Mixer Design Research Articles

РАЗРАБОТКА УНИФИЦИРОВАННЫХ МЕХАНИЗМОВ ПРИВОДА БЕТОНОСМЕСИТЕЛЕЙ ПРИНУДИТЕЛЬНОГО ДЕЙСТВИЯ

The issue of choosing a rational number of drive mechanisms of concrete mixers of forcing action based on unification is considered. The analysis of unification methods of various systems is carried out. It is represented by successive logical steps that provide a rational approach to the creation of promising designs and an increase in the technical level of mixers. The proposed methodology for unifying the mechanisms of rotary mixers allows the development of new, productive, energy-saving mixers with reliable mechanisms for driving working bodies.
 The mixing process in rotary mixers is described. It is distinguished by the design feature and operating mode of the working body, which made it possible to choose the optimal speed mode of operation. Analysis of the design of foreign promising rotary mixers with planetary drive mechanisms allows offering a unified modular planetary gearbox as a drive. It allows optimal composing of the concrete mixer design, reducing weight, maintenance and repair costs, by improving the quality of workmanship and reliability.

Synergy between flow and light fields and its applications to the design of mixers in microalgal photobioreactors

BackgroundMixers are usually inserted into microalgal photobioreactors to generate vortices that can enhance light/dark cycles of algal cells and consequently enhance biomass productivity. However, existing mixer designs are usually developed using a trial-and-error approach that is largely based on the designer’s experience. This approach is not knowledge-based, and thus little or no understanding of the underlying mechanisms of mixer design for mixing performance of photobioreactors is attained. Moreover, a large pumping cost usually accompanies mixer introduction, and this cost is not favorable for practical applications. This study aims to improve this situation.ResultsIn addition to the individual effects of flow and light fields, improving the synergy (coordination) between these fields may markedly enhance the L/D cycle frequency with a lower increase in pumping costs. Thus, the idea of synergy between flow and light fields is introduced to mixer design. Better synergy can be obtained if (a) the vortex core and L/D boundary are closer to each other and (b) the vortex whose core is too far from the L/D boundary is removed. The synergy idea has two types of applications. First, it can facilitate a better understanding of known numerical and experimental results about mixer addition. Second, and more importantly, the idea can help to develop new rules for mixer design. A helical mixer design is provided as a case study to demonstrate the importance and feasibility of the synergy idea. An effective method, i.e., decreasing the radial height of the helical mixer from the inner side, was found, by which the L/D cycle frequency was enhanced by 10.8% while the pumping cost was reduced by 23.8%.ConclusionsThe synergy idea may be stated as follows: the enhancement of L/D cycle frequency depends not only on the flow and light fields individually but also on their synergy. This idea can be used to enhance our understanding of some known phenomena that emerge by mixer addition. The idea also provides useful rules to design and optimize a mixer for a higher L/D cycle frequency with a lower increase in pumping costs, and these rules will find widespread applications in PBR design.

Numerical Investigation of SCR Mixer Design Optimization for Improved Performance

The continuous increase in the number of stringent exhaust emission legislations of marine Diesel engines had led to a decrease in NOx emissions at the required level. Selective catalyst reduction (SCR) is the most prominent and mature technology used to reduce NOx emissions. However, to obtain maximum NOx removal with minimum ammonia slip remains a challenge. Therefore, new mixers are designed in order to obtain the maximum SCR efficiency. This paper reports performance parameters such as uniformity of velocity, ammonia uniformity distribution, and temperature distribution. Also, a numerical model is developed to investigate the interaction of urea droplet with exhaust gas and its effects by using line (LM) and swirl (SM) type mixers alone and in combination (LSM). The urea droplet residence time and its interaction in straight pipe are also investigated. Model calculations proved the improvement in velocity uniformity, distribution of ammonia uniformity, and temperature distribution for LSM. Prominent enhancement in the evaporation rate was also achieved by using LSM, which may be due to the breaking of urea droplets into droplets of smaller diameter. Therefore, the SCR system accomplished higher urea conversion efficiency by using LSM. Lastly, the ISO 8178 standard engine test cycle E3 was used to verify the simulation results. It has been observed that the average weighted value of NOx emission obtained at SCR outlet using LSM was 2.44 g/kWh, which strongly meets International Maritime Organization (IMO) Tier III NOx (3.4 g/kWh) emission regulations.

