Istraživanje fenomena aerosola formiranog od emulzija mineralnih i drugih ulja u vodi

Abstract

Predmet istraživanja ove doktorske disertacije je bio formiranje i proučavanje osobina i ponašanja organskih aerosola nastalih atomiziranjem stabilnih emulzija dominantno pod dejstvom centrifugalne sile. Korišćene su vodene emulzije komercijalnih sredstava za hlađenje i podmazivanje (SHP), koja se koriste pri obradi metalnih odlivaka. Cilj istraživanja je bio ispitati i objasniti uticaj koncentracije SHP emulzije, brzine strujanja vazduha, prirode kako ulja, tako i osobina emulzija, kao što su gustina, viskoznost, površinski napon, kao i udaljenost od mesta atomiziranja na masenu koncentraciju, broj i veličinu kapi aerosola u kontrolisanim laboratorijskim uslovima. Uslovi eksperimenta isključili su uticaj toplote nastale kao posledica trenja alata i delova koji se obrađuju. Pored toga isključeno je prisustvo čvrstih mikronskih čestica koje potiču od delova koji se obrađuju, kao i prisutvo plivajućeg hidrauličnog ulja i mikroorganizama koji uvek prate realan industrijski fluid. Eksperimentalni program je realizovan na tri komercijalna SHP sredstva različitog porekla. Proučavani su aerosoli formirani atomiziranjem emulzije tri različite koncentracije uljne faze: 1, 6 i 10 %. Pri jednakim eksperimentalnim uslovima ispitivan je i aerosol formiran, od vode korišćene za pripremu emulzija. Određene su osobine ulja i emulzija koje su od značaja za atomiziranje tečnosti. Proučavan je i uticaj brzine ventilacionog vazduha na osobine aerosola. Eksperimenti su realizovani pri brzinama vazduha od 1, 3, 6, 8 m/s. Uzorkovanje aerosola je realizovano u komori, na ulazu u ventilacini vod i duž ventilacione cevi dužine 8m na pet mernih tačaka koje se nalaze na 0,5, 1, 2, 4, 6, 8 m u odnosu na komoru. Značajan doprinos ove doktorske disertacije je postavljanje teorije da atomiziranjem emulzije kao heterogene tečnosti, nastaje heterogen aerosol, pri čemu mogu nastati kapi različite prirode, između ostalog i kapi čistog ulja. Na taj način je objašnjen fenomen da porastom koncentracije emulzije raste veličina kapi nastalog aerosola. Aerosoli nastali od koncentrovanijih emulzija pokazuju uređenije strujanje kroz ventilacionu cev, što je od značaja za uspešnije projektovanje ventilacionih sistema i filtara za njihovu separaciju u cilju zaštite zdravlja radnika i zaštite okoline.

This PhD Thesis presents an experimental study of organic aerosols formed from stable water emulsions, predominantly by centrifugal force under laboratory conditions. Emulsions of metalworking fluids (MWF) were used in the experiments. The aim of this investigation was to explain the influence of MWF emulsion concentration, oil and emulsion properties (density, viscosity, and surface tension), air velocity, as well as distance from atomization generator on aerosol behavior and properties as size distribution, mass and number concentration. The experimental conditions excluded the influence of the heat arising from the friction between the tool and the workpieces. In this way the mechanism of aerosol formation by the evaporation/condensation is minimized. Besides, the presence of solid micrometer sized particulates originated from the work piece is excluded, as well as the presence of tramp oil and microorganisms, always accompanying a real industrial fluid. Three different commercial MWFs were investigated at three different oil-in-water emulsion concentrations, 1, 6, and 10 % respectively. Water aerosol was investigated under same experimental conditions. Properties of MWF oils and emulsion, which are important for liquid atomization, were determined. Influence of ventilation air velocity on aerosol properties was investigated as well. Experiments were realized under four different air velocities: 1, 3, 6, and 8 m/s. Samples were taken at three different points: at the camber, at the entrance of ventilation pipe, and at five sampling points along the pipe. Ventilation pipe was 8 m long, and sampling point were at 0.5, 1, 2, 4, 6, 8 m from the aerosol camber. The main contribution of this dissertation is the new theory that atomization of emulsion as a heterogeneous fluid leads to the formation of heterogeneous aerosol, containing droplets of a different nature, including droplets of pure oil. This theory explains the phenomenon that the aerosol droplet sizes increase with the increase of the emulsion concentration. Obtained results show that aerosols formed from the emulsions of higher concentration (6 and 10 %) have less chaotic flow through the ventilation pipe. This observation is important for better design of ventilation systems and filters for mist separation in order to protect human health and the environment.