Технические науки. Рубрика в журнале - Бюллетень науки и практики
Статья научная
The ship’s central cooling water system is one of the most important systems serving the main engine. With the progress of society, the design and construction of ships increasingly need to develop in the direction of environmental protection and energy-saving. Taking the 59,990 t bulk carrier as the research object , this paper proposes that based on the frequency conversion control of the seawater pump and supplemented by the energy-saving scheme of pulsation enhanced heat exchange, the frequency conversion control of the seawater pump is realized by adjusting the speed according to different working conditions. At this time, adding pulsation enhanced heat transfer technology can generate forced convection, increase the turbulence of the fluid in the tube, and introduce convection into the boundary layer, and at the same time produce cavitation, which can improve the heat transfer efficiency of the equipment. After using the seawater pump frequency conversion control and pulsation enhanced heat exchange program, the energy consumption is about 36% of that before the system was installed. The data shows that the program achieves the purpose of environmental protection and energy-saving and has a certain reference value for engineering research.
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Research on modeling and simulation of doubly fed induction wind turbine based on MATLAB/Simulink
Статья научная
This paper first introduces the structure of doubly fed wind power generation system and the working principle of doubly fed induction generator in detail and establishes the corresponding mathematical model of doubly fed wind power generation unit. The control part of wind power generation system based on doubly fed induction generator includes rotor side control and stator side control. The rotor side control adopts the vector control strategy based on stator flux orientation of the double-fed induction generator connected to the grid, and the working principle is analyzed in detail, and the main part of the simulation modeling is given. Stator side control adopts vector control strategy of grid-connected inverter control, and its working principle is analyzed in detail, and the main part of simulation modeling is also given. In order to verify the correctness and feasibility of the system, the simulation experiment platform of doubly fed wind turbine under this control strategy is built by using Matlab/Simulink simulation platform, and its simulation analysis is carried out in detail.
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Research on ventilation and heat dissipation performance of trailer power station
Статья научная
The results show that the use of CFD software to simulate the ventilation and heat dissipation of the trailer power station cabin, Get the flow field and temperature field in the cabin, The position of the highest temperature in the vehicle cabin can be determined quantitatively, which provides a useful reference for the design of the cabin structure of the trailer power station and the arrangement of the equipment in the vehicle. Moreover, the simulation results are in good agreement with the experimental results. It shows that the selected Realizable k-ε Turbulence Model can more accurately simulate the air flow field in the cabin of the trailer power station. It also shows that the model simplification method used in the calculation and the setting of analytical conditions are reasonable.
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Research progress of type P copper (I) oxide in the field of light energy utilization
Статья обзорная
Copper (I) oxide Cu2O, as a representative intrinsic P-type inorganic semiconductor material, has been widely used in the field of optical energy utilization, such as photovoltaic, photocatalysis, photodegradation and other fields, and has an extremely important position. For a long time, the literature on Cu2O’s application technology in the field of light energy utilization is relatively scattered and independent, resulting in a certain degree of obstacles and difficulties to obtain relevant technical knowledge and have a deep understanding of its internal principles. According to the application of Cu2O in the field of light energy utilization in recent years, it is mainly divided into three modules (photovoltaic, photocatalysis, photodegradation, photodegradation), and mainly summarizes the classification, principle and characteristics of Cu2O application in the field of light energy and prospects the optimization method and development direction of the application in the field of Cu2O light energy. This review aims to provide reference and guidance for the optical energy applications of Cu2O and other related inorganic oxide semiconductors.
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Review on nearest level modulation methods based on MMC
Статья научная
In view of the relevant situation of offshore wind power research, development and construction at home and abroad, as well as the energy crisis facing the world, we have ushered in a new opportunity and outbreak period for the development of new energy. Therefore, higher requirements are placed on the power supply, and the key technology for the design of offshore wind power flexible DC transmission high-power converters is proposed. The Modular Multi-level Converter (MMC) topology can only use a lower switching frequency to obtain higher power Waveform quality. The output voltage waveform can effectively reduce the switching loss and filter capacity and improve the efficiency and economy of the converter. Among them, the method based on Level Modulation (NLM) is usually the preferred method. This paper introduces the topology and working principle of the modular multilevel converter (MMC) in detail and describes the improved modulation method for NLM in detail. The advantages, disadvantages and application occasions of different improved modulation techniques are summarized, which provides a reference for the engineering application of MMC.
