用混合语言编程技术开发锅炉启动过程模拟计算软件

利用Visual C 、Fortran和Matlab的混合语言编程技术,设计开发了亚临界锅炉启动过程模拟计算软件.该软件用Visual C 编制人机界面,通过该界面可以实现数据的输入、修改,锅炉启动过程模拟计算,以及计算结果曲线的绘制及打印输出;模拟计算程序用Fortran语言实现;计算结果的图形显示通过Visual C 调用MATLAB实现.利用该软件对某600 MW锅炉冷态启动过程进行了模拟计算.结果表明,该软件可以正确的模拟锅炉的启动过程,直观、方便的实现数据的输入、过程计算以及计算结果的分析,为优化、分析锅炉启动过程提供了一种有效的工具.     

Energy and material flow analysis: Application to the storage stage of clay in the roof-tile manufacture

Energy and material flow analysis (EMFA) comprises a whole family of tools to optimize the consumption of energy, raw material, water and the discharge of effluents by pursuing systematically internal flows of energy and mass in production processes. Computer software with various degrees of complexity are available to facilitate this analysis.

In this paper, EMFA is applied to the case of the manufacture of roof tiles in a ceramic industry. The stage under evaluation is the storage of clay. A computational tool, Umberto, was used for the analysis. This software allows visualizing the process, units and flows, to analyze from an environmental point of view the effluents and the costs involved as well as to carry out both the mass and energy balances. As the main objective of this study is to implement an EMFA tool into our system, so that it can operate more efficiently and reduce its environmental impact, the evaluation of flows and stocks was made using the performance indicators provided by Umberto. The iterative capability of the software allows the identification of improvement potential, by a quantitative comparison of input and output data with target values.     

二甲醚发动机电控低压燃料喷射系统的设计

针对二甲醚燃料低粘性、高蒸汽压以及容易与空气形成混合气的特性，开发了电控低压燃油喷射系统，进行了系统的总体设计、电子控制单元(ECU)的软硬件开发和在油泵台架上的试验。电控系统软件采用实时模块化编程，具有编程灵活，移植性和扩展性好的特点。试验结果表明，在新开发系统的驱动下，喷油器启合及时，喷射有力，雾化效果好；所开发的软件能实现信号采集、发动机各丁况控制，满足了发动机正常运行、反馈控制及信号采集的实时性要求。     

埋地换热器理论模型与周围土壤温度数值模拟

提出内热源型埋地换热器理论模型，建立换热器周围土壤热湿传递物理数学模型。内热源模型综合考虑热湿迁移、土壤物性等各方面因素，将埋设于土壤中的换热器处理为等效内热源。采用专业多孔介质计算软件Autough2对模型进行模拟计算。着重模拟计算不同土壤物性、不同换热器运行方式对单根U型垂直埋管换热器周围土壤温度场影响的模拟计算与分析。     

节理参数对水电站地下洞室围岩地震反应的影响研究

以节理受力特性为出发点,基于FLAC3D软件平台,改进了Interface单元的法向刚度及切向刚度的输入取 值方法,定义了节理参数的敏感度,并以含有一给定方向节理的某实际水电站地下洞室为背景建立了数值试验模 型,根据场地条件输入人工地震波进行地震反应分析,探讨了对洞室围岩地震反应影响较大的节理参数,以期为 含节理的地下岩石洞室动力稳定性分析提供参考。     

Probabilistic modeling of transient heat transfer and assessment of thermal reliability of fibrous insulation under aerodynamic heating conditions

In present paper, the probabilistic thermal analysis of the fibrous insulation subjected to aerodynamic heating conditions was performed to account for the uncertainties such as material properties, loading conditions and geometrical variations. The statistical analysis of thermal response showed that the response temperature was significantly dependent on time and location. Large variations in the statistics parameters were observed at the location where temperature slip occurred for the first one minute of entry. To identify the dominant variables which most influence temperature response scatter, the correlation coefficients of various variables were computed. The results showed that the aerodynamic heating temperature and initial temperature had significant effects for the considered locations. However, the extinction coefficient, the specific heat of virgin material and the solid fraction ratio had non-negligible effect on the back side temperature scatter of fibrous insulation. Furthermore, the relationship between the probabilistic thermal reliability and thickness factor of safety was developed. Quantitative as well as qualitative information is provided in the present methodology, which is valuable to the thermal analysis, design and testing of fibrous materials.     

