Mixture Of Silicone Oil Research Articles

"Honeycomb" Photothermal Lubricated Porous Foam with Low-Temperature, Weak-Light, Anti-Icing/Deicing, and Long-Lasting Lubrication Properties.

The prevalence of icing in nature has become a significant threat to human work and life, prompting the development of more energy-efficient active/passive combination anti-icing/deicing technologies. In order to overcome the disadvantage of the poor durability of superhydrophobic surfaces, lubricated surfaces inspired by nepenthes have been preferred. In this study, a paraffin and silicone oil-infused photothermal foam (PSIPF) with excellent overall performance was prepared using polypyrrole (PPy) as a photothermal conversion material, a mixture of silicone oil and paraffin as a lubricating fluid, and melamine foam (MF) as a carrier. The surface adhesive strength is less than 20 kPa at -20 °C, the melting time is only 1018 s at an irradiance of 200 W/m2 and -20 °C (0.2 sun), and surface droplets do not freeze within 1 h at -10 °C. Furthermore, the surface exhibits excellent mechanical durability and stability, maintaining optimal lubrication properties following repeated cycles of icing/deicing, water rinsing, and immersion for 2 days in acid and alkaline conditions. This photothermal lubricated surface with excellent anti-icing/deicing properties at low temperatures and in weak-light environments provides a wider range of applications for equipment at high latitudes and high altitudes.

Effects of Increased Tooth Clearance on the Performance of a Labyrinth Seal With Oil-Rich Bubbly Laminar Flow

Abstract In recent years, multiphase pumps have become more and more popular because of the capability to simplify the process, reduce the footprint, and lower the cost. To compensate for the axial thrust force, an annular seal is normally used as a balance piston seal, and the labyrinth seal is one of the choices. A typical labyrinth seal consists of a surface with teeth and a smooth surface. The teeth are either on the rotor or the stator. To protect the machine, one side (either the teeth or the smooth surface) is made of a material that can be safely sacrificed during a rub. After the rub, the teeth clearance is increased. This paper studies the impact of the increased teeth clearance on the performance of the labyrinth seal under oil-rich bubbly flow conditions. The test fluid is a mixture of silicone oil (PSF-5cSt) and air with inlet gas volume fraction (GVF) up to 9%. Tests are conducted with pressure drop (PD) = 34.5 bars, rotor speed ω = 5 krpm, and radial tooth clearance Cr = 0.102 mm and 0.178 mm. Test results show that, for all test conditions (before and after injecting air bubbles into the oil flow), increasing Cr from 0.102 mm to 0.178 mm increases the mass flow rate by about 40% but barely changes the test seal's rotordynamic coefficients, i.e., the increased tooth clearance would not change the pump vibration performance.

Instability and symmetry breaking in binary evaporating thin films over a solid spherical dome

Abstract

Hybrid Magnetorheological Composites for Electric and Magnetic Field Sensors and Transducers.

We present a simple, low-cost, and environmental-friendly method for the fabrication of hybrid magnetorheological composites (hMCs) based on cotton fibers soaked with a mixture of silicone oil (SO), carbonyl iron (CI) microparticles, and iron oxide microfibers (F). The obtained hMCs, with various ratios () of SO and F, are used as dielectric materials for manufacturing electrical devices. The equivalent electrical capacitance and resistance are investigated in the presence of an external magnetic field, with flux density B. Based on the recorded data, we obtain the variation of the relative dielectric constant (), and electrical conductivity (), with , and B. We show that, by increasing , the distance between CI magnetic dipoles increases, and this leads to significant changes in the behaviour of and in a magnetic field. The results are explained by developing a theoretical model that is based on the dipolar approximation. They indicate that the obtained hMCs can be used in the fabrication of magneto-active fibers for fabrication of electric/magnetic field sensors and transducers.

