Microstructure Characteristics and Apparent Viscosity of Hypereutectic Al-24%Si Alloy Melt During Semi-solid State Stirring

The microstructural evolution and apparent viscosity of hypereutectic Al-24%Si alloy during semi-solid state shearing were studied with a Searte type viscometer. When the alloy melt was continuously stirred from 720 degreesC to eutectic temperature, the primary Si crystals were gradually changed from elongated platelets to near-spherical shapes. It was found that some nondendritic a-phase formed when the melt was stirred below 585 degreesC. The experiment showed that the semi-solid stirring had strong effect on inhibiting the anisotropic growth of Si crystals during solidification. The apparent viscosity of the alloy melt increased slowly with the decreasing of temperature before the formation of nondendritic alpha -phase, which caused the dramatic increase of apparent viscosity.

Energy Dissipation and Apparent Viscosity of Semi-solid Metal during Rheological Processes PartⅡ:Apparent Viscosity

This study investigated the rheological properties of semi-solid metal. An analytical model of apparent viscosity was built up based on analysis of energy dissipation during rheological processes such as slurry preparing, delivering and model filling. The rheological properties of SSM （semi-solid metal） slurry was described by an analytical model in terms of microstructural parameters, which consist of effective solid fraction, particle size and shape, and flow parameters such as mean velocity, fluctuant velocity and relative velocity between liquid and solid phase. The model was verified in the experiment of A356 alloys with a coaxial double-bucket rheometer. And the maximum relative error between the theoretical value and measured one is less than 20%. The results of experiment and theoretical calculation also indicate that the microstructural parameters and flow parameters are two major factors that affect the apparent viscosity of semi-solid alloys, and fluctuant velocity and relative velocity between liquid and solid phase are the key factors to distinguish between steady and transient rheological properties.

Energy Dissipation and Apparent Viscosity of Semi-solid Metal during Rheological Processes PartⅠ: Energy Dissipation

The energy dissipation caused by the viscous force has great effects on the flow property of semi-solid metal during rheological processes such as slurry preparing, delivering and cavity filling. Experimental results in this paper indicate that the viscous friction between semi-solid metal and pipe wall, the collisions among the solid particles, and the liquid flow around particles are the three main types of energy dissipation. On the basis of the hydromechanics, the energy dissipation calculation model is built. It is demonstrated that the micro-structural parameters such as effective solid fraction, particle size and shape, and flow parameters such as the mean velocity, the fluctuant velocity of particles and the relative velocity between the fluid and solid phase, affect the energy dissipation of semi-solid metal.

Effects of the extrusion and enzymatic extrusion treatment on the apparent viscosity of degerminated maize grits

Apparent viscosity is an important parameter for glucose syrup production.which is greatly affected by particle size and concentration of samples.In order to analyze the factors influencing the apparent viscosity,the particle size distribution,steady shear flow behavior,temperature,and time sweep test of native degerminated maize grits(NDMG),extruded degerminated maize grits(EDMG),and enzymatically extruded degerminated maize grits(EEDMG)with different particle sizes(passed through 20,40,60,80,and 100 mesh sieves)and concentrations(water-sample ratios:2:1,3:1,5:1,10:1,and 20:1)were investigated.All samples passed through different mesh sieves showed a gradient and a relatively concentrated distribution,and slurries had typical shear-thinning properties.Apparent viscosity increased with increasing particle size and concentration.The lowest apparent viscosity was attained from the samples obtained at 100+mesh and 20:1 water-sample ratio.Moreover,the sample with a 20:1 water-sample ratio showed the most stable apparent viscosity in the temperature sweep test.In the time sweep test,the power law equation with high determination coefficients(R^(2)=0.9446,0.9382)and low root mean square error(RMSE=0.0002)had the best fit to the experimental data of the EDMG and EEDMG samples passed through 100+mesh.Overall,the lower apparent viscosities of the EDMG and EEDMG samples obtained at 100+mesh and 20:1 water-sample ratio can improve the activity and accessibility of enzymes for glucose syrup production.This study provides critical insight into decreased apparent viscosity and expands the uses of EDMG and EEDMG in the glucose syrup sector.

