Flow Distribution Problem Research Articles

Optimal Power Flow Calculation Based on Improved Crossover Algorithm

Abstract Aiming at the optimization problem of power flow distribution in power system, this paper puts forward a method for calculating the optimal power flow of power network based on the improved crisscross algorithm. The fast convergence crisscross optimization algorithm (FCSO) is based on the traditional crisscross optimization algorithm (CSO) to improve the efficiency and accuracy of solving the Optimal Power Flow, OPF) problem. Based on the original double crossover operator, the improved algorithm puts forward a brand-new operator-central crossover operator, which alternates with transverse crossover operator according to certain rules, In order to improve the quality of single search and accelerate convergence, each individual in the population performs crossover operation with the current optimal individual in turn, and then performs competition operator to selectively approach the current global optimal individual. Finally, combined with experimental verification, the optimal power flow calculation of reactive power optimization based on FSCO has obvious practical effects in improving network voltage quality and reducing line loss, The average voltage increase ratio of 220kV bus and 110kV bus is 0.676% and 0.855% respectively, and the loss reduction rate reaches 3.51%, Compared with CSO, the convergence and calculation speed of FSCO proposed in this paper is faster, the convergence curve is smoother, and the average time consumption is increased to 59.53% compared with CSO, In the case of obtaining the same precision solution, the optimization time is obviously shortened, the timeliness of the optimal solution in regulation operation is effectively improved, and the problem of reactive power optimization in power system can be well solved.

Multi-Split Configuration Design for Fluid-Based Thermal Management Systems

Abstract High power density systems require efficient cooling to maintain their thermal performance. Despite this, as systems get larger and more complex, human expertise and insight may not suffice to determine the desired thermal management system designs. To this end, a framework for automatic architecture exploration is presented in this article for a class of single-phase, multi-split cooling systems. For this class of systems, heat generation devices are clustered based on their spatial information, and flow splits are added only when required and at the location of heat devices. To generate different architectures, candidate architectures are represented as graphs. From these graphs, dynamic physics models are created automatically using a graph-based thermal modeling framework. Then, an optimal fluid flow distribution problem is solved by addressing temperature constraints in the presence of exogenous heat loads to achieve optimal performance. The focus in this work is on the design of general multi-split heat management systems. The methods presented here can be used for diverse applications in the domain of configuration design. The multi-split algorithm can produce configurations where splitting can occur at any of the vertices. The results presented include three categories of problems and are discussed in detail.

Global supply chain flow planning for Chinese manufacturing under the BRI: An SFG-DRO method

The Belt and Road Initiative (BRI) has fostered the free flow of commodities and optimal distribution of resources for the global manufacturing supply chain (GMSC), meanwhile confronted with risks and uncertainties. This paper proposes the SFG-DRO method, which can well solve the flow distribution problem of GMSC under the BRI with uncertainties. The proposed method combines trend prediction from the stochastic frontier gravity (SFG) model with 1-Wasserstein fuzzy set-based distributionally robust optimization (DRO). Additionally, this paper integrates the principles of the column and constraint generation (C&CG) algorithm with the particle swarm optimization (PSO) algorithm to handle the above two-stage nonlinear problems efficiently. The results show that the SFG-DRO distribution method significantly reduces transportation costs by 25% and enhances security. By examining flow distribution across three key BRI channels, this paper identifies underexploited markets along the southward channel and substantial market potential with security risks along the northeast sea-land channel, proposing relevant improvement suggestions.

Conversion augmentation of an industrial NH3 oxidation reactor by geometry modification to improve the flow and temperature pattern uniformity using CFD modeling