Preswirl and Mixed-Flow (Mainly Liquid) Effects on Rotordynamic Performance of a Long (L/D = 0.75) Smooth Seal

Abstract Measured results are presented for rotordynamic coefficients and mass leakage rates of a long smooth annular seal (length-to-diameter ratio L/D = 0.75, diameter D = 114.686 mm, and radial clearance Cr = 0.200 mm) tested with a mixture of silicone oil (PSF-5cSt) and air. The test seal is centered, the seal exit pressure is maintained at 6.9 bars-g while the fluid inlet temperature is controlled within 37.8–40.6 °C. It is tested with three inlet-preswirl inserts, namely, zero, medium, and high (the preswirl ratios (PSRs), i.e., the ratio between the fluid's circumferential velocity and the shaft surface's velocity, are in ranges of 0.10–0.18, 0.30–0.65, and 0.65–1.40 for zero, medium, and high preswirls, respectively), six inlet gas-volume fractions GVFi (0%, 2%, 4%, 6%, 8%, and 10%), four pressure drops PDs (20.7, 27.6, 34.5, and 41.4 bars), and three speeds ω (3, 4, and 5 krpm). The targeted test matrix could not be achieved for the medium- and high-preswirl inserts at PD ≥ 27.6 bars due to the test-rig stator's dynamic instability issues. Spargers were used to inject air into the oil, and GVFi values higher than 0.10 could not be consistently achieved because of unsteady surging flow downstream from the sparger mixing section. Leakage mass flow rate m˙ and rotordynamic coefficients are measured, and the effect of changing inlet preswirl and GVFi is studied. The test results are then compared with predictions from a two-phase, homogeneous-mixture, bulk-flow model developed in 2011. Generally, both measurements and predictions show little change in m˙ as inlet preswirl changes. Measured m˙ remains unchanged or slightly increases with increasing GVFi, but predicted m˙ decreases. Measured m˙ is comparable to predicted values but consistently lower. Dynamic-stiffness coefficients are measured using an ensemble of excitation frequencies and curve-fitted well by frequency-independent stiffness Kij, damping Cij, and virtual mass Mij coefficients. Planned tests with the medium- and high-preswirl inserts could not be accomplished at PD = 34.5 and 41.4 bars because the seal stator became unstable with any finite injection of air. The test results show that the instability arose because the seal's direct stiffness K became negative and increased in magnitude with increasing GVFi. The model predicts a drop in K as GVFi increases, but the test results dropped substantially more rapidly than predicted. Also, the model does not predict the observed strong tendency for K to drop with an increase in preswirl in moving from the zero-to-medium and medium-to-high preswirl inserts. The authors believe that the observed drop in K due to increasing GVFi is not explained by either (a) a reverse Lomakin effect from operating in the transition flow regime or (b) the predicted drop in K at higher GVFi values from the model. A separate and as yet unidentified two-phase flow phenomenon probably causes the observed results. The negative K results due to increasing GVFi and moving from the zero to medium, and medium to high preswirl observed here could explain the instability issue (sudden subsynchronous vibration) on a high-differential-pressure helico-axial multiphase pump (MPP), reported in 2013. Effective damping Ceff combines the stabilizing effect of direct damping C, the destabilizing effect of cross-coupled stiffness k, and the influence of cross-coupled mass mq. As predicted and measured, increasing inlet preswirl significantly increases k and decreases Ceff, which decreases the seal's stabilizing properties. Ceff increases with increasing GVFi—becomes more stable.

Acoustical Studies on Beryllium Oxide/Silicone Oil Nanofluids

Molecular interactions of Silicone oil based Beryllium oxide nanofluids have been studied using ultrasonic parameters at room temperature. BeO nanoparticles synthesized by chemical precipitation method was used to prepare silicone oil based BeO nanofluids. BeO nanofluids were prepared by dispersing synthesized BeO nanoparticles in the Silicone Oil base fluid with the help of sonication. Ultrasonic velocity for particle-fluid mixtures of Silicone oil with BeO has been carried out for different volume fraction (0 to 0.003) at 0.0005 intervals at room temperature. The data experimentally measured has been used to estimate the various acoustical and thermodynamical parameters. The behavior of these parameters in this particle fluid system has been discussed in terms of inter/intramolecular interactions with respect to concentration. The particle base fluid molecular interactions in the nanofluids cause an increment in velocity value of Silicone oil based nanofluids. The propagation of ultrasonic waves causes impedance which increases the intermolecular distance between the molecules. The transmission and reflection modes of sound waves in the nanoparticle and base fluid molecules are noted by the specific acoustic impedance. It is noted that the acoustic impedance value increases with rise in concentration owing to the molecular interaction between BeO and silicone oil fluid molecules affecting the structural arrangement.

