Blade Stirrer Research Articles

High-temperature dynamic corrosion mechanisms of austenitic stainless and carbon steels in nitrates for concentrating solar power

Abstract: In this paper, to simulate the dynamic corrosion mechanisms of metals exposed to a high-temperature molten salt mixture of NaNO3–KNO3, the experimental samples made of commonly used stainless steel alloys such as 304 (with/without welds) and Q275 were suspended, along with stirring blades, in a specially designed stirred kettle to obtain their corrosion characteristics. For the experimental samples, the Q275 surface exhibited significant quantities of Fe3O4 and Fe2O3, while 304 generated FeCr2O4, Cr2O3, and MgFe2O4 with protective effects. The microstructure of the welding zone in 304 exhibited considerable disparities compared to that of the base material, consequently leading to augmented susceptibility towards localized corrosion. The uneven distribution of chromium in the welding zone resulted in intergranular corrosion and alterations in the crystal structure. Moreover, experimental studies have demonstrated that NO3- in the molten salt undergoes decomposition to generate oxygen ions, which contribute to the corrosion reaction. Notably, under all test conditions, the corrosion rate of samples exhibited the following ranking: 304 (without welds) < 304 (with welds) < Q275.

Development of Vacuum-Steam Combination Heating System for Pasteurization of Sprout Barley Powder

The processing of sprout vegetables in powder form has been known to extend the shelf-life by retaining nutritional values; however, sprout powder products were exposed to a variety of contaminants, such as microbial contaminants, during processing and storage. Therefore, the proper treatment for removing the contaminants in the powder was required without compromising their quality properties. This study was conducted (1) to determine a suitable pasteurization method for sprout barley powder, and (2) to investigate the effect of vacuum-steam heating combination treatment on the quality change and the lethality of microorganisms in sprout barley powder. The heating pattern of sprout barley powder was elucidated with a vacuum-thermal combination system consisting of a vacuum chamber, overhead stirrer, far-infrared heater, and PID (Proportional-Integral-Differential) controller. In addition, the mixing patterns of sprout barley powder, depending on the types of stirring blades, were evaluated by discrete element modeling using EDEM™ software. The vacuum-steam combination heating system was fabricated using the investigated pre-design factors. The quality change in sprout barely powder was evaluated by measuring the microbial inactivation, CIE values (L*, a*, b*, ΔE), and water activity (aw). During the pasteurization process, steam could be directly injected into the chamber at regular intervals for two hours to transfer moisture and heat to the powder. By combining steam and vacuum conditions, the population of E. coli O157:H7 in the powder was reduced by 4.33 log CFU/g, eliminating all E. coli O157:H7 in the powder. In addition, the water activity (aw) of the powder was significantly decreased in a vacuum pressure environment without the quality deterioration.

A continuum model for the segregation of bidisperse particles in a blade mixer

AbstractThe process of blending powders using stirring blades involves complicated granular flows, particle‐scale mechanisms, and blade–particle interactions, which is challenging to predict and control. This article proposes a continuum‐based model for such a process by incorporating the flow rheology, isotropic particle diffusion and the percolation of granular materials. A method combining finite element method (FEM), finite difference method (FDM), and immersed boundary method (IBM) is developed to numerically implement the continuum model and applied to a cylindrical blade mixer. The model well describes the tempo‐spatial distribution of small/large particles in the stirring process, such as the accumulation of small particles in the vicinity of blades. Remarkably, this model can capture the various intricate effects of blade parameters, including the blade rake angle, rotating speeds, filling level, and the friction coefficient of the mixer wall. It is therefore promising for optimizing the blade mixers in industries.