BackgroundThe optimization of flow and temperature patterns in industrial reactors is crucial for achieving efficient and uniform chemical reactions. This study's major goals are to pinpoint possible areas for improvement in the NH3 oxidation reactor's performance and to deal with the problem of uneven flow distribution inside the reactor. MethodsIn this study, the reactor building design has been changed by extending the feed pipeline vertically and increasing the number of incoming feed streams in order to achieve uniformity in the property distribution on the catalyst surface of an industrial NH3 Oxidation reactor. Thus, using the CFD approach and the finite volume method, a three-dimensional model has been suggested. The results are contrasted with the actual geometrical configuration. The property alteration along the catalyst surface and the reactor length have been assessed. Significant findingsBy expanding the feed pipeline, the flow pattern at the reactor entry is fully developed and becomes uniform. As a result, NO2 production could go up by as much as 11 %. The rates of NH3 conversion, NO yield, and HNO3 generation consequently increased by 12.5 %, 3.1 %, and 8.0 %, respectively. Additionally, this alteration results in a uniform distribution of temperature and pressure across the catalytic surface, prolonging the lifetime of the catalyst. The pressure and temperature difference over the surface of the catalyst with the original reactor configuration was also found to be approximately 250 Pa and 423.15 K, according to the data. Pressure and temperature difference were reduced to 15 Pa and 273.15 K, respectively, as the feed line's length was increased at the same time.

Numerical Simulations of Carbon-Fibre Impregnation with a Polymer as an Anisotropic Permeability Medium.

The impregnation process of carbon fibres with polymers is challenging to model due to the system's complexity, particularly concerning the following aspects: the complex rheology of the polymeric matrices and the presence of solid, continuous fibres, both with anisotropic properties, and the interaction between solid and fluid, which can change the displacement of fibres into a cyclic dependence. In this work, an interesting approach was considered by setting the fibres as a porous medium whose properties were calculated with microscale/macroscale cycle modelling. In the microscale modelling stage, two main assumptions can be made: (i) a homogeneous distribution with a representative cell or (ii) a stochastic distribution of fibres. The solution to the abovementioned flow and fibre distribution problem can severely differ with only a slight change in a single parameter for a given set of processing parameters. Therefore, the influence of some of them during the fibre impregnation process was evaluated, allowing a shortcut for the polymer through a gap between fibres and the bottom wall of the extrusion die. The range of investigated values regarding the gap enables one to cover good impregnation conditions up to the occurrence of the shortcut and consequent poor impregnation quality. These studies were performed with numerical simulations with circa 126,000 degrees of freedom, considering the discretisation mesh elements and the unknowns (pressure and two velocity components).

An Analytical Model Coupled with Orthogonal Experimental Design Is Used to Analyze the Main Controlling Factors of Multi-Layer Commingled Gas Reservoirs

The majority of China’s multi-layer low permeability tight gas reservoirs are currently being extracted through the method of multi-layer co-production. However, due to the significant disparity in physical properties and varying degrees of pressure depletion among the production layers, elucidating the primary factors influencing the productivity contribution of each gas layer remains challenging. A multi-factor analytical model is proposed for commingled gas wells with multiple layers. An unstable model is established for the production of commingled layers, and the problem of flow distribution is addressed using the Duhamel convolution principle. The Laplace transform is subsequently employed to derive the solution in the Laplace domain, which can be inverted utilizing the Stehfest inversion algorithm to obtain a real-time domain solution. The influence of reservoir factors on the stratification contribution rate has been comprehensively analyzed, encompassing permeability, porosity, initial pressure, drainage radius, and layer thickness. The orthogonal test design was employed to conduct range analysis and variance analysis separately, yielding the primary and secondary order as well as influence weight of the five factors. The findings demonstrate that, within this gas reservoir, the discharge radius, thickness, and porosity are identified as the primary factors influencing gas well productivity. Furthermore, seven horizontal flow charts illustrating the double-layer gas reservoir and five horizontal flow charts depicting single-factor variations in the double-layer gas reservoir were constructed. These charts provide a clear visualization of the impact of each reservoir factor on stratification’s contribution rate. In contrast to previous studies, this novel approach presents a comprehensive optimization framework that ranks the influence weights of individual factors and identifies the most significant factors impacting multi-layer gas reservoirs. The presented method also serves as a foundation for the subsequent selection of multi-layer gas reservoirs, formulation of gas well stimulation measures, and efficient development.