Apparent viscosity of mixed particle system in pulsed gas-solid separation fluidized bed

The apparent viscosity reflects the resistance of the fluidized medium in the bed to the beneficiation particles,which directly affects the separation time and mismatch content.So,the falling-ball method was used to measure the apparent viscosity of a binary medium in a pulsed fluidized bed by varying the gas velocity,pulsation frequency,and fine particle content.The results show that with increasing gas velocity and fine particle content,the apparent viscosity of the bed gradually decreased,whereas it first decreased and then increased with pulsation frequency increasing and achieved a minimum value in the range of 4-6 Hz.Within limits,the adjustment of gas velocity and fine content can effectively reduce the apparent viscosity and improve the separation process.A model for predicting the apparent viscosity in a pulsation separation fluidized bed was established with good accuracy.

An experimental study on the viscosity of SPAM solutions with a new correlation predicting the apparent viscosity of sulfonated polyacrylamides

Being one of the most commonly performed EOR methods, polymer injection is used to increase themobility ratio and decrease water relative permeability to allow the injected fluid to sweep more oiltowards the production well. Before the polymer solution is injected into the reservoir through the injection wells, the process of polymer injection must be simulated using commercial numerical reservoirsimulators. In order to be able to simulate the process, the viscosity behavior of the solution must beknown. Therefore, a model is required to estimate the viscosity of the injected fluids versus shear rateand polymer concentration. In this study, a new mathematical function based on the power-law fluidequation is presented, which can be applied to predict the viscosity of SPAM solutions. The two requiredparameters of the power-law equation are obtained by fitting a power-law function to the viscosity-shearrate data. Samples in different polymer concentrations (using two SPAM polymers with different molecular weights) were prepared and their viscosity was measured against different shear rates. The results were fitted to the power-law equation and their corresponding power-law parameters wererecorded. A mathematical function was introduced and tested for each parameter. The new functionscombined with the power-law equation were used to estimate the viscosity of different polymer solutions with different SPAM concentrations. The results showed that the model is capable of estimating theviscosity with acceptable precision. Furthermore, it is applicable in various temperatures and watersalinities.

Bulk and bubble-scale experimental studies of influence of nanoparticles on foam stability

Influence of silicon oxide(SiO_2) and aluminum oxide(Al_2O_3) nanoparticles on the stability of nanoparticles and sodium dodecyl sulfate(SDS) mixed solution foams was studied at bulk and bubble-scale. Foam apparent viscosity was also determined in Hele-Shaw cell In order to investigate the foam performance at static and dynamic conditions. Results show that the maximum adsorption of surfactant on the nanoparticles occurs at 3 wt% surfactant concentration. Foam stability increases while the foamability decreases with the increasing nanoparticle concentration. However, optimum nanoparticle concentration corresponding to maximum foam stability was obtained at 1.0 wt% nanoparticle concentration for the hydrophilic SiO_2/SDS and Al_2O_3/SDS foams. Foam performance was enhanced with increasing nanoparticles hydrophobicity. Air-foams were generally more stable than CO_2 foams.Foam apparent viscosity increased in the presence of nanoparticles from 20.34 mPa·s to 84.84 mPa·s while the film thickness increased from 27.5 μm to 136 μm. This study suggests that the static and dynamic stability of conventional foams could be improved with addition of appropriate concentration of nanoparticles into the surfactant solution. The nanoparticles improve foam stability by their adsorption and aggregation at the foam lamellae to increase film thickness and dilational viscoelasticity. This prevents liquid drainage and film thinning and improves foam stability both at the bulk and bubble scale.

Study of action mechanisms and properties of Cr^(3+) cross-linked polymer solution with high salinity

Performance characteristics of partially hydrolyzed polyacrylamide （HPAM） and cross- linked polymer （CLP, Cr^3＋ as the cross linker） solutions have been investigated. A Brookfield viscometer, rheometer, dynamic light scattering system, and core flow device have been used to measure the viscosity, viscoelasticity, polymer coil dimensions, molecular configuration, flow characteristics, and profile modification. The results show that, under conditions of high salinity and low HPAM and Cr^3＋ concentrations, cross-linking mainly occurred between different chains of the same HPAM molecule in the presence of Cr^3＋, and a cross-linked polymer （CLP） system with a local network structure was formed. Compared with an HPAM solution of the same concentration, the apparent viscosity of the CLP solution increased slightly or remained almost unchanged, but its viscoelasticity （namely storage modulus, loss modulus, and first normal stress difference） increased, and the resistance coefficient and residual resistance coefficient increased significantly. This indicates that the CLP solution exhibits a strong capability to divert the sequentially injected polymer flood from high-permeability zones to low- permeability zones in a reservoir. Under the same HPAM concentration conditions, the dimensions of polymer coils in the CLP solution increased slightly compared with the dimensions of polymer coils in HPAM solution, which were smaller than the rock pores, indicating that the cross-linked polymer solution was well adapted to reservoir rocks. Core flood experiments show that at the same cost of reagent, the oil recovery by CLP injection （HPAM-1, Cr^3＋ as the cross linker） is 3.1% to 5.2% higher than that by HPAM- 2 injection.

