Determination of receiver consumption characteristics using computer simulation

The problem of implementing the detonation mode of fuel combustion in thermal propulsion systems has been widely studied last decade. There are many works on fundamental and applied research on pulsating detonation. Solid propellant detonation engines can develop significant forces for a short time at low structural masses, and therefore they are ideal for auxiliary systems for the removal of separated rocket parts. In addition, detonation processes can be used to create control forces for correcting the trajectory of aircraft. All these facts determine the relevance of the area of work. For studying detonation installations, it is necessary to create test stands, but the design of test installations is an urgent and complex optimization problem. It is advisable to solve this problem with the help of computer simulation. In the existing experimental methods, for designing, it is necessary to determine in advance the geometric parameters of receivers and pipelines that provide the necessary gas consumption for firing tests of detonation rocket engines. The work is devoted to the development of a method for determining the flow characteristics of a receiver with a pipeline of complex configuration based on the constructed model of the stand. Based on the initial data, a computer simulation of the air leakage process from the receiver was carried out, for which the Solid Works software package was used. The places of pressure drop, maximum flow rate, and air mass flow are determined. The low value of the flow rate factor is due to the complex configuration of the pipeline with numerous bends and two bellows. Comparison of calculation results with experimental data was held. The difference between the experimental and calculated values does not exceed 3.6%. The obtained information is used to select the required value of the oxidizer excess coefficient during firing tests of detonation rocket engine models. Keywords: flow rate, gas leakage, receiver, model.

Calculation algorithm for operating parameters of steam-compressive chilling machine with adsorptive chillling unit

The work is focused on the development of an effective algorithm for calculating the operational characteristics of a steamcompressive chilling machine with an adsorptive chilling unit, which involves a cold box, an adsorber, an evaporator and a condenser, water being used as a refrigerant. An algorithm for calculating the operating parameters of the adsorptive chilling unit has been developed, which includes the determination of the cooling capacity of the steam compressor refrigeration unit, the heat load on the condenser, the power consumed by the compressor, the coefficient of performance of the steam compressor refrigeration unit, as well as the calculation of the mass of water, the mass of the adsorbent, the refrigerating capacity, the coefficient of performance of the adsorptive chilling unit and the coefficient of useful energy utilization of a steam compressive chilling machine with an adsorption chilling unit. The chilling capacity and the coefficient of performance of the adsorption chilling unit are estimated under the operating conditions of a typical steam compression chilling machine. The crucial factors affecting the efficiency of the adsorptive chilling unit are analyzed. It has been established that the chilling capacity, the coefficient of performance of the adsorption refrigeration module and the energy efficiency of the installation are determined by the thermal load on the condenser, and, therefore, by the mass of water that is desorbed and evaporated. The coefficient of performance of the adsorption chilling unit and the efficiency of the steam compressor chilling machine with the adsorptive chilling unit are estimated to be 0.878 and 4.64. The criteria for the selection of adsorbents for the adsorption module are analyzed. The temperature of regeneration is determined by the temperatures in the condenser, and the limit adsorption affects the mass of the adsorbent and the size of the adsorber. A comparison of the efficiency of adsorptive chi l l ing uni t based on silicoaluminophosphates and composite adsorbents «silica gel – sodium acetate» is carried out. The prospects of using composites «silica gel – СН3СООNa» are shown. The optimal composition of the composite was established, which corresponds to the minimal size of the adsorber, (80% sodium acetate and 20% silica gel). The prospects of using adsorptive conversion of thermal energy for utilization of low-potential thermal energy during the operation of steam compressive chilling machine are shown. Keywords: adsorptive conversion of heat energy, composite adsorbent, steam compressive chilling unit, adsorption, adsorptive capacity.