Experimental Study of the Static and Dynamic Characteristics of a Long (L/D = 0.75) Labyrinth Annular Seal Operating Under Two-Phase (Liquid/Gas) Conditions

AbstractA two-phase annular-seal stand at the Turbomachinery Laboratory of Texas A&M University is utilized to experimentally investigate a labyrinth seal operating under two-phase flow conditions (a mixture of silicone oil and air). A long labyrinth seal (length-to-diameter ratio L/D = 0.75, diameter D = 114.729 mm, and radial clearance Cr = 0.213 mm) is tested at a supply pressure of 62 bars-g with inlet gas volume fraction GVFi ranging from 90 to 100%. Tests were conducted at three pressure ratios PR (0.3, 0.4, 0.5), three rotating speeds (5, 10, 15 krpm), six GVFi (90%, 92%, 94%, 96%, 98%, and 100%), and three inlet-preswirl inserts, namely, zero, medium, and high. Specifically, the ratio between the fluid's circumferential velocity and the shaft surface's velocity are in ranges of 0.0–0.2, 0.5–1.6, and 0.5–2.7 for the zero, medium, and high preswirls respectively. The direct dynamic stiffness KΩ is negative. As GVFi decreases (more liquid), KΩ becomes more negative for the zero preswirl. The effect of changing GVFi on KΩ for the medium and high preswirls is not as clear as for the zero preswirl. For the zero preswirl, as GVFi decreases, the cross-coupled dynamic stiffness kΩ and direct damping C damping increase. However, the effective damping Ceff values converge to almost the same positive value for higher frequencies. Hence, there is no significant effect of change in GVFi for the zero preswirl. For the high preswirl, as GVFi decreases, kΩ decreases and C increases. As GVFi decreases, Ceff becomes less negative and eventually becomes positive for frequencies higher than Ωc. This result indicates that at certain frequencies, the presence of liquid can make the labyrinth seals with high preswirl more stable. For the seal tested, a compressor running at 15 krpm and PR (ratio of seal exit pressure and seal inlet pressure) = 0.5 with the first critical speed of 7500 rpm (125 Hz) would experience an increase in stability with presence of liquid in the flow stream for the medium and high preswirls. However, for the range of GVFi considered here, if swirl brakes are used in a compressor application to reduce the preswirl, there would be no impact of liquid presence on the stability of the compressor. Concerning static measurements, leakage rate m˙ increases with decreases in GVFi but remains unchanged with increasing preswirl.

Magnetic flux density effect on electrical properties and visco-elastic state of magnetoactive tissues

Magnetoactive tissues are prepared from a mixture of silicone oil (SO) and various volume concentrations Φ of carbonyl iron (CI) microparticles impregnated in a cotton cloth. The obtained tissues are examined as dielectric materials for manufacturing electrical capacitors. By using the plane capacitor method, we show that the relative dielectric permittivity, apparent viscosity, modulus of elasticity, and the components of deformations and of mechanical tensions can be sensibly influenced by an external magnetic field and by Φ. These effects make the obtained tissues versatile candidates for applications which require textiles consisting of conductive fillers, powders, yarns etc. embedded into non-conductive fabric fibers and with pre-established strength and flexibility. An immediate application is in fabrication of magnetic field sensors for detection of magnetic flux densities in the range 40÷180 mT.

Burkholderia cepacia, a cause of post pars plana vitrectomy silicone oil related endophthalmitis: clinico-pathological presentation and outcome of management

AimTo report the long-term outcome of the management of a series of culture proven post pars plana vitrectomy endophthalmitis in which the infective agent was in the silicone oil used as an endotamponade. The isolates were Burkholderia cepacia and Pseudomonas aeruginosa.MethodA retrospective interventional reporting of a series consisting of a cluster of five cases.CasesFive consecutive patients received the same batch of 5000-centistoke silicone oil as endotamponade at the conclusion of vitreoretinal surgery and presented with features of acute intraocular inflammation, which was due to an infective cause. The infective organism isolated from the mixture of silicone oil and fluid was B. cepacia in three out of the initial cluster of four eyes and P. aeruginosa in the fifth eye.Outcome of managementThe initial 4 eyes evolved into eyes with poor vision (hand motion, perception of light and no perception of light), advanced proliferative vitreoretinopathy, hypotony, phthisis bulbi and cornea opacity. The poor visual outcome was deemed to be consequent to delay in removal of the silicone oil, despite use of intravitreal, systemic and topical antibiotics. The fifth case, because of the heightened index of suspicion gained from the preceding four cases, had a prompt removal of the silicone oil, vitreal lavage with antibiotics, and intravitreal injection of antibiotics and steroid. He regained a 6/9 vision.ConclusionGram-negative bacilli can colonize silicone oil resulting in post pars plana vitrectomy endophthalmitis. The index of suspicion for this should be high and can be managed successfully with prompt removal of the silicone oil, microbial sensitive antibiotic lavage of the vitreous cavity, followed by a repeat tamponade.

