scholarly journals Experimental determination of the energy efficiency of rotors of vertical-axis wind turbines for autonomous power supply on land and at sea

2018 ◽  
Vol 245 ◽  
pp. 06016 ◽  
Author(s):  
Nikolai Shishkin ◽  
Roman Il’in
Keyword(s):  
Power Supply ◽  
Experimental Studies ◽  
Rotation Frequency ◽  
Vertical Axis ◽  
Geometrical Parameters ◽  
Horizontal Axis Wind Turbine ◽  
A Value ◽  
First Time ◽  
Supply Systems

For the first time, experimental studies have been performed to assess the effect of flaps with triangular elements on the operation of the N-Darrieus and Savonius rotors. It has been established that the rotational speed of the original N-Darrieus and Savonius rotors having blades with flaps is greater than the rotation frequency of the N-Darrieus and Savonius rotors of the known construction by 18%, and the power factors of the N-Darrieus and Savonius rotors are for 17% and 19% more. Optimization of the geometrical parameters of the blades can lead to an increase in the power factor of the N-Darrieus rotor up to a value of 0.72, which is higher than the maximum possible value of 0.45 for the horizontal axis wind turbine. It is advisable to aggregate N-Darrieus rotors with Savonius rotors having a large starting torque. The upgraded N-Darrieus and Savonius rotors, as well as the combined rotors based on them, can be used in power supply systems for various objects on land and at sea.

Calculating the aerodynamics of vertical axis wind turbines

2012 ◽  
Vol 34 (3) ◽  
pp. 169-184 ◽  
Author(s):  
Hoang Thi Bich Ngoc
Keyword(s):  
Wind Turbine ◽  
Incidence Angle ◽  
Vertical Axis ◽  
Rotor Blades ◽  
Vertical Axis Wind Turbine ◽  
Horizontal Axis Wind Turbine ◽  
Velocity Triangle ◽  
Relationship Of ◽  
The Relationship

Vertical axis wind turbine technology has been applied last years, very long after horizontal axis wind turbine technology. Aerodynamic problems of vertical axis wind machines are discussible. An important problem is the determination of the incidence law in the interaction between wind and rotor blades. The focus of the work is to establish equations of the incidence depending on the blade azimuth, and to solve them. From these results, aerodynamic torques and power can be calculated. The incidence angle is a parameter of velocity triangle, and both the factors depend not only on the blade azimuth but also on the ratio of rotational speed and horizontal speed. The built computational program allows theoretically selecting the relationship of geometric parameters of wind turbine in accordance with requirements on power, wind speed and installation conditions.

scholarly journals Method for determining the maximum load of consumers in city power supply systems

2019 ◽  
Vol 139 ◽  
pp. 01078 ◽  
Author(s):  
A.G. Saidkhodjaev ◽  
A.M. Najimova ◽  
A.K. Bijanov
Keyword(s):  
Power Supply ◽  
Maximum Load ◽  
High Accuracy ◽  
New Method ◽  
Electrical Networks ◽  
Electric Networks ◽  
Reliable Determination ◽  
Supply Systems

In this article, we propose a new method for determining the maximum load of electric consumers in urban electric networks, which differs from existing methods in more accurate and reliable determination of the maximum loads. Based on the determination of the maximum loads of the objects of urban electrical networks, it is concluded that the proposed methods are determined by high accuracy and minor errors.

scholarly journals Timely determination of static stability margins in power supply systems equipped with distributed generation installations

2021 ◽  
Vol 25 (1) ◽  
pp. 31-43
Author(s):  
Yu. N. Bulatov ◽  
A. V. Kryukov ◽  
К. V. Suslov ◽  
A. V. Cherepanov
Keyword(s):  
Distributed Generation ◽  
Power Supply ◽  
Computer Modelling ◽  
Dynamic Modelling ◽  
Electrical Network ◽  
Electrical Networks ◽  
Stability Margins ◽  
Emergency Control ◽  
Supply Systems

The article aims to develop a methodology to ensure timely determination of the margins of static aperiodic stability in power supply systems, at the nodal points of which distributed generation units are installed. The authors used mathematical methods and algorithms based on the application of limiting regime equations. Transitional processes were analysed for various points in the space of controlled mode parameters according to the simulation modelling in Matlab using the Simulink and SimPowerSystems packages. On the basis of the obtained results, an effective technique for analysing stability margins in electrical networks with distributed generation units was implemented. This method is applicable in design problems, as well as in operational and emergency control. The conducted theoretical analysis and computer modelling showed the effectiveness of the proposed methodology for calculating stability margins; the nondegeneracy of the Jacobi matrix of limiting regime equations at the solution point ensures the guaranteed reliability of the results. It was shown that an alternative approach to solving the problem of timely determination of aperiodic stability margins can be implemented on the basis of limiting regime equation with increased nonlinearity. Dynamic modelling of an electrical network with distributed generation units confirmed the correctness of determining the stability margins calculated using limiting regime equations. The developed technique can be recommended for practical use in the design of power supply systems or in operational control of synchronous generators. In particular, the presented methodology can be used to implement a multi-agent emergency control system for distributed generation installations located in generalpurpose distribution electrical networks. 

