Synthetic Ester Oil Research Articles

Assessment of Thermophysical Performance of Ester-Based Nanofluids for Enhanced Insulation Cooling in Transformers

Nanotechnology provides an effective way to upgrade the thermophysical characteristics of dielectric oils and creates optimal transformer design. The properties of insulation materials have a significant effect on the optimal transformer design. Ester-based nanofluids (NF) are introduced as an energy-efficient alternative to conventional mineral oils, prepared by dispersing nanoparticles in the base oil. This study presents the effect of nanoparticles on the thermophysical properties of pure natural ester (NE) and synthetic ester (SE) oils with temperature varied from ambient temperature up to 80 °C. A range of concentrations of graphene oxide (GO) and TiO2 nanoparticles were used in the study to upgrade the thermophysical properties of ester-based oils. The experiments for thermal conductivity and viscosity were performed using a TC-4 apparatus that follows Debby’s concept and a redwood viscometer apparatus that follows the ASTM-D445 experimental standard, respectively. The experimental results show that nanoparticles have a positive effect on the thermal conductivity and viscosity of oils which reduces with an increase in temperature.

Improvement of the lubrication performance of an ester base oil with coated ferrite nanoadditives for different material pairs

In the present work, lubrication properties (friction and wear) of a synthetic ester oil, tris(2-ethylhexyl) trimellitate (TOTM) containing ferrite nanoparticles coated with oleic acid (F3O4-OA) were investigated for two different material pairs: steel ball-steel disc and silicon nitride ball-steel disc. Thus, four TOTM nanolubricants were formulated: TOTM + 0.010 wt% Fe3O4-OA, TOTM + 0.015 wt% Fe3O4-OA, TOTM + 0.020 wt% Fe3O4-OA and TOTM + 0.025 wt% Fe3O4-OA showing all of them a moderate time stability due to the oleic acid coating. Wettability behaviour of the ferrite-based nanolubricants on steel surface was analysed, revealing that the addition of Fe3O4-OA nanoparticles in TOTM decreases the contact angle between the steel surface and TOTM lubricant surface. Friction sliding tests were performed with the neat TOTM and with the formulated nanolubricants under a 20 N of load. All nanolubricants showed lower coefficients of friction than those reached with TOTM base oil for both material pairs. Worn area was significantly reduced for all Fe3O4-OA concentrations in the steel-steel contact and for the highest concentrations in the silicon nitride-steel contact. Specifically, the largest achieved reductions were for the TOTM + 0.010 wt% F3O4-OA nanolubricant: 43% reduction in friction (silicon nitride-steel) and reductions of 17% in wear track width, 42% in wear track deep and 36% in area (steel-steel). In addition, roughness analysis and Raman microscopy of the tested discs showed that tribofilm formation and surface repairing mechanisms occur.

Effect of Zeolite Addition on Partial Discharge and Dielectric Behavior of Thermally Aged Synthetic Ester Fluid Under External Magnetic Field

In recent times, ester based liquids have met high standards and are being considered as potential alternatives over mineral oil transformer insulation. This paper investigates the effect of adding micro-porous zeolite to the thermally aged synthetic ester oil (SEO) to evaluate its electrical performance under the influence of external local magnetic field variation from 0 mT to 165 mT. It is observed that the Corona Inception Voltage (CIV) and Particle Levitation Voltage (PLV) have a declining tendency with ageing, in the presence of magnetic field. Under the influence of magnetic flux density ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\simeq 160$ </tex-math></inline-formula> mT), the detected UHF signal was dominant at low frequencies (400 MHz - 900 MHz). The UHF voltage signals peak-to-peak magnitude demonstrates that the discharge magnitude increases with increased ageing duration. Further, it was observed that the addition of zeolite in the synthetic ester liquid tends to improve the electrical performance of the aged oil. The fluorescence spectroscopic analysis shows a shift of the fluorescence maxima together with increased intensity in samples with zeolite as compared to the samples without zeolite addition, which shows a relatively lower concentration of the polar contamination. The frequency dielectric spectroscopy also confirms that synthetic ester specimens showed improved dielectric properties after the zeolite treatment.