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Simplification and verification of o-xylene fuel mechanism
Статья научная
The increasing demand for energy due to economic globalization has led to the exploration of different types of fuels, including aromatic hydrocarbon fuels. Xylene is an essential aromatic hydrocarbon fuel and an important component of kerosene. This study employs the error propagation directed relationship diagram (DRGEP) and sensitivity analysis (SA) to simplify the reaction mechanism of o-xylene. The ignition delay time and laminar flame velocity predicted by the fuel mechanism under different w375orking conditions are compared with pre-simplified experimental data. The study proposes a mechanism consisting of 298 reactions and 64 components to describe the combustion reaction of xylene. The simplified mechanism's ability to reproduce experimental results is assessed, and the results reveal that the simplified mechanism effectively reproduces the experimental results, indicating its potential usefulness in practical applications. This study has significant implications for the development of more efficient and sustainable energy sources. By providing insights into the combustion behavior of xylene, researchers can develop more accurate models for predicting the performance of this fuel under a range of conditions. This, in turn, can inform the development of new technologies that can help meet the growing demand for energy in a more sustainable and environmentally friendly way. Overall, this study contributes to our understanding of the combustion behavior of xylene, highlighting its potential as a sustainable energy source and offering a potential avenue for further research in this field.
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Simulation analysis of non-concentric squeeze film damper
Статья научная
Squeeze film dampers are components that provide additional damping for rotating motors. In general, in order to achieve the best results of the squeeze film damper, it is necessary to appropriately increase the damping value, reduce the stiffness and set a reasonable eccentricity. In the process of designing the squeeze film damper, we can apply the rotor dynamics module of COMSOL software to model and simulate it, so as to achieve better simulation results and lay a foundation for the subsequent development and design of the product. In COMSOL software, in order to simplify the modeling of rotor components, we usually model squeeze film dampers based on the damping coefficient. The model calculates the damping coefficient for a short squeeze film damper and compares the results with the analytically calculated values. In addition, the damping coefficient depends on the position of the journal in the damper, i.e., the magnitude of the eccentricity. In this paper, by analyzing the dimensionless damping coefficient, bearing stiffness, journal displacement, and fluid load at different eccentricity, and plotting the fluid pressure distribution and the average oil film flow rate of the squeeze film damper, we can find the most suitable range of eccentricity and the damage-prone part of the damper, which can provide an important reference for the actual design of the squeeze film damper.
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Статья научная
The quality of the control system depends on various factors such as the characteristics of the controlled object, the control scheme, the form and size of interference, etc. In a control system where the characteristics of the object and the hardware and software have been basically determined, the control quality of the system depends on the control algorithm. The control algorithm will make the motion process control have better speed, accuracy and stability. The study of control law is an important part of the control system design of the entire six-degree-of-freedom test bench. The characteristics of the controlled object and the existence of interference in this control system require the designed control law to have the characteristics of strong robustness, certain intelligence, and easy implementation, so as to achieve stable and precise control of the system and achieve the control indicators required by the system. The control strategy of this six-degree-of-freedom test bench adopts Fuzzy PID control, which combines fuzzy theory with the mature traditional PID control theory and uses fuzzy theory to tune the three control parameters of PID to form a parameter self-tuning Fuzzy PID control Device. The Fuzzy PID control strategy is simulated by MATLAB simulation software.
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Simulation of ship trajectory in waves based on STAR-CCM+
Статья научная
The reliable ship motion trajectory signal provides a basis for six-degree-of-freedom test bench to simulate ship motion in waves. The characteristics of ship motion in waves were analyzed. Aiming at the problem of complex hull shape and large displacement at sea, the dynamic overlapping grid technique was used. Based on STAR-CCM+, the free surface was solved by CFD (Computational Fluid Dynamics) numerical simulation method. The numerical model of ship motion in waves was established, and the DFBI (Dynamic Fluid Body Interaction) method was used to simulate the ship motion in the waves. The ship’s motion trajectory was obtained in the regular and irregular heading waves, which provides important support for the six-degree-of-freedom test bench wave simulation system.
