Records with Subject: Modelling and Simulations
Showing records 1 to 25 of 96. [First] Page: 1 2 3 4 Last
One-Dimensional Modeling of an Entrained Coal Gasification Process Using Kinetic Parameters
Moonkyeong Hwang, Eunhye Song, Juhun Song
November 16, 2018 (v1)
Keywords: coal gasification, entrained flow, equilibrium model, kinetic parameters, parameter studies, reactor model
A one-dimensional reactor model was developed to simulate the performance of an entrained flow gasifier under various operating conditions. The model combined the plug flow reactor (PFR) model with the well-stirred reactor (WSR) model. Reaction kinetics was considered together with gas diffusion for the solid-phase reactions in the PFR model, while equilibrium was considered for the gas-phase reactions in the WSR model. The differential and algebraic equations of mass balance and energy balance were solved by a robust ODE solver, i.e., an semi-implicit Runge⁻Kutta method, and by a nonlinear algebraic solver, respectively. The computed gasifier performance was validated against experimental data from the literature. The difference in product gas concentration from the equilibrium model, and the underlying mechanisms were discussed further. The optimal condition was found after parameter studies were made for various operating conditions.
Simulation of Wind Speed in the Ventilation Tunnel for Surge Tanks in Transient Processes
Jiandong Yang, Huang Wang, Wencheng Guo, Weijia Yang, Wei Zeng
November 16, 2018 (v1)
Keywords: hydroelectric power plants, numerical simulation, surge tank, transient process, ventilation tunnel, wave superposition, wind speed
Hydroelectric power plants’ open-type surge tanks may be built in mountains subject to the provision of atmospheric air. Hence, a ventilation tunnel is indispensable. The air flow in the ventilation tunnel is associated with the fluctuation of water-level in the surge tank. There is a great relationship between the wind speed and the safe use and project investment of ventilation tunnels. To obtain the wind speed in a ventilation tunnel for a surge tank during transient processes, this article adopts the one-dimensional numerical simulation method and establishes a mathematical model of a wind speed by assuming the boundary conditions of air discharge for a surge tank. Thereafter, the simulation of wind speed in a ventilation tunnel, for the case of a surge tank during transient processes, is successfully realized. Finally, the effective mechanism of water-level fluctuation in a surge tank and the shape of the ventilation tunnel (including length, sectional area and dip angle) for the... [more]
Numerical Investigation of a Tuned Heave Plate Energy-Harvesting System of a Semi-Submersible Platform
Kun Liu, Haizhi Liang, Jinping Ou
November 16, 2018 (v1)
Keywords: heave plate, semi-submersible, tuned mass damper (TMD), Wave Energy, wave energy converter
A novel tuned heave plate energy-harvesting system (THPEH) is presented for the motion suppressing and energy harvesting of a semi-submersible platform. This THPEH system is designed based on the principle of a tuned mass damper (TMD) and is composed of spring supports, a power take-off system (PTO) and four movable heave plates. The permanent magnet linear generators (PMLG) are used as the PTO system in this design. A semi-submersible platform operating in the South China Sea is selected as the research subject for investigating the effects of the THPEH system on motion reduction and harvesting energy through numerical simulations. The numerical model of the platform and the THPEH system, which was established based on hydrodynamic analysis, is modified and validated by the results of the flume test of a 1:70 scale model. The effects of the parameters, including the size, the frequency ratio and the damping ratio of the THPEH system, are systematically investigated. The results show t... [more]
Experimental and Numerical Studies of a High-Head Francis Turbine: A Review of the Francis-99 Test Case
Chirag Trivedi, Michel J. Cervantes, Ole G. Dahlhaug
November 16, 2018 (v1)
Keywords: computational fluid dynamic (CFD), Francis turbine, hydropower, pressure, turbulence, uncertainty, velocity
