АЛГОРИТМ ПРОЕКТУВАННЯ АВТОМАТИЗОВАНИХ ЗМІШУВАЛЬНИХ КОМПЛЕКСІВ БЕЗПЕРЕРВНОЇ ДІЇ ДЛЯ СИПКИХ МАТЕРІАЛІВ

Purpose. Creation of design algorithm of continuous action mixing complexes that will allow defining parameters of the equipment proceeding from requirements to quality, productivity and the set compounding of mixture.Methodology. The method of discrete elements, classical mechanics positions, theory of solids contact interaction, method of mathematical modeling are used in the work.Findings. The paper proposes a generalized algorithm for designing a continuous mixing complex for bulk materials. The procedure for designing a centrifugal mixer, the flow shapers, plate feeders and conical-cylindrical hoppers are presented. Calculations of design and technological parameters are carried out on the basis of information about the physical and mechanical properties of bulk components particles, requirements for equipment performance and the mixture homogeneity. The results of calculations of the mixing complex for the three-component mixture used for the production of polyethylene film are presented. To test the proposed algorithm, a mathematical model based on the discrete elements method is created. The mixing process is modeled and the coefficients of inhomogeneity of each of the components in the finished mixture are determined. The obtained results confirmed that the proposed algorithm allows to determine the parameters of the mixing complex, which ensure compliance with the specified requirements for the quality and the equipment performance.Originality. Mathematical models of bulk motion dynamics in mixing complexes are improved, which include bunker devices, plate feeders, flow shapers and continuous centrifugal mixer, taking into account the bulk motion discrete nature.Practical value. The obtained results allow calculating the design and technological parameters of the equipment that is a part of the continuous mixing complex according to the set productivity, recipe and requirements to the mixture homogeneity.

Mathematical Modelling and Control of COVID-19 Transmission in the Presence of Exposed Immigrants

In this paper, a mathematical model for COVID-19 pandemic that spreads through horizontal transmission in the presence of exposed immigrants is studied. The model has equilibrium points, notably, COVID-19-free equilibrium and COVID-19-endemic equilibrium points. The model exhibits a basic reproduction number, R0 which determines the elimination and persistence of the disease. It was found that when R0 < 1, then the equilibrium becomes locally asymptotically stable and endemic equilibrium does not exists. However, when R0 > 1, the equilibrium is found to be stable globally. This implies that continuous mixing of exposed immigrants with the susceptible population will make the eradication of COVID-19 difficult and endemic in the community. The system is also proved qualitatively to experience transcritical bifurcation close to the COVID-19-free equilibrium at the point R0 = 1. Numerically, the model is used to investigate the impact of certain other relevant parameters on the spread of COVID-19 and how to curtail their effect.

Recent Enhancements for Coiled Tubing Descaling Treatments in Middle East

Successful coiled tubing (CT) descaling interventions require control of several key aspects, including fluid leakoff into the formation, proper surface solids handling, and controlled hydrogen sulfide (H2S) release at the surface. Successful treatment control is achieved by monitoring the surface and downhole parameters. The recently introduced pressure and fluid management system, crosslinked foam-based fluid, and a fluid mixing system for CT descaling treatments pose challenges that require enhancements to these elements for successful treatment. The pressure and fluid management system was enhanced to include a new high-rate mud/gas separator to 1) increase gas/fluid separation capacity and avoid foam flowing to flare, 2) rig up the flare line with inclination to allow all water to be drained and prevent formation gas flowing to flare lines, and 3) increase retention time for better foam breaking and material settling. A liquid flowmeter was also added to improve influx and leakoff control by monitoring the volume of liquid injected and matching the volume of liquid returned on surface in addition to the level gauges on the return tanks of the pressure and fluid management system. The foamed-based fluid breaking system and H2S presence in returns were mitigated by removing crosslinker and introducing an H2S scavenger on returns whereas foam breaking was enhanced by additional breaker injection points on returns. Fluid mixing capabilities were enhanced by the introduction of an on-the-fly continuous mixing system that sped up and simplified the mixing process. The mud/gas separator efficiently separated the gas from liquid, leading the gas to be burnt at flare and the liquid to be processed in the pressure and fluid management system. It further helped in preventing the liquid flowing to flare, which lessened the risk of flare shutdown and H2S ventilation. The on-the-fly continuous mixing system provided a faster and more-efficient mixing process as an alternate to batch mixing. These system-controlled metering, mixing, and monitoring capabilities significantly reduced the crew and equipment footprint, leading to minimizing the health, safety, and environment (HSE) concerns and cost savings. The fluid flowmeter allowed efficient choke and bottom-hole pressure control. Fluid flowmeter readings helped in choke and bottom-hole pressure reading adjustments based on amount of fluids pumped and matching the same amount of fluids returned at the surface. It prevented the fluid leakoff into the formation or influx of gas into the wellbore. Additionally, this new process created better control of downhole differential pressure during the scale cleanup and transportation. This project integrated different technologies and techniques that can be utilized for descaling treatment enhancements. The recent enhancements to the CT descaling operation resulted in greater efficiency, cost savings, reduced formation damage, and safe operations.