Application of methods for modeling hydraulic and non-isothermal steady states of gas transmission systems

In the article, for the first time, an attempt was made to justify the effectiveness of the application of new generalized methods of the theory of hydraulic circuits for modeling stationary modes of operation of gas transmission systems of complex structure and configuration. A classification of the main models of a steady gas flow is given for individual elements of the system, including traditional ones, those implicitly specified in terms of flow rate and dependent on the pressure of the working medium. Generalized flow distribution models are proposed that take into account all these cases. Conditions for the applicability of generalized methods that ensure the existence and uniqueness of the solution to the flow distribution problem are considered. The characteristics of these methods and final algorithms are given, which provide confident convergence and require less computational costs compared to existing methods. Numerical examples illustrating such possibilities are given.

Improving transport logistics of extractive industry products in the context of capacity constraints on the railways

Purpose. To improve the distribution methods of freight flows on the railway network under conditions of capacity constraints. Methodology. Methods of railway operation theory and operations research were used. The problem of cargo flow distribution on the railway network was solved as a multi-product (interchangeable cargoes) transport linear programming problem with capacity constraints in the network form. The average cost of freight transportation is established by the methods of probability theory. Findings. In the course of the research the methods of cargo traffic calculation on the railway network are improved. The proposed approach to the formalisation of the task makes it possible to take into account the presence of different cargoes to be transported, capacity constraints of some railway network sections, as well as non-linear nature of dependence between the volume and cost of transportation. To meet the requirement of consignors equal access to public carrier services, the method for calculating the cost of transportation for an individual consignor is improved. Originality. Scientific novelty of the paper consists in improvement of methods of cargo traffic distribution on the railway network and tariffing of cargo transportation services in conditions of restricted supply capacity of separate sections. Practical value. The extractive industries have a steady flow of goods. The main logistic tasks in this case are to ensure transportation of the given volume of cargo and reduce the cost of transport services. Using the proposed mathematical methods of optimization allows you to get higher-quality solutions compared to the method of technical-economic comparison of options, which provides an overall cost reduction for cargo transportation. The improved method of tariffication of transportation can reasonably allocate the savings from reducing the cost of transportation among cargo consignors and thus reduce their logistics costs.

Optimization of an air-cooled battery module with novel cooling channels based on silica cooling plates

Introduction of additional media for battery thermal management system can improve the thermal management performance. In particular, silica cooling plate is the flexible media which could avoid unwanted collisions applied into battery module. In this paper, a novel U-type parallel air-cooled battery module is proposed by constructing cooling channels with silica cooling plates. Firstly, a three-dimensional coupled model with validated battery heat generation term is established to calculate the distribution of flow and temperature fields of battery module. During the operating process, silica cooling plates could not only act as the heat sink/conductor to improve the cooling performance, but also form the channels to change the airflow paths for uniformity problem of flow distribution. Compared with the traditional U-type parallel air-cooled module, the largest average temperature of the battery cell is reduced by 10.00 K, and the temperature difference of the battery module is reduced from 4.29 K to 1.84 K, with a decreasing rate of 57%. To further improve the module temperature uniformity, a tapered inlet manifold contracted from the center to both sides is designed. Moreover, a flow baffle structure is performed by extending downward the silica cooling plates in cooling channels. The flow distribution in the latter part of the channels is improved remarkably by using the developed structure design after the module optimization. The results show that for the module with the tapered inlet manifold and flow baffles, the module with 3 flow baffles and 6 mm in extension length achieves the best module temperature uniformity. The temperature difference of the battery module decreases to 0.61 K, which is further reduced by 67% compared with the original module combined with silica cooling plates. The proposed air-based method with novel cooling channels would provide a new insight for the design of battery thermal management in the future.

A Calculation Method of Passenger Flow Distribution in Large-Scale Subway Network Based on Passenger-Train Matching Probability.