Study on cavern evolution and performance of three mixers in agitation of yield-pseudoplastic fluids

The hydrodynamic performance of three mixers single shaft central mixer(SSC), single shaft off-centred mixer(SSO), dual shaft off-centred mixer(DSO), was investigated in the mixing of yield-pseudoplastic fluids(xanthan gum solutions) in the laminar regime. To explore and determine the efficiency of three mixers, both numerical and experimental approaches were adopted. The fluid rheology was described by the Herschel–Bulkley rheological model. Computational fluid dynamics was employed to simulate the apparent viscosity distribution, mixing time, and the flow pattern inside the stirred tank. The developed model was validated through experimentally measured torque. The influence mechanism of the rotational speed and fluid rheology on the cavern evolution was explored deeply. The performances of three mixers in this work were compared at the constant power input and fluid rheology with respect to the flow pattern, mixing time, and mixing efficiency. The results verify that the faster the rotating speed, the greater influence of the fluid rheology on the cavern evolution, and the more uniform apparent viscosity distribution. Moreover, the mixing time decreases continuously as the increasing power consumption per unit volume, and the dimensionless mixing time of DSO mixer was nearly 42.8% and 6.1% shorter than that of SSC and SCO mixer at the same Reynolds number, respectively. According to the mixing efficiency criteria, these data also revealed that DSO was more efficient than SSC and SSO.

Steady State Rheological Characteristic of Semisolid Magnesium Alloy

Isothermal compressive experiments at different temperatures, strain rates and holding time for semisolid AZ91D, Zr modified AZ91D and MB15 alloy with higher solid volume fraction were carried out by using Gleeble-1500D simulator and the true stress-strain curves were given directly. The relationship of apparent viscosity vs temperature, shear rate and holding time of the three kinds of semi-solid magnesium alloys, as well as isothermal steady state rheological characteristic and mechanical behavior were studied. The results show that the three magnesium alloys had the characteristic of shear-thinning. The rheological characteristic of the semi-solid MB15 is different from that of semi-solid AZ91D. The semi-solid MB15 has higher apparent viscosity and deformation resistance.

Rheological behavior of semi-solid 7075 aluminum alloy at steady state

The further application of semi-solid processing lies in the in-depth fundamental study like rheological behavior. In this research, the apparent viscosity of the semi-solid slurry of 7075 alloy was measured using a Couette type viscometer. The effects of solid fraction and shearing rate on the apparent viscosity of this alloy were investigated under different processing conditions. It can be seen that the apparent viscosity increases with an increase in the solid fraction from 10% to 50% （temperature 620 ℃ to 630 ℃） at steady state. When the solid fraction was fixed, the apparent viscosity can be decreased by altering the shearing rate from 61.235 s-1 to 489.88 s-1 at steady state. An empirical equation that shows the effects of solid fraction and shearing rate on the apparent viscosity is fitted： ηα = [0.871 - 0.00849. γ0.74924]. exp（3.7311, fs） . The microstructure of quenched samples was examined to understand the alloy＇s rheological behavior.

Effects of L.F04,the Active Fraction of Lycopus lucidus, on Erythrocytes Rheological Property

Objective: To study the effects of L.F04, the active fraction of Lycopus lucidus, on erythrocytes rheological property so as to investigate its mechanism in promoting blood circulation and removing blood stasis. Method: The effects of L.F04 (used for treatment for 10 days in different dosages) on deformability, aggregation and membrane liquidity of erythrocytes (MLE) as well as whole blood apparent viscosity (η_b) were examined on the basis of rat model of blood-stasis syndrome induced by venous injection of high molecular weight dextran. Result: As compared with the normal control group, the model group's RBC deformability and MLE were lower, and the aggregation of erythrocytes and η_b were higher. Compared with the model group, both L.F04 0.612g/kg and 0.306g/kg showed significant effect in improving deformability and inhibiting aggregation of red blood cells (RBC) and reducing blood viscosity. The trend of improving MLE was also shown. Conclusion: L.F04 could significantly improve the abnormal rheological property of erythrocytes.