ВЛИЯНИЕ КОНСТРУКТИВНО-РЕЖИМНЫХ И ТЕХНОЛОГИЧЕСКИХ ПАРАМЕТРОВ ШНЕКОЛОПАСТНОГО СМЕСИТЕЛЯ НА ПОТРЕБЛЯЕМУЮ ИМ МОЩНОС

The purpose of the study – is the equipment improvement for dry mixing of crumbled feed with substantiation of de-sign and operating parameters. The use of complete feed mixtures is possible only with the use of special techno-logical equipment – feed mixers, producing mixture homogeneity meeting livestock requirements. The costs of pur-chasing, operating and maintaining mixers ultimately affect the cost of livestock production. Accordingly, it is neces-sary to aim efforts at the reduction of these costs. This can be achieved by reducing the specific energy costs for the mixing process, which largely depend on the mixer design, its working parts operation and the efficiency of the mix-ing process and power consumption needed for mixing process. No method of power consumption estimation of mixers with combined working parts according to theoretical studies obtained, having alternating in regard to exe-cution and purpose areas. Power consumption needed for the mixing process is one of the main components of the operating costs for the mixing equipment, ultimately determining the specific energy costs for the mixing process – is one of the important specification of any mixer. The research methodology provided a theoretical basis for the relationship of the mixer parameters on the power consumption during mixing process. Equations for determining the power consumption for the parts were submitted in regard to auger conveyor, the first and the second transport-ing and throwing blades. The expression for determination of power consumption for mixing process from the an-gle of installation mixing and transporting blades, the filling ratio of the mixer and the frequency of rotation of the working parts have been received. The obtained and given expressions allow to determine the power values for the mixing process with an error of no more than 5%, with the values of the studied parameters of the mixer within the boundaries of the experiment.

АНАЛИТИЧЕСКОЕ ОПИСАНИЕ ПОКАЗАТЕЛЕЙ РАБОТЫ СМЕСИТЕЛЯ СЫПУЧИХ МАТЕРИАЛОВ С ВИНТОВЫМИ ЛОПАСТЯМИ

The aim of the study is to reduce the energy consumption of the blade mixer for bulk materials in regard to its de-sign parameters. Preparation of feed mixtures is carried out mainly by mixers of various designs, as well as extrud-ers and other auger equipment. Widespread horizontal mixers with blades mounted on a rotating shaft are wide-spread and used. They are distinguished by the ability to achieve the necessary smooth mixture within short oper-ating time. The main purpose of the proposed mixer is the preparation of dry mixtures of bulk feed components. The intended use of the mixer is the preparation of concentrated animal feed n agricultural production. In Samara SAA, the design of the blade mixer with screw blades was developed based on the literature review and analysis of the technological process of mixers. The mixer consists of a body with a horizontal shaft with radial trapezoidal screw blades. The proposed blades allow to direct forces in such a way that the total (resulting) projection of the resistant force of the material along the shaft will tend to zero due to the changing angle of the profile and width of the blades. At the same time, an axial force will be created at the edge of the blade at a certain radius, which facili-tates to unload mixer through the discharge opening. The expressions of specific energy consumption for mixing, as well as the work duration of the mixer cycle are given. An expression allowing estimation of an average flow rate of bulk material from the discharge opening of the mixer is obtained. It is established that the position of the gate regulating the area of the discharge opening can affect the volume of the portion simultaneously processed by the mixer, filling volume of mixer and the quality of the mixture.

Counter‐rotating vortex shedding generated by acoustic excitations in confined mixing layers

AbstractUltrafast mixing enhancement has been realized in confined mixing layers at an optimal forcing frequency, under which the flow exhibits the strongest mixing. The fast mixing is accompanied by the so‐called counter‐rotating vortices (CRVs). In this investigation, by using particle imaging velocimetry (PIV) and laser‐induced fluorescence, the conditions of generating CRVs in confined mixing layers are theoretically and experimentally investigated. To generate CRVs, (a) the acoustic particle displacement must be larger than the summation of the curvature radius of the trailing edge and the thickness of the Stokes layer, and (b) the temporal derivative term of the vorticity equation should be larger than the convective term of the mean vorticity generated by the mean flow. This study enhances our understanding on vortex shedding dynamics and enables novel designs of fast mixers for continuous operations in process industry.

