Theoretical Analysis of Fully Conservative Difference Schemes with Adaptive Viscosity

For the equations of gas dynamics in Eulerian variables, a family of two-layer in time completely conservative difference schemes with space-profiled time weights is constructed. Considerable attention is paid to the methods of constructing regularized flows of mass, momentum, and internal energy that do not violate the properties of complete conservatism of difference schemes of this class, to the analysis of their amplitudes and the possibility of their use on non-uniform grids. Effective preservation of the balance of internal energy in this type of divergent difference schemes is ensured by the absence of constantly operating sources of difference origin that produce "computational"entropy (including those based on singular features of the solution). The developed schemes can be easily generalized in order to calculate high-temperature flows in media that are nonequilibrium in temperature (for example, in a plasma with a difference in the temperatures of the electronic and ionic components), when, with the set of variables necessary for describing the flow, it is not enough to equalize the total energy balance.

Problems of sustainable “green” development of alternative energy

The paper analyzes the known risks of power supply failure in the case of further development of renewable energy sources. The use of FMEA analysis allowed to analyze the significance of various risks of alternative energy. It is shown that the use of the FMEA method is becoming one of the most important areas of technosphere safety for the further development of alternative energy. The introduction of the share of alternative energy into the total energy balance leads to a decrease in the share of traditional sources of energy generation. In turn, a decrease in the share of traditional sources of energy production in the case of a combination of unfavorable natural factors causes to the collapse of the energy supply system and causes a complete shutdown of alternative energy.

Dynamics of interphase interaction between components during mixing

The processes of mixing, whipping, and foaming are essentially uniform and consist in dispersing the gas in a liquid. When mixing and whipping, the mixture of components is swollen due to the mechanical action; increased in volume water-insoluble protein substances (gluten proteins) form a three-dimensional spongy mesh continuous structure. It is called a gluten frame. It determines the elastic and resilient properties of the medium. Therefore, the purpose of the study is to establish the relationship between the gas holding capacity of the medium and the energy expended on the hydration of the components. The study solves the task of determining the gas holding capacity of the medium with variable parameters of the height of the liquid phase from the mixing intensity, the duration of transient processes for the formation of the full volume of the gas-liquid medium, the duration of the transient process for the dispersed gas phase yield. The difference between the levels before the gas phase formation and during the mixing (aeration) mode determines the value of the gas holding capacity. In this context, we concluded that it is expedient to completely destabilize the established modes by changing the operating modes in the working body in the flow system. An additional effect on the system is the change of hydrodynamic regimes due to the unstable dynamics of the dispersed gas phase formation. The generation of the dispersed gas phase means the presence of energy expenditure on the interphase layer formation, which should be considered in the total energy balance. At the same time, another feature should be mentioned. Part of the gas phase, which existed and continues to exist in the new mode after mixing, enters the mode of a transient process. Therefore, the most effective mixing occurs while adhering to the shifted mode for dosing components in a suspended state and the mechanical impact of the working body. Based on the given objectives and conditions of sponge dough mixing, we determined the requirements for the mixer design and found that the supply of components should last at least 45 seconds. During this period, hydration occurs and energy consumption is declining.

Seamless Shifting Control Based on Power Balance Method in Emergency Braking Condition

Implementation of multi-speed transmission for battery electric vehicle (BEV) is considered as one of effective methods in improving dynamic capability, reducing power consumption and downsizing the powertrain. Considering two trends of automotive technology, advanced driving assistance system (ADAS) and BEV electric powertrain, equipped with a two-speed transmission, can enhance the performance of automatic emergency braking systems (AEBS). When downshift operation is executed during regenerative braking, the multi-speed transmission in first gear can provide adequate brake force capacity for hard braking requirement, improving efficiency of energy recovery of drive motor as well as eliminating the dynamic lag of active braking booster. To ensure both the braking command and downshift requirement, a seamless clutch-to-clutch shifting control strategy based on power balance method is developed by analyzing the frictional work of two friction clutches inside the gear box and the transformation process of kinetic energy of rotational mechanical elements. To maintain the total energy balance of the powertrain as the control objective, the active power compensation of the drive motor during shifting fills the energy gap of the whole transmission system. With the estimation of clutches’ friction torque and shifting stage analyzer, optimal drive motor torque command can be numerically solved and a complete shifting control flow is designed in this study. Simulation results demonstrate the effectiveness of proposed control method in achieving seamless downshifting during regenerative braking, enhancing AEBS performance and improving energy recovery efficiency.