Enhanced inhibition of talc flotation using acidified sodium silicate and sodium carboxymethyl cellulose as the combined inhibitor

The flotation separation of chalcopyrite and talc is challenging due to their similar natural floatability characteristics.Besides,it is usually difficult to effectively inhibit talc by adding sodium carboxymethyl cellulose(CMC)alone during chalcopyrite flotation.Here,a combined inhibitor comprising acidified sodium silicate(ASS)and CMC was employed to realize effective flotation separation of chalcopyrite and talc,and the combined inhibition mechanism was further investigated.Microflotation results showed that adding ASS strengthened the inhibitory effect of CMC on talc and improved the separation of chalcopyrite and talc.The zeta potential,Fourier transform infrared,and X-ray photoelectron spectroscopy analysis indicated that CMC was mainly adsorbed on the talc surface via hydroxyl and carboxyl groups.Moreover,the addition of ASS improved the adsorption of carboxyl groups.Furthermore,the adsorption experiments and apparent viscosity measurements revealed that adding ASS dispersed the pulp well,which reduced the apparent viscosity,improved the adsorption amount of CMC on the talc surface,and enhanced the inhibition of talc in chalcopyrite flotation.

THE INVESTIGATION ON THE RHEOLOGICAL BEHAVIOR OF SEMI-SOLID ALUMINUM ALLOY DURING DIE CASTING

Under the condition of die casting and reheating temperature of 570-580 degC, the rheological behavior of semi-solid aluminum alloy (A356) is pseudoplasticity at the shearrate of 2X10^-1X10^4s^(-1), and also shows dilatancy at the rate over 10~6s^(-1).

Rheological Behavior of Semi-Solid AZ91D Magnesium Alloy at Steady State

The rheological behavior of semi-solid AZ91D magnesium alloy was investigated in isothermal steady state condition. The effects of stirring temperature and shearing rate on apparent viscosity of semi-solid alloy slurry at steady state were discussed. The results show that the apparent viscosity of semisolid AZ91D alloy increases with increasing solid fraction. It increases slightly before the solid fraction reaches a certain value, about 0.4, and then goes up rapidly aider the solid fraction reaches the critical value. However, the apparent viscosity decreases with increasing shearing rate, and the reduction amplitude is higher when the solid fraction is higher. According to the experimental data, an empirical equation that shows the effect of solid fraction and sheafing rate on the apparent viscosity of semi-solid AZ91D alloy can be built as ηa=9.7×10^-2 exp（13.87fs）γ^-0.58.

Artificial neural network approach for rheological characteristics of coal-water slurry using microwave pre-treatment

Detailed experimental investigations were carried out for microwave pre-treatment of high ash Indian coal at high power level(900 W) in microwave oven. The microwave exposure times were fixed at60 s and 120 s. A rheology characteristic for microwave pre-treatment of coal-water slurry(CWS) was performed in an online Bohlin viscometer. The non-Newtonian character of the slurry follows the rheological model of Ostwald de Waele. The values of n and k vary from 0.31 to 0.64 and 0.19 to 0.81 Pa·sn,respectively. This paper presents an artificial neural network(ANN) model to predict the effects of operational parameters on apparent viscosity of CWS. A 4-2-1 topology with Levenberg-Marquardt training algorithm(trainlm) was selected as the controlled ANN. Mean squared error(MSE) of 0.002 and coefficient of multiple determinations(R^2) of 0.99 were obtained for the outperforming model. The promising values of correlation coefficient further confirm the robustness and satisfactory performance of the proposed ANN model.

