Effects of multiple shapes for steady flow with transformer oil+Fe_(3)O_(4)+TiO_(2) between two stretchable rotating disks

In this study,we examine the effects of various shapes of nanoparticles in a steady flow of hybrid nanofluids between two stretchable rotating disks.The steady flow of hybrid nanofluids with transformer oil as the base fluid and Fe_(3)O_(4)+TiO_(2)as the hybrid nanofluid is considered.Several shapes of Fe_(3)O_(4)+TiO_(2)hybrid nanofluids,including sphere,brick,blade,cylinder,and platelet,are studied.Every shape exists in the same volume of a nanoparticle.The leading equations(partial differential equations(PDEs))are transformed to the nonlinear ordinary differential equations(ODEs)with the help of similarity transformations.The system of equations takes the form of ODEs depending on the boundary conditions,whose solutions are computed numerically by the bvp4c MATLAB solver.The outputs are compared with the previous findings,and an intriguing pattern is discovered,such that the tangential velocity is increased for the rotation parameter,while it is decreased by the stretching values because of the lower disk.For the reaction rate parameter,the concentration boundary layer becomes shorter,and the activation energy component increases the rate at which mass transfers come to the higher disk but have the opposite effect on the bottom disk.The ranges of various parameters taken into account are Pr=6.2,Re=2,M=1.0,φ_(1)=φ_(2)=0.03,K=0.5,S=-0.1,Br=0.3,Sc=2.0,α_(1)=0.2,γ=0.1,E_(n)=2.0,and q=1.0,and the rotation factor K is within the range of 0 to 1.

A rapid method for determination of acid value in transformer oil by PPy modified electrode

A polypyrrole-modified glassy carbon electrode （PPy/GC electrode） was prepared and its electrocatalytic behavior towards naphthoquinone in the presence of acid was characterized by linear sweep voltammetry （LSV）. A well-defined new reduction peak appeared at a more positive potential than the original reduction peak. The new reduction peak current was linearly related to the acid value （AV） of oil. Based on it, a rapid electrochemical method for determining AV of transformer oil was developed using PPy/GC electrode. A working curve was obtained in the AV range of 0.01 to 0.40 mg（KOH）.g^-1, with a sensitivity of 39.42 μA0.5/（mg（KOH）.g-l） and the detection limit of 0.0014 mg（KOH）.g^-1 （signal-to-noise ratio is 3, standard deviation is 2.247%）. Moreover, the proposed method has been successfully applied to AV determination of several transformer oil samples with advantages of rapidness, high sensitivity and accuracy compared to the conventional method.

Decomposition of Transformer Oil Under Ultrasonic Irradiation During Degassing Process

In the degassing process of transformer oil with ultrasonic waves, decomposition of the oil was observed. Light hydrocarbons, including methane, ethane, ethylene, acetylene, propane etc, were found to be released continuously from the oil into headspace within a closed vial placed in an ultrasonic field. The gases came from decomposition of hydrocarbon molecules under cavitation effect.

Influence analysis of local heat source on internal temperature distribution of power transformer

Oil immersed power transformer is the main electrical equipment in power system.Its operation reliability has an important impact on the safe operation of power system.In the process of production,installation and operation,its insulation structure may be damaged,resulting in partial discharge and even breakdown inside the transformer.In this paper,S9-M-100/10 oil immersed distribution transformer is taken as the research object,and the distribution laws of electromagnetic field and temperature field in transformer under normal operation,inter turn short circuit and inter layer short circuit are simulated and analyzed.The simulation results show that under normal conditions,the temperatures at the oil gap between the transformer core and the high and low voltage windings and the middle position of the high-voltage winding are high.When there are inter turn and inter layer short circuit faults,the electromagnetic loss of the fault part of the transformer increases,and the temperature rises suddenly.The influence of the two faults on the internal temperature field of the transformer is different,and the influence of the inter turn short circuit fault on the temperature nearby is obvious.The analysis results can provide reference for the thermal fault interpretation and fault classification of transformer.