Hydraulic turbines are widely used to meet real-time electricity demands. Computational fluid dynamic (CFD) techniques have played an important role in the design and development of such turbines. The simulation of a complete turbine requires substantial computational resources. A specific approach that is applied to investigate the flow field of one turbine may not work for another turbine. A series of Francis-99 workshops have been planned to discuss and explore the CFD techniques applied within the field of hydropower with application to high-head Francis turbines. The first workshop was held in December 2014 at the Norwegian University of Science and Technology, Norway. The steady-state measurements were conducted on a model Francis turbine. Three operating points, part load, best efficiency point, and high load, were investigated. The complete geometry, meshing, and experimental data concerning the hydraulic efficiency, pressure, and velocity were provided to the academic and indu... [more]
Effects of Reynolds Number on the Energy Conversion and Near-Wake Dynamics of a High Solidity Vertical-Axis Cross-Flow Turbine
Peter Bachant, Martin Wosnik
November 16, 2018 (v1)
Keywords: cross-flow turbine, marine hydrokinetic energy, Reynolds number, scale model, turbine performance, vertical-axis wind turbine (VAWT), wind energy
Experiments were performed with a large laboratory-scale high solidity cross-flow turbine to investigate Reynolds number effects on performance and wake characteristics and to establish scale thresholds for physical and numerical modeling of individual devices and arrays. It was demonstrated that the performance of the cross-flow turbine becomes essentially R e -independent at a Reynolds number based on the rotor diameter R eD ≈ 10⁶ or an approximate average Reynolds number based on the blade chord length R ec ≈ 2 × 10⁵ . A simple model that calculates the peak torque coefficient from static foil data and cross-flow turbine kinematics was shown to be a reasonable predictor for... [more]
High Order Modeling of Overdamped Continuous Processes
Francisco Sanchez Careaga, Carlos Narvaez
November 2, 2018 (v1)
Keywords: Dynamic System Analysis, Process Control, Process Identification, Process Modeling
The dynamic response of continuous processes is a key issue for their control. To represent this
response, first order models are used, mainly because of their simplicity and the lack of simple methods for parameter estimation of higher order models. Although first order models may be sufficient in many cases, there are times when a higher order model needs to be used to achieve good control. This paper presents a simple graphical procedure for the estimation of the two time constants, the gain, and the dead time of a second order linear model. The procedure uses only four readings from the step response curve of the processes, and very simple formulas to determine parameter values.
Un Nuevo Método de Identificación de Procesos Continuos no Oscilatorios de Alto Orden
Francisco Sanchez Careaga
October 30, 2018 (v1)
Keywords: Dynamic System Analysis, Process Control, Process Intensification, Process Modelling
Continuous processes with time delay, in general, have been represented by using first order models with time delay (FOMTD). For this models, the parameter can be graphically estimated by plotting the process response when a step is applied to the manipulated variable. For higher order process, the FOMTD have poor results and the second order models with time delay (SOMTD) are more suitable for identifying the process. Nevertheless there is no simple graphic method for estimating the parameters of the SOMTD.

This research presents a simple graphic method for estimating the second order model with time delay parameter. The method requires to read four point of the process response when a step change in the manipulated variable is applied. From these readings the values of the time delay, gain and time constants of the SOMTD model are estimated.

Moreover, in this research, and alternative approximation of the time delay is proposed, this to avoid unstable zeros on the controller e... [more]
Los procesos continuos con tiempo muerto, generalmente han sido representados utilizando modelos de primer orden con tiempo muerto (FOPDT). Para este modelo, los parámetros pueden ser estimados gráficamente utilizando la gráfica de la respuesta del proceso, al aplicársele un escalón en la manipulación del mismo. Para procesos de alto orden, los modelos FOPDT dan pobres resultados y los modelos de segundo orden con tiempo muerto (SOPDT) son los más indicados para responder a las necesidades de identificación. Sin embargo no existe un método gráfico sencillo para estimar los parámetros del modelo SOPDT.

