Main Geometrical Parameters Research Articles

EXAMINATION OF SELECTED GEOMETRICAL PARAMETERS OF WHEELSETS OF ELECTRIC MULTIPLE UNIT

The aim of the work is to investigate changes in the values of selected geometrical parameters of electric multiple unit (EMU) wheelsets as a function of mileage. Based on the conducted analysis of the literature, it was found that the problem of proper diagnostics and maintenance of wheelsets, as an element that directly affects the level of safety of railway vehicle traffic, is very up-to-date and justified. This work presents the characteristics of the geometrical parameters of the wheelset that were subjected to the tests. According to the terminology of EN 13715:2020-12, the geometrical parameters of the wheelset subjected to tests were characterized. As part of the research work, data from measurements of the values of the main geometrical parameters of the outer contour of the wheelsets were collected and systematized from 204 measurement sheets of vehicles. Data were collected from specially developed registers and databases. The research and analyses confirm the existence of a correlation between changes in the values of diagnostic characteristics of flange thickness and height and flange steepness as a function of kilometrage. The intensity of wheel rim wear changes depending on the conditions under which the vehicle is operated. The wheelsets’ diagnostic characteristics were not fully predictable, which makes it difficult to forecast their future values. Based on the obtained results, actions that increase the durability of the wheels were proposed. For example, it is reasonable to assign vehicles to different routes so that the wheel rims wear evenly, eliminating the need for the subsequent accumulation of repairs and wheelset replacements before repair at the P4 level. Moreover, it is advisable to undertake work on the change of identification of basic individual primary characteristics of the wheel’s external contour into primary characteristics of a collective nature. As a result of such action, it is possible to indicate the probability of occurrence of non-uniformity of values of diagnostic characteristics on the wheel circumference could be limited and the phenomenon of occurrence of measurement errors could be minimized.

Effects of pipe turns on vertical helically coiled tube heat exchangers for water heating in a household refrigerator

A new coupled numerical model of the overall vapor-compression cycle and water heater was developed in order to analyze the influence of condenser coil designs on the heat transfer process of a helical coil heat exchanger immersed in a storage tank. The model was developed using the CFD code ANSYS Fluent. In the numerical simulation, the helical condenser coil was treated as an internal heat source and the initial heat flux was obtained from experimental results and delivered to each coil element in the CFD model as boundary condition.The coupled model was validated with experimental results and showed that the numerical results of the proposed model are in good agreement with the experimental data with the deviation of ± 1.6%. Then, the impact of the main representative geometrical parameter on the overall heat transfer coefficient and water temperature distribution was investigated. The results indicated that the temperature distribution and overall heat transfer coefficient increase with the increase of the pipe turns of a helically coiled tube heat exchanger.

Weight analysis on geometric parameters of ejector under high back pressure condition of SOFC recirculation system

With advantages of no parasitic energy consumption, small size, and low noise, ejector is a promising choice for the solid oxide fuel cell (SOFC) anode gas recirculation system. However, it is difficult to design an ejector with good performance under the high back pressure condition of the SOFC system. In this paper, weight analysis on key geometric parameters of ejector is carried out based on the result of an experimentally validated ejector simulation model. Four main geometric parameters that have the most significant effect on ejector performance, namely the ejector diameter ratio (Dr), mixing chamber length (Lm), diffuser length (Ld), and nozzle outlet position (NXP), are analyzed in detail. The Dr has a decisive influence on the momentum exchange in the mixing phenomenon between the primary flow and secondary flow in the mixing chamber where the normal shock position changes accordingly. The Lm mainly affects the intensive mixing flow which leads the normal shock to appear prematurely. The Ld should be long enough for boosting back pressure and reducing the effect on the mixing process. The NXP has no effect on the normal shock position. The results show that the critical back pressure increases with the rise of normal shock position and the impact weight of Lm, Ld and NXP can be treated as 21∶10∶1 approximately and the Dr is thought to be a decisive factor. This weight analysis method will be helpful for designing ejectors used in the high back pressure condition of the SOFC anode recirculation system.