A thermo-solid coupling model for disk discontinuous deformation analysis to simulate heating and stirring particles in rotary drums

This paper develops a new thermo-solid model by coupling the disk discontinuous deformation analysis (DDDA) model with the discrete thermal element method (DTEM), named as DDDA-DTEM model, to simulate the particle heating-stirring processes in rotary drums. A disk-disk and a disk-line segment heat conduction model are respectively established based on DTEM, and their acceptability for simulating the heat conduction in disk system is verified. After that, the DDDA-DTEM model is used to simulate the particle heating-stirring processes in rotary drums. Four factors that influence the heat conduction are analyzed, which unravels that 15 rpm rotational speed, 2 to 6 medium-sized stirring blades and 20% loading rate can help to obtain high-quality processing results. Model performance shows that the established DDDA-DTEM model is a feasible tool to simulate the heating and stirring particles in rotary drums, which may help to optimize schemes for granular material processing and designing equipment in industry.

Experimental Study of Stirring and Resin-Blocking Devices for Improving the Performance of Resin-Anchored Cable Bolts

Resin anchoring promotes the development of high-strength cable bolts for underground rock support. However, the resin anchoring the cable bolt must be very effective in soft rock. Using conventional anchoring methods, the anchoring force provided by cable bolts in soft rock is low, and achieving high-strength support is difficult. Aiming to address these problems, this study developed a method to stir the resin more completely and thereby improve the uniformity of the resin and increase its density in the anchoring area. The problem was investigated using theoretical analysis, numerical simulations, and laboratory and field tests. A method for improving the cable bolt anchoring quality is proposed and stirring and blocking devices (SBDs) for resin-anchored rock cable bolts are developed. The stirring device has three stirring blades on its top and the blocking device’s diameter is slightly smaller than the diameter of the borehole. Both devices have protruding left-handed threads on their surfaces. The mechanisms for improving cable bolt anchoring quality are demonstrated. The main conclusions drawn from this study are that the devices can effectively improve resin uniformity and increase the density of resin in the anchoring area. This improves the quality of the anchorage and thus enhances mine safety. The field test showed that compared with the anchoring force of conventional cable bolts, the anchoring force provided by cable bolts using the SBDs were increased by more than 30%. The SBDs are easy to install and have practical significance for improving cable bolt anchoring force.

Influence of stirrer blade design on stir casting of Al Mg Cu/12% SiC composite

Aluminium metal matrix composites are generally produced employing stir casting technique. The effect of stirrer blade on stir casting of aluminium composite with 12 wt% SiC, 4 wt% magnesium and 2 wt% copper was observed. The composites were prepared with 6061 base metal using three different design of stirrer blade which created different vortex fluid flow while stirring. Due to high density of SiC particles, it tries to settle in lower part of the molten metal matrix. Hence change in vortex technique by stirrer design modification can have influence on the mechanical and microstructure behaviour of the composites. The aluminium SiC composite are evaluated by mechanical properties and microstructure analysis based on stirrer blade design used while stir casting. The change in blade stirrer shows variation in testing tensile strength and hardness. The optical microstructure and SEM images were observed to analyze the cast structure and reinforcement distribution in the composites. The SiC particles were appeared to distribute along the grain boundaries of the composite and also cast defects were observed. Composite prepared with alternate peddle blade produced best mechanical properties.

Abrasive wear and optimal installation angle of concrete double-horizontal shaft mixer stirring blades

The quality of a building desponds directly on the quality of concrete, and mixing is the key process of concrete production. However, a mixing blade is severely worn and has a relatively short life during the mixing process because of severe friction between the concrete material and the double-horizontal shaft mixer stirring blades. This study uses the abrasion mechanism of a mixer and the abrasive wear formula as bases to analyze the theoretical maximum line wear rate $$\eta$$ of an experimental prototype at five blade installation angles, and obtain the optimal installation interval and optimal installation angle. Results indicate that the wear rate of different blade installation angles changes significantly. The wear rate at 45° is the largest, and the corresponding theoretical life is only 125 days. By contrast, the wear rate at 35° is the smallest, and the corresponding theoretical life is 192 days. The change rule of the maximum line wear rate $$\eta$$ of the blade is obtained through the wear line chart, and the performance curve and evaluation function are fitted using MATLAB. The three aspects of stirring quality, energy consumption, and wear loss are quantitatively analyzed. The best installation angle and interval are 31.8° and 30°–34°. This study can provide a reference for the design choice of the installation angle of the mixing blade of concrete mixers.