En esta investigación se presenta un método gráfico sencillo para estimar los parámetros del modelo de segundo orden con tiempo muerto. El método consiste en la lectura de cuatro puntos de la gráfica de respuesta del proceso real al aplicársele un cambio tipo escalón en la manipulación. De esas lecturas se estiman los valores del tiempo muerto, de la ganancia, y de las constantes de t... [more]
A novel sustainable design for production of liquid fuels
Leila Hoseinzade, Thomas A Adams II
October 30, 2018 (v1)
In this study, a novel biomass-gas-and-nuclear-to-liquids (BGNTL) process is proposed. In this process, nuclear heat is used as the heat source of a steam methane reforming (SMR) process. In a prior work, a rigorous model was developed for the integrated nuclear heat and steam methane reforming process in the gPROMS software package. This model was applied to simulate the integrated nuclear heat and SMR section of BGNTL in Aspen Plus within the other process sections. The BGNTL process was considered for producing different fuels including gasoline & diesel or dimethyl ether (DME). Carbon capture and sequestration (CCS) is considered as an optional section. The performance of the BGNTL process was compared against a non-nuclear process called biomass-and-gas-to-liquids (BGTL). The efficiency, economics, and environmental impact analyses show that the BGNTL process to produce DME is the most efficient, economic and environmentally friendly process among the considered designs. As a resu... [more]
Techno-economic System Analysis for SOFC/GT Hybrid System Accounting for Degradation Effects
Haoxiang Lai, Thomas Adams II
October 30, 2018 (v1)
Keywords: Modeling and simulation, Process design, SOFC/GT Hybrid, Technoeconomic Analysis
Solid oxide fuel cells (SOFCs) produce power with higher efficiency and lower greenhouse gas emission than conventional power production systems such as coal/natural gas power plants. However, a major challenge with SOFCs is that they degrade over time, leading to a short lifetime and limiting their commercialization. When operated in constant power mode—the most common way of baseload power production—the lifetime of an SOFC is as short as around 1.5 years. As an SOFC starts to degrade, the fuel rate and current density must increase in order to compensate and keep power production at a constant level. This compounds the problem by actually increasing the rate of degradation further, resulting in an exponentially increasing degradation rate and therefore a short lifetime.
It has recently been found that by operating the SOFC differently with constant voltage instead of power, the degradation rate can be slowed such that the cell lifetime can be increased to around 13-14 years. In th... [more]
Coke Oven Gas Conversion Efficiency Improvement by System Upgrading to Combined Cycle Power Plant
Lingyan Deng, Thomas Adams II
October 25, 2018 (v4)
Keywords: Coke oven gas, combined cycle power plant, GAMS optimization, MDEA desulphurization
Coke oven gas (COG) is one of the main by-products generated from steel refineries. In most cases, COG is used only to generate low pressure steam for process heat needs or for small amounts of electricity production. Carbon emissions are inevitable in this COG utilization method. However, carbon emissions are no longer free: the federal government has proposed a minimum carbon tax scheme which incentivises the steel industry to upgrade their present system in order to maintain their profitability. Based on a local steel refinery case study, we propose retrofitting the plant with a combined cycle power plant (CCPP) using COG as fuel input in order to help reduce CO2 emissions and increase energy efficiency. However, COG contains a significant amount of sulphur compounds which have to be removed before it can be used as fuel input for CCPP. Therefore, a MDEA based desulphurization process is proposed to reduce the main sulphur content (H2S) in COG to less than 1 ppmv. ProMax is used to... [more]
A Lithium-Ion Battery Simulator Based on a Diffusion and Switching Overpotential Hybrid Model for Dynamic Discharging Behavior and Runtime Predictions
Lan-Rong Dung, Hsiang-Fu Yuan, Jieh-Hwang Yen, Chien-Hua She, Ming-Han Lee
October 23, 2018 (v1)
Keywords: battery simulator, diffusion model, equivalent circuit model (ECM), linear extrapolation, overpotential, rate capacity effect, recovery effect
A new battery simulator based on a hybrid model is proposed in this paper for dynamic discharging behavior and runtime predictions in existing electronic simulation environments, e.g., PSIM, so it can help power circuit designers to develop and optimize their battery-powered electronic systems. The hybrid battery model combines a diffusion model and a switching overpotential model, which automatically switches overpotential resistance mode or overpotential voltage mode to accurately describe the voltage difference between battery electro-motive force (EMF) and terminal voltage. Therefore, this simulator can simply run in an electronic simulation software with less computational efforts and estimate battery performances by further considering nonlinear capacity effects. A linear extrapolation technique is adopted for extracting model parameters from constant current discharging tests, so the EMF hysteresis problem is avoided. For model validation, experiments and simulations in MATLAB a... [more]