NEWEST TECHNOLOGY OF PRODUCTION AND USE THE BIOFUELS

The article presents a comparative characteristic of solid fuel materials, the elemental composition of the combustible and working masses. The calculation of the main geometrical parameters of the gas generator for a specific productivity of 350 kg/(m2∙h) was made. The results of the economic feasibility of the fuel gasification process are presented, and the profit from the introduction of biofuel technology is also estimated. The calculations presented in the work testify to the efficiency and expediency of using biofuels as energy resources of Ukraine. Bibl. 5, Tab. 2.

Simulation of large-scale forest fire parameters

Topicality. There is an urgent need to select the main energy, geometric and thermophysical parameters of forest fires, as well as to assess the main parameters of these fires, including unexplored fire tornadoes and wave processes caused by fires. Purpose. To develop mathematical models of physical processes caused by large-scale forest fires, evaluate the main parameters of these fires, including unexplored fire tornadoes and wave processes caused by fires. Methods. Analytical review of the research problem, theoretical and computational, mathematical modeling, systematic analysis of the set of physical effects. Results. The results of the analysis of the parameters of forest fires and related physical processes caused by large-scale fires are presented. The main energy, geometric and thermophysical parameters of large-scale forest fires are proposed. These include: energy, power, duration, area of fires, as well as the length, intensity and speed of the combustion front, heat flux density, power flux density, torch height, heat and smoke rise height, convection speed, etc. Simple analytical physical and mathematical models of the main parameters of large-scale forest fires have been created. A model of a fiery tornado is proposed. The obtained ratios allow us to estimate the main parameters of fire tornadoes that accompany large-scale forest fires. These include radius, angular velocity, tangential velocity, maximum height and rate of rise of the heated formation. It is shown that, depending on the size of the vortex, the parameters of the fiery tornado vary widely. These relationships make it possible to analyze and evaluate the main parameters of wave processes generated by forest fires. Such parameters are energy, relative share of energy, range of periods of acoustic radiation, etc. The main parameters of forest fires and related physical processes are calculated. It is shown that depending on the area of the fire, these parameters vary widely. Conclusions. Mathematical models of physical processes caused by large-scale forest fires have been developed, by means of which the parameters of the main effects have been calculated.

HEAT TRANSFER IN COIL HEAT EXCHANGERS WITH VARYING GEOMETRIC CHARACTERISTICS

Coil-type heat exchangers are widely used in power industry and medical and electronic technology due to the relatively simple design of their basic elements, low operating costs, reliability and long service life. The process of designing the devices with coil heat exchangers requires choosing the tube surface configuration and taking into consideration the specific operating conditions, as well as thermophysical properties and parameters of the working fluid. One of the important factors that hinder the wider use of coil heat exchangers is the lack of reliable engineering techniques for calculating the heat transfer and aerodynamic drag. 
 This study aimed to improve the technique of calculating the heat transfer and aerodynamics of coil heat exchangers by modifying the dependences that take into consideration the specific operating conditions and allow determining the design characteristics of one-layer recuperative coil heat exchangers mounted in annular channels under the conditions of partially twisted working fluid flow. In order to do that, the authors conducted a physical experiment using a test setup, both of which are described in the article in detail.
 The analysis of the experimental results on heat transfer in a coil heat exchanger under forced gas convection and laminar flow of the working fluid helped to establish the dependence of the heat transfer coefficient on the main geometric parameters of the heat exchanger and to determine the allowances taking into consideration the extent to which the heat transfer intensity is impacted by the step characteristics of the tube bundle and the gap between the tube bundle and the heat exchanger housing, thus making it possible to optimize the geometric characteristics of the coil heat exchangers mounted in annular channels for specific operating conditions.

