Vol 15, No 3 (2021)
Articles
Experimental studies of the effect of a hybrid inverter on power quality
Abstract
The integration of alternative energy sources and various technologies of distributed generation with power electronic converters in electrical networks leads to an increase in the diversity of the network, but at the same time to the tightening of the requirements of various standards, for example, a limited harmonic composition of the generated current, continuous operation of the device with voltage distortion, etc. Taking this fact into account, the paper presents the results of experimental studies of the effect of a hybrid inverter on power quality indicators at the point of common connection. A laboratory bench was developed. It consists of a three-phase hybrid inverter, a storage battery, a linear load in the form of an active resistance and a capacitor unit. The inverter has been connected to the power supply for parallel operation to supply the load in the form of active resistance. The modes of battery charging and power delivery to the network with two variations of the system resistance were investigated. The power output from the inverter varied from 500 W to 2 kW in the mode of generating electricity to the grid, and in the range from 50 to 300 W in the battery charging mode. As a result of laboratory studies, the dependences of the total harmonic current distortion (THDI) were obtained for various operating modes of the inverter and system resistances. On the basis of the obtained results, an algorithm for the selection of methods and means to ensure electromagnetic compatibility during operation of the load and a hybrid inverter with energy storage was developed. It makes it possible to reduce the effect of hybrid inverters on the voltage distortion of the supply network.
2-9
Increasing the efficiency and safety of operation of underground tunnel escalators. Management of risks
Abstract
The purpose of the article is to find mechanisms for ranking and arbitrating needs (a set of technical actions) sufficient to ensure the required level of reliability and safety of transportation of increasing passenger traffic. The object of the research is the escalator facilities, and the subject is the system of maintenance and repair. Scientific novelty is the use of information technologies containing a combination of mathematical tools that implement the necessary functionality for the digital transformation of the system of maintenance and repair of the escalator facilities of the underground. At the beginning of the article, the object of application, the goal and objectives of the concept of digital transformation, its architecture and functions, as well as implementation features are described. Further, the work focuses on maintaining the reliability and safety of transportation of passenger traffic as the main functions of the concept. Then there are presented the situations of risk (events) and a generalized model of their formation, revealing the cause-and-effect complex. After that, the tasks and the risk management process itself are shown. These are based on determining the magnitude of risk, which initial data are extracted from the information space containing electronic documents, including data on work (technical impacts), and the result is correlated with various scales. In addition, the mathematical apparatus of risk management includes matrices, which are used by decision support strategies. The mathematical apparatus described in the work implements a mechanism for ranking and arbitrating needs (a set of technical actions), which, in turn, is an integral part of the methodology for increasing the durability, reliability and safety of operation of escalators and associated infrastructure. The presented concept allows, in case of a shortage of resources, to form a complex of impacts for the most problematic elements, and to transfer the operation of escalator elements and related infrastructure facilities to a system according to the state that contributes to a reasonable increase in the assigned service life while maintaining sufficient safety levels. In conclusion, the expected practical results of the implementation of the concept are presented.
10-22
Method for calculating technical characteristics and parameters of movement of scale models of wheeled vehicles, ensuring the similarity of the processes during testing
Abstract
Nowadays, when designing new vehicle models, there is a need to test certain solutions for the formation of a technical appearance both by simulation methods and on production samples. Full-scale road tests of vehicles make it possible to maintain full dynamic similarity during the experiment, but they can be carried out only after manufacturing of a vehicle prototype, which requires a lot of material costs. One of the ways to solve this problem is to create models that are a reduced copy of the designed vehicle. The main difficulty that appears when testing a scale model of vehicle is the need to accurately reproduce the conditions that occur when driving in real road conditions. The purpose of this paper is to find a relationship between the parameters of a production vehicle and a scale model for experimental development of algorithms for the dynamic stabilization of a wheeled vehicle. A method for calculating the technical characteristics and motion parameters of scale models for real full-scale wheeled vehicles while ensuring the similarity of the ongoing processes for scale models and for production vehicles is proposed on the basis of the theory of similarity. The main dependences for scale factors for force, kinematic and dimensional factors are obtained. The similarity of the occurring processes was confirmed by the methods of simulation modeling of the movement of a scale model and a full-scale wheeled vehicle.