A Droplet-Reactor System Capable of Automation for the Continuous and Scalable Production of Noble-Metal Nanocrystals.

Noble-metal nanocrystals with well-controlled shapes or morphologies are of great interest for a variety of applications. To utilize these nanomaterials in consumer products, one has to produce the colloidal nanocrystals in large quantities while maintaining good control over their physical parameters and properties. Droplet reactors have shown great potential for the continuous and scalable production of colloidal nanocrystals with controlled shapes. However, the efficiencies of most previously reported systems are still limited because of the complex post-treatment procedures. For example, the mixture of silicone oil and an aqueous suspension of solid products has to be separated by leveraging their miscibility and difference in density, while the solid products often need to be purified and concentrated by centrifugation. Herein, we report the design and construction of a droplet-reactor system that include new features such as a homemade unit for the automatic separation of silicone oil from the aqueous phase as well as a cross-flow filtration unit for the effective purification and concentration of the nanocrystals. Using various types of Pd nanocrystals as examples, we have demonstrated the feasibility of using this system to automatically produce and collect samples with uniform sizes and well-controlled shapes.

Interrogating flow development and phase distribution in vertical and horizontal pipes using advanced instrumentation

The characterization of two-phase flow in both vertical and horizontal pipes is important in oil/gas transportation. As the pipe orientation may change from well to well, it is also important to understand the characteristic responses expected of a two-phase mixture to a change in pipe inclination. This study concerns the changes in the void fraction, structure frequency and structure velocity that occur within an air–silicone oil mixture as a function of the pipe orientation. Experimental data were obtained from the combined use of electrical capacitance tomography (ECT) and wire mesh sensors (WMS), which allow the 3D visualization of the flow patterns. The reported experiments were performed on a 67 mm diameter pipe, in a flow loop, in which a pipe section may be inclined at angles of between −5 or 90° to the horizontal. For this study, the inclined pipe was either set at an angle of 0 or 90 to the horizontal, which correspond to a horizontal or vertical pipe setting, respectively. The results of flow development using the PDF of void fraction obtained at 3 measurement locations; ECT 1, ECT 2 and WMS at 4.4, 4.489 and 4.92 m, respectively, showed that the flow is fully developed and statistically stable for the vertical two-phase flow. While on the other hand, the flow is in rapid development for the horizontal two-phase flow scenario at same liquid and gas superficial velocities. The processed data reveal the differences in flow distribution produced by the pipe inclination. Within the vertical pipe configuration spherical cap bubbles, slug and churn two phase flow patterns were observed, whilst plug, slug and stratified wavy two-phase flows were identified in the horizontal configuration of the pipe. It is concluded that a plot of mixture superficial velocity against average void fraction may be used to provide a qualitative assessment of the flow patterns observed, regardless of pipe inclination. The two-phase flow variables that are concluded to significantly influence the distribution coefficient, C0, and drift velocity, VD, are the pipe orientation and flow patterns.

Applications of artificial neural network (ANN) method for performance prediction of the effect of a vertical 90° bend on an air–silicone oil flow

Knowledge of how the presence of a bend can change the flow patterns of a gas–liquid mixture is important for the design of multiphase flow systems, particularly to prevent burn-out and erosion–corrosion. Burn-out and erosion–corrosion both have serious implications for heat and mass transfer. The objective of this work therefore is to train an artificial neural network (ANN), a powerful interpolation technique, to predict the effect of a vertical 90o bend on an air–silicone oil mixture over a wide range of flow rates. Experimental data for training, validation, testing and final prediction were obtained using advanced instrumentation, wire mesh sensor (WMS) and high speed camera. The performance of the models were evaluated using the mean square error (MSE), average absolute relative error (MAE), Chi square test (X2) and cross correlation coefficients (R). The performance discriminator X2 for prediction of average void fraction is 2.57e-5 and that for probability density function (PDF) of void fraction MAE is 0.0028 for best performing models. The well trained ANN is then used to predict the effects of the two input parameters individually. The predicted results show that for the before the bend scenario, the most effective input parameter that reflects a change in flow pattern is the gas superficial velocity. On the other hand, the most unfavourable output parameter to measure after the bend is the average void fraction based on the fact that the flow near the bend is a developing one.