Selection Criteria for Biplane Wing Geometries by Means of 2D Wind Tunnel Tests

This paper presents a study based on wind tunnel research on biplane configurations. The objective of this research is to establish an experimental basis for relationships between the main geometrical parameters that define a biplane configuration (stagger, decalage, gap, and sweep angle) and the aerodynamic characteristics (CL, CD). This experimental study focuses on a 2D approach. This method is the first step towards dealing with the issue, and it allows the variables involved in the tests to be reduced. The biplane configuration has been compared with the monoplane configuration to analyze the viability for implementing the biplane configuration in the field of application for micro air vehicles (MAV). At present, the biplane and other unusual configurations have not been a common design for MAV; however, they do have unlimited future potential. A set of experimental tests were carried out on various biplane configurations at low Reynolds numbers, which allowed the criteria for selecting the best wing configuration to be defined. The results obtained here show that the biplane configuration provides a higher maximum lift coefficient (CLmax) than the planar wing (monoplane). Furthermore, it has a larger wetted surface than the planar configuration, so the parasitic drag increases for the biplane configuration. This research is focused on a drone flight regime (low Reynolds number), and in this case, the parasitic drag (profile drag) has an important role in the total drag of the airplane. This study considers whether the reduction in the induced drag due to three–dimensional configuration (biplanes, box–wings, and joined–wings) can reduce the total drag or if the increase in the parasitic drag is bigger. Additionally, the increase in lift and the decrease in parasitic drag (profile drag) will be studied to determine if they have a greater influence on the performance of the airplane than the increase in structural weight. Further research is planned to be performed on 3D prototypes, with the selected configurations, and applied to nonconventional wing planforms.

Study on thermal performances of a horizontal ground heat exchanger geothermal system with different configurations and arrangements

Horizontal ground heat exchanger (HGHE) is a low-cost shallow geothermal exploitation method compared with vertical ones, but it needs more land area. Optimizing geometrical configurations and arrangements of ground heat exchangers is desirable to enhance heat exchange per unit land area. However, a comprehensive study on different HGHE configurations and arrangements considering atmosphere-soil-HGHE interaction is still inadequate. To this end, thermal performances of four configurations, including slinky, spiral, multi-tube with serial connection and tiled tubes, are compared based on a 3D numerical model for HGHE considering atmosphere conditions variation and humidity migration. Effects of main geometrical parameters on HGHE performance and economical efficiency are investigated for these four configurations. Finally, different tube arrangements of multi-tube HGHE are designed and their thermal performances are analyzed. Results indicated that longer HGHE tube length has better thermal performance but lower economical efficiency, thus being not advisable for the HGHE design. Among these four configurations, multi-tube with serial connection shows the best thermal performance. Increasing the tube spacing is beneficial for reducing the tube mutual interference and enhance the heat exchange per unit land area, which is recommendable. Results are expected to provide meaningful suggestions for the HGHE design.

NNetEn2D: Two-Dimensional Neural Network Entropy in Remote Sensing Imagery and Geophysical Mapping

Measuring the predictability and complexity of 2D data (image) series using entropy is an essential tool for evaluation of systems’ irregularity and complexity in remote sensing and geophysical mapping. However, the existing methods have some drawbacks related to their strong dependence on method parameters and image rotation. To overcome these difficulties, this study proposes a new method for estimating two-dimensional neural network entropy (NNetEn2D) for evaluating the regularity or predictability of images using the LogNNet neural network model. The method is based on an algorithm for converting a 2D kernel into a 1D data series followed by NNetEn2D calculation. An artificial test image was created for the study. We demonstrate the advantage of using circular instead of square kernels through comparison of the invariance of the NNetEn2D distribution after image rotation. Highest robustness was observed for circular kernels with a radius of R = 5 and R = 6 pixels, with a NNetEn2D calculation error of no more than 10%, comparable to the distortion of the initial 2D data. The NNetEn2D entropy calculation method has two main geometric parameters (kernel radius and its displacement step), as well as two neural network hyperparameters (number of training epochs and one of six reservoir filling techniques). We evaluated our method on both remote sensing and geophysical mapping images. Remote sensing imagery (Sentinel-2) shows that brightness of the image does not affect results, which helps keep a rather consistent appearance of entropy maps over time without saturation effects being observed. Surfaces with little texture, such as water bodies, have low NNetEn2D values, while urban areas have consistently high values. Application to geophysical mapping of rocks to the northwest of southwest Australia is characterized by low to medium entropy and highlights aspects of the geology. These results indicate the success of NNetEn2D in providing meaningful entropy information for 2D in remote sensing and geophysical applications.