The ever-increasing travel demand has brought great challenges to the organization, operation, and management of the subway system. An accurate estimation of passenger flow distribution can help subway operators design corresponding operation plans and strategies scientifically. Although some literature has studied the problem of passenger flow distribution by analyzing the passengers’ path choice behaviors based on AFC (automated fare collection) data, few studies focus on the passenger flow distribution while considering the passenger–train matching probability, which is the key problem of passenger flow distribution. Specifically, the existing methods have not been applied to practical large-scale subway networks due to the computational complexity. To fill this research gap, this paper analyzes the relationship between passenger travel behavior and train operation in the space and time dimension and formulates the passenger–train matching probability by using multi-source data including AFC, train timetables, and network topology. Then, a reverse derivation method, which can reduce the scale of possible train combinations for passengers, is proposed to improve the computational efficiency. Simultaneously, an estimation method of passenger flow distribution is presented based on the passenger–train matching probability. Finally, two sets of experiments, including an accuracy verification experiment based on synthetic data and a comparison experiment based on real data from the Beijing subway, are conducted to verify the effectiveness of the proposed method. The calculation results show that the proposed method has a good accuracy and computational efficiency for a large-scale subway network.

Topography optimisation of fluid flow between parallel plates of spatially-varying spacing: revisiting the origin of fluid flow topology optimisation

This paper presents a topography optimisation model for fluid flow with varying channel height. First, the origin of topology optimisation for fluid flow problems is revisited. Here, a Poiseuille-based frictional resistance term was first introduced by Borrvall and Petersson (Int J Numer Methods Fluids 41(1):77–107, 2003) to parametrise regions of solid and fluid. However, the traditional model only works for true topology optimisation, where it is used to approximate solid regions as areas with very small channel height and, thus, very high frictional resistance. Herein, it is shown that if the channel height is allowed to vary continuously, the minimum channel height is relatively large and/or meaning is attributed to intermediate design field values, then the predictions of the traditional model are wrong. To remedy this problem, this work introduces an augmentation of the mass conservation equation to allow for continuously varying channel heights. The proposed planar model describes fully developed flow between two plates of varying channel height. It allows for a significant reduction in the number of degrees of freedom, while generally ensuring a high accuracy for low-to-moderate Reynolds numbers in the laminar regime. The accuracy and limitations of both the traditional and proposed models are explored using in-depth parametric studies. The proposed model is used to optimise the height of the fluid channel between two parallel plates and, thus, the topography of the plate surfaces for a flow distribution problem. Lastly, it is shown that when introducing penalisation into the proposed height-based design parametrisation, the proposed model can produce designs of similar performance as the traditional resistance term interpolation. Thus, the proposed model bridges a gap between topography and topology optimisation of fluid flow, since it is able to perform both seamlessly with good accuracy.

Development of an information system and software for effective building evacuation plan

The main goal of the work is to create the optimal emergency evacuation plan in general education institutions according to the schedule at a certain time. The work developed an information model of the evacuation system, taking into account the schedule of classes and classrooms. The methodology of the system approach, which ensures the compatibility of heterogeneous devices to find an operationally optimal evacuation plan in real time, was developed. A conceptual scheme of an evacuation system using heterogeneous sources of receiving and transmitting information about emergencies is proposed. Determined the input and output sources of receiving and transmitting information about the number of people in the building. Developed software for the rapid and most effective evacuation of people from the educational institution and can be used for other types of buildings. The importance of this work is the creation of an integrated evacuation information system based on mathematical modeling of multi-criteria optimization problem of flow distribution and design, construction technology receiving and transmitting data and information notification systems for the selected type of building. in order to adopt an operational evacuation plan. The results of this paper allow the systematic organization of evacuation training, preparing resources so that in the event of an emergency it is possible to quickly respond and conduct the evacuation process to avoid major consequences. The use of information technology greatly increases the efficiency of evacuation systems, so the development of new integrated and intelligent info-communication approaches to solve the problem of evacuation is currently very relevant

Dynamic regulation method of distributed generation in distribution network under 5G network

Aiming at the problem of uneven power flow distribution caused by distributed power supply access, which leads to high voltage deviation and active network loss, a dynamic control method of distributed power supply in 5G network is proposed. The distributed topology structure of the distribution network under 5G network is generated, and the static topology information is extracted to establish the power partition. The distribution network in each area is connected to its own bus through different feeders. The distribution network reconstruction period is divided in the partition, and the network reconstruction period and the corresponding switch action scheme are determined. The state of distributed power supply was estimated according to reconstruction period and active/reactive power balance index, and the stability of dynamic control was determined. Based on the stability control, the dynamic control model of distributed power supply is established, and the network voltage can reach the preset target by adjusting the power of power switch. The simulation results show that the average voltage deviation of the proposed control method is 1.976, which is 4.431 and 3.783 lower than those based on data drive and flexible load regulation, respectively. The active power network loss of the control method in this paper is 0.342 MW, which is 0.385 MW and 0.346 MW lower than that of the control method based on data drive and flexible load regulation, respectively. Therefore, this method can improve the absorption capacity of distributed power supply and promote the power flow reciprocity of distribution network.

