CFD Investigation Of Mixing Of Yield-Pseudoplastic Fluid With Anchor Impeller

The Anchor impeller, which is a close clearance impeller, produces high shear near the vessel wall and is recommended for mixing of highly viscous fluids. A thorough search of the literature suggests that few publications have beeen devoted to the computational fluid dynamics (CFD) modeling of mixing of non-Newtonian fluids with the anchor impeller. Thus the objectives of this study are (i)to generate a 3-D flow field for mixing of yield-pseudoplastic fluid in a flat bottom cylindrical tank equipped with two-and four-blade anchor impellers using CFD modeling technique, (ii) to evaluate the effects of fluid rheology agitator speed, number of blades, vessel clearance and impeller blade width on power consumption, mixing time and flow patterns, and (iii) to determine the optimum value of clearance to diameter ratio and impeller blade width to diameter ratio on the basis of minimum mixing time. The study was carried out for a yield-stress pseudoplastic fluid, using a CFD package (Fluent), to simulate the 3-D flow domain generated in a cylindrical tank equipped with two-and four-blade anchor impellers. The multiple reference frame (MRF) technique was employed to model the rotation of impellers. The rheology of the fluid was approximated using the Herschel-Bulkley model. To validate the model, CFD results for the power were compared to experimental data. After the flow fields were calculated, the simulations for tracer homogenization was performed to simulate the mixing time. The effect of impeller speed, fluid rheology, and number of impellers on power consumption, mixing time, and flow pattern were explored. The optimum values of c/D (clearance to diameter) and w/D (impeller blade width to diameter) ratios were determined on the basis of minimum mixing time.

CFD Investigation Of Mixing Of Yield-Pseudoplastic Fluid With Anchor Impeller

The Anchor impeller, which is a close clearance impeller, produces high shear near the vessel wall and is recommended for mixing of highly viscous fluids. A thorough search of the literature suggests that few publications have beeen devoted to the computational fluid dynamics (CFD) modeling of mixing of non-Newtonian fluids with the anchor impeller. Thus the objectives of this study are (i)to generate a 3-D flow field for mixing of yield-pseudoplastic fluid in a flat bottom cylindrical tank equipped with two-and four-blade anchor impellers using CFD modeling technique, (ii) to evaluate the effects of fluid rheology agitator speed, number of blades, vessel clearance and impeller blade width on power consumption, mixing time and flow patterns, and (iii) to determine the optimum value of clearance to diameter ratio and impeller blade width to diameter ratio on the basis of minimum mixing time. The study was carried out for a yield-stress pseudoplastic fluid, using a CFD package (Fluent), to simulate the 3-D flow domain generated in a cylindrical tank equipped with two-and four-blade anchor impellers. The multiple reference frame (MRF) technique was employed to model the rotation of impellers. The rheology of the fluid was approximated using the Herschel-Bulkley model. To validate the model, CFD results for the power were compared to experimental data. After the flow fields were calculated, the simulations for tracer homogenization was performed to simulate the mixing time. The effect of impeller speed, fluid rheology, and number of impellers on power consumption, mixing time, and flow pattern were explored. The optimum values of c/D (clearance to diameter) and w/D (impeller blade width to diameter) ratios were determined on the basis of minimum mixing time.

Investigation of the basic laws of cutting root crop tops

Purpose: to study the basic laws of cutting some plant materials, the knowledge of which will justify the rational parameters of a small unit for mechanization of removing the root crop tops. Materials and methods. The study was carried out experimentally on a computerized dynamometric unit, according to a non-compositional plan of the second order, using two most common types of root crops in cultivation in small holdings: table carrots and radishes. The value of the specific resistance of cutting tops was taken as an optimization parameter. Results. The study has shown that such factors as the blade incidence angle to the cutting direction, the blade width and the blade speed at the beginning of cutting are crucial and significantly affect the energy consumption of the top removal process. The most significant parameter is the blade width, the degree of influence of which is 2.2–18.2 times greater than the degree of influence of the other two factors. On average, a decrease in the blade width from 0.5 to 0.1 mm leads to a 3–5-fold decrease in the specific cutting force of the top, which confirms the prospects of using ultra-thin replaceable blades instead of a durable wide-faceted blade in the design of the plant-top removing machines. It was also found that at a blade speed of about 0.2 m/s and its blunted blade (b ≈ 0.5 mm), the tops are not cut, but crumpled or (in some cases) deflected by the knife. Conclusions. In general, the study allows to recommend the following rational parameters and operating modes of a small unit for mechanizing the root crops tops removal: the blade incidence angle to the cutting direction is from 30 to 45°; the blade width is about 0.1 mm; cutting speed is about 0.33 m/s.

Design of Crushing Mechanism of Mobile Straw Granulator

Background: Crop straw is a valuable renewable biological resource. In this study, a mobile straw granulator was designed to fully and efficiently use crop straw. The key crushing mechanism device of the mobile straw granulator was also designed in detail. Methods: The first three natural frequencies and vibration modes of the crushing roller are obtained by applying ANSYSWorkbench software to the modal analysis of the crushing roller. Results: The lowest natural frequency of the crushing roller was 165.83 Hz, which was higher than its working frequency of 30 Hz and would not cause resonance. Three factors and three levels were tested using the average resistance of the blade as an index and the blade edge angle, the blade thickness, and the blade end width as the test factors. Conclusion: The optimal parameter combination obtained by software analysis is blade edge angle of 30°, blade thickness of 8 mm, and blade width of 75 mm. With this parameter combination, the blade power consumption is the smallest, the service life is the largest, and the crushing effect is the best.

