/pdf/structural-and-kinematic-analysis-of-a-stirred-tank-2e6migsmmn.pdf

Structural and kinematic analysis of a stirred tank planetary drive

Mechanisms with intermittent movement of the output link are widely used in drives of automatic and semi-automatic machines. Currently, the most widespread are the mechanisms of a permanent structure with one-way coupling (ratchet, anchor mechanisms) and mechanisms of a variable structure (Maltese mechanisms, star mechanisms, incomplete gears), however, they are characterized by high loads on the links due to impacts that occur at the beginning or end of the phase movement. The aim of this work is the structural synthesis of actuators, in which the rotational motion of the input link is converted into intermittent motion of the output link, while the kinematic chain does not open during the cycle of the mechanism. As a synthesis method, a structural mathematical model is used in the form of a system of equations that describes the relationship between the quantitative and qualitative composition of the links and kinematic pairs of the future mechanism, its mobility, the number of connections to the rack and other structural parameters. Based on the results of structural synthesis, planetary gear schemes with elliptical gears are constructed, which, with certain gear sizes, allow intermittent motion of the output shaft. A geometric analysis of the mechanisms with elliptical gears is carried out, as a result of which the principle of their action is shown, link position plans are constructed and the output shaft rotation angle functions are obtained. Since the motion with stops is carried out without breaking the kinematic chain, the developed mechanisms are more reliable and compact in comparison with existing analogues, and can be recommended for wide practical application. Possible structural designs of the synthesized mechanisms and examples of use as part of a conveyor and mixer drive with intermittent movement of the impeller are shown.Mechanisms with intermittent movement of the output link are widely used in drives of automatic and semi-automatic machines. Currently, the most widespread are the mechanisms of a permanent structure with one-way coupling (ratchet, anchor mechanisms) and mechanisms of a variable structure (Maltese mechanisms, star mechanisms, incomplete gears), however, they are characterized by high loads on the links due to impacts that occur at the beginning or end of the phase movement. The aim of this work is the structural synthesis of actuators, in which the rotational motion of the input link is converted into intermittent motion of the output link, while the kinematic chain does not open during the cycle of the mechanism. As a synthesis method, a structural mathematical model is used in the form of a system of equations that describes the relationship between the quantitative and qualitative composition of the links and kinematic pairs of the future mechanism, its mobility, the number of connections to the rack a...

/pdf/structural-synthesis-and-geometry-analysis-of-planetary-2us55s6dek.pdf

Structural synthesis and geometry analysis of planetary intermittent motion mechanisms with elliptical gears

Abstract In process engineering as chemical and biotechnological industry, agitated vessels are commonly used for various applications; mechanical agitation and mixing are performed to enhance heat transfer and improve specific Physico-chemical characteristics inside a heated tank. The research subject of this work is a numerical investigation of the thermo-hydrodynamic behavior of viscoplastic fluid (Casson–Papanastasiou model) in a stirred tank, with introducing a new anchor impeller design by conducting some modifications to the standard anchor impeller shape. Four geometry cases have been presented for achieving the mixing process inside the stirred vessel, CAI; classical anchor impeller, AI1; anchor impeller with added horizontal arm blade, AI2 and AI3 anchor impeller with two and three added arm blades, respectively. The investigation is focused on the effect of inertia and plasticity on the thermo-hydrodynamic behavior (flow pattern, power consumption, and heat transfer) by varying the Reynolds number (Re = 1, 10, 100, 200), Bingham number (Bn = 1, 10, 50), in addition to the effect of geometry design in the overall stirred system parameters. The findings revealed an excellent enhancement of flow pattern and heat transfer in the stirred system relatively to the increase of inertia values. Also, an energy reduction has been remarked and the effect of anchor impeller shape. AI3 geometry design significantly improves the flow pattern and enhances heat transfer by an increased rate of 10.46% over the other cases. 

/pdf/investigation-of-mixing-viscoplastic-fluid-with-a-modified-2djwo18a.pdf

Investigation of mixing viscoplastic fluid with a modified anchor impeller inside a cylindrical stirred vessel using Casson–Papanastasiou model

Mechanical stirrers are widely used in chemical, petrochemical, food, construction and many other industries. Currently, a large number of stirred tank actuators with various types of the impeller motion have been developed, and at the moment the most promising constructions are rotationally reciprocating stirred tanks, since they make it possible to ensure high intensity of heat and mass transfer processes in the reactor, to eliminate stagnant zones and to increase the velocity gradient of the stirred liquid. As an actuator, the author proposes to use a planetary gear with elliptical gearwheels, which allows to convert the rotational motion of the motor shaft into a rotationally reciprocating motion of the impeller. For the design and manufacture of stirred tank, it is necessary to investigate its kinetostatics. In the article, the force analysis of the planetary actuator of the mixing device was carried out, as a result of which the design schemes were obtained and expressions were found for determining reactions in kinematic pairs. This will allow further calculations of the elements of kinematic pairs and links for strength, as well as determining the efficiency of the actuator.

Kinetostatics of Rotationally Reciprocating Stirred Tank Planetary Actuator

Rotationally reciprocating mixing, in which a plate impeller slowly rotates back and forth for only half a rotation, shows excellent fluid mixing performance at Re > 40. On the other hand, since vertical flow disappears at Re < 10, two-dimensional fluid mixing proceeds in the horizontal cross section of a cylindrical vessel, producing segmented mixing regions with a pair of central poor mixing zones. In this study, we investigated the usefulness of an anchor-type impeller in the expectation of enhancing two-dimensional fluid mixing under a laminar regime by utilizing the fluid flow through the central clearances. First, we examined the effect of the clearance size on the spreading behavior of tracer particles by numerical simulation. Time series of Poincaré sections are used to classify the tracer particles depending on their spreading behavior, which is then quantified by newly defined mixing ability. It is then elucidated that even a narrow central clearance could avoid the segmentation of the mixing region, while a vast central clearance produces additional isolated mixing regions in the clearance due to stable vortex flows. The tracer particles could uniformly spread in the entire circular cross section by increasing the impeller width and adjusting the flow rate in the central and wall clearances without segmentation. Furthermore, the experimental observation of streaklines could also demonstrate that the uniformity of the fluid mixing performance is improved considerably. 

Tomoya Date

Papers

Application of a Rotationally Reciprocating Plate Impeller on Crystallization Process

Enhancement of laminar mixing by an anchor impeller with rotationally reciprocating motion