Energy management strategy for FCEV considering degradation of fuel cell

ABSTRACT The energy management strategy (EMS) is a key technology to improve the economy and durability of fuel cells. To overcome the shortcomings of most existing strategies, a novel EMS based on game theory is proposed. The power flow modes are mainly divided into four modes, and the power flow distribution problem is modeled as a noncooperative game problem. Different preferences of the power sources are quantified through their individual utility functions. The Nash equilibrium is used to balance the different preferences of the independent power sources. The proposed EMS contributes to better performance in three areas: energy economy, maintaining ultracapacitor state of charge (SOC), and durability of fuel cell. According to the results, compared with the fuzzy control strategy and the power follow strategy, the equivalent hydrogen consumption of the proposed strategy is reduced by 7% and 4.57%, respectively, and the durability of the fuel cell is improved by 125% and 21.8% under the WLTP driving cycle.

Marketing Resource Allocation Strategy Optimization Based on Dynamic Game Model

Game theory has become an important tool to study the competition between oligopolistic enterprises. After combing the existing literature, it is found that there is no research combining two‐stage game and nonlinear dynamics to analyze the competition between enterprises for advertising. Therefore, this paper establishes a two‐stage game model to discuss the effect of the degree of firms’ advertising input on their profits. And the complexity of the system is analyzed using nonlinear dynamics. This paper analyzes and studies the dynamic game for two types of application network models: data transmission model and transportation network model. Under the time‐gap ALOHA protocol, the noncooperative behavior of the insiders in the dynamic data transmission stochastic game is examined as well as the cooperative behavior. In this paper, the existence of Nash equilibrium and its solution algorithm are proved in the noncooperative case, and the “subgame consistency” of the cooperative solution (Shapley value) is discussed in the cooperative case, and the cooperative solution satisfying the subgame consistency is obtained by constructing the “allocation compensation procedure.” The cooperative solution is obtained by constructing the “allocation compensation procedure” to satisfy the subgame consistency. In this paper, we propose to classify the packets transmitted by the source nodes, and by changing the strategy of the source nodes at the states with different kinds of packets, we find that the equilibrium payment of the insider increases in the noncooperative game with the addition of the “wait” strategy. In the transportation dynamic network model, the problem of passenger flow distribution and the selection of service parameters of transportation companies are also studied, and a two‐stage game theoretical model is proposed to solve the equilibrium price and optimal parameters under Wardrop’s criterion.

Reengineering the “Oil and Gas of Russia” Software to Meet the Requirements of Current Resilience Studies in the Gas Industry

Research into energy models often has to rely on the functionality provided by legacy software that cannot correctly satisfy the needs of the researcher due to the request to perform tasks that were not provided by the developer during the creation of these products. To solve these problems, reengineering of legacy software is used. In particular, it was decided to reengineer software to solve the problem of flow distribution in the gas transmission system (GTS) and find bottlenecks in it with the aid of geographic information technology. The main disadvantages of the legacy software were the inability to add a new calculation scheme or modernize it, and the inability to use geocode. The reengineering methods applied involve: 1) analysing legacy software for module connectivity; 2) choosing a framework with the capability to develop geographic information systems; 3) reworking the architecture of the software module to implement the function of adding objects of the calculation model; 4) integrating software with an embedded database management system for compactness and the ability to save changes made. These solutions made it possible to update the software and give the researcher a convenient tool for creating and correcting calculation schemes using geographic information technologies for help. Geocoding support enables the expansion of the existing energy models by adding objects based on the data provided by geographic information services for the requested tag and the research to determine new optimal solutions for transporting energy resources.