An effective approach for improving flotation recovery of molybdenite fines from a finely-disseminated molybdenum ore

An effective flotation approach is proposed for improving the recovery of molybdenite fines from a finely-disseminated molybdenum ore. To maximize the flotation recovery of molybdenum, process mineralogy of raw ore, contrast tests, optimization of operation conditions and particle size analysis were systematically investigated. Process mineralogy suggests that in the raw ore, 61.63% of molybdenite particles distribute in the 〈20 pm size fraction, and intergrow with muscovite and pyrite as the contained and disseminated type. Contrast tests indicate that conventional flotation responds to poor collection efficiency for particles less than 25 pm. Oil agglomerate flotation （OAF） process demonstrates an obvious superiority in improving the flotation recovery of molybdenite fines. Furthermore, the flotation results of OAF process reveal that the dosage of transformer oil plays a critical role on the average size of collected mineral particles （d（0）, agglomerates （d^0） and the molybdenum recovery. In addition, industrial tests illustrate that compared with the Mo-S bulk flotation approach, OAF process not only increases Mo recovery and grade of molybdenum concentrate by 22.75% and 17.47% respectively, but also achieves a sulfur concentrate with a superior grade of 38.92%.

气相色谱-质谱法测定变压器油正构烃含量

The micro content and the C-distribution of micro normal paraffin hydrocarbon in naphthenic base transformer oil are analyzed and determined by GC-MS.The repeatability of the Quantitative analysis by mass chromatogram and internal standard method is high,and the recovery is 95%-105%.Normal paraffin hydrocarbons from C13-C23 were affirmed in naphthenic base transformer oil and their content is less than 1%.

Catalytic adsorptive desulfurization of mercaptan,sulfide and disulfide using bifunctional Ti-based adsorbent for ultra-clean oil

Ultra-deep desulfurization of transformer oil is of great demand among power industry.In this work,the effective and deep removal of various types of organosulfurs,including mercaptan,sulfide and disulfide via catalytic adsorptive desulfurization(CADS)using bifunctional Ti-based adsorbent is reported.Compared to adsorptive desulfurization(ADS),dramatically improvement of the organosulfur uptakes were achieved under CADS process.The equilibrium adsorption capacity at 5 μg∙g^(-1) S reached up to 15.7,33.4,11.6 and 11.9 mg∙g^(-1) for propyl mercaptan(n-PM),dimethyl sulfide(DMS),di-t-butyl disulfide(DTBDS)and dibenzyl disulfide(DBDS),which was 262,477,97 and 128 times to that of ADS process,respectively,and was the highest among the reported desulfurization adsorbents.Moreover,it achieved superior breakthrough capacity of 2050,530 and 210 ml F·(g A)^(-1) at the breakthrough S concentration of 1 μg∙g^(-1) of the commercial transformer oil S containing 10,50 and 150 μg∙g^(-1),respectively.The effectiveness of CADS is associated to the transformation of sulfur species to higher polar sulfonic species with the assistance of mild oxidant,which can be readily captured by silanol groups on SiO2 through Hbonding interaction.The excellent recyclability of the adsorbent can be realized through solvent washing or oxidative air treatment.This work provides an effective and economic approach for the elimination of trace amount of mercaptan,sulfide and disulfide from transformer oil.

放电对变压器油特性的影响(英文)

Petroleum based oils,the so-called mineral oils,are used for impregnating solid insulations or filling products of very large number of electric materials:transformers,reactors,cables,bushings,circuit breakers,tap changers, etc.In these equipments,oil is exposed to electrical stress and may experience electrical discharges under certain circumstances.Since the electrical stress is unavoidable in power equipments,the ability of oil to resist decomposition under electrical stress is of great importance for the safety of these devices.Electrical stress together with heat and moisture,in the presence of oxygen,oxidises the oil producing free radicals,acids and sludge that are deleterious to the transformer.In this paper,the effect of electrical discharges on oil properties is reported.The results indicate that quality of oil is considerably affected with increasing voltage stress.Comparing oil properties before and after voltage application allows assessing the outcome of random secondary chemical reactions between large oil born free radicals.

Electrical insulating liquid: A review

Insulating liquid plays an important role for the life span of the transformer.Petroleum-based mineral oil has become dominant insulating liquid of transformer for more than a century for its excellent dielectric and cooling properties.However,the usage of petroleum-based mineral oil,derived from a nonrenewable energy source,has affected the environment for its nonbiodegradability property.Therefore,researchers direct their attention to renewable and biodegradable alternatives.Palm fatty acid ester,coconut oil,sunflower oil,etc.are considered as alternatives to replace mineral oil as transformer insulation liquid.This paper gives an extensive review of different liquid insulating materials used in a transformer.Characterization of different liquids as an insulating material has been discussed.An attempt has been made to classify different insulating liquids-based on different properties.