23-30
Study of the effect of finite element dimensions on the simulation accuracy of adhesive bonding in automotive structures
Abstract
This article studies the effect of finite element dimensions on the accuracy of simulation of adhesive bond in automotive structures using the LS-Dyna software package. The simulation was carried out under quasi-static loading for an “overlapped” adhesive joint. The properties and destruction of the adhesive material in the direction of shear were evaluated. The characteristics of the adhesive layer were obtained from experiments using a hydraulic press and other devices according to international standards ASTM 638-03 and DIN 54451-11.1978 with different sliding speeds and adhesive layer thicknesses. It was revealed from experiments that the properties of the adhesive material strongly depend on the deformation rate and the thickness of the adhesive layer, so this had to be taken into account when modeling. To solve this problem, 12 variants of finite element models were solved and evaluated, including by comparing with the results of experiments for glued “overlapped” joints. As a result of the analysis of the stress-strain states of models of an adhesive joint under quasi-static loading in the LS-Dyna software package, the recommended size and number of layers of finite elements were obtained for modeling an adhesive joint in automotive structures. The rational size of the facets of a volumetric finite element is 2 × 2 mm2, taking into account the modeling errors and the cost of computer time for the calculation in relation to multivariate calculations of structures at the design stage. It was determined the recommended number of layers of finite elements in the finite element model by the thickness of the adhesive layer, that should be selected for a highly accurate description of the gluing properties and ensuring the efficiency of calculations. At the same time, it was revealed that an increase in the number of layers of finite elements insignificantly increases the accuracy of modeling and significantly increases the required computer time for the calculation.
31-41
Assessment of vehicle damage from the point of a complex technical system with its own structure
Abstract
There is considered a part of the study of post-repair reliability of vehicles from the point of a complex technical system in the form of an algorithm for evaluating diagnostic parameters (probable connections). The problem of the reliability of vehicles in operation is legally put under the control of the President of the Russian Federation and is included in the strategy for ensuring road safety until 2023, which is part of the National Project “Safe Roads”.
The initial data of the study at the stage of evaluating probable connections are the parameters of the vehicle movement in the pre-accident time interval and the voltage acting at the contact point of the object, which is obtained based on these parameters. The main method of assessment is the calculation of cells of different types using the grid method, depending on the nature of the damage to the vehicle. In order to decompose the contact point into cells of different types, it is recommended to use appropriate certified measuring instruments and certified equipment: flaw detectors and so on. For the convenience of using the algorithm and reducing the error of using the given mathematical model in a comprehensive assessment of the reliability of vehicles, the article provides a definition of the reduced volume and correction coefficients.
The output data of the algorithm for evaluating diagnostic parameters are the updated values of stresses at the contact point of the object under study, as well as a detailed picture of the distribution of strain energy in the object. As a result, the obtained values can be used for further evaluation of changes in the regulated values of the vehicle properties established by the manufacturer and controlled within the framework of the failure prevention system or technical inspection.
42-48
Research on molecular energy storage
Abstract
This article provides a comparative analysis of various energy storage devices. A detailed review and analysis of molecular energy storage units is carried out, their main characteristics and parameters, as well as their application areas, are determined.
The main types of molecular energy storage are determined: electric double layer capacitors, pseudo capacitors, hybrid capacitors. Comparison of the characteristics of various batteries is given. The parameters of various energy storage devices are presented. The analysis of molecular energy storage devices and accumulators is carried out. Ttheir advantages and disadvantages are revealed.
It has been shown that molecular energy storage or double layer electrochemical capacitors are ideal energy storage systems due to their high specific energy, fast charging and long life compared to conventional capacitors.
The article presents oscillograms of a lithium-ion battery with a voltage of 10.8 V at a pulsed load current of 2A of a laptop with and without a molecular energy storage device, as well as oscillograms of a laptop with DVD lithium-ion battery with a voltage of 10.8 V with a parallel shutdown of a molecular energy storage device with a capacity of 7 F and without it. The comparative analysis shows that when the molecular energy storage unit with a 7 F capacity is switched on and off, transient processes are significantly improved and there are no supply voltage dips. The dependences of the operating time of a 3.6 V 600 mAh lithium-ion battery at a load of 2 A for powering mobile cellular devices with and without a molecular energy storage are given. It is shown that when the molecular energy storage device is switched on, the battery operation time increases by almost 20%.
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Identification of vehicle directional parameters using the sigma-point Kalman filters
Abstract
The article discusses the problem of identifying the parameters of the vehicle's directional movement, which are necessary for the operation of active safety systems (SAB). The inability to determine some of the parameters necessary for the functioning of the SAB by direct measurements with on-board sensors (due to the absence of corresponding sensors in production vehicles) makes it relevant to use indirect computational methods for identifying these parameters, which are based on mathematical structures called observers.
The purpose of this work is to create a system for identifying vehicle motion parameters, which, using the measurements available on board the vehicle and the mathematical apparatus of the theory of observers and optimal filters, indirectly determines unmeasured parameters that are important for the operation of active safety systems.
Based on the analysis of existing methods and tools, a diagram of the observer of the parameters of the vehicle's directional movement using the sigma-point Kalman filter is proposed. The observer identifies the lateral component of the vehicle speed vector, the coefficients of the lateral adhesion of the tires to the supporting surface and the wheel slip angles using the vehicle dynamics model and on-board inertial sensors that measure the linear acceleration and yaw rate of the vehicle.