An Algorithm to Translate Building Topology in Building Information Modeling into Object-Oriented Physical Modeling-Based Building Energy Modeling
WoonSeong Jeong, JeongWook Son
October 23, 2018 (v1)
Keywords: building energy modeling, Building Information Modeling, building topology, object-oriented physical modeling
This paper presents an algorithm to translate building topology in an object-oriented architectural building model (Building Information Modeling, BIM) into an object-oriented physical-based energy performance simulation by using an object-oriented programming approach. Our algorithm demonstrates efficient mapping of building components in a BIM model into space boundary conditions in an object-oriented physical modeling (OOPM)-based building energy model, and the translation of building topology into space boundary conditions to create an OOPM model. The implemented command, TranslatingBuildingTopology, using an object-oriented programming approach, enables graphical representation of the building topology of BIM models and the automatic generation of space boundaries information for OOPM models. The algorithm and its implementation allow coherent object-mapping from BIM to OOPM and facilitate the definition of space boundaries information during model translation for building thermal... [more]
Two-Dimensional Simulation of Mass Transfer in Unitized Regenerative Fuel Cells under Operation Mode Switching
Lulu Wang, Hang Guo, Fang Ye, Chongfang Ma
October 23, 2018 (v1)
Keywords: numerical simulation, operation mode switching, regenerative fuel cell, transport phenomenon, two-dimensional
A two-dimensional, single-phase, isothermal, multicomponent, transient model is built to investigate the transport phenomena in unitized regenerative fuel cells (URFCs) under the condition of switching from the fuel cell (FC) mode to the water electrolysis (WE) mode. The model is coupled with an electrochemical reaction. The proton exchange membrane (PEM) is selected as the solid electrolyte of the URFC. The work is motivated by the need to elucidate the complex mass transfer and electrochemical process under operation mode switching in order to improve the performance of PEM URFC. A set of governing equations, including conservation of mass, momentum, species, and charge, are considered. These equations are solved by the finite element method. The simulation results indicate the distributions of hydrogen, oxygen, water mass fraction, and electrolyte potential response to the transient phenomena via saltation under operation mode switching. The hydrogen mass fraction gradients are smal... [more]
Phase Change Materials-Assisted Heat Flux Reduction: Experiment and Numerical Analysis
Hussein J. Akeiber, Seyed Ehsan Hosseini, Mazlan A. Wahid, Hasanen M. Hussen, Abdulrahman Th. Mohammad
October 23, 2018 (v1)
Keywords: heat flux, melting temperature, phase change material (PCM), wax
Phase change materials (PCM) in the construction industry became attractive because of several interesting attributes, such as thermo-physical parameters, open air atmospheric condition usage, cost and the duty structure requirement. Thermal performance optimization of PCMs in terms of proficient storage of a large amount of heat or cold in a finite volume remains a challenging task. Implementation of PCMs in buildings to achieve thermal comfort for a specific climatic condition in Iraq is our main focus. From this standpoint, the present paper reports the experimental and numerical results on the lowering of heat flux inside a residential building using PCM, which is composed of oil (40%) and wax (60%). This PCM (paraffin), being plentiful and cost-effective, is extracted locally from waste petroleum products in Iraq. Experiments are performed with two rooms of identical internal dimensions in the presence and absence of PCM. A two-dimensional numerical transient heat transfer model i... [more]
Enhancing LVRT of DFIG by Using a Superconducting Current Limiter on Rotor Circuit
Flávio Oliveira, Arthur Amorim, Lucas Encarnação, Jussara Fardin, Marcos Orlando, Selênio Silva, Domingos Simonetti
October 22, 2018 (v1)
Keywords: crowbar, doubly fed induction generator (DFIG), low voltage ride-through (LVRT), superconducting current limiter (SCL), voltage sags, wind turbines
This paper have studied the dynamic of a 2.0 MW Doubly Fed Induction Generator (DFIG) during a severe voltage sag. Using the dynamic model of a DFIG, it was possible to determine the current, Electromagnetic Force and flux behavior during three-phase symmetrical voltage dip. Among the technologies of wind turbines the DFIG is widely employed; however, this machine is extremely susceptible to disturbances from the grid. In order to improve DFIG Low Voltage Ride-Through (LVRT), it is proposed a novel solution, using Superconducting Current Limiter (SCL) in two arrangements: one, the SCL is placed between the machine rotor and the rotor side converter (RSC), and another placed in the RSC DC-link. The proposal is validated through simulation using PSCAD™/EMTDC™ and according to requirements of specific regulations. The analysis ensure that both SCL arrangements behave likewise, and are effective in decrement the rotor currents during the disturbance.