Experimental study of the hydrodynamic behaviour of slug flow in a horizontal pipe

This paper investigates the unsteady hydrodynamic behaviour of slug flow occurring within an air–silicone oil mixture, within a horizontal 67mm internal diameter pipe. A series of slug flow regime experiments were performed for a range of injected air superficial velocities (0.29–1.4ms−1) and for liquid flows with superficial velocities of between 0.05–0.47ms−1. A pair of Electrical Capacitance Tomography (ECT) probes was used to determine: the slug translational velocities of the elongated bubbles and liquid slugs, the slug frequencies, the lengths of elongated bubbles and the liquid slugs, the void fractions within the elongated bubbles and liquid slugs. The pressure drop experienced along the pipe was measured using a differential pressure transducer cell (DP cell). A comparative analysis of the current experimental data and that previously published experimental confirms good agreement.

Two-Photon Induced Fluorescence Energy Transfer in Polymeric Nanocapsules Containing CdSexS1–x/ZnS Core/Shell Quantum Dots and Zinc(II) Phthalocyanine

We report activation of a photodynamic therapy photosensitizer, zinc phthalocyanine, by Forster resonant energy transfer (FRET) from two-photon absorption excited CdSexS1–x/ZnS quantum dots coencapsulated in multifunctional biocompatible polymer nanocapsules. Polymer nanocapsules (100 nm size) were prepared via solvent/evaporation method using Poloxamer 403 as the polymer component, Cremophor EL as the surfactant and mixture of silicone oil with hydrogenated caprylyl olive oil esters as the oil phase. UV–vis–NIR absorption and multiphoton fluorescence studies confirmed successful coencapsulation of both components of the FRET system. The energy transfer between the quantum dots as donors and Zn phthalocyanine molecules as acceptors was studied using steady-state photoluminescence and time-correlated single photon counting techniques. The changes in the lifetime of the QDs emission indicate that the excitation of ZnPc occurs not only through reabsorption but also through FRET. The generation of the reactiv...

Magnetic field induced modulated phases in a ferrofluid lutidine silicone oil mixture

A mixture of an ester based ferrofluid with silicone oil and 2,6-lutidine is exposed to an external magnetic field. We find a region of composition of the ternary mixture, where weak magnetic fields of the order of a few kA m-1 induce a modulated phase with a pattern characterized by equilibrium size droplets of the minority phase immersed into the extended majority phase. While the pattern resembles in many ways the pattern of immiscible magnetic fluids, the dependence of the characteristic parameters of the pattern on the magnetic field are completely different than in immiscible fluids. We theoretically explain the pattern formation as a magnetic field induced polymerization of magnetic particles into magnetic chains that goes along with a reduction of the entropy of mixing. This entropy reduction causes the Ostwald ripening of chains into mesoscopic droplets the size of which is limited by repulsive dipolar interactions between the chains.

Comparison of experimental and Computational Fluid Dynamics (CFD) studies of slug flow in a vertical riser

This paper presents a comparison of the results obtained from experiments and CFD studies of slug flow in a vertical riser. A series of two experimental investigations were carried out on a 6m vertical pipe with a 0.067m internal diameter charged with an air–silicone oil mixture. For the first set of experiments, the riser was initially full of air, and then liquid and gas flows set to liquid and gas superficial velocities=0.05 and 0.344m/s, respectively, electrical capacitance tomography (ECT) and wire mesh sensor (WMS) transducers were employed. In the second one, the riser was initially full of (static) liquid, and then liquid and gas flows set to liquid and gas superficial velocities=0.05 and 0.344m/s, respectively, only ECT was used. A characterisation of the observed slug flow regimes was carried out. This includes the evaluation of the instantaneous distribution of the phases over the pipe cross-section, the Probability Density Function (PDF) of void fraction, time series of cross-sectional void fraction, Power Spectral Density (PSD), structure velocity of the Taylor bubble, lengths of the liquid slug and Taylor bubble and void fractions in the liquid slug and Taylor bubble. The simulation results were validated both qualitatively and quantitatively against experimental data. A reasonably good agreement was observed between the results of the experiment and CFD.