Feasibility of Studying Fuel Mixer Design for High Power Engines Using Completely Biogas

Nowadays, the original source of mineral fuel for engines was depleting increasingly while combustion products make the environment to be polluted, CO2emission which caused many greenhouse gases; this also makes crude oil prices fluctuate and rise. They tend to use biogas as a fuel for internal combustion engines which have been interested in the powerful countries. Supply of biogas from the waste of farms, flour production, fish processing, landfills, etc., with hundreds or thousands of cube meter of biomass daily leads demand on high-power generators using biogas in order to make good use of produced gas. This article introduces a technology solution for fuel engines using purely large-capacity biogas and operating under compression type fire. Accordingly, the tubular biogas Venturi mixer with electronic controller has been used to supply the mixture of fuel to engine. The CDI-DC ignition circuit provides a high voltage of 28kV for forced combustion of the mixture. Experimental results show that the mixer operates stably, well controlled and allows adjusting the ratio of air/fuel, as well as easily changing its speed when it is used as a hybrid engine for the generator. Some results of performance evaluation of biogas mixer will be presented in this article.

Powder flow and mixing in a continuous mixer operating in either transitory or steady-state regimes: Mesoscopic Markov chain models

Continuous powder mixing is gaining interest in the industrial community concerned with more and more functional powder products. The understanding of powder flow and mixing/segregation of particles as well as their translation into models that can be used in process monitoring and control is a major issue. In the present work, we describe the development of different mesoscopic Markov chain models that are based on interconnected compartments or cells delimited in the mixing chamber. The general structure of the chain allows the derivation of either homogeneous or non-homogeneous markovian models, for which transition probabilities are state-dependent.The models can be adapted to simulate variations of outflow rate, outlet mixture composition, hold-up weights and the distribution of these at the level of the compartments, during processing, including stationary and transitory phases. This is applied to a Gericke 500 GCM® continuous mixer for either pure powders or their mixtures, in the latter case through the consideration of a Markov chain for each component. The models are fed by independent experiments that allow for the determination of the probabilities and the rules governing their change with the processing step, in particular during the transitory regimes. Agreement is found between model calculation and experimental data for a wide range of configurations. The models can catch the variations of hold-up weights and internal or outlet flow rates at any rotational stirrer's speed during mixer start and steady state. They can reproduce the variations of the outflow rate, and therefore mixture composition, when dealing with a mixture of two components. This is also presented for two nominal compositions.Conclusions are drawn in terms of process monitoring and control. It gives insights for process intensification, in particular for mixer design and the feeding configuration.

A coupled-line balun for ultra-wideband single-balanced diode mixer

A multi-section coupled-line balun design for an ultra-wideband diode mixer is presented in this paper. The multi-section coupled-line balun was used to interface with the diode mixer in which it can deliver a good impedance matching between the diode mixer and input/output ports. The mixer design operates with a Local Oscillator (LO) power level of 10 dBm, Radio Frequency (RF) power level of -20 dBm and Intermediate Frequency (IF) of 100 MHz with the balun characteristic of 180° phase shift over UWB frequency (3.1 to 10.6 GHz), the mixer design demonstrated a good conversion loss of -8 to -16 dB over the frequency range from 3.1 to 10.6 GHz. Therefore, the proposed multi-section coupled-line balun for application of UWB mixer showed a good isolation between the mixer’s ports.

Design of CMOS Reconfigurable Passive Down-conversion Mixer for LTE MTC Receiver

A reconfigurable passive down-conversion mixer is fabricated in standard 65nm TSMC RF CMOS technology and presented in this paper. Different from traditional mixers, transconductor stage in this design is variable, and the transconductance stage uses a second-order low-pass transimpedance amplifier composed of Tow-Thomas structure to form a current-limited filter with adjustable bandwidth. From 900MHz to 1920MHz, The mixer circuit achieves flexible gains(5/11/19/26dB) and variable IF bandwidth(5/7.5/10MHz) with 4-bit control words, while linearity, noise figure and other indicators will also be adapted to suit the requirements of different communication standards.Under the maximum gain, its noise figure NF is 7.8dB; and under the minimum gain, its IIP3 is about 14.6dBm. It drains a current of 3.4/6.3mA from a 1.2V voltage supply at different gain mode.