An improved disk discontinuous deformation analysis model for simulating particle mixing process in rotary drums

This paper develops an improved disk discontinuous deformation analysis (DDDA) model to simulate mixing particles in rotary drums. The original DDDA is improved by developing a disk-movable line segment contact model to motivate the constant movements of the disks during the mixing operation. The analytical solution of the movement of a single disk in a rotary drum is achieved by building a force analysis model, and the improved DDDA is validated by comparing this analytical solution with the proposed numerical simulation. Then, the improved DDDA is utilized to simulate mixing 8805 disks in a rotary drum, during which the influences of rotational speed and layouts of stirring blades are studies. Model performance shows that, the improved DDDA is a feasible tool to simulate the particle mixing process in rotary drums, which may optimize schemes for mixing particles and designing mixing equipment in industry.

A new approach for nanofinishing of complicated-surfaces using rotational abrasive finishing process

ABSTRACT Ultra-precise finishing of parts with complicated geometry has faced many limitations using traditional methods due to the use of rigid tools. This study aims to introduce a new mechanism by developing a rotational abrasive finishing (RAF) operation, where the simultaneous rotation mechanism of a workpiece and the stirring-chamber is used in the opposite directions. In this paper, the associated velocities and forces in the developed RAF technique, the effects of stirring blades rotary speed, working gap as well as various meshing of abrasive grits on material removal (∆m), surface roughness variation rate (∆Ra) the percentage of surface improvement (%∆Ra), and the surface roughness value (Ra), on one of the most important cutting tools, i.e. drill bit, were examined. The research outcomes demonstrated that with increasing the speed of the stirring-chamber combined with the selecting larger abrasive grits, ∆m and ∆Ra will increase, while an increment in working gap resulted in a decrease in ∆m and ∆Ra. Also, reducing surface roughness from micrometer scale to nanometer (from initial value 547 nm to final value 69 nm) resulted in an 87% enhancement in the surface quality. Therefore, the superiority of RAF technique in ultrafinishing of various work parts can be demonstrated theoretically and experimentally.

Al6061 Reinforced Al2O3 Metal Matrix Composite Produced by Double Blade Stir Casting

Demand for materials with excellent mechanical properties and lightweight increase in a recent year especially for high-performance applications. Aluminum reinforced Al2O3 composite (AMC) provide this superior property. Therefore in this research, aluminum alloy 6061 was used as a matrix and Al2O3 with 10 and 15 Vf-% as a reinforced for making metal matrix composites while magnesium as a wetting agent was used various from 8, 10 to 15 wt-% to improve the wettability between Al and Al2O3 since aluminum was poor wetting with ceramic. Al alloy 6061 was melted at 800 oC and magnesium was added into Al molten, then Al2O3 particles were poured into the melt. The process using double stirrer with a rotational speed of 1000 rpm for 3 minutes to distribute all Al2O3 particles in the Al melt and all the gas bubble formed was removed by flushing an Argon for 2 minutes. The composites produced then characterized both mechanical properties and microstructural analysis. The focus of this research is to investigate the effect of Al2O3 and Mg on the mechanical properties of composites. The result showed that the optimum tensile strength was 202 MPa which was obtained in composite with 10% Vf-% Al2O3 and 10 wt-% Mg. Moreover, hardness and wear resistant to composite increased with the addition of Al2O3 and Mg content due to good wetting in composites with 10 wt-% Mg. The double blade stirrer has contributed to the random distribution of Al2O3 particles in the molten Al. The microstructure observations showed that the composites yield pores and impaired the mechanical properties of composites.

