Наукове обґрунтування параметрів періодичного мішування водно-борошняних сумішей та створення високоефективного обладнання

Abstract

Дисертацію присвячено моделюванню процесу змішування компонентів водно-борошняних сумішей і визначенню раціональних геометричних і кінематичних параметрів робочого органу змішувальної машини періодичної дії. Отримані структурно-механічних характеристик суміші, дозволили побудувати функціональні залежності напруження зсуву і в’язкості суміші від швидкості, деформації, які використані в подальшому при аналітичному моделюванні процесу. Побудовано аналітичні залежності розподілу швидкостей, об’ємної витрати, крутного моменту і витраченої потужності, які залежать від геометричних і кінематичних характеристик робочого органу та структурно-механічних характеристик суміші. Доведено вплив кінематичних і геометричних параметрів, а також положення ротора в середині змішувальної чаші на зміну активної потужності приводу і встановлено раціональний час готовності водно-борошняної суміші. Визначені оптимальні експлуатаційні характеристики роторного змішувача, що мінімізують енергетичні витрати, створюють максимальні робочі тиски та підтримують продуктивність не менше заданої. Такими параметрами є зовнішній діаметр робочого органу d, діапазон розмірів якого буде становитиме (0,365…0,396)D та швидкість його обертання – 1500 об/хв. The thesis is devoted to modeling the process of mixing components of water-flour mixtures(WFM) and the definition of rational geometric and kinematic parame-ters of the working body of mixing machine periodic action. An experimental setup was developed and physical modeling of the mixing pro-cess. Analysis of the structural and mechanical characteristics of the mixture by means of rotational viscosimetry made it possible to construct functional dependences of the viscosity shear stress of the mixture on the strain rate, which were used in further ana-lytical modeling of the mixing process. The expediency of using the proposed rotor-type construction for mixing is proved, which is confirmed by the graph of the change in the concentration of the dis-persed phase in the dispersed medium already at about 15 seconds of the process. At the heart of the proposed design of the working body, the task of creating a highly efficient mixer with non-stationary flows of matter, which by virtue of their cyclicity leads to the creation of a pulsating effect, which activates the process of mix-ing the components of the mixture. The second task that is performed is the transfer of the process into the interior of the rotor in which predictable and controlled favorable kinematic processing conditions can be created. Analytic dependences of velocity distribution, volumetric flow, torque and power consumption on mixing are constructed, which depend on the geometric and structural-mechanical characteristics of the mixture and are recommended for use in the design of equipment. Structural and mechanical characteristics of the WFM and the influence of the main technological parameters of humidity and temperature on them have been estab-lished. The influence of kinematic and geometric parameters, as well as the position of the working organ in the middle of the mixing bowl on the change of the active drive power, has been experimentally proved and the rational time of readiness of the WFM has been established. Optimal performance characteristics of the rotary mixer are minimized, minimizing energy costs, creating maximum operating pressures and maintaining productivity of at least the specified. Such parameters are the geometry of the working element, the range of which will be (0,365…0,396)D and the speed of its rotation – 1500 rpm. The influence of the pulsating pressure created inside the rotor, which depends on the eccentricity, is confirmed. At a value of e = 0,007 m, the average particle size of the solid phase and the agglomerate size will be the smallest, and their total quantity is greatest, which indicates the quality of the mixture obtained. A method is proposed that allows determining the amount of mechanical energy input required to achieve the optimum consistency of the finished product. The design of a device for mixing liquid semi-finished products has been developed. Unsteady flows of matter are combined in it, which, due to their cyclicity, lead to the creation of a pulsation effect, which activates the process of mixing the components of the mixture with the transfer of the process of the rotor, in which predictable and controlled. The results of the research have been introduced into the educational process of NUFT, implemented in the production workshop No.4 of Private Joint Stock Company “Kyivkhlib”, which is confirmed by the acts of introducing scientific research into production.