hole inclination angle on the rotational speed of the disk and the system efficiency was studied experimentally and numerically. It was established that the optimal inclination angle is a 20° angle that results in the maximum efficiency of the proposed system. In the experiment, three polishing discs with hole inclination angles of 0°, 20°, and 30° were studied; the discs were rotated using four air pressure values: 0.2, 0.3, 0.4, and 0.5 MPa. It was found that the optimal inclination angle of holes was 20° and that the fastest rotational speed, i.e. 1900 1/min, was reached at a maximum air pressure of 0.5 MPa

Tribological adhesion of particles in acoustic field

This paper investigates interaction between two particles in acoustic field. It is shown that additional oscillating movements of particles occur as a result of plain acoustic wave action. This sufficiently increases the probability of collisions between particles. Micro-displacements in the collision zone help to remove various pollutants, oxidation products and adsorbed gas molecules from surfaces of particles. Strong adhesive bonds are formed in the contact area between the particles

Investigation of vibrational behavior of friction pair under starved lubrication conditions

The paper presents results of measurements of radial vibrations of steel friction pair "rotating roller – fixed segment" under starved and amply lubricated boundary lubrication conditions. Experiments were conducted on computerized tribometer, the friction pair was lubricated with mineral motor oil. Vibrations were measured by means of accelerometer attached to the loaded element of friction pair – segment. Results are presented as vertical vibration spectra of segment versus lubrication mode and loa

Numerical Simulation of a Pulsating Flow Generated in an Ejector

This paper presents a numerical simulation of a pulsating flow generated inside an ejector; the flow is intended to oxidize ferrous iron (Fe2+) dissolved in drinking water to ferric iron (Fe3+). The pulsating flow ejector can be used in water treatment systems where the water is saturated with oxygen before being treated by filters. It is shown that the pulsating flow is generated due to fluctuations in the pressure, density, and velocity of the flow inside the ejector. It is established that the flow pressure inside the ejector varies from 0.513 to 0.0719 MPa, the flow density varies from 4.64 to 0.66 kg/m3, and the flow velocity varies from 0 to 590 m/s. Numerical simulation results have shown that an acoustic field is generated inside the ejector during the mixing of air with water, which accelerates the coagulation of iron particles. The obtained sound power level value of 100 dB shows that the pulsating flow ejector can be used for non-reagent water treatment

An Investigation Into Fault Diagnosis in a Rotor-Bearing System with Dampers Used in Centrifugal Milk Separators

This paper deals with the problems encountered in the fault diagnosis in damped rotor-bearing systems used in centrifugal milk separators. It is shown that direct bearing vibration measurements are more reliable than indirect (through rotor housing) vibration measurements. However, in most cases it is not possible to measure bearing vibrations directly. The factors causing large diagnostic measurement errors, such as the influence of the vibration damping system, step-up gear and electric motor noise are discussed in the paper. It is established that vibration measurements of the damping system are noninformative and cannot be used to diagnose faults in bearings. It is proposed to use the vibration spectra correlation to predict bearing failures in rotor-bearing systems of this type

Matavimų rezultatų, gautų matuojant sudėtingos geometrinės formos detales 3D skeneriais ir koordinatine matavimo mašina, lyginamoji analizė

This study compares the dimension measurements results obtained for two parts that had convex and concave parabolic profiles. Three different measurement systems were employed for measurements: coordinate measuring machine (CMM), 3D laser and 3D photometric scanners. It was found using Student’s t – test that results obtained by CMM measuring system are statistically significantly (p < 0.001) more accurate than results obtained by means of 3D laser and 3D photometric scanners. It was also established that results obtained by means of 3D laser scanning system are statistically significantly more accurate (p < 0.05) than those obtained by means of 3D photometric scanning system. Santrauka Straipsnyje lyginami dviejų detalių matmenų matavimų rezultatai, gauti skirtingomis matavimo sistemomis: koordinatine matavimo mašina (KMM), 3D lazeriniu skeneriu ir 3D fotometriniu skeneriu. Buvo matuojamos iškilaus ir įgaubto paraboloidinio profilio detalės. Išanalizavus matavimo rezultatus gauta, kad KMM matavimo sistema gauti rezultatai pagal Stjudento t kriterijų (t-test) statistiškai reikšmingai (p < 0,001) tikslesni už rezultatus, gautus 3D lazeriniu ir fotometriniu skeneriais. Taip pat nustatyta, kad rezultatai, gauti 3D lazerine skenavimo sistema, yra statistiškai reikšmingai tikslesni (p < 0,05) už gautuosius 3D fotometrinio skenavimo sistema. Reikšminiai žodžiai: KMM, fotometrinis skeneris, lazerinis skeneris, 3D modelis