Ball-end milling cutter design method towards the maximum material removal rate under surface roughness constraints

Cutter design and selection, as one of the indispensable tasks in discrete parts' manufacturing process planning, has seldom been investigated in terms of high machining quality and machining efficiency. In order to fill this gap, this paper studies the influences of main geometric parameters of ball-end cutter (helix angle, flute number, cutter radius) on surface roughness and material removal rate (MRR). Firstly, it is revealed that the fundamental reason why the helix angle affects the cutting force coefficients is the oblique angle, not the axial height or axial position angle. And a novel method of cutting force coefficients prediction for newly designed cutter based on local helix angle is proposed. Then, the influences of cutter parameters on surface roughness and MRR are investigated by theoretical and experimental method. Based on this analysis, cutter evaluation models for machining quality and machining efficiency are established, respectively. Particle swarm optimization (PSO) is used as optimization method to search the optimal cutter. Finally, a novel cutter design method combined with cutter evaluation models is proposed to obtain better surface performance and machining efficiency. According to the experimental results, it can be proved that the cutter designed by this method can maximize MRR under the constraint of meeting the parts' surface roughness requirements. This is of great significance for improve parts' performance and reduce machining cost.

Modeling and optimization of graphene ballistic rectifiers

We present a simulation framework based on the combination of Monte Carlo transport and Landauer-Buttiker formalism to model and optimize ballistic rectifiers exploiting the long mean-free-path of graphene. The influence on the responsivity (i.e. the induced voltage normalized by the impinging power) of the main geometrical parameters, of bias and of different scattering mechanisms is critically analyzed.

Development of an analytical model for determining the magnetic leakage flux through the stator teeth of a synchronous electric machine with a fractional tooth winding

As a result of the study of a two-dimensional finite element model of the magnetic field of a synchronous electric machine with fractional tooth windings, typical magnetic fluxes (fundamental, edge effect, scattering) in its magnetic system have been identified. The analysis of the degree of influence of magnetic fluxes of the edge effect and scattering on the magnitude of the main magnetic flux is carried out and equivalent circuits of the magnetic circuit of the studied synchronous electric machine with fractional tooth windings are constructed for different positions of the stator teeth relative to the rotor poles. An analytical model has been developed to determine the main magnetic flux through the coil of the working winding of a synchronous electric machine with fractional toothed windings. A feature of the proposed model is taking into account the dependence of the main magnetic flux through the coil of the working winding on the coordinate of the rotor position, the magnetic fluxes of the edge effect and scattering. The developed model allows solving the problem of quantitative determination of the value of the main magnetic flux through the coil of the working winding with high accuracy. In addition, the proposed model makes it possible to determine the influence of the main geometrical parameters of the magnetic circuit on the nature of the change in the main magnetic flux through the coil of the working winding with the least amount of time. The developed analytical model can be applied in the process of optimizing a synchronous electric machine with fractional tooth windings.

PlumeTraP: A New MATLAB-Based Algorithm to Detect and Parametrize Volcanic Plumes from Visible-Wavelength Images

Tephra plumes from explosive volcanic eruptions can be hazardous for the lives and livelihoods of people living in the proximity of volcanoes. Monitoring and forecasting tephra plumes play essential roles in the detection, characterization and hazard assessment of explosive volcanic events. However, advanced monitoring instruments, e.g., thermal cameras, can be expensive and are not always available in monitoring networks. Conversely, visible-wavelength cameras are significantly cheaper and much more widely available. This paper proposes an innovative approach to the detection and parametrization of tephra plumes, utilizing videos recorded in the visible wavelengths. Specifically, we have developed an algorithm with the objectives of: (i) identifying and isolating plume-containing pixels through image processing techniques; (ii) extracting the main geometrical parameters of the eruptive column, such as the height and width, as functions of time; and (iii) determining quantitative information related to the plume motion (e.g., the rise velocity and acceleration) using the physical quantities obtained through the first-order analysis. The resulting MATLAB-based software, named Plume Tracking and Parametrization (PlumeTraP), semi-automatically tracks the plume and is also capable of automatically calculating the associated geometric parameters. Through application of the algorithm to the case study of Vulcanian explosions from Sabancaya volcano (Peru), we verify that the eruptive column boundaries are well recognized, and that the calculated parameters are reliable. The developed software can be of significant use to the wider volcanological community, enabling research into the dynamics of explosive volcanic eruptions, as well as potentially improving the use of visible-wavelength cameras as part of the monitoring networks of active volcanoes. Furthermore, PlumeTraP could potentially find a broader application for the analysis of any other plume-shaped natural or anthropogenic phenomena in visible wavelengths.