Measurement of Tan-delta and DC Resistivity of Synthetic Ester Based Oil Filled with Fe2O3, TiO2 and Al2O3 Nanoparticles

ABSTRACT The dielectric properties of insulating liquids are very important for their application as insulation and coolant in electrical devices like transformers. It is important to monitor the health condition of transformers for uninterrupted and economical power supply. For this purpose, the simple insulating materials like pressboard and mineral oils are used. This paper presents an eco-friendly alternative to mineral oil in the form of the synthetic ester oil-based nanofluids. This paper aims to present the effect of nanoparticles on the dielectric dissipation factor and electrical resistivity of ester-based oil. In this paper, we are testing synthetic ester oils for DC resistivity and dielectric dissipation factor (Tan-delta) at different temperatures starting from room temperature up to 80°C by incorporating nanoparticles with 0.02 weight% concentration. Nanoparticles used in this study are Fe2O3, TiO2 and Al2O3. Synthetic ester oil is used as the base oil for testing. These oils are manufactured from raw materials that are basically formed by combining acids and alcohols. The heating chamber is used to heat the oil for different temperatures. Insulation resistance (IR) tester and oil dissipation factor meter are used to determine DC resistivity and dielectric dissipation factor (DDF) of simple synthetic ester oil and nano oil respectively. This paper presents the effect of nanoparticles and temperature on dielectric properties of synthetic ester-based oils.

THE EFFECT OF THE BIOCARBON TYPE ON THE TRIBOLOGICAL CHARACTERISTICS OF GREASES MANUFACTURED WITH VEGETABLE AND SYNTHETIC BASE OILS

The article presents the tribological characteristics of plastic greases in which the dispersing phase was vegetable (rapeseed) oil or synthetic ester oil (Priolube). The lithium stearate was used as a thickener in an amount sufficient to obtain a composition in the second consistency class, and the functional additives were biocarbon produced in the process of pyrolysis of the following plant waste: flax straw, wheat straw, corn leaves and stalks, and cherry stones. The compositions containing 5% m/m of biocarbon were prepared and the influence of the type of biocarbon on the tribological properties of the obtained plastic greases was assessed. The tribological characteristics of the grease compositions were determined using the T-02 tester in accordance with the requirements of the relevant standards. The influence of the applied biocarbon on the anti-wear (Goz) and anti-seize (Pt, poz) properties of plastic greases made with vegetable and synthetic basis was determined. It was found that some of the biocarbon, especially those derived from the pyrolysis of corn waste, significantly improve the tribological properties of plastic greases, both those based on plant and synthetic sources.

Streaming Electrification of Nycodiel 1255 Synthetic Ester and Trafo EN Mineral Oil Mixtures by Using Rotating Disc Method

Power transformers are the main element of an electric power system. The service life of these devices depends to a large extent on the technical condition of their insulation system. Replacing mineral oils with natural or synthetic ester (retrofilling process) may increase the efficiency and operational safety of transformers, and also limit their adverse environmental impact. It is technically unfeasible to completely remove mineral oil from a transformer. Its small residues form a mixture with fluid ester, with different physicochemical and electric properties. Streaming electrification is one of the phenomena which, under unfavorable conditions, may damage the insulation system of a forced oil cooled transformer. It is necessary to run prophylactic tests for the ECT (electrostatic charging tendency) of insulating liquid mixtures from the point of view of transformer retrofilling, which is being used more often than before. The article presents the results of studies on selected physicochemical, and electrical properties, and the ECT of mixtures of fresh and aged Trafo EN mineral oil with Nycodiel 1255 synthetic ester. In this regard, the density, the kinematic viscosity, the conductivity, and the relative dielectric constant were measured. The molecular diffusion coefficient was determined using Adamczewski’s empirical dependency. The streaming electrification was tested in a rotating disc system. The impact of the rotation time, the diameter, and the disc’s rotation speed on the amount of the electrification current generated were analyzed. In addition, the co-relation between the electrification current and the composition of the mixture was determined using fresh and aged mineral oil. On the basis of the electrification model, the volume density of the qw charge was calculated, which is a parameter defining the ECT of insulating liquids. Based on the results, it was concluded that the synthetic ester is characterized by a higher susceptibility to electrification than the mineral oil. However, combining synthetic ester with a small amount (up to 20%) of fresh or aged mineral oil significantly reduces its ECT, which is beneficial from the point of view of retrofilling power transformers.