Real Domestic Hot Water Consumption in Residential Buildings and Its Impact on Buildings’ Energy Performance—Case Study in Poland

A building’s energy consumption is assessed considering the energy required for heating, cooling, lighting, and domestic hot water (DHW). Methodologies used to calculate energy certificates in European Union countries consider hot water consumption rates per person or per heated (floor) area, giving wide-ranging values (35–88 dm3/person/day). Using extreme parameters, it is possible to obtain a primary energy index that meets the legal requirements, although unrealistically large proportions of domestic hot water use relative to the total energy balance of the building may marginalize the influence of other components, such as fluctuations in heating, ventilation, or lighting. In the current work, the DHW consumption of three residential buildings was measured to verify the energy consumption for hot water preparation. Investigations were conducted based on the consumption of natural gas for DHW preparation. Experimentally obtained water consumption rates were determined per m2 of a dwelling and per person living in the building. The calculated indicators (0.85 ± 0.005 dm3/m2/day and 27.4 ± 1.4 dm3/person/day) were lower than those used for energy certifications of buildings. The experimentally obtained indicators were used in further theoretical energy assessments of six residential buildings. By adopting the designated indicators, the analyzed buildings met the legally required primary energy value (<70 kWh/m2/year) when using natural gas as a heat source. Applying more realistic DHW consumption values resulted in more accurate energy certifications.

Explicit higher-order schemes for molecular dynamics problems

Рассмотрены явные симплектические разностные схемы Рунге–Кутты–Нистрема (RKN) с числом стадий от 1 до 5 для численного решения задач молекулярной динамики, описываемых системами с распадающимися гамильтонианами. Для числа стадий 2 и 3 параметры RKN-схем получены с помощью техники базисов Гребнера. Для числа стадий 4 и 5 новые схемы най дены с применением метода численной оптимизации Нелдера–Мида. В частности, для числа стадий 4 получены четыре новые схемы. Для числа стадий 5 получены три новые схемы в дополнение к четырем схемам, известным в литературе. Для каждого конкретного числа стадий найдена схема, являющаяся наилучшей с точки зрения минимума ведущего члена погрешности аппроксимации. Верификация схем осуществлена на задаче, имеющей точное решение. Показано, что симплектическая пятистадийная RKN-схема обеспечивает более точное сохранение баланса полной энергии системы частиц, чем схемы более низких порядков точности. Исследования устойчивости схем выполнены с помощью программного пакета Mathematica. The Runge–Kutta–Nyström (RKN) explicit symplectic difference schemes are considered with a number of stages from 1 to 5 for the numerical solution of molecular dynamics problems described by systems with separable Hamiltonians. For the numbers of stages 2 and 3, the parameters of the RKN schemes are obtained using the Gröbner basis technique. For the number of stages 4 and 5, new schemes were found using the Nelder–Mead numerical optimization method. In particular, four new schemes are obtained for the number of stages 4. For the number of stages 5, three new schemes are obtained in addition to the four schemes, which are well-known in the literature. For each specific number of stages, a scheme is found being the best in terms of the minimum of the leading term of the approximation error. Verification of the schemes is carried out on a problem that has an exact solution. It is shown that the symplectic five-stage RKN scheme provides a more accurate conservation of the total energy balance of the particle system than schemes of lower orders of accuracy. The stability studies of the schemes were performed using the Mathematica software package.

Transient Energy Models of Housing Facilities Operation

Buildings are the main consumer of energy resources in the total energy balance of the countries in Central and Eastern Europe, the main energy consumption is allocated for heating. Efficient use of energy resources for heating needs to a large extent depends on the efficiency of regulation of heating systems. In the article, dynamic mathematical models of a two-room typical apartment in Ukraine, built in 2016, were developed in Matlab and EnergyPlus software environment. The simulations were carried out using IWEC hourly climate data for the city of Kyiv. The results of simulations of thermal energy consumption in Matlab are characterized by a larger range of fluctuations of the heating system load, which is typical for the real operating conditions of the system with the controller of ON/OFF type. In EnergyPlus it is assumed that the gas boiler operates continuously in the ON mode. In the research, the change of load on the apartment heating system was studied at different numbers and locations of air temperature control sensors installation, according to which the controller of the autonomous gas boiler operates.