Mass transfer during bubble-free polymer devolatilization: a systematic study of surface renewal and mixing effects

This paper deals with a systematic study of bubble-free polymer devolatilization. Experimental degassing tests are combined with a surface renewal analysis. For this purpose, a simplified extruder model is used as representative rotating degassing machine. It is a partially filled agitator vessel with a blade stirrer. A model substance system consisting of highly viscous polydimethylsiloxane as polymer and 1,1,2-trichloro-1,2,2-trifluoroethane as volatile allows the experiments to be carried out at ambient temperature. The driving force for the mass transfer is achieved by reducing the partial pressure in the gas phase via an inert gas flow of nitrogen. This allows the specific investigation of the mechanism of film degassing. The temporal decrease in the concentration of volatiles in the polymer solution is measured thermogravimetrically at three different filling levels and three different rotational speeds in a total of 18 test series. At the same time, the free surfaces and renewal times are determined by video recordings and numerical simulations. For this, the free CFD software OpenFOAM is used with a VOF-based free surface solver. The numerical results are validated by the experiments. It is shown that the deviations of the measured mass transfer data from the theoretical predictions of the common surface renewal models depend on the degassing degree. Mixing is the decisive factor which can be taken into account in the form of a corrected model for the design of degassing machines. Furthermore, it is shown that the gas-side mass transfer resistance is not negligibly small in all cases.

PENGARUH PENGGUNAAN KOLEKTOR PLAT DATAR PADA PENGERING PADI TIPE DRUM DRYER

Rice is one of food items consumed by most Indonesian people. Rice quality is a matter that must be considered in rice production. Rice quality can be improved by proper post-harvest handling, one of which is the drying process. The drying process can be done by drying under the sunshine and drying by using a dryer. Drying under the sunshine takes a long time, is difficult to control, depends on the weather, is easily contaminated and requires a large place. To overcome this problem, a dryer is needed. The dryer used is the drum dryer type. This drum dryer also utilizes mechanical energy from the gasoline engine so that it can rotate the drum. On the inner surface of the drum, stirring blades are installed. This dryer also uses heat coming from internal channel wall solar collectors. In this experiment was carried out with 4 free variations, namely: motor rotation, air flow velocity, intensity of solar radiation and cycle time. Three or four data are taken from each variation. When the experiment is taking place, varied parameters and planned parameters such as temperature absorber, ambient temperature, collector outlet air temperature and drying chamber temperature are measured. And at the final of the experiment for each variation, final mass of dried rice are measured. From the result of research, it can be concluded that the optimum rice mass reduction rate was obtained for each variation, namely at 905.1 rpm motor rotation, 10 m/s air flow rate, 948 W/m2 intensity of solar radiation and 30 minutes rotation time.

PENGARUH SUHU REAKSI, KECEPATAN PENGADUKAN DAN WAKTU REAKSI PADA PEMBUATAN SABUN PADAT DARI MINYAK KELAPA (Cocos nucifera L.)

&#x0D; Soap is a cleanser made by chemical reactions between sodium hydroxide or potassium hydroxide with fatty acids from vegetable oils or animal fats. Soaps can be made by several methods, namely saponification and neutralization methods, in this study carried out by saponification method. In the saponification method there are several problems namely operating conditions which include reaction temperature, stirring speed and stirring time. Therefore, need to do research to determine the best conditions of saponification reaction, namely reaction speed, operating temperature and reaction time using an impeller type multiple pitch blade turbine with research variables reaction temperature 60 oC, 70 oC, and 80 oC, stirring speed 300 rpm,400 rpm and 500 rpm and reaction time of 45minutes, 60 minutes, and 75 minutes. Saponification reaction is carried out by heating coconut oil and inserting 30% NaOH slowly and then stirring with a multiple pitch blade stirrer. The product will be analyzed by testing alkaline levels, moisture content and pH of the soap. The best operating conditions obtained from this study were at a temperature of 70 oC, reaction time of 60 minutes, stirring speed of 400 rpm with a pH value of 9.4 and an alkaline level of 0.073 and a moisture content of 9.8.&#x0D;

Influence of the flow field on α-cyclodextrin glycosyltransferase production by Escherichia coli BL21.