Empirical Validation of a Thermal Model of a Complex Roof Including Phase Change Materials
Stéphane Guichard, Frédéric Miranville, Dimitri Bigot, Bruno Malet-Damour, Teddy Libelle, Harry Boyer
October 22, 2018 (v1)
Keywords: building thermal simulation, model optimization, model validation, phase change materials (PCMs)
This paper deals with the empirical validation of a building thermal model of a complex roof including a phase change material (PCM). A mathematical model dedicated to PCMs based on the heat apparent capacity method was implemented in a multi-zone building simulation code, the aim being to increase the understanding of the thermal behavior of the whole building with PCM technologies. In order to empirically validate the model, the methodology is based both on numerical and experimental studies. A parametric sensitivity analysis was performed and a set of parameters of the thermal model has been identified for optimization. The use of the generic optimization program called GenOpt® coupled to the building simulation code enabled to determine the set of adequate parameters. We first present the empirical validation methodology and main results of previous work. We then give an overview of GenOpt® and its coupling with the building simulation code. Finally, once the optimization results a... [more]
A Numerical Study on System Performance of Groundwater Heat Pumps
Jinsang Kim, Yujin Nam
October 22, 2018 (v1)
Keywords: coefficient of performance, groundwater heat pump, heat exchanger, regression analysis, UA value
Groundwater heat pumps have energy saving potential where the groundwater resources are sufficient. System Coefficients of Performance (COPs) are measurements of performance of groundwater heat pump systems. In this study, the head and power of submersible pumps, heat pump units, piping, and heat exchangers are expressed as polynomial equations, and these equations are solved numerically to determine the system performance. Regression analysis is used to find the coefficients of the polynomial equations from a catalog of performance data. The cooling and heating capacities of water-to-water heat pumps are determined using Energy Plus. Results show that system performance drops as the water level drops, and the lowest flow rates generally achieve the highest system performance. The system COPs are used to compare the system performance of various system configurations. The groundwater pumping level and temperature provide the greatest effects on the system performance of groundwater hea... [more]
Distributing Characteristics within Fuel Cell Stacks with features that Fuel/Air Manifolds Penetrated through Plane Zone and Open Outlet Manifold
Dai Fen Chen
September 19, 2018 (v1)
Keywords: 3D large scale simulating, Flow and temperature distribution characteristics, Solid oxide fuel cell stack, Structure features
Although many numerical models based on different fuel cell stack designs have been developed in past decades, most of the achieved optimized results are greatly dependent on the specific designs, cell numbers and geometric values. Achieving the general relationship between the structure features and distribution trends of key physics items, that is independent on the specific design would be high instructive. To achieve high volumetric/gravimetric power density and simple manufacturing process, both fuel and air manifolds of a solid oxide fuel cell (SOFC) stack are always designed to place within cell plane zone and penetrated through it; and open outlet manifold is also adopted. In this study, the three dimension large scale multi-physics numerical model for a typical SOFC stack with the above two design features is well completed by carefully coupling momentum, mass, energy and quasi electrochemical reaction equations. Then, the general relations between these structure features and... [more]
Maintenance Factor Identification in Outdoor Lighting Installations Using Simulation and Optimization Techniques
Ana Ogando-Martínez, Javier López-Gómez, Lara Febrero-Garrido
September 21, 2018 (v1)
Keywords: artificial lighting, calibration, GenOpt, radiance, Simulation, street light points
This document addresses the development of a novel methodology to identify the actual maintenance factor of the luminaires of an outdoor lighting installation in order to assess their lighting performance. The method is based on the combined use of Radiance, a free and open-source tool, for the modeling and simulation of lighting scenes, and GenOpt, a generic optimization program, for the calibration of the model. The application of this methodology allows the quantification of the deterioration of the road lighting system and the identification of luminaires that show irregularities in their operation. Values lower than 9% for the error confirm that this research can contribute to the management of street lighting by assessing real road conditions.