Analysis of the diffusive mass transport in the anode side porous backing layer of a direct methanol fuel cell

In this work we present an analysis of the mass transport in the anode side porous backing layer of a direct methanol fuel cell (DMFC). The effective transport coefficient of different backing layers at various compressions was measured and compared to two different literature models and a single particle random walk simulation which accounts for details of the geometrical fibre microstructure. Based on the measured values of the effective transport coefficient limiting current densities for diffusive transport were calculated taking into account geometric boundary conditions and anisotropic and inhomogeneous backing layer properties. Comparison with the measured values for the limiting current in fuel cell operation shows qualitative agreement. A systematic underestimation indicates that also other transport processes contribute significantly to the mass transfer at the used experimental setup.     

Numerical Investigation of Energy-Efficient Receiver for Solar Parabolic Trough Concentrator

In this paper, a thermal analysis of an energy-efficient receiver for solar parabolic trough concentrator is presented. Various porous receiver geometries are considered for the performance evaluation of a solar parabolic trough concentrator. Numerical models are proposed for a porous energy-efficient receiver for internal heat gain characteristics and heat loss due to natural convection. The internal flow and heat transfer analysis is carried out based on a RNG k-? turbulent model, whereas external heat losses are treated as a laminar natural convection model. The numerical models have been solved using the commercial engineering package, FLUENT. The thermal analysis of the receiver is carried out for various geometrical parameters, such as fin aspect ratio, thickness, and porosity, for different heat flux conditions. The inclusion of porous inserts in tubular receiver of solar trough concentrator enhanced the heat transfer about 17.5% with a pressure penalty of 2 kPa. The Nusselt number correlation is proposed based on the extensive numerical data for internal heat transfer inside the receiver. The proposed model is compared with more well-known natural convection models. A comparative study is carried out with different porous geometries to evolve an optimum configuration of energy-efficient receivers.     

Design tool for estimating metal hydride storage system characteristics for light-duty hydrogen fuel cell vehicles

The U.S. Department of Energy (DOE) has developed the Framework model to simulate fuel cell-based light-duty vehicle operation for various hydrogen storage systems. This transient model simulates the performance of the storage system, fuel cell, and vehicle for comparison to DOE's Technical Targets using four drive cycles. Metal hydride hydrogen storage models have been developed for the Framework model. Despite the utility of this model, it requires that material researchers input system design specifications that cannot be easily estimated. To address this challenge, a design tool has been developed that allows researchers to directly enter physical and thermodynamic metal hydride properties into a simple sizing module that then estimates the systems parameters required to run the storage system model. This design tool can also be used as a standalone MS Excel model to estimate the storage system mass and volume outside of Framework and compare it to the DOE Technical Targets. This model will be explained and exercised with existing hydrogen storage materials.     

A whole range hygric material model: Modelling liquid and vapour transport properties in porous media

This paper addresses the modelling of hygric material coefficients bridging the gap between measured material properties and the non-linear storage and transport coefficients in the transfer equation. The conductivity approach and a bundle of tubes model are the basis. By extending this model with a mechanistic treatment of serial and parallel structured transport, a semi-empirical material model is developed. Deriving the transport properties from the pore structure of the material, the model provides a physical basis whereas a high flexibility and adjustability is obtained by the coupling with the mechanistic model. The required minimum input data are basic standard material properties. The model is very suitable for sophisticated research as well as for a broad application to porous materials in general.     