Prospects for Reducing the Negative Anthropogenic Impact on the Environment as a Result of the Development of Renewable Energy in the Russian Regions

The publication analyzes the anthropogenic impact of renewable (alternative) energy on the environment by assessing its specific material intensity. A specific feature of alternative energy, there is practically no emissions and discharges into the environment, however, the construction of power plants and their operation can significantly change the existing material flows in the geographic shell of the Earth, which in the future inevitably leads to the degradation of natural geosystems. This requires the use of a special criterion for assessing the material intensity of the specified sector of the economy. To analyze the material intensity, the criterion of total Material Input – numbers was used, which allows the entire set of natural resources to be presented as a single value, and thus to compare the energy operating on fossil fuels and power plants of renewable energy. At this point in time, the share of alternative energy in the total energy balance of the country is small, amounting to 0.14%, however, a number of scenarios assume its significant increase in the future period of time. The study was based on a hypothetical scenario of complete replacement of traditional energy with alternative energy sources. It has been established that this will reduce the level of material intensity of the Russian energy sector by 6.93 times. In 31 Russian regions, this value will be higher than the national average, and the reduction in the specific material intensity of the industry will reach values from 7.00 to 32.67 times, which will significantly reduce the anthropogenic impact of this economic sector on natural geosystems. A particularly high effect is expected in the regions with developed coal energy and included in the Ural, Siberian and Far Eastern federal districts. The conclusion is that the replacement of traditional energy with alternative energy will significantly reduce the anthropogenic impact of this sector of the economy due to a decrease in material intensity.

Investigation of Correlation Between Process Energy Balance and Phase Shift Variation of Chatter Vibration in Spindle Speed Variation

It is widely known that the spindle speed variation (SSV) is an effective technology for chatter suppression, especially in the turning or boring process. Its simple optimal design, however, is not a simple task. In the past, certain research works considered the chatter onset from the perspective of process energy balance in a vibration cycle. The phase shift between previous (i.e., outer modulation) and present vibrations (i.e., inner modulation) of chatter is a key factor in the process energy balance. The SSV can be conceptually interpreted as a technique that continuously perturbs the phase shift between the inner and outer modulations, thereby changing the process energy balance. Simply put, the chatter energy can be controlled by applying the SSV to suppress the chatter. This study investigates the correlation between the process energy balance and phase shift behavior in the sinusoidal SSV through numerical energy simulation. The results indicate that the phase shift at the maximum spindle speed is an important factor to minimize the total energy balance (i.e., to dissipate the chatter energy) in the SSV cycle. This probably corresponds to the fact that the beat vibration tends to occur near the maximum spindle speed in the SSV. The insights gained from this study are anticipated to serve as a guideline for shaping the phase shift profile in the SSV to effectively suppress chatter vibration.

Synthesis of the law of optimal control of the system of active dynamic stabilization of the movement of a self-propelled vehicle with a mounted working body

The paper is devoted to the development of systems and technical devices for reduction of dy-namic loads acting on operators and the supporting system of self-propelled vehicles. The goal of the paper is to develop an algorithm and a law of optimal control of the stabilization system. The set of tasks to be solved for this is determined, the requirements for the information field are highlight-ed, the element base of the stabilization system is substantiated. The problem of optimal control of the stabilization system is formulated. The development of a law of control of the stabilization sys-tem of the movement of self-propelled wheeled vehicles based on the principle of active inertial vi-bration damping is presented. The law of optimal control of the stabilization system with the possi-bility of correcting the requirements for attenuation and the type of transient process was developed. On the basis of quadratic integral criteria, the indicators for assessing the quality of system control are distinguished. It is substantiated that for the system of stabilization of the harvester body it is necessary to regulate the output variables, such as the angular velocity of the body and the angle of the longitudinal inclination of the harvester body. A linearized model of the longitudinal-angular motion of the combine is considered, the equations that connect the laws of the disturbed motion of the body and the law of optimal control are presented. With the help of simulation modeling, the effectiveness of the proposed stabilization method and the law of control of the stabilization system in terms of reducing the longitudinal angles of inclination of the body when driving on an asphalt-concrete highway and a dirt road are shown. The effectiveness of the proposed law of control for suppressing the pitch of the combine body during emergency braking is shown. The calculated values of the power spent on control of the stabilization system for the considered driving modes are given. On the basis of calculations, it is shown that in the total energy balance of the combine, the power consumption for control is insignificant, which confirms the efficiency of the proposed stabilization method and the law of control. Conclusions are drawn, stages and directions of further research are determined.