On the Accuracy of Three-Dimensional Actuator Disc Approach in Modelling a Large-Scale Tidal Turbine in a Simple Channel
Anas Rahman, Vengatesan Venugopal, Jerome Thiebot
September 21, 2018 (v1)
Keywords: actuator disc, Telemac3D, tidal energy, turbulence, wake analysis
To date, only a few studies have examined the execution of the actuator disc approximation for a full-size turbine. Small-scale models have fewer constraints than large-scale models because the range of time-scale and length-scale is narrower. Hence, this article presents the methodology in implementing the actuator disc approach via the Reynolds-Averaged Navier-Stokes (RANS) momentum source term for a 20-m diameter turbine in an idealised channel. A structured grid, which varied from 0.5 m to 4 m across rotor diameter and width was used at the turbine location to allow for better representation of the disc. The model was tuned to match known coefficient of thrust and operational profiles for a set of validation cases based on published experimental data. Predictions of velocity deficit and turbulent intensity became almost independent of the grid density beyond 11 diameters downstream of the disc. However, in several instances the finer meshes showed larger errors than coarser meshes... [more]
Flow Simulation of Artificially Induced Microfractures Using Digital Rock and Lattice Boltzmann Methods
Yongfei Yang, Zhihui Liu, Jun Yao, Lei Zhang, Jingsheng Ma, S. Hossein Hejazi, Linda Luquot, Toussaint Dono Ngarta
September 21, 2018 (v1)
Keywords: CT, digital rock, Lattice Boltzmann method, microfractures, pore-scale simulations
Microfractures have great significance in the study of reservoir development because they are an effective reserving space and main contributor to permeability in a large amount of reservoirs. Usually, microfractures are divided into natural microfractures and induced microfractures. Artificially induced rough microfractures are our research objects, the existence of which will affect the fluid-flow system (expand the production radius of production wells), and act as a flow path for the leakage of fluids injected to the wells, and even facilitate depletion in tight reservoirs. Therefore, the characteristic of the flow in artificially induced fractures is of great significance. The Lattice Boltzmann Method (LBM) was used to calculate the equivalent permeability of artificially induced three-dimensional (3D) fractures. The 3D box fractal dimensions and porosity of artificially induced fractures in Berea sandstone were calculated based on the fractal theory and image-segmentation method,... [more]
PC Implementation of a Real-Time Simulator Using ATP Foreign Models and a Sound Card
Renzo G. Fabián Espinoza, Yuri Molina, Maria Tavares
September 21, 2018 (v1)
Keywords: ATP, digital real-time simulation, foreign models, hardware-in-the-loop, intelligent electronic device, MODELS
This work reports the personal computer implementation of a real-time simulator based on the widely used Electromagnetic Transients Program, version Alternative Transients Program (EMTP-ATP) software for testing protection and control devices. The proposed simulator was implemented on a conventional PC with a GNU/Linux operative system including a real-time kernel. Using foreign models programmed in C, ATP was recompiled with the PortAudio (sound card I/O library) with tools for writing and reading the parallel port. In this way, the sound card was used as a digital-to-analog converter to generate voltage waveform outputs at each simulation time step of the ATP, and the parallel port was used for digital inputs and outputs, resulting in a real-time simulator that can interact with protection and control devices by means of hardware-in-the-loop tests. This work uses the minimum possible hardware requirements to try to implement a real-time simulator. Due to the limitation of two channel... [more]
Variable Parameters for a Single Exponential Model of Photovoltaic Modules in Crystalline-Silicon