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Simulation of waste heat recovery from ship boiler exhaust gas
Статья научная
The heat pipe type waste heat recovery system can effectively reduce energy consumption when the ship is sailing in a polar region, so it has great engineering application value. In order to improve the design of the heat pipe waste heat recovery system and ensure that the design parameters meet the design requirements, this project has carried out a three-dimensional simulation analysis of the internal flow field of the heat pipe waste heat recovery system. Through reasonable model processing, application of boundary conditions, and the assignment of physical attributes the flow field characteristics of the key positions of the heat pipe type waste heat recovery system were obtained scientifically and effectively. The model was simulated and calculated, and the flue gas temperature distribution in the evaporator heat exchange tube, the overall temperature distribution of the waste heat recovery system, and the temperature change curve from the cold water entering the condenser to the steady state were obtained. The change curve of the thermal efficiency of the system during the temperature of the flue gas from the evaporator to the steady state.
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Статья научная
Recently, more and more scholars have devoted themselves to researching new methods of vibration reduction and noise reduction by manipulating the elastic waves in the structure to achieve the purpose of vibration reduction and noise reduction. To this end, a new type of ‘acoustic black hole’ structure is proposed, which reduces structural vibration while avoiding problems such as mass increase. In this paper, the vibration damping performance of the structure is mainly calculated by finite element software, and the energy concentration effect of the thin plate containing the acoustic black hole is verified by finite element analysis. A thin plate structure with four acoustic black holes is proposed. The calculation shows that the structure has obvious vibration reduction effect, and the vibration reduction effect can reach more than 20dB at high frequency.
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Smart counters for implementation in integrated smart grid
Статья научная
This article discusses the concept of Smart Grid and its elements, in particular, smart counters are considered that are an integral part of the intelligent power system, since these counters not only read the consumed electricity but also collect data, transmit and monitor information.
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Some specifications of diesel engine running on gaseous fuel
Статья научная
The paper dwells on the effectiveness the transition of diesel transport-energy equipment to the alternative gaseous fuel, as well as its specific design features. There is justified the possibility of the ignition of a gaseous fuel mixture through the assessment of dosing of the explosive charge, and its influence on the functioning of the process of a gas-air mixture combustion. There are also described the possible positive phenomena, which have sprung during the operation on gaseous fuel.
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South Caucasus transport corridor and potential for its development
Статья научная
The South Caucasus, as an energy-intensive region and transport corridor linking the markets of Asia and Europe, has long played an important strategic role in the trade, economic and political context of East-West relations. Within the framework of economic cooperation between the states of the Caucasus, the creation of a single automated information system for the customs control of transit is necessary for the exchange of information on goods and vehicles in real time. The implementation of these approaches will facilitate the effective utilization of transit potential of the South Caucasus Transport Corridor.
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Статья научная
Harnessing and further development of the transit potential of Georgia are closely linked to the country’s overall socio-economic development, effective use of its advantageous transport-geographical location and, in general, the successful functioning of the Eurasian transport corridor. The growth in the volumes of freight flows and increasing competitiveness in the transport corridor, along with other factors, depends on the effective work of customs services of the countries located across the corridors. The establishment and implementation of a Single Automated System of Customs Clearance and Control of Transit Goods will be a step forward in effective management and control of transit procedures, which will significantly reduce the time of customs clearance of transit goods and contribute to the reduction of financial costs of the economic operators.