scholarly journals Interlaboratory study of the method for direct determination of volatile compounds in alcoholic products using ethanol as internal standard

2020 ◽  
pp. 74-87
Author(s):  
Siarhei V. Charapitsa ◽  
Svetlana N. Sytova ◽  
Anton L. Korban ◽  
Lidia N. Sobolenko ◽  
Vladimir V. Egorov ◽  
...  
Keyword(s):  
Volatile Compounds ◽  
Volatile Component ◽  
Experimental Studies ◽  
Internal Standard ◽  
Direct Determination ◽  
Interlaboratory Study ◽  
Significance Level ◽  
First Time ◽  
Standard Solutions

A collaborative interlaboratory study of the method of direct determination of volatile compounds in spirit drinks and alcoholic products was performed. The proposed method employs ethanol, the major volatile component of an alcoholic product, as an internal standard. For the experiment realization, 9 laboratories from 4 countries – Belarus, Czech Republic, Turkey, Russia – were supplied with standard solutions for gas chromatographic measurements. Five aqueous ethanol 40 % (v/v) standard solutions containing target compounds in concentrations ranging from 10 to 400 mg/L of absolute alcohol were gravimetrically prepared and delivered to the participants. The interlaboratory study was evaluated according to the ISO 5725 standards and the «EuroChem» guide. The repeatability limits (within-laboratory precision) varied between 0.4 and 7.5 % for all samples and compounds, showing a sufficiently high repeatability of the method. The reproducibility limits (between-laboratory precision) were found to vary within a satisfactory range of 0.5–10.0 %. Precision of the method was well within the range predicted by the Horwitz equation for all analytes. In the study experimental estimation of trueness was performed for the first time. Analysis of the obtained results showed that the bias of the method is insignificant at the significance level 5 %. The experimentally determined concentrations of the analytes compared well to the gravimetrical values, thus showing very satisfactory accuracy of the method. The results of the interlaboratory study confirmed that the method «ethanol as internal standard» is robust and reliable and can be used as a standard method for the determination of volatile compounds in water-ethanol samples. Moreover, this method can be validated in any one laboratory without performing additional experimental studies based on the results obtained by validation of the traditional method.

scholarly journals Determination of the plasticity of metals by impact indentation of a spherical indenter

2021 ◽  
Vol 66 (4) ◽  
pp. 483-495
Author(s):  
A. P. Kren
Keyword(s):  
Strain Rate ◽  
Experimental Studies ◽  
Spherical Indenter ◽  
Full Plasticity ◽  
Energy Ratios ◽  
Materials Used ◽  
Plasticity Parameter ◽  
First Time ◽  
Impact Microindentation

The problems of measuring the plastic characteristics of metals are considered. It is shown that the characteristics of materials used to compare their plasticity are not comparable and depend in the different degrees on the values of strain, strain rate, and modulus of elasticity. At the same time, the value of plasticity is more physically substantiated, which is determined by the ratio of plastic strain to total strain. It is shown that one of the optimal methods for measuring plasticity (plasticity index) is indentation. The possibility of using impact microindentation for this purpose is studied and expressions are proposed that allow calculating the plasticity based on the results of a single indentation of a spherical indenter. The specialties of the calculation of strain for this type of testing are shown. It was found that the values of plasticity obtained from the ratios of the depths of the plastic and elastic penetration of the indenter are equivalent to the values calculated from the energy ratios upon impact. Experimental studies have been carried out on metals with different hardness and type of crystal lattice. For the first time, the effect of strain rate, deformation, and impact energy (initial impact velocity) on the calculated value of plasticity when a sphere is impressed with strain rates of ~ 103 s–1 is shown. It is shown that when the strain corresponding to the onset of full plasticity during indentation is reached, the maximum sensitivity of the measured plasticity parameter for various metals is achieved.

scholarly journals Determination of optimal location for installation of symmetry facilities in 0.4 kV power supply systems with motor-drive load

2018 ◽  
Vol 58 ◽  
pp. 03014
Author(s):  
Victoria Romanova
Keyword(s):  
Power Supply ◽  
Asynchronous Motor ◽  
Optimal Location ◽  
Economic Feasibility ◽  
Motor Drive ◽  
Capacity Loss ◽  
Electrical Grids ◽  
Cross Platform ◽  
Supply Systems

This article considers the issue for creation of computer-aided program designed for determination of optimal location for installation of symmetry facilities in 0.4 kV power supply systems with motor-drive load in conditions of asymmetry of voltages. The developed program is implemented by means of C# programing language in Microsoft Visual Studio 2012 programming environment using the embedded cross-platform data base SQLite. The program is designed for making electrotechnical calculations during designing, modernization and operation of electrical grids with available motor drive load. It ensures plotting of schematic circuits for 0.4 kV power supply system sections with installed symmetry facilities. The program will enable quick and exact calculation of power capacity loss, determination of economic feasibility for taking special measures to eliminate the asymmetry of voltages, and to determine optimal application and location of symmetry facilities. Using the program in motor-drive load power supply systems will enhance the asynchronous motor reliability and efficiency.