Simulation of aeromechanics of the grinding process in a centrifugal mill

The article discusses aeromechanical processes in a centrifugal mill at different speeds of rotation in order to establish the regularities of the kinematics of the flow of a heterogeneous medium in the grinding chamber of the mill, its interaction with the working body and the classification of the crushed material when removed from the grinding chamber. The study of gas dynamics of processes in the flow path of a centrifugal mill has been carried out. The trajectories of streams, velocity and pressure fields were investigated. The influence of various factors on the efficiency of the classification and the maximum diameter of particles removed from the grinding chamber was revealed. The regularities of the movement of a heterogeneous medium, its interaction with the working body and the classification of the crushed material when removed from the grinding chamber were established, the gas dynamics of processes in the flow path of a centrifugal mill was studied. The main way to increase the speed of air flows is to increase the flow of transport air, which in turn affects the aerodynamics of the processes in the grinding chamber of the mill, productivity and grinding time of the material. Processes of gas dynamics in a compressed medium of the flow path of a centrifugal mill were described by a system of non-stationary Navier-Stokes equations of continuity, energy and equation of state in approximation of the turbulence model. Analysis of the results of mathematical modeling of processes in the working chamber showed that the air flow carries out a complex rotational movement in the transverse and longitudinal sections with the formation of local zones of increased turbulence. As a result of numerical modeling and analysis of the results, factors have been identified that make it possible to intensify the process of material grinding. The flows have a pronounced ballistic trajectory. They start their movement from the center of the bottom of the grinding chamber and move along the walls of the chamber while rotating in a spiral and moving down the wall of the hollow shaft. It is observed that the point of separation of the flows rotating in the lower part of the grinding chamber and the flows moving in the upper part is on 60% of the height of the chamber. Keywords: modeling, centrifugal mill, finite element method, Navier-Stokes equation.

Project-computer technology in teaching english academic writing to students of linguistic higher educational institutions

Teaching writing in English is one of the principal tasks of English training of students in linguistic higher educational institutions, i.e. of training future teachers of English, translators, and applied linguists. This is due to the fact that written speech is more and more taking the position of the leading form of international communication in English as the global/planetary language of such communication, especially if that communication is professional, and, in particular, the academic one. For students of linguistic higher educational institutions, the main constituent of their English writing training is teaching them English academic writing (i.e. writing academic essays) because gaining command of just such writing skills serves as the basic means of mastering the skills of writing in English the most sophisticated types of written papers, such as professional articles, theses, presentation texts, etc. This kind of teaching only now begins to be researched in Ukrainian methodology of foreign language instruction, while using the project-computer methodology for that has not been researched at all as yet. This was the stimulus for choosing the above-mentioned issue as the subject matter of consideration in this article. It analyzes the project-computer technology developed by the authors and consisting of 12 stages of forming students’ academic essay writing skills in three selected subgenres of such essays (“personal opinion,” “for and against,” “problems and solutions”). All these stages are divided into the stages of off-line (purely project stages) and stages of blended off-line – on-line and purely on-line learning activities (project-computer stages). The characteristics of every stage are discussed and the model of the teaching/learning process in the conditions of using project-computer technology is suggested. The information concerning the practical efficiency of this technology is given. The conclusion is made about the rationality of introducing such a technology into courses of English at both linguistic and non-linguistic higher schools. Keywords: linguistic higher educational institution, academic writing in English, project-computer technology, stages of developing academic writing skills.

Study of the motion of incompressible gas in a vortex heat generator

The article presents the results of the performed analytical and experimental studies of the hydrodynamics of the translationalrotational motion of a viscous incompressible gas flow in the working space of a vortex heat generator of variable geometry, analytically determined the dependences of the effect of device performance, confuser opening angles, confuser channel width on the hydrodynamic parameters of the device and, as a consequence, its energy efficiency. The degree of energy efficiency of the swirler screw for the operation of a vortex heat generator at various loads on the working path has been experimentally estimated, according to the Euler number EUc. It has been proven that the energy efficiency of its operation is on average 35% higher when the swirler screw is installed. The influence of the geometry of the nozzle on the axial symmetry and smoothness of the flow of incompressible gas in the vortex chamber is investigated. It was found that the specified indicator is most satisfactory for a nozzle with a rectangular cross-section. The distribution of the temperature field of a moving incompressible gas along the height of the vortex chamber is investigated depending on the taper angle. The distribution of angular velocities along the axis of the flow swirler is investigated at various values of productivity. It was found that the angular velocity decreases according to the law of potential fluid flow. A mathematical model has been developed to optimize the operating modes and parameters of the vortex heat generator. A software block was built based on the mathematical package MathCAD version 11 for the implementation of the developed mathematical model. An optimal design of a vortex heat generator with a variable geometry of the working space has been developed, which has been tested in laboratory conditions. Laboratory studies have proven its high energy efficiency at the level of modern standards and the feasibility of using the device for heating buildings and structures in industry and the domestic sector. Keywords: incompressible gas, hydrodynamics of an incompressible gas flow, vortex motion, mathematical model, equation of motion, continuity equation, vortex heat generator, thermal energy, cavitation, turbulence, vortex zone, MathCAD package.