Design of Curved-type Impeller Foundry Sand Mixer

Design of Curved-type Impeller Foundry Sand Mixer

Research of the mixing process in vortex static type devices

Mixing in chemical technology is used to intensify chemical and heat-mass transfer processes, as well as for preparing emulsions, suspensions and obtaining homogeneous systems. The simplest way to carry out the process, which does not require an additional supply of mechanical energy, is to mix in a direct-flow environment, which only requires flow energy. Analysis of the existing designs of direct-flow mixers showed that the use of swirling devices of various types in order to increase the efficiency of the process is very promising. This article describes a study of the influence of the geometrical dimensions of the screw on the efficiency of mixing a two-component mixture using the FlowVision software package.

Finding the optimal design of a passive microfluidic mixer.

The ability to thoroughly mix two fluids is a fundamental need in microfluidics. While a variety of different microfluidic mixers have been designed by researchers, it remains unknown which (if any) of these mixers are optimal (that is, which designs provide the most thorough mixing with the smallest possible fluidic resistance across the mixer). In this work, we automatically designed and rationally optimized a microfluidic mixer. We accomplished this by first generating a library of thousands of different randomly designed mixers, then using the non-dominated sorting genetic algorithm II (NSGA-II) to optimize the random chips in order to achieve Pareto efficiency. Pareto efficiency is a state of allocation of resources (e.g. driving force) from which it is impossible to reallocate so as to make any one individual criterion better off (e.g. pressure drop) without making at least one individual criterion (e.g. mixing performance) worse off. After 200 generations of evolution, Pareto efficiency was achieved and the Pareto-optimal front was found. We examined designs at the Pareto-optimal front and found several design criteria that enhance the mixing performance of a mixer while minimizing its fluidic resistance; these observations provide new criteria on how to design optimal microfluidic mixers. Additionally, we compared the designs from NSGA-II with some popular microfluidic mixer designs from the literature and found that designs from NSGA-II have lower fluidic resistance with similar mixing performance. As a proof of concept, we fabricated three mixer designs from 200 generations of evolution and one conventional popular mixer design and tested the performance of these four mixers. Using this approach, an optimal design of a passive microfluidic mixer is found and the criteria of designing a passive microfluidic mixer are established.

An Installation for Fast and Safe Preparation of Working Mixtures in Reactors of Pulsed Chemical HF(DF) Lasers

A system for preparing working mixtures in reactors of pulsed chemical lasers based on the F2 + H2(D2) reactions is described. The design of a compact capillary mixer has been developed; its throughput of up to 2 (L atm)/s has been experimentally attained. A method for supplying gases using flow-control washers with holes operating in the critical mode is proposed. It provides a constant flow rate of mixed gases during the whole run-in. The described technology for preparing the working mixture of a pulsed chemical HF(DF) laser is theoretically analyzed and experimentally tested.

Extrusion-Based Multiple Material Mixer Design in Food Printing

Extrusion-Based Multiple Material Mixer Design in Food Printing

Understanding the Role of Additive Manufacturing Knowledge in Stimulating Design Innovation for Novice Designers

Additive manufacturing (AM) is recognized as a disruptive technology that offers significant potentials for innovative design. Prior experimental studies have revealed that novice designers provided with AM knowledge (AMK) resources can generate a higher quantity and quality of solutions in contrast with control groups. However, these studies have adopted coarse-grain evaluation metrics that fall short in correlating AMK with radical or architectural innovation. This deficiency directly affects the capturing, modeling, and delivering AMK so that novel opportunities may be more efficiently utilized in ideation stage. To refine the understanding of AMK's role in stimulating design innovation, an experimental study is conducted with two design projects: (a) a mixer design project, and (b) a hairdryer redesign project. The former of which aims to discover whether AMK inspiration increases the quantity and novelty of working principles (WP) (i.e., radical innovation), while the latter examines the influence of AMK on layout and feature novelty (i.e., architectural innovation). The experimental study indicates that AMK does have a positive influence on architectural innovation while the effects on radical innovation are very limited if the example illustrating the AMK is functionally irrelevant to the design problem. Two strategies are proposed to aid the ideation process in maximizing the possibility of identifying AM potentials to facilitate radical innovation. The limitations of this study and future research plans are discussed.