Effect of ultrafine kaolinite particles on the flotation behavior of coking coal

Kaolinite,as a mineral in fine coal,has an important influence on the flotation of coal particles.In this study,the effects of ultrafine kaolinite particles on the flotation recovery of coal particles were investigated.Flotation tests were carried out using a mixture of coal particles and different amounts of ultrafine kaolinite particles.Combined with the Stefan–Reynold theory,the effect of liquid film drainage rate between coal bubbles in a kaolinite suspension was calculated.The yield of flotation clean coal increases quickly with the increasing content of ultrafine kaolinite particles.The ultrafine kaolinite particles can reduce the surface tension of the suspension,weaken the bubble coalescence,and stabilize the structure of the froth layer.In addition,the ultrafine kaolinite particles increase the apparent viscosity of the flotation pulp slightly.It is concluded that the role of ultrafine kaolinite particles on the positive effect of froth properties conceals the negative effect on the liquid film drainage rate between coal particles and bubbles caused by the kaolinite particles,which ultimately leads to an increasing yield of clean coal with an increasing content of kaolinite particles.This study is important for understanding the influence of ultrafine kaolinite on coal particle flotation.

Characterization of lauryl betaine foam in the Hele-Shaw cell at high foam qualities(80%-98%)

Lauryl betaine(LB)as an amphoteric surfactant carries both positive and negative charges and should be able to generate stable foam through electrostatic interaction with nanoparticles and co-surfactants.However,no previous attempts have been made to investigate the influence of nanoparticles and other co-surfactants on the stability and apparent viscosity of LBstabilized foam.In this study,a thorough investigation on the influence of silicon dioxide(SiO2)nanoparticles,alpha olefin sulfonate(AOS)and sodium dodecyl sulfate(SDS),on foam stability and apparent viscosity was carried out.The experiments were conducted with the 2D Hele-Shaw cell at high foam qualities(80%-98%).Influence of AOS on the interaction between the LB foam and oil was also investigated.Results showed that the SiO2-LB foam apparent viscosity decreased with increasing surfactant concentration from 0.1 wt%to 0.3 wt%.0.1 wt%SiO2 was the optimum concentration and increased the 0.1 wt%LB foam stability by 108.65%at 96%foam quality.In the presence of co-surfactants,the most stable foam,with the highest apparent viscosity,was generated by AOS/LB solution at a ratio of 9:1.The emulsified crude oil did not imbibe into AOS-LB foam lamellae.Instead,oil was redirected into the plateau borders where the accumulated oil drops delayed the rate of film thinning,bubble coalescence and coarsening.

Influences of Polycarboxylate Superplasticizers on Rheological Behavior of Low-cement Castables

Influences of different superplasticizers （ STP. KSJSTO and LMS-P） on rheological behavior of low-cement castables and the mechanisms were analyzed. The shear stress and viscosity under different shear rates of matrix slurry were determined using a NXS-I IA rotary viscometer. Effects of different admixtures on the rheological properties of slurry was analyzed theoretically. Sodium tripolyphosphate and poly＇carboxylate superplasticizers KS-JSTO and LMS-P） can improve the fluidity and initial setting time. With STP. the slurry is plastic flow. With KS-JS70 or LMS-P increasing, the slurrv changes from plastic.flow, pseudoplastic flow to dilatant flow successively. Th, e optimum dosages of STP. KS-JSTO and LMS-P are 0. 15%. 0. 25% and 0. 40%, respectively. KS-JS70 and LMS-P can significantly reduce the slurry viscosity and shear stress to improve the workability of construction. Both shear stress and viscosity shall be taken into account for on-site construction.

Flow Characteristics of Large-Scale Liquefaction-Slip of the Loess Strata in Shibei Tableland, Guyuan City,Induced by the 1920 Haiyuan M81/2 Earthquake

Based on the dynamic triaxial liquefaction test of the loess samples which are taken from Shibei tableland,Guyuan City,Ningxia,China,the characteristics of dynamic strain,dynamic stress and pore water pressure are studied under cyclic loading.Triaxial shear test is conducted immediately after the sample reaches liquefaction point.During the test,the property of the liquefied soil is analyzed through fluid mechanics method,whereby the fluidity of the liquefied soil is represented by apparent viscosity.The results show that the fluidity of liquefied loess changes from“shear thickening”to“shear thinning”as the shear force continues,and the fluidity of liquefied loess is closely related to its structure.In addition,in the process of forming a new stable state,the apparent viscosity and deviant stress change with axial strain in a similar approach.When the sample reaches its stable state,it meanwhile shows a relatively stable apparent viscosity.According to the fluid mechanics and the law of conservation of energy,the slip distance of the liquefied soil is estimated,and the results are in good agreement with the field investigation results.