Dielectric properties of mixed mineral and synthetic ester oil

The dielectric properties of 20% synthetic ester oil mixed with mineral oil were studied for its potential applications as an insulator in transformers. The corona inception voltage of mixed oil under AC and DC voltages was measured by the ultra-high frequency (UHF) technique. A statistical study of the breakdown voltage of mixed oil under AC, DC and standard lightning impulse voltages was carried out to obtain a database which would be useful for designing transformer insulation. Further, the mixture was subjected to continuous breakdown studies under AC voltage with lightning impulse voltages, at regular intervals and characterised through measurement of interfacial tension, flash point, ionic mobility as well as UV–vis spectroscopy and frequency-domain spectroscopy studies to understand the liquid's chemical stability. The results of the study have shown that the mixture was stable even after several breakdowns. The ionic mobility and polarisation current have increased, indicating higher losses in the oil. UHF signal energy analysis and phase-resolved partial discharge analysis have revealed a reduction in discharge activity with mixed oils.

Dielectric properties of silica based synthetic ester nanofluid

This work studies the impact of silica nanoparticles on the dielectric properties of synthetic ester oil. A stable nanofluid is prepared by addition of surfactant. With addition of nanoparticles there is an increment in dielectric constant and decrement in dielectric loss constant. An attempt is made to understand the conduction mechanisms in uniform field and non-uniform electric field configuration by means of analysing the mobility of ions. Under uniform electric field stress (<0.1 kV/mm), by means of conduction current measurement with polarity reversal, the ionic mobility, conductivity, ionic concentration and ionic radius are deduced. There is a reduction in ionic mobility by addition of nanoparticle and surfactant. To understand the conduction mechanisms in high electric field condition, the current-voltage characteristics of the nanofluid are measured. Using this data, apparent mobility due to electrohydrodynamic motion is estimated, giving a lower mobility in the case of nanofluid, which could be the cause of the increased corona inception voltage.

Energy Distribution of Optical Radiation Emitted by Electrical Discharges in Insulating Liquids

This article presents the results of the analysis of energy distribution of optical radiation emitted by electrical discharges in insulating liquids, such as synthetic ester, natural ester, and mineral oil. The measurements of optical radiation were carried out on a system of needle–needle type electrodes and on a system for surface discharges, which were immersed in brand new insulating liquids. Optical radiation was recorded using optical spectrophotometry method. On the basis of the obtained results, potential possibilities of using the analysis of the energy distribution of optical radiation as an additional descriptor for the recognition of individual sources of electric discharges were indicated. The results can also be used in the design of various types of detectors, as well as high-voltage diagnostic systems and arc protection systems.

Dielectric Performance of Magneto-Nanofluids for Advancing Oil-Immersed Power Transformer

Recently, nanofluids are introduced in the power utilities for the dielectric performance enhancement of power transformer oil. The compactness and fault improvement of the power transformers has resulted in the necessity of next-generation insulating fluid with inflated dielectric properties. This article investigates the dielectric performance of the novel ester oil-based magnetic nanofluids with different nanoparticles under different electric stress conditions. Two biodegradable fluids used as the base liquid for the experiment are synthetic ester oil and natural ester oil while three magnetic nanoparticles used to synthesize nanofluids are iron (II, III) oxide, cobalt (II, III) oxide, and iron phosphide. The concentrations of the nanoparticles are varied to optimize the characteristics of the prepared nanofluids. The dielectric breakdown and relative permittivity of the nanofluids have been experimentally investigated. Further, the breakdown predictions have been performed using Weibull statistical distribution-based regression analysis. The experimental results show the improvement in the characteristics of prepared nanofluids with the change in nanoparticle concentration as compared with the host fluids.