scholarly journals Material and Structural Modeling Aspects of Brain Tissue Deformation under Dynamic Loads

Materials ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 271 ◽  
Author(s):  
Monika Ratajczak ◽  
Mariusz Ptak ◽  
Leszek Chybowski ◽  
Katarzyna Gawdzińska ◽  
Romuald Będziński
Keyword(s):  
Brain Tissue ◽  
Human Subjects ◽  
Experimental Studies ◽  
Material Modeling ◽  
Geometrical Parameters ◽  
Dynamic Loading Conditions ◽  
Technological Improvements ◽  
The Impact ◽  
The Brain

The aim of this work was to assess the numerous approaches to structural and material modeling of brain tissue under dynamic loading conditions. The current technological improvements in material modeling have led to various approaches described in the literature. However, the methods used for the determination of the brain’s characteristics have not always been stated or clearly defined and material data are even more scattered. Thus, the research described in this paper explicitly underlines directions for the development of numerical brain models. An important element of this research is the development of a numerical model of the brain based on medical imaging methods. This approach allowed the authors to assess the changes in the mechanical and geometrical parameters of brain tissue caused by the impact of mechanical loads. The developed model was verified through comparison with experimental studies on post-mortem human subjects described in the literature, as well as through numerical tests. Based on the current research, the authors identified important aspects of the modeling of brain tissue that influence the assessment of the actual biomechanical response of the brain for dynamic analyses.

scholarly journals ANALYSIS OF THE COMPETITIVENESS INCREASE OF ENERGY-EFFICIENT DESIGNS OF WIND TURBINES OF VARIOUS TYPES

2017 ◽  
pp. 42-50 ◽  
Author(s):  
Roman Albertovich Ilyin ◽  
Nickolai Dmitrievich Shishkin
Keyword(s):  
Wind Turbines ◽  
Power Supply ◽  
Wind Farms ◽  
Vertical Axis ◽  
Payback Period ◽  
Capital Investments ◽  
Horizontal Axis Wind Turbines ◽  
The Cost ◽  
Supply Systems ◽  
Specific Capital

The structural analysis of wind turbines (WT) shows that along with horizontal-axis wind turbines (HAWT) there are now widely used vertical-axis wind turbines (VAWT). Significant advantages of the combined type VAWT on the basis of wind turbines of Darrieus and Savonius make them most promising for further improvement and wide application. Power of the wind turbine depends on the angle of the vector of the wind flow to the axis of rotation of the wind motor. The presence of control systems makes the wind turbines HAWT "slow" because of long reaction. As a result, the utilization of wind energy of the powerful HAWT can be reduced to 0.15-0.25 and become lower than that of VAWT, amounting to 0.20-0.40. Calculations show that the payback period of wind turbines increases from 2 to 50 years, with the increase of specific capital investments in wind turbines from 25 000 RUB/kW to 150 000 RUB/kW (from 417 up to 2500 $/kW), reducing the cost of the displaced electricity from 2.0 RUB/kW·h to 5.0 RUB/kW·h. Specific capital investments in wind turbines with a payback period of 7.0 years should not exceed 53 000 RUB/kW (884 $/kW). It seems quite reasonable to use HAWT and VAWT of the big capacity to create wind farms connected to a centralized grid. HAWT and VAWT with capacity up to 30 kW can be used for autonomous power supply of objects remoted from the centralized power supply systems.

A Way to Enhance the Efficiency of a Vertical Axis Wind Turbine

2019 ◽  
Vol 889 ◽  
pp. 410-417
Author(s):  
Quang The Phan ◽  
Thị Thu Hà Phan ◽  
Ahmed Sherif El-Gizawy ◽  
Thị Hồng Mai Phan
Keyword(s):  
Wind Turbine ◽  
Urban Areas ◽  
Vertical Axis ◽  
Speed Ratio ◽  
Force Analysis ◽  
Vertical Axis Wind Turbine ◽  
Horizontal Axis Wind Turbine ◽  
New Model ◽  
Low Efficiency

Vertical Axis Wind Turbine (VAWT) can perform better than Horizontal Axis Wind Turbine (HAWT) because VAWTs are relatively simple, quiet, and easy to install. It can take wind from any directions, and operate efficiently in urban areas where turbulent wind conditions usually happen. The weakest point for its configuration, however, is its low efficiency so more intensive research is required.Actual VAWT performance can be predicted based on a determination of the forces acting on blades that produce the turbine’s torque. Thus, this paper proposed a new model of force analysis for calculation of VAWT’s performance and a way to enhance the efficiency of VAWT through proper variations of the pitch angles. Additionally, in order to increase the efficiency of the VAWT for a given tip speed ratio, the solidity in term of blade’s number can be adjusted.Results show that right changes in the value of pitch angles and proper selection of the number of blades can considerably increase the efficiency of the turbine and reduce amplitude of turbine’s torque variation. The new model of force analysis can be helpful for aerodynamic analysis of the VAWT turbine for its better design.

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