Mathematical modeling of chilling process of polymer tube billets

There are many works about producing of polymer tubes. But less attention is paid to the process of chilling of polymer products. The chilling of polymer tube billets, as most polymer processing processes, is a non-isothermal process. This means that it is necessary to solve the heat problem. Accurate calculation of the heat balance is one of the main components for the final result of the extrusion process. The mathematical model had been created for process of chilling of polymer tube billets after extrusion in this work. Several mathematical models of heating process for heat and power equipment have been created. Different calculation schemes, methods and equations for its solution are suggested. The mathematical model for process of chilling of polymer tube billets after it extrusion can be considered an expansion of research. The mathematical model is based on cylindrical coordinate system with assumption of axisymmetric along angular coordinate. The initial problem statement considered non-stationary process. A transition was made to the differential equation in partial derivatives along two linear coordinates. Solution of this equation was found using the operation method (Laplace integral transform method). The final solution of the problem (after direct and reverse Laplace transform) was obtained from the Bessel function. It was calculated in MathCAD with the help of built-in functions and computing modules. The mathematical model was created for modeling and optimization of process of chilling of polymer tube billets. The results of calculation were presented as graphs that make it possible to characterize the adequacy of the materials. Keywords: mathematical model, balance equation, Laplace transform, program block.

Numerical verification of the efficiency of global optimization methods

In this paper, new difficult test problems are proposed to test the numerical efficiency of global optimization methods. These are problems of unconstrained optimization with unknown solutions. The proposed test problems are inseparable and have arbitrary dimensions. The author also proposes to include the test functions by J. Nie in the list of test functions for numerical verification of the effectiveness of methods. These functions are also inseparable functions of arbitrary dimensions with unknown solutions. The proposed test problems have many local extrema. Testing the effectiveness of global optimization methods for such functions is simplified. If the method allows improving the found solutions to test problems, then it will be more effective. The existing global optimization methods are compared with the exact quadratic regularization method developed by the author. This method is compared with known software packages that implement modern methods of global optimization. These packages include several methods. The best of them use convex relaxation of the problem to obtain estimates of solutions with subsequent use of local optimization programs. But even such powerful packages have difficulties in solving the considered test problems. Some test problems, for example, with the Rana or Egg Holder function, have been solved by different methods for over 20 years. During this time, no method has allowed obtaining results that are obtained by the method of exact quadratic regularization. For almost all complex test problems with unknown solutions, this method yielded better solutions. Sometimes the advantage of this method was significant, as is the case with the Rana test function. The essence of the exact quadratic regularization method is to transform any global optimization problem to maximize the square of the Euclidean norm of a vector on a convex set. This problem is computationally much simpler. Often, with such a transformation, the multimodal problem becomes unimodal, which is easy to solve. Keywords: test problems, global optimization, unimodal problems, multimodal problems, numerical methods.

Applied use of the Arduino NANO as Wi-Fi of the guided movable device

The development of a Wi-Fi-controlled video machine using Arduino NANO is described. The connection diagram of Arduino NANO and additional modules is presented. The relevance of the topic under development is emphasized by the increasing demand for the use of remotely controlled video devices. A Wi-Fi-controlled video device (machine) was developed, which is powered by a battery that is connected to the charge controller module with microUSB. Possible battery life is 5-6 hours without recharging. In the process of developing a Wi-Fi-controlled video machine, a large amount of work was carried out, including adding the necessary libraries for the correct writing of programs and determining the necessary conditions for the functioning of the device. Program (sketch) for controlling the engines of the machine is also developed; the main components for creating the device are identified. For the mobile camera application to work, it is necessary to download the JoyLite application from the AppStore or PlayMarket; after which the smartphone “connects” to the Wi-Fi network and the SANNCE HD 720p camera. In the software part of the development of a Wi-Ficontrolled video machine using Arduino NANO in the Arduino IDE software environment, the program (sketch) was developed for the SANNCE HD 720p “JoyLite” mobile application. This program configures the signals from the stepper motors of the camera to asynchronous motors of the machine, as well as adjusting the speed of the wheels. During the tests of the device, it turned out that the Wi-Fi-controlled video machine has a sensitivity to speed impacts, namely, the speed should exceed 255 r./s. The developed Wi-Ficontrolled video machine can be used in various fields. For example, the device can be used in systems such as «Smart Home» or in security systems, or be implemented as a training project in the course of robotics. Keywords: Wi-Fi, microcontroller, Arduino NANO, video device, remotely controlled device.