Steady State Counterbalance Valve Modeling with the Influence of Synthetic Ester Oils Using CFD

Steady State Counterbalance Valve Modeling with the Influence of Synthetic Ester Oils Using CFD

Thermal performance of transformers filled with environmentally friendly oils under various loading conditions

The transformer thermal performance is a crucial issue that should be considered in the design stage. Recently, natural and synthetic ester oils have been proposed as environmentally friendly oils to substitute conventional mineral oil. This paper aims to evaluate the transformer thermal performance when using these environmentally friendly oils under different loading power factors. Three commercial types of environmentally friendly oils are considered, Midel 1204 and Midel 1215 as natural esters and Midel 7131 as a synthetic ester. Thermal-related properties of these esters are experimentally evaluated. These results include viscosity, thermal conductivity, specific heat capacity, and density. The experimental data is used to find a best representative formula for the thermo physical properties of these oils as a function of operating temperature by using least square regression method. A model 3D CFD COMSOL model is built including heat transfer model and laminar flow model to calculate the rated top oil temperature (TOT) and the rated winding hottest spot temperature (HST) for these environmentally friendly oils and for mineral oil. The rated output TOT and HST from COMSOL are used as inputs for a developed MATLAB model through which TOT and HST all day long can be obtained. Using these models, the TOT and HST for transformers filled with mineral oil and environmentally friendly oils are obtained. Also, the transformer aging and loss of life are assessed with these oils for the different scenarios of the loading power factor (PF). Finally, the annual energy losses of the transformer, their cost, and their impact on greenhouses gases emissions and corresponding environmental cost are evaluated as key issues for making proper decisions toward using environmentally friendly oils. It was found that using environmentally friendly oils reduces significantly the transformer aging compared to using mineral oil for different loading PFs.

Comparison of the oxidation resistance of synthetic ester oils DOA and TDTM: Experimental evaluation and theoretical calculation

AbstractThe oxidation behavior of the synthetic ester oils di‐isooctyl adipate (DOA) and tri‐isodecyl trimellitate (TDTM) was investigated by analysing the oxidation induction time and oxidation onset temperature via pressure differential scanning calorimetry tests, and the variation in viscosity after oven accelerated oxidation tests. Moreover, theoretical calculations of the fractional free volumes and oxygen diffusion coefficients of DOA and TDTM were performed, and atomistic‐scale insights into the oxidative mechanisms of both oils were proposed based on reactive molecular dynamic (RMD) simulations. Better oxidation resistance for TDTM was confirmed with experimental observations. RMD results indicated that the C―O bonds of the alcohol chain and ester group of DOA were susceptible to oxidation. However, only the dissociation of the C―O bond of the alcohol chain initiated the oxidation of TDTM. Additionally, more degradation fragments for DOA were identified, along with the formation of a polymerized product, while no large molecules formed for TDTM.

Effect of un‐inhibited synthetic ester oil based high dielectric CaCu3Ti4O12(CCTO) nanofluid for power transformer application

Environmental friendly insulating oils are sought after as an alternative to polychlorinated biphenyls and mineral oil. The ester-based insulating oils are the industry preferred choice as they are fire resistant and non-toxic in nature. They also have moisture tolerance capability and oxidation stability are quite higher in synthetic ester due to its stable chemical structure than seed-based natural ester oil. In this work, attempts were made to develop un-inhibited synthetic-ester-based high dielectric permittivity CaCu3Ti4O12 (CCTO) nanofluids. These nanofluids were investigated for the critical parameters such as AC breakdown voltage, dielectric permittivity, loss tangent, DC resistivity, interfacial tension, viscosity, flash point and acidity properties as per the procedure outlined in IEC and ASTM standards. It has been observed that the addition of nanopowder in un-inhibited oil results decrement in overall critical properties. These results suggest that these un-inhibited ester oils are well suitable for high-voltage transformer application in the present form and the combination of oxidation inhibitor and nanoceramic in the ester oils would give rise to enhanced critical parameters.