Bazı Üzüm Çeşitlerinde ve Asma Anaçlarında Yaprak Alanının Belirlenmesi

The amount and area of the leaves should be at an optimum level in order to maintain the product quality and not to adversely affect the vine growth. Because carbohydrates, which are essential for omca and are mostly stored in fruit and wood, are formed by leaves after photosynthesis. Leaf area can be used in many areas. Among these, photosynthesis capacity and plant growth rate may. Various tools and methods (planimetry, leaf area meter, width-product, weight-area calculation, image processing programs, etc.) are used in determining leaf area. In this study, 3 American grape rootstocks (5BB, 110 R, 1103 P) and 5 grapes (Alphonse Lavallée, Italıa, Mıchele Palierı and Narince, Yalova İncisi) were used as material. 20 shoots with 15-25 nodules were taken from the rootstocks and varieties of the omca and the leaves were photocopied according to the order of the node. The actual field values of the leaves were measured with a planimeter. Leaf stem and leaf width and length of the leaves were also measured. Regression analysis was performed between leaf stem, leaf blade width and length, leaf blade × length values and real area. The maximum leaf area on one shoot was 5 BB (2484 cm2) from rootstocks and Narince (2126 cm2) from varieties. All three rootstocks gave the average value of the leaf found in 9th node. In terms of node number, which gives an average value according to the varieties, Alphonse Lavallée, Mıchele Palierı and Yalova İncisi varieties came to the forefront in 11th node. The 13th in Narince cultivar and the 12th in Italia cultivar gave the closest value to the average.

First characterization of a new perturbation system for gust generation: the chopper

We present a new system for the generation of rapid, strong flow perturbations in the aerodynamic wind tunnel at École Centrale de Nantes. The system is called the chopper, and it consists of a rotating bar cutting through the inlet of a wind tunnel test section, thus generating an inverse gust that travels downstream. The flow generated by the chopper is investigated with respect to the rotational frequency using an array equipped with hot-wires that is traversed downstream in the flow field. It is found that the gust can be described as a superposition of the mean gust velocity, an underlying gust shape, and additional turbulence. Following this approach, the evolution of the mean gust velocity and turbulence intensity are presented, and the evolution of the underlying inverse gust shape is explained. The turbulence is shown to be characterized by an integral length scale of approximately half the chopper blade width and a turbulence decay according to E(f)∝f-5/3.

Characterization of a new perturbation system for gust generation: The Chopper

We present a new system for the generation of rapid, strong flow disturbances in a wind tunnel that was recently installed at Ecole Centrale Nantes. The system is called the chopper, and it consists of a rotating bar cutting through the inlet of a wind tunnel test section, thus generating a gust that travels downstream. The flow generated by the chopper is investigated with respect to the rotational frequency using an array equipped with hot-wires that is traversed downstream the flow field. It is found that the gust can be described as a superposition of the mean gust velocity, an underlying gust shape and additional turbulence. Following this approach, the evolution of the mean gust velocity and turbulence intensity are presented, and the evolution of the underlying gust shape is explained. The turbulence is shown to be characterized by an integral length scale of approximately half the chopper blade width and a turbulence decay according to E(f) ∝ f−5/3.

TECHNOLOGICAL PROCESS OF SOIL LOOSENING BY FLAT CUTTING BLADE AND TINE

Purpose: to study the technological process of loosening the soil with a flat-cutting blade and a tine. Materials and methods: the methods of analyzing the power impact on the tine, as well as the theoretical provisions of failure hypotheses are used. As an object of research, the working bodies of tools with a horizontal cutting edge were considered, namely, flat-cutting blades which are used for overall tillage. Results: as a result of studies it was found that the main parameters of flat-cutting blades include: operating width Bi, opening angle 2γ, crumbling angle β0, edge angle i0, band width b, which determine the blades shape and the nature of the impact on the soil. When considering the layout of the soil deformation zones, i. e., the simultaneous combined effect of the tine and plowshares of the horizontal blade, it was found that the zones for obtaining fine soil fractions increase, and a decrease in the thickness t of tine and the operating width of the share B affects the crumbling value. This, in turn, allows regulating the zones for obtaining fine soil fractions and determining the optimal composition of blade width and tine thickness for better crumbling. Conclusions: according to the research results, it was found that the generalized estimated indicator (W) of options for deep tillage ranges from 0.82 to 0.84, for shallow loosening from 0.84 to 0.87, and for surface shallow tillage from 0.845 to 0.870. For loosening soil with mixing crop residues with soil particles, the option W = 0.84 with a vertical tine t = 2.0 cm and a blade operating width of 42.0 cm is acceptable. For surface and presowing tillage, the most suitable options are WX = 0.87 and WXI = 0.85, allowing carrying tillage to a depth of 6–10 cm.