Development of computer modeling methods in proteomics

The need for modern research in the field of biomedical sciences is to solve the problem of improving the accuracy of the results of electrophoretography in their common form and substantiating the conclusions based on such experiments, in particular, increasing the accuracy of protein identification. Calculation problems in this direction are solved by both universal and specialized computer systems, the variety of which is due, firstly, to the specific needs of the natural sciences, and, secondly, by the mathematical apparatus that is used for fairly voluminous calculations. Usually, in this case, methods of mathematical statistics are used, but in this case the use of stochastic data analysis was not sufficiently correct due to the lack of a representative sample or its heterogeneity. In connection with these needs, a computer package FANSPREL – «Fuzzy ANalysis System for Protein Electrophoresis» was created for processing electrophoregrams and identifying proteins using fuzzy mathematics methods based on algorithms developed by the authors in previous studies. An approach is proposed based on the determination of a fuzzy scale based on the results of processing fuzzy data of known proteins, recognition of proteins obtained from the results of research, and comparison of proteins among themselves based on the results of experiments. The mathematical part of the information system is the construction of an approximation of the membership function based on the obtained data of a curve with four parameters and the construction of a fuzzy scale model, determination of fuzzy masses of proteins and their comparison by conjunction of fuzzy values, and subsequent defuzzification of the results. The system makes it possible to more accurately identify proteins, in particular to distinguish between those whose masses were identified as the same with other forms of processing with a certain accuracy or an undefined result was obtained. The program has a user-friendly interface, provides a standard form of input and output data, and is tested for solving problems of experiments that took place for the immediate needs of agriculture, in particular to improve various types of soil that is used to grow corn. Keywords: fuzzy modeling, electrophoregrams, computer system.

Modeling of acetylene synthesis process in ChemCAD and features of SCADA connection using OPC technology

The article examines the features of constructing mathematical models in modern universal modeling programs and their further use using OPC technology in control systems for processes of chemical technology based on SCADA systems. The objective is to study the features of information exchange using OPC technology between the universal ChemCAD simulator and the modern SCADA system TRACE-MODE 6 using the example of a mathematical model of a kinetic reactor for the synthesis of acetylene. To achieve this goal, a mathematical model of a kinetic reactor for the synthesis of acetylene based on a model of a continuous stirring reactor has been developed in the ChemCAD simulation software environment. The reactor was tuned and the parameters of material flows were experimentally selected. A study of the process of synthesis of acetylene was carried out according to a mathematical model, a graphical dependence of the yield of acetylene on temperature was obtained and its analysis was carried out, according to the results of which the temperature providing the maximum yield of acetylene was established. With the help of OPC technology, information exchange between the model and the control system of the acetylene synthesis process is carried out, which is based on the modern SCADA system TRACE-MODE 6. A graphical dependence is obtained describing the transient process of the system through the acetylene output channel when using a PID controller and perturbing with a change in the task. The analysis of the transient process revealed the absence of transport lag, which is explained by the calculated nature of the control object and is impossible for a real technological process. To solve the problem, an experiment was carried out, according to the results of which a method for emulating transport lag using the functionality of the information channels of the SCADA system was proposed. The graph of the transient process of the system through the acetylene outlet channel was obtained, which confirms the effectiveness of the proposed method of emulation of transport delay when using external calculation models in SCADA systems. Keywords: mathematical modeling, universal modeling programs, OPC, control systems, SCADA-based control, TRACE-MODE, ChemCAD.