Isopropyl alcohol: A replacement for tertiary-butyl alcohol in pollen preparations

We propose an alternative dehydrating agent for the preparation of pollen samples mounted in silicone oil. Isopropyl alcohol (propan-2-ol, or ‘IPA’) proves to be miscible with both water and silicone oil, and unlike tertiary-butyl alcohol (2-methyl-2-propanol, or ‘TBA’), the conventional dehydrating agent, IPA does not freeze at room temperature. Pollen preparations using IPA are therefore less problematic, especially in cold weather. Photos of fossil pollen samples prepared three months previous using IPA as a dehydrating agent show no difference to those prepared at the same time using TBA. We observed no size difference between Corylus avellana pollen grains dehydrated with IPA compared to those dehydrated using TBA in identically prepared samples. We also find that IPA evaporates from the pollen residue and silicone oil mixture more readily than TBA.

Experimental study of the hydrodynamic behaviour of slug flow in a vertical riser

This paper presents an investigation of the hydrodynamics of slug flow in a vertical 67mm internal diameter riser. The slug flow regime was generated using a multiphase air–silicone oil mixture over a range of gas (0.42<USG<1.35m/s) and liquid (0.05<USL<0.38m/s) superficial velocities. Electrical capacitance tomography (ECT) was used to determine: the velocities of the Taylor bubbles and liquid slugs, the slug frequencies, the lengths of Taylor bubbles and the liquid slugs, the void fractions within the Taylor bubbles and liquid slugs and the liquid film thicknesses. A differential pressure transducer was used to measure the pressure drops along the length of the riser. It was found that the translational velocity of a Taylor bubble (the structure velocity) was strongly dependent on the mixture superficial velocity. As the gas superficial velocity, was increased, the void fraction and the lengths of the liquid slugs and the Taylor bubbles were observed to increase. The increase in gas superficial velocity causes an increase in the frictional pressure drop within the pipe, whilst the total pressure drop (which is a sum of the hydrostatic and frictional pressure drop) along the length of the riser decreases. In addition, the frequencies of the liquid slugs were observed to increase as the liquid superficial velocity increases, but to be weakly dependant on the gas superficial velocity. The manual counting method for the determination of slug frequency was found to be in good agreement with the power spectral density (PSD) computed method.

Nanoinclusions in Cryogenically Quenched Nanoemulsions

Nanodroplets containing mixtures of silicone oil and squalene are dispersed in a simple aqueous surfactant solution, quenched in liquid ethane, and examined using cryogenic transmission electron microscopy (CTEM). Depending on the phase of ice that forms around the nanodroplets and on the composition of the oil mixture, nanoinclusions can be observed inside oil nanodroplets, independent of surfactant type. Our observations suggest that these nanoinclusions arise from nucleation of vapor cavities as the water freezes and expands while the oil remains liquid during the quench.

The structural stability of AlPO4-5 zeolite under pressure: Effect of the pressure transmission medium

The structural stability of AlPO4-5 zeolite (AFI) has been studied as a function of pressure up to 34.4 GPa in a diamond anvil cell by using synchrotron x-ray diffraction. It is found that the AFI structural stability can be enhanced significantly when a mixture of silicone oil and liquid nitrogen is used as pressure transmission medium (PTM). In this case, the crystalline-to-amorphous transition pressure for AFI increased to be 15.9 GPa, much higher than that of 8.5 GPa observed in the experiment by using silicone oil as PTM. We found that the average distance of the interplanar crystal spacing along to most planes was expanded obviously when liquid nitrogen is used as one component in the PTM. The presence of liquid nitrogen in the PTM also affects the structural evolution of the AFI channel under pressure. The results demonstrated that nitrogen molecules can be inserted into the channels of porous zeolite AFI single crystals, exerting a supporting effect against the structure collapse of AFI and thus improving their structural stability.