The computational fluid dynamics (CFD) software package Fluent was utilized to simulate the flow field of Escherichia coli (E. coli) BL21 fermentation in a 50L automatic bioreactor for producing α-cyclodextrin glycosyltransferase (α-CGTase) in this study. 4-down-pumping propeller (4DPP), 6-curved-blade disc turbine (6CBDT), and Rushton turbine (RT) were assembled to form eight impeller combinations (C1-C8). Through flow field simulating, four referential impeller combinations, in which C6, C7, and C8 were three layers stirring blades and C1 as a control, were selected to carry out batch fermentation experiments (TC1, TC6, TC7, and TC8) for validation. The correlation analysis between simulation results and experimental measurements indicated that TC6 (tank equipped with C6 impeller combination) exhibited lower enzymatic activity though it had the better mixing effect, fastest oxygen uptake rate (OUR), and maximum specific growth rate (µ) in the initial stage, which was just to the contrary in TC8. It was revealed by next fed-batch fermentation experiments in TC6 and TC8 that TC6 was considered as excellent flow field properties brought about the higher µ of E. coli BL21 and fast acetic acid (HAc) accumulation, which resulting in a serious inhibition on α-CGTase expression and this negative effect could not be removed. As a result, there should be a threshold of HAc accumulation rate which brought about a terrible inhibitory effect on α-CGTase expression. Moreover, the yield of α-CGTase activity reached 231.38U mL- 1 in TC8, which elevated 31.74% compared to that obtained in TC1.

Effects of liquid feed rate and impeller rotation speed on heat transfer in a mechanically fluidized reactor

A mechanically fluidized reactor (MFR) is a novel and compact reactor used for biomass pyrolysis. Endothermic biomass pyrolysis requires heat provided from the wall of the MFR. Meanwhile, mixing with a vertical stirrer helps achieve effective heat transfer from the wall to the bed. Here, the heat transfer characteristics between the wall of a 1.0-L MFR and its bed of mechanically fluidized sand particles were studied. An induction heating system was used to heat the wall, while a vertical blade stirrer was used for mixing. Heat transfer measurements were carried out using silica sand particles, having three average Sauter mean diameters: 190, 300, and 600μm. The overall wall-to-bed heat transfer coefficients were estimated using temperature measurements taken during continuous injection of water onto the fluidized bed. The overall heat transfer coefficient for bed temperatures of 500–700°C increased as particle size increased or superficial velocity of the vaporized liquid increased. Effect of impeller rotation speed also was investigated. Typically, the overall heat transfer coefficient increased as rotation speed increased. The wall-to-bed heat transfer coefficients obtained in this study are comparable to estimates from traditional bubbling fluidized beds, even at vapor velocities below the minimum fluidization velocity.

ON-SITE VERIFICATION OF REAL-TIME CHECKING SYSTEM FOR IMPROVED RANGE BY HIGH-PRESSURE INJECTING GROUND IMPROVEMENT

In contrast to the mechanical stirring method in which the ground soil and the modifyingmaterial are mixed and stirred by stirring blades and the improved body is formed in the ground, the highpressure injection stirring method is a method in which the improved diameter is changed due to soilcondition and so on. There is a possibility that it can be changed with, and a method for easily confirming theshape, particularly the improved diameter, is highly desired. In this research, the authors propose and proposea method that can make visualization of this improvement situation and confirm the improved diameter inreal time. Confirmation was made by measuring water quality in multiple items. From the results, it wasconfirmed that pH and the values of the other 5 items changed at the same time. And the change was due tothe arrival of the cement slurry. Therefore, it can be said that real-time measurement is possible byvisualization of improved diameter by water quality measurement conducted this time.