Ali F. Murtaza, Umer Munir, Marcello Chiaberge, Paolo Di Leo, Filippo Spertino
September 21, 2018 (v1)
Keywords: I-V curve tracer, maximum power point (MPP), modeling of photovoltaic (PV) module, PV simulator, Rp and Rs estimations
The correct approximation of parallel resistance (Rp) and series resistance (Rs) poses a major challenge for the single diode model of the photovoltaic module (PV). The bottleneck behind the limited accuracy of the model is the static estimation of resistive parameters. This means that Rp and Rs, once estimated, usually remain constant for the entire operating range of the same weather condition, as well as for other conditions. Another contributing factor is the availability of only standard test condition (STC) data in the manufacturer’s datasheet. This paper proposes a single-diode model with dynamic relations of Rp and Rs. The relations not only vary the resistive parameters for constant/distinct weather conditions but also provide a non-iterative solution. Initially, appropriate software is used to extract the data of current-voltage (I-V) curves from the manufacturer’s datasheet. By using these raw data and simple statistical concepts, the relations for Rp and Rs are designed. Fi... [more]
Thermal Characteristics Investigation of the Internal Combustion Engine Cooling-Combustion System Using Thermal Boundary Dynamic Coupling Method and Experimental Verification
Junhong Zhang, Zhexuan Xu, Jiewei Lin, Zefeng Lin, Jingchao Wang, Tianshu Xu
September 21, 2018 (v1)
Keywords: combustion, cooling system, dynamic coupling, engine performance, multiphase flow
The engine cooling system must be able to match up with the stable operating conditions so as to guarantee the engine performance. On the working cycle level, however, the dynamic thermo-state of engines has not been considered in the cooling strategy. Besides, the frequent over-cooling boiling inside the gallery changes the cooling capacity constantly. It is necessary to study the coupling effect caused by the interaction of cooling flow and in-cylinder combustion so as to provide details of the dynamic control of cooling systems. To this end, this study develops a coupled modeling scheme of the cooling process considering the interaction of combustion and coolant flow. The global reaction mechanism is used for the combustion process and the multiphase flow method is employed to simulate the coolant flow considering the wall boiling and the interphase forces. The two sub-models exchange information of in-cylinder temperature, heat transfer coefficient, and wall temperature to achieve... [more]
Analysis of Propagation Delay for Multi-Terminal High Voltage Direct Current Networks Interconnecting the Large-Scale Off-Shore Renewable Energy
Muhammad Haroon Nadeem, Xiaodong Zheng, Nengling Tai, Mehr Gul, Sohaib Tahir
September 21, 2018 (v1)
Keywords: high voltage direct current (HVDC) protection, multi-terminal HVDC, propagation delay
Voltage-source-converter-based multi-terminal high voltage direct current (MTDC) networks are extensively recognized as a viable solution for meeting the increasing demand of electrical energy and escalating penetration of renewable energy sources. DC faults are major limitations to the development of MTDC networks. The analysis of variable constraints has become mandatory in order to develop a reliable protection scheme. This paper contributes in assessing the propagation delay with the analytical approximation in MTDC networks. The propagation delay is analyzed in the time domain by taking only the forward traveling wave into account and considering the initial voltage step of magnitude at the fault position. Numerous simulations were carried out for different parameters and arrangements in Power System Computer Aided Design (PSCAD) to explore the proposed expressions. The results accurately depicted the time development of fault current. The results obtained from the real-time digit... [more]
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