Synthetic ester oil based high permittivity CaCu&lt;inf&gt;3&lt;/inf&gt;Ti&lt;inf&gt;4&lt;/inf&gt;O&lt;inf&gt;12&lt;/inf&gt; (CCTO) nanofluids an alternative insulating medium for power transformer

Green insulating oils are the present industry need for an alternative insulation to mineral oil due to its higher bio-degradability. Synthetic ester oil plays a prominent role by compromising all the critical parameters for better adaptability to power transformers. Presently, high dielectric nano-additive based enhancement studies have been targeted for the development of newer insulation with improved dielectric withstand levels. The present work deals with synthetic ester oil based high dielectric permittivity CCTO (CaCu 3 Ti 4 O 12 ) nanofluids. The dielectric, physical and chemical properties are examined according to the applicable IEC and ASTM standards. The breakdown voltage enhancements found for AC (41.6%) and lightning impulse (17.3 %) has been observed. Also, a decrement in loss tangent and increment in dielectric permittivity has been observed. An increment in volume fraction loading results in an increment in partial discharge inception voltage, thermal conductivity and flash point properties. Hence, based on overall enhancement performance, <0.01% CCTO is considered as the optimum addition to synthetic ester oil which is considered as an alternative medium as well as next generation fluid for power transformers.

Investigation on the Tribological Behaviour of Modified Jatropha Oil with Hexagonal Boron Nitride Particles as a Metalworking Fluid for Machining Process

Bio-based oil from vegetable oils was recently explored as an alternative solution to petroleum-based oil. However, the application of vegetable oils as metalworking fluids (MWFs) for machining process is still not widespread. The objective of this study was to investigate the tribological behaviour of modified vegetable oils, in comparison with synthetic ester (SE) and crude jatropha oil (CJO). In this study, the CJO was chemically modified via transesterification process to develop modified jatropha oil (MJO5). MJO5 was then blended with the hexagonal boron nitride (hBN) particles at various concentrations ranging between 0.05 to 0.5wt.%. The friction and wear test was performed using four ball tribotester. An experiment on orthogonal cutting process was carried out to evaluate the machining performances in terms of cutting force, cutting temperature, chip thickness and tool-chip contact length. The results reveal that the mixture of 0.05wt.% of hBN particles in the MJO5-based oil (MJO5a) outperformed the SE in terms of friction and wear. MJO5a showed excellent machining performances by reducing the machining force and temperature, which related to the formation of thinner chips and small tool-chip contact length. MJO5a is the best substitute to SE as sustainable MWFs in the machining operation with regards to the environmental and health concern.

Cordial physico-chemical characteristics of some trimethylolpropane triesters as base synthetic lubricant for turbo- jet aircrafts

The use of synthetic ester oils is presently an absolute necessity. Polyols ester type is the preferable synthetic lubricant to meet the demands of the lightweight gas turbine engine that used in civilian and military air crafts overcoming the lack ability of mineral lubricants. In this work, trimethylolpropanetributyrate, triheptanoate and trinonanoate esters were prepared using Dean Stark apparatus under specified optimum conditions verifying a conversion of 96.8–98.5% within 5.3–6.3 h. The esters were characterized by; i.r., elementary and average mean molecular weight determination, density, viscosity…etc. Some of their cordial properties were correlated to their chain length and some correlations were deduced. Comparison of these properties with the French Air specification 3514 (Nato 0–150) and those for the commercial turbonycoil 13B which is used for French aircrafts indicates that, some of the prepared esters are suitable as base turbine oils. These synthetic base oils may be blended with addition of the appropriate additives to produce final turbine oil for air crafts of speed regime coming towards supersonic.