Mixing and operability characteristics of mechanically fluidized reactors for the pyrolysis of biomass

Mixing characteristics of a novel Mechanically Fluidized Reactor (MFR), a continuous, cylindrical, mechanically mixed reactor developed for biomass pyrolysis in the ICFAR laboratory, have been investigated with the specific objective of selecting the optimal stirrer geometry for fast pyrolysis of biomass. The MFR does not use any fluidization gas and its stirrer provides the required mixing between the injected biomass and the bed material while effectively breaking any possible agglomerate. In addition, good mixing is crucial to achieve effective heat transfer characteristics between the heaters and the bed, and between the bed and the biomass particles.In conventional fluidized beds, the torque required to mix the bed decreases as the superficial velocity of its fluidization gas increases, becoming constant above a critical superficial velocity which is a function of the stirrer characteristics. For the MFR, a method has been developed to monitor the torque and the power required to mechanically mix a bed of low density particles with the natural bed aeration resulting from the formation of gases and vapors during pyrolysis.In this study, three different shaped stirrers were first compared at various rotational speeds by artificially aerating the bed with nitrogen at different superficial velocities to simulate the generation of vapors and gases during pyrolysis. Furthermore, different fluidization gases were used in order to simulate the different characteristics of vapors produced during pyrolysis and, specifically, to evaluate the effects of their density and viscosity. The critical aeration rate at which the stirrer torque becomes constant is similar for all the stirrers.The second part of this study focused on actual wood pyrolysis tests. The reactor was first supplied with nitrogen above the critical aeration rate. Then, the nitrogen was shut off and wood pellets were fed into the reactor. The formation of pyrolysis gases and vapors greatly decreased the power required to mix the bed and this reduction was dependent on the type of stirrer.The stirrers were ranked in terms of their performance in minimizing the pyrolysis time. The vertical blade stirrer resulted in the smallest pyrolysis time and power consumption. Additionally no segregation of the biomass pellets was observed. Hence, gases and vapors were formed at the optimum location for effective aeration.The findings of this project have provided a better understanding of the MFR technology when used for the pyrolytic processing of biomass materials.

Development and Characterization of Aluminium Based Matrix Using 5% Fly Ash

Stir casting technique is a conventional and cheap method for the fabrication of Metal Matrix Composites (MMCs). In the present research, Al-6063 as matrix material and fly ash as particulate reinforcement was fabricated with the help of stir casting technique to produce low cost AMC. In this work, the effect of height of stirring blades was investigated with variable speeds. The wt% of fly ash kept constant to 5%. To obtain the influence of these parameters on the mechanical properties of cast samples, hardness test, Charpy Impact test and SEM/EDS were performed on the cast samples.

A novel stirrer design and its application in submerged fermentation of the edible fungus Pleurotus ostreatus.

In this study, a straight diagonal-pitched blade stirrer was designed, built and characterized in a 5-L fermenter. Compared with the six straight blade Rushton turbine, the power consumption of the new stirrer is lower at a given speed under conditions of no ventilation. The oxygen transference is poorer at the same agitation speed in the cultivation conditions and scales investigated, which confirms that the shear stress of the new stirrer is lower and the gas dispersion is weaker. The new stirrer was installed in a 5-L bioreactor and evaluated in submerged fermentation of the edible fungus Pleurotus ostreatus. The results showed that the maximum dry weight of mycelium is increased by 47% and reached 7.47g/L, and the maximum laccase activity is increased by 15% up to 2,277U/L. Glucose consumption was also found to be relatively faster. The power consumption is 2.8% lower than that of the Rushton turbine.

Fouling of a Heated Rod in a Stirred Tank System

A batch stirred tank device has been developed for measuring fouling from oil samples. The unit consists of a baffled tank equipped with a centrally mounted long blade stirrer, and an electrically heated rod located at 40% of the radius of the tank. Heat transfer from the rod was first characterized. The velocity field was measured, from which the approach velocity to the probe was determined, which allowed the wall shear on the heating probe to be calculated from a literature equation. Fouling of a heavy oil fraction was studied in 1- to 2-day experiments with bulk oil temperatures typically at 320°C, initial probe surface temperatures to 536°C, and stirrer speeds of 100–900 rpm. Micrometer-sized iron oxide particles were added to the oil, such that fouling was due to a combination of particle deposition and coke formation. Deposition rates were measured thermally from the change in heat transfer coefficient when fouling was relatively heavy, and by thickness and mass accumulation when fouling was light. Effects of oil type, film temperature, stirrer rotation speed (or probe wall shear stress), and concentration of suspended particles on deposition rate and deposit composition are presented.