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Study of a laboratory circuit with a warm baseboard in pulse mode
Статья научная
The increasing global energy demand is a problem that people have been paying attention to, people’s demand for energy is increasingly urgent, and improving energy efficiency has become a hot topic in this century. Studies have shown that pulsating flow has an important effect on heat transfer, and it has been concluded in most literatures that turbulent pulsation can enhance heat transfer in different degrees. Pulsation heat transfer is a comprehensive heat transfer process, and the best heat transfer performance can be achieved only when the thermal resistance of each part is reasonably coordinated. Based on the principle of hydraulic shock, this paper develops a device with warm substrate which can be used to increase the pulsating pressure and enhance the heat transfer efficiency of pulsating flow. Firstly, the construction scheme of the experimental device is proposed, and the working principle of the experimental device is described in detail. The complex impedance, frequency function, amplitude-frequency characteristic and phase-frequency characteristic are obtained by mathematical transformation of power supply circuit. Finally, the frequency response of the circuit is constructed.
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Study of dynamic characteristics of clay solution under the influence of vibration
Статья научная
It is known that with the help of a vibrating sieve for vibration separation (separation) of a clay solution, the following technological problems are solved: cleaning the clay solution from drilled rocks and separating it into fractions, i.e. sorting. Signs of separation of drilled rocks from clay solution using vibration are the size of the drilled rocks, the shape and density of the clay solution itself, etc. It has been shown that in order to improve the basic technological characteristics of the vibrating sieve, it is necessary to study the behavior of the clay solution in the vibrating sieve.
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Study on heat transfer performance of non-integral capillary core sintered uniform plate
Статья научная
This paper mainly introduces the sintering process of the monolithic capillary wick and analyzes the influence of different copper powder particle size, filling rate, copper powder shape and heat source size on the heat transfer performance of the isothermal plate. The experimental results show that: (1) For the isothermal plate sintered with spherical copper powder, the capillary force of large particle size copper powder is small, but the flow resistance is also small, and the performance of the isothermal plate sintered with large particle size copper powder is better. (2) In the case of low filling rate, the isothermal plate is dried due to insufficient return fluid. In the case of high filling rate, on the one hand, the thickness of the liquid film at the evaporation end of the isothermal plate is large, resulting in additional thermal resistance. On the other hand, the thin film evaporation mode will be transformed into pool boiling mode, which will reduce the heat transfer performance. (3) Spherical copper powder sintered plate with regular shape has the best performance, while dendritic copper powder sintered plate has relatively high thermal resistance. (4) The heat source area has a great influence on the thermal resistance of the plate. Under the same heating power, the thermal resistance of the small area heat source is much higher than that of the large area heat source; The thermal resistance of sintered copper plate is lower than that of pure copper plate under two heat source areas.
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Study on the effect of diaphragm booster on the pulsed heat transfer of cooling system
Статья научная
This paper has developed a diesel engine cylinder liner and cooling water heat exchange enhancement device, including diesel engine cylinder liner, cylinder liner water cooler, hydraulic accumulator, check valve, diaphragm booster, centrifugal water pump, pulse valve and Conical tube. As well as the pulsating circulation system and booster system composed of equipment. The device heats the heat generated by the diesel engine cylinder liner in a pulsating circulation system through a cylinder circulator in a pulsating circulation system to exchange heat with the external low-temperature seawater. By controlling the opening and closing of the pulsating valve in the pulsating circulation system, fluid is generated in the pipe. Pulsing and hydraulically impacting the diaphragm booster connected near the pulsation valve pipeline, the fluid at the outlet of the diaphragm booster is subjected to hydraulic shock and circulates in a closed booster circuit connected to the diaphragm booster and passes through the cone during the flow...
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Test of the layout of the correction circuit with a plate heat exchanger
Статья научная
Pulse enhanced heat transfer technology is introduced, and a plate heat exchanger is designed. A pulsating valve is installed at the outlet of the heat exchanger to pulsate the heat medium. Pulsating and non-pulsating heat transfer tests are carried out on the same heat exchanger. On the basis of experiments, the effective temperature difference, heat flow and convective heat transfer coefficient of the heat exchanger at different pulse frequencies are analyzed by combining the theory of pulse enhanced heat transfer technology, heat transfer capacity, heat flow and convective heat transfer coefficient. Find the relationship between pulsation frequency of heat transfer effect of heat exchanger. The experimental results show that the heat exchanger has high heat transfer efficiency under the experimental conditions when there is pulsation.
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