The observer's performance and adequacy was confirmed by comparing the parameters he identifies with direct measurements made during road tests of the vehicle. There was used a root-mean-square error of identification as a measure for assessing the accuracy with respect to direct measurements of the parameters of course movement. An additional assessment of the adequacy is made by comparing the identified grip characteristic (the dependence of the coefficient of adhesion on the slip angle) with the characteristic obtained by approximation using a mathematical model of the tire. The assessment showed a good quality of identification of course movement parameters provided by the developed observer, which gives grounds to consider it a useful tool for research and development of active safety systems.
57-69
Investigation of the environmental performance of a diesel engine when operating on multicomponent biofuel
Abstract
Local types of fuels occupy 33.6% in the fuel balance of the Kirov region. The share of consumption of local fuels in the region is one of the highest in Russia.
The Vyatka State University (VyatSU) in cooperation with the Belarusian State Agricultural Academy (BSAA) carry out the tests of the operation of automotive diesel engines on fuels with rapeseed oil (RO) and ethanol (E) additives, and spark internal combustion engines with generator gas (GG) additives. A new area of work of the scientific school is the study of the use of multicomponent compositions of biofuel compositions (MKBTK-15 and MKBTK-25). The use of such compositions as a fuel compensates some of their distinctive properties for further use in internal combustion engines without changing the design and adjustments.
The use of alternative fuels (AF) in internal combustion engines is a main topic for research. However, the use of any AF requires that the environmental indicators of the engine remain within acceptable limits. An important task is to determine the dependences of the emissions of toxic components on the load.
The use of MKBTK-15 and MKBTK-25 as AF for engines will improve the environmental situation in the region and reduce the need for commercial fuel. The operation of a diesel engine on multicomponent biofuel compositions makes it possible to reduce the smoke content of exhaust gases by 65% and 85%, the content of total nitrogen oxides remains at the same level or slightly decreases.
There is a slight increase in the content of carbon dioxide СО2 up to 22.3%, but the solutions to this problem are already known. One of the ways is to preserve and increase boreal forests, which have great potential for absorbing greenhouse gases.
70-75
A virtual test bench for determining the loads in the air suspension of the rear trolley of a truck at the early stages of design
Abstract
To determine the maximum loads acting in the rear air suspension of a truck at the early stages of design there was used computer modeling based on solving equations of dynamics of solids and implemented in the Recurdyn software. The components of the developed virtual test bench, including hinges, power connections, drive axles, a wheel-hub assembly with a wheel and a support platform, are considered in detail. The test bench is controlled using a mathematical model created in the environment for calculating the dynamics of rigid bodies and associated with a solid suspension model by standard software tools of the application. The test bench is controlled using a mathematical model created in the environment for calculating the dynamics of rigid bodies and associated with a solid suspension model by standard software tools of the application. The use of such a test bench makes it possible to determine the loads in the hinges and power connections of the suspension, to determine the mutual positions of the links for each load mode, to increase the accuracy of the calculation of loads in comparison with the flat kinematic and force calculation. The mathematical model of the virtual test bench allows to carry out numerous parametric studies of the suspension without the involvement of expensive full-scale prototypes. This makes it possible at the early stages of design to determine all hazardous modes, select rational parameters of the elements, and reduce design costs.
The paper shows the results of modeling the operation of a virtual test bench with an air suspension in the most typical loading modes, identifying the most dangerous modes. The efficiency and adequacy of the mathematical model of the suspension was proved. Examples of determining the force in all the joints of the structure, the choice of maximum loads for design calculations when designing the air suspension of vehicle were shown.
76-86
Finding the optimal compressor impeller material to improve the efficiency of the turbocharging system
Abstract
Vehicles powered by diesel engines are equipped with superchargers in order to improve the efficiency of vehicles. The efficiency of the turbochargers themselves partly depends on the optimum performance of their impellers, which in turn is achieved by choosing the right impeller materials. An important property of the material of the turbine wheel is heat resistance to the incoming exhaust gases, and for the compressor wheel it is the resistance to the pressure of the air simultaneously supplied to it and forced by it.
In this paper, the issue of increasing the efficiency of the turbocharging system is considered in the context of comparing three materials (nickel and titanium alloys, structural steel), which are proposed for the manufacture of a compressor impeller by designing its model using computer software products. The measurements of real turbocharging elements and their characteristics are transferred to CREO, where the required dimensions are calculated and other necessary calculations are carried out, which are then imported into ANSYS for the purpose of subsequent research, including thermal and structural analyzes. Comparison of the analysis results allows us to conclude that the nickel alloy is superior to other materials under consideration in terms of its minimum susceptibility to deformation and obtaining the lowest total heat flux in the compressor impeller, and to recommend this material for use in turbocharging or for its subsequent comparison with previously not considered materials, which, as suggested in the study, to some extent can contribute to an increase in the efficiency of the vehicle.
87-94