Halogen-free ionic liquids as synthetic ester oil antiwear additives

PurposeThis paper aims to investigate the tribological properties of 1,4-bis(2-ethylhexyl) sulfosuccinate anion-based ionic liquids (ILs) when used as lubricant additives in synthetic ester oil.Design/methodology/approachThe 1,4-bis(2-ethylhexyl) sulfosuccinate anion-based ILs containing different cation-imidazolium and organo-ammonium were synthesized and characterized. Their tribological performances as lubricant additives were assessed on ball-on-flat tribological tester. Their compatibility with typical additives (such as viscosity improver, antioxidant, pour point depressant and anti-rusting agent) were evaluated on a four-ball friction and wear tester.FindingsIt was found that the synthesized ILs demonstrated more effective friction reduction and antiwear properties than the base synthetic ester oil. The ILs worked well with the other typical additives, such as viscosity improver, antioxidant, pour point depressant and anti-rusting agent.Originality/valueThe results of the experimental studies demonstrated the potential of 1,4-bis(2-ethylhexyl) sulfosuccinate anion-based ILs as additives for improving friction reduction and antiwear abilities of synthetic ester oil.

Correlation between current-voltage characteristics and DC field grading for dielectric liquid used in wet-mate DC connector

Subsea DC transmission and distribution system is a promising technology for powering subsea oil and gas fields with high power, long distance and ultra-deepwater depth. In subsea DC transmission and distribution, wet-mate (WM) connectors are considered as a challenging component due to the complicated electrical field distribution in the insulation system and harsh undersea wet-mating environmental conditions. In order to design reliable liquid insulation systems for subsea connectors, it is essential that the behavior of the DC-stressed liquid insulation be fully characterized for thorough understanding. In this paper, liquid conduction phenomena in synthetic ester oil are studied using the current-voltage characteristics and electric field distribution mapping based on the Kerr electro-optic effect. The correlations between the current-voltage characteristics and DC field grading among different electrode gaps and oil types were analyzed. The experimental results suggest that for applied voltage less than the saturation voltage (V s ), the conduction is dominated by ion dissociation in the bulk oil. Correspondingly, the liquid conduction is ohmic and with formation of heterocharges around the contacts giving symmetrical field distribution. At applied voltage higher than saturation voltage (V s ), this bulk conduction will transit to extrinsic dominated conduction with carriers injected through liquid-electrode interfaces. Under such carrier injection, the corresponding field distribution becomes asymmetrical. In addition to the laboratory experiments, computer simulations with an ion drift-diffusion conduction model taking into account electrode injection were carried out to validate the experimental field distribution at different electrode gaps. The effect of electrode material on the electric field distribution in the oil is investigated and implications for wet-mate connector design principles are presented.

Impulse performance of synthetic esters based-nanofluid for power transformer

The lightning impulse breakdown characteristics of a silica nanoparticle based-nanofluid and base oil gaps between electrodes in Type-I and Type-II electrode systems, described in this paper, has been investigated. Based on the analysis of the test results, it has been found that both the mineral oil and synthetic ester oil-MIDEL 7131 based-nanofluid with greater amount of moisture content has higher impulse breakdown strength as compared to its base oil counterparts, with low moisture, in both electrode geometries. Unlike in Type-I electrode system, where there is a linear increase in the enhancement of impulse breakdown strength in nanofluid with nanoparticle concentration level; the enhancement is almost steady in Type-II electrode system, giving an average increase of up to 32% relative to its base oil in the case of synthetic ester while the same is 15% in case of mineral oil, and thus provides interesting possibilities of improvements in the design of insulation structure in ester transformer operating at 400 kV or above. Further, the volt-time characteristics reflect superior performance of nanofluid in withstanding fast events as compared to both base mineral oil and synthetic ester oil. The testing of nanofluid presented, as per the ASTM D3300, for small gap spacing between electrodes considered, will be helpful in assessing the wide scope of the standard in nanofluid research in electric power industry.