Increasing the Efficiency of Milling Stainless Steels by Using Lubricating-Cooling Technological Medium

This article considers the possibility of increasing the efficiency of end milling by using a modified lubricating-cooling technological medium, based on a water-miscible cutting fluid. The conditions for the effective use of modified coolant in processing stainless steels ensuring a decrease in cutting forces and therefore a decrease in vibrations, which contributes to an increase in the quality of manufactured products have been determined. A decrease in cutting forces is due to the presence of oleic acid in the modified cutting fluid, containing surfactants, forming a dense lubricating film on the surface of the cutting tool. When mixing oleic acid in a water-miscible cutting fluid, a special soap solution significantly improving the solubility is used. However, over time, stratification of liquids occurs. To ensure the homogeneity of the medium, a special device has been developed that allows continuous mixing of the compositions, due to the presence of impellers with differently oriented blades. To save a lubricant, the technology of minimum lubrication was used, which allows the lubricant to be supplied to the cutting zone in portions (dosed) using the Noga Minicool device.

Effect of Time Delays in Characterizing Continuous Mixing of Aqueous Xanthan Gum Solutions

Aqueous xanthan gum solutions are non-Newtonian fluids, pseudoplastic fluids possessing yield stress. Their continuous mixing is an extremely complicated phenomenon exhibiting non idealities such as channeling, recirculation and stagnation. To characterize the continuous mixing of xanthan gum solutions, three dynamic models were utilized: (1) a dynamic model with 2 time delays in discrete time domain, (2) a dynamic model with 2 time delays in continuous time domain, and (3) a simplified dynamic model with 1 time delay in discrete time domain. A hybrid genetic algorithm was employed to estimate the model parameters through the experimental input-output dynamic data. The extents of channeling and fully-mixed volume were used to compare the performances of these three models. The dynamic model parameters exerting strong influence on the model response were identified. It was observed that the models with 2 time delays gave a better match with the experimental results.

Effect of Time Delays in Characterizing Continuous Mixing of Aqueous Xanthan Gum Solutions

Aqueous xanthan gum solutions are non-Newtonian fluids, pseudoplastic fluids possessing yield stress. Their continuous mixing is an extremely complicated phenomenon exhibiting non idealities such as channeling, recirculation and stagnation. To characterize the continuous mixing of xanthan gum solutions, three dynamic models were utilized: (1) a dynamic model with 2 time delays in discrete time domain, (2) a dynamic model with 2 time delays in continuous time domain, and (3) a simplified dynamic model with 1 time delay in discrete time domain. A hybrid genetic algorithm was employed to estimate the model parameters through the experimental input-output dynamic data. The extents of channeling and fully-mixed volume were used to compare the performances of these three models. The dynamic model parameters exerting strong influence on the model response were identified. It was observed that the models with 2 time delays gave a better match with the experimental results.