Modelling and optimization of integrated distributed flow shop scheduling and distribution problems with time windows

Production and distribution are two essential activities in supply chain management. Currently, integrated production and distribution problems receive much attention because decision-makers devote to improving the operation efficiency of both stages and try to achieve an optimal solution. This work proposes an integrated distributed production and distribution problem with consideration of time windows, in which a set of jobs (i.e., customer orders) needs to be assigned among factories and the jobs are processed on flow shop environments at their associated factories. Then, the completed jobs are delivered by capacitated vehicles to customers in different regions while satisfying given time windows as much as possible. Accordingly, to optimally solve the proposed problem, a mixed integer programming model with minimizing total weighted earliness and tardiness has been established. For the optimization task, an enhanced brain storm optimization algorithm with some particular strategies is designed to handle the considered problem. To assess the performance of the proposed optimization method, several experiments by adopting a set of benchmark test problems are performed, and state-of-the-art optimizers are chosen for comparisons. The obtained optimization results exhibit that the designed algorithm significantly outperforms its rivals and can be considered as an excellent optimizer for solving the studied problem. Besides, compared with the CPLEX solver, the designed optimizer also performs much better for solving large-size problems.

IMPROVING THE DESIGNING METHOD OF THERMAL NETWORKS: SERIAL CONNECTION OF STREAMS

The paper presents an approach to the design of technical systems, the elements of which are interconnected and carry out an internal exchange of energy. The above analysis showed that for heat-exchange equipment when combining devices into systems, only iterative methods are currently used, a representative of which is Pinch analysis.A limitation of the iterative approach is the impossibility of obtaining an exact solution to such problems, which can only be achieved by analytical methods, which also make it possible to reveal some effects in systems that are practically unavailable for numerical solution. This indicates the absence of a rigorous proof of the existence of a solution and a problem in the construction of approximate solutions, due to the need to involve complementary hypotheses.The topological representation of the system modules allows us to consider the architecture as a network, which contributes to the analysis of the connections between the constituent elements and the identification of their mutual influence. Highlighted the typical connections of network elements such as serial, parallel, contour, which allows to unify the principles of building connections in the system. As an optimality criterion, the NTU parameter was chosen, which includes the heat exchange surface and is usually used when searching for a solution for heat exchangers of moving objects.An analytical solution to the problem of flow distribution and energy exchange efficiency in a system of two series-connected heat exchangers is obtained. His analysis showed that the formulation of the design problem based on the definition of matrix elements in relation to determinants allows not only to meet the requirements for the system, but also to determine the design parameters of its elements that satisfy their extreme characteristics.

Generalization of Methods for Calculating Steady-State Flow Distribution in Pipeline Networks for Non-Conventional Flow Models

This paper proposes generalized models and methods for calculating flow distribution in hydraulic circuits with lumped parameters. The main models of the isothermal steady-state flow of medium are classified by an element of the hydraulic circuit. These models include conventional, implicitly specified by flow rate, and pressure-dependent ones. The conditions for their applicability, which ensure the existence and uniqueness of a solution to the flow distribution problem, are considered. We propose generalized nodal pressure and loop flow rate methods, which can be applied regardless of the forms of specific element models. Final algorithms, which require lower computational costs versus the known approaches designed for non-conventional flow models, are substantiated. Proposed models, methods, algorithms, and their capabilities, are analytically and numerically illustrated by an example of a fragment of gas transmission network with compressor stations.

Research on double-layer model of cold chain Network based on Genetic Algorithm

Based on the self-run cold chain logistics model dominated by large chain supermarkets, this paper establishes a double-layer programming model of fresh agricultural products cold chain logistics network optimization model of large chain supermarkets. The upper model is the total cost optimization model of cold chain logistics network, which solves the location problem of distribution points and the optimization problem of vehicle path. The lower level model is the optimized model of customer time satisfaction, which solves the problem of supermarket flow distribution. Finally, an example is given and an improved genetic algorithm is used to solve the two-layer programming model, which proved the double-layer model has certain theoretical and practical significance.