Optimization of Architectural Thermal Envelope Parameters in Modern Single-Family House Typologies in Southeastern Spain to Improve Energy Efficiency in a Dry Mediterranean Climate

The increasing regulatory requirements for energy efficiency in Europe imply a significant increase in insulation and solar control of buildings, especially in hot and semi-arid climates with high annual insolation such as the Spanish Mediterranean southeast. The consequences in architectural design to optimize compliance with the new technical and regulatory requirements of nearly zero-energy buildings are high. This paper analyzes the energy performance of a modern single-family house on the Spanish Mediterranean coast. The objective is to determine which design parameters most influence the energy improvement of this case study in order to establish design strategies that can be generalized to other new construction or energy retrofit projects, taking into account the specific characteristics of the warm and semi-arid Mediterranean climate. The scientific novelty of the work is to demonstrate that the design criteria of most modern single-family houses built or rehabilitated in the Spanish Mediterranean in the last decade comply with the energy efficiency requirements of Directive 2010/31/EU but are not specifically adapted and optimized for the special characteristics of the dry Mediterranean climate. This is the case of the house studied in this paper. The methodology used consisted of a systematized study of the main construction and geometric parameters that most influence the thermal calculation of this project: the thermal insulation thickness, thermal transmittance of the glazing, solar control of the glazing, total solar energy transmittance of the glazing with the movable shading device activated, size of glazing and the size of façade overhangs. The results obtained show that the use of mobile solar protection devices in summer, such as awnings or blinds, reduces the cooling need in summer up to 44% and the overall annual energy need (Cooling + Heating) up to 20%. This implementation is more efficient than increasing the thermal insulation of facades and glazing, reducing the size of windows or increasing overhangs. The most optimal solution is the simultaneous modification of several parameters. This reduces both heating need in winter and cooling need in summer, achieving an overall reduction in an annual need of 48%. This multiple solution improves the annual energy performance of the house much more than any solution consisting of modifying a single individual parameter. The results determine trends, explanations and deductions that can be extrapolated to other projects.

МЕТОДИКА СОЗДАНИЯ КОНЕЧНО-ЭЛЕМЕНТНОЙ МОДЕЛИ ПРОКСИМАЛЬНОЙ ЧАСТИ ПЛЕЧЕВОЙ КОСТИ ПО ДАННЫМ КОМПЬЮТЕРНОЙ ТОМОГРАФИИ

The article describes the process of creating an average three-dimensional computer geometric model based on computed tomography data of patients over the age of 60 with signs of osteoporosis. The technique of creating a finite element model of the proximal part of the average humerus on the basis of computed tomography data is described. An algorithm is presented that describes the sequence of necessary actions to create a finite element model of the proximal part of the average humerus. The main geometrical parameters of the proximal humerus are highlighted. The tabular form presents the geometric mean parameters of the proximal humerus for a man and a woman from the study sample of patients. Various known methods for analyzing the distribution of bone density are displayed, and a proprietary method for measuring the density of the proximal humerus is presented. In a tabular form, according to the Hounsfield unit scale, the average densitometric parameters for the selected sectors of the average female and male proximal humerus are presented. A method is presented for reconstructing a computerized three-dimensional geometric model of the proximal humerus on the basis of computed tomography data using the free software InVesalius. An example of the development of a finite element mesh of the proximal humerus with subsequent verification calculation in ANSYS is presented. The average statistical finite element model developed on the basis of computed tomography data, taking into account the uneven distribution of bone density, will be used in the future for the design and virtual testing of various options of the humerus fixator.

Identification of flood‐prone areas with GeoFlood: Lessons learned from the Tiber River case study

AbstractFlood mapping is a vital component for sustainable land use in flood‐prone areas. Due to the frequency of flood events, local authorities demand effective yet simple methods for the preliminary identification of flood‐prone areas at large scales to subsequently define mitigation strategies. We focus here on the workflow GeoFlood, a parsimonious model which uses only high‐resolution Digital Terrain Models (DTMs) to define the geomorphological and hydrological information necessary for flood inundation mapping, thus allowing for large‐scale simulations at a reasonable computational cost. The purpose of the present study is to investigate the conditions under which GeoFlood is able to correctly reproduce inundation scenarios (with an assigned return period) and their flooding characteristics. Specifically, we analyze its performance over a highly urbanized area, the mid‐lower portion of the Tiber River (Italy). We simulated the 200‐year return period scenario and compared the results to those provided by the local authority. A sensitivity analysis is performed to quantify the influence of the main geometric and hydraulic parameters involved. Results show that GeoFlood produces rapid flood estimation than can be used in support of standard costly methods over large scales, quickly pointing out the critical flood‐prone areas, with consideration of all the uncertainties involved.