Mixing study of non-spherical particles using DEM

In the last decade, granular flows have been studied extensively using DEM simulations. But only a little work has been done using non-spherical or real-shape particles even in the latest publications using powerful simulation tools making such study a need of the hour. This is important because the understanding of these particle shapes is crucial for design and development of real-life industrial mixers. In this work, we employed DEM (discrete element method) approach and used open-source simulation software LIGGGHTS to study the flow and mixing behaviour of polydisperse, non-spherical cohesionless particles in a cylindrical tank mixer. The mixer was agitated by using a four-bladed impeller and a blade-rake angle of 135°. We studied the flow and mixing behaviour by analysing particle velocities, contact forces and mixing performance. The mixing was quantified using a latest subdomain-based mixing index introduced by [1]. Different particle shapes were employed and expressed in terms of circularity/sphericity. We used seven different shapes in addition to spherical shape used for benchmarking. It is learnt that as we sway from circularity or sphericity, the mixing performance decreases. The complex (or in fact the real) shape particles are observed to have lower mixing performance compared to spherical particles under similar conditions.

INDUSTRIAL MIXING OF PARTICULATE SOLIDS: PRESENT PRACTICES AND FUTURE EVOLUTION

Powder mixing is a part of our everyday life, but is the source of major industrial preoccupations. Mixing is widely used in many industries but until now design of mixing technology and mixing equipment belongs sooner to engineering art than to scientifically based calculation. Each branch of industry develops its own experience in the field mostly based on time and labour consuming expe-rimental research, and very often the obtained results cannot be used directly in another branch, i.e., the problem of mixing simulation and calculation is far from universality. This is why it is very im-portant to separate from particular sectorial problems the general intersectorial problems of theory and practice of mixing and concentrate the attention of researchers and engineers on them solution to build the general basis for scientifically based design of mixing technology and equipment. Current problems are associated with the definition of the homogeneity of the mixtures, the ways of measuring it, the sampling errors and techniques, the segregability of the mixtures in the powder handling operations, mixer choice, as well as mixer conception. In this paper, we review such aspects and try to draw some perspectives from a combined industrial experience – chemical engineering approach: the development of on-line monitoring techniques to assess homogeneity and further con-trol the process; the improvement of mixer’s scale up procedures, as well as the optimisation of mixer design and operation; the development of new mixing technologies, multifunctional, nearly “universal”, with a special emphasis on continuous processes; the completion of the actual standards on powder homogeneity by introducing structural information.

Energy-saving technological complexes and equipment for producing composite materials

Processing of natural and technogenic materials, utilization of industrial waste, production of goods at the first stage are associated with the grinding of materials. Traditional grinders often do not fully perform their functions, while they have high specific energy consumption and large metal consumption. In addition, for the production of composite materials, it is necessary to mix the original components efficiently, which is not always possible in typical mixer designs. The solution of the problems of joint grinding and mixing is considered in this article. In addition, it is necessary to mix the original components efficiently for the production of composite materials, which is not always possible in typical mixer designs. The solution of the problems of co-grinding and mixing is considered in this article.

Design and Optimization of a Direct-Conversion Double-Balanced Mixer for RF Receiver Front-End

Differential implementation is becoming highly favoured in RFIC (radio frequency integrated circuit) design, notably its high immunity to common-mode noises, acceptable rejection of parasitic coupling, and increased dynamic range. One specific RF front-end building block that is usually designed as a differential circuit is the mixer. This technical paper presents a study of a differential mixer, notably the double-balanced mixer implemented on a direct-conversion architecture in a standard 90nm CMOS (complementary metal-oxide semiconductor) process. Operating frequency is set at 5GHz, which is a typical frequency for RF (radio frequency) receiver. Impedance matching was essential to fully optimize the mixer design. The direct-conversion double-balance mixer design eventually achieved conversion gain of 11.463dB and noise figure of 16.529dB, comparable to mixer designs from past research and studies.