The Hydrodynamics of Translational−Rotational Motion of Incompressible Gas Flow within the Working Space of a Vortex Heat Generator

The paper presents the results of analytical and experimental studies of the hydrodynamics of the translational−rotational motion of incompressible gas flow within a working space of a variable-geometry vortex heat generator. The terminal velocity and pressure have been identified analytically. The effect of vortex generation on the ratio of the parameters has been analyzed. A mathematical model has been developed with a simplified design scheme that simulates the movement inside a vortex channel with fixed elements. On the basis of mathematical modelling, the influence of the apparatus-constructive (AC) design of the working space of a vortex heat generator on the generation of vortices inside the apparatus has been analyzed. The influence of the main geometric and hydrodynamic parameters of the device on the indicators of its energy efficiency has been investigated. The obtained models show the critical regions where the most intense cavitation zones are possible. An analysis of the hydrodynamics of the incompressible gas motion within the working space of the newly designed vortex heat generator with variable geometry has helped define both the terminal velocity and pressure. In addition, the effect of the facility geometry on the generation of vortices favoring cavitation was determined. The model studies have been carried out in terms of liquid loading changes in the 0.001–0.01 m3/s range. The changes in a velocity field within a working channel have been analyzed for the channel geometry, where a cone angle γ is 0° to 25°, with 130, 70, and 40 mm widths for the working channel. It has been identified that a sufficient axial symmetry of the heat carrier along a vortex accelerator enables the heat carrier inlet through a turbulizing nozzle. The dependence of the nozzle area, the effect on the efficiency of the vortex heat generator angle of attack of the vortex accelerator, and the ratio of the length and diameter of the vortex zone of the heat generator to its energy efficiency in general have been defined experimentally. These studies could be instrumental in the design of vortex heat generators whose geometry corresponds to the current requirements concerning energy efficiency. It has been found that the geometry of the vortex accelerator improves the operation of the heat generator by 35% in comparison with similar available designs.

Optimal focal curve of spherical mirrors used in a high resolution UV-A spectrograph

The present study concerns the determination of the optimal focal curve of the reflected beam from a spherical mirror. This study has been used in a stigmatic high resolution UV-A spectrograph operating in UV-A region. As a light source we have used a low pressure air discharged lamp while the light detector was a cooled CCD camera with a resolution of 1600×1200 pixels. Locating it on the optimal position along the useful spectral range allows us to exploit the full resolution provided by the spectrograph. An analytical expression of the focal curve has been derived as a function of the main geometrical parameters of the spectrograph and the focusing spherical mirror. A set of experimental validation tests have been performed recording several band heads and the associated molecular rotational lines of nitrogen provided by the lamp. The obtained result has been used in high resolution spectroscopy relevant to air fluorescence yield determination in Ultra High Energy Cosmic Ray research.

Parameters and Ratios of Metal Cylindrical Mesh Shells

Finite element modeling, calculation and analysis of metal cylindrical mesh shells are carried out. The choice of the surface topology is justified and the recommended ratios of overall dimensions are adopted. The criteria for determining the stability of the grid are given. The limits of permissible curvature and the main geometric parameters are obtained. The effect of increasing the rigidity and height of the structure on the work of the mesh surface is analyzed. Patterns of changes in nodal deviations and internal force factors of vulnerable areas of the shell are revealed. The results of changes in the shape and features of the critical deformation of the system are presented.

РАСЧЕТ РОТОРНОГО АППАРАТА ДЛЯ ПРОИЗВОДСТВА ГРАФЕНОСОДЕРЖАЩИХ СУСПЕНЗИЙ

The article considers the calculation of a rotary apparatus with movable blades for the production of graphene-containing suspensions, which are used to modify structural and functional materials with improved performance characteristics. The rationale is given for the expediency of obtaining graphene plates by the method of shear exfoliation of graphite directly in liquids that are part of these materials. The kinetics of the exfoliation process in inorganic and organic liquids has been investigated, and according to the results of the analysis, dependences are proposed for calculating the main operating and geometric parameters of rotary apparatus with movable blades.