Design tool for estimating chemical hydrogen storage system characteristics for light-duty fuel cell vehicles

The U.S. Department of Energy (DOE) developed a vehicle Framework model to simulate fuel cell-based light-duty vehicle operation for various hydrogen storage systems. This transient model simulates the performance of the storage system, fuel cell, and vehicle for comparison to Technical Targets established by DOE for four drive cycles/profiles. Chemical hydrogen storage models have been developed for the Framework for both exothermic and endothermic materials. Despite the utility of such models, they require that material researchers input system design specifications that cannot be estimated easily. To address this challenge, a design tool has been developed that allows researchers to directly enter kinetic and thermodynamic chemical hydrogen storage material properties into a simple sizing module that then estimates system parameters required to run the storage system model. Additionally, the design tool can be used as a standalone executable file to estimate the storage system mass and volume outside of the Framework model. These models will be explained and exercised with the representative hydrogen storage materials exothermic ammonia borane (NH₃BH₃) and endothermic alane (AlH₃).     

Simplified Thermoelastoplastic Models for Determination of Global and Local Stress in Coke Drums

Coke drums as major pressure vessels in delayed coking process experience cyclic thermal and mechanical loading during operation. The elastic-plastic behavior of coke drums including global and local (hot and cold spot) stress distribution has been analyzed using finite element analysis (FEA) method in our previous study. Here, instead of using FEA simulations, simplified theoretical models (STM) for global and local stress determination are developed. The global stress model is developed based on a single cladded shell element with temperature and pressure loading cycle. The local stress model is built on an axisymmetric circular cladded plate experiencing a non-uniform temperature distribution history. With the same input data, stress and strain values estimated by the STM are consistent with those from the FEA. An ease-of-use software package with built-in STMs is developed. It is the objective of this paper to show that STM can be a very time- and cost-saving analysis tool for general industrial users compared to professional commercial FEA software.     

Thermal buckling and postbuckling responses of geometrically imperfect FG porous beams based on physical neutral plane

Abstract

Considering the third-order shear deformation and physical neutral plane theories, thermal postbuckling analysis for functionally graded (FG) porous beam are performed in this research. The cases of shear deformable functionally graded materials (FGM) beams with initial deflection and uniformly distributed porosity are considered. Geometrically imperfect FG porous beams with two different types of immovable boundary conditions as clamped–rolling and clamped–clamped are analyzed. Thermomechanical nonhomogeneous material properties of the FG porous beam are assumed to be temperature and position dependent. FG porous beams are subjected to different types of thermal loads as heat conduction and uniform temperature rise. Heat conduction equation is solved analytically using the polynomial series solution for the one-dimensional condition. The governing equilibrium equations are obtained by applying the virtual displacement principle. Assuming von Kármán type of geometrical nonlinearity, equilibrium equations are nonlinear and are solved using an analytical method. A two-step perturbation technique is used to obtain the thermal buckling and postbuckling responses of FG porous beams. The numerical results are compared with the case of perfect FGM Timoshenko beams without porosity distribution based on the midplane formulation. Parametric studies of the perfect/imperfect FG porous beams for two types of thermal loading and boundary conditions are provided.     

Heat transfer and friction factor correlations for packed bed solar air heater for a low porosity system

An experimental investigation has been carried out on a low porosity packed bed solar air heater. This investigation covers a wide range of geometrical parameters of wire screen matrix, i.e. wire diameter 0.795 to 1.40 mm, pitch 2.50 to 3.19 mm and number of layers from 5 to 12. The correlations have been developed for the Colburn j factor and friction factor for a low range of porosities from 0.667 to 0.880 and packing Reynolds number range from 182 to 1168. It is observed that both the heat transfer coefficient and the friction factor are strong functions of geometrical parameters of the porous packed bed. A decrease in porosity increases the volumetric heat transfer coefficient.     

Comparison study of two different testing methodologies used to characterize an opaque solar component

The work described in this paper was aimed at comparing two different testing methodologies, set up in order to define performance properties and reliability of passive or hybrid solar components. The former facility is based on the use of outdoor real-size Test Cells, designed to simulate a conventional living environment with a thermal mass distributed approximately in the same way as in a real dwelling. The latter uses an indoor real-size test cell reproducing a common piece of a dwelling; such a cell can assume various spatial arrangements and simulate in a cyclic way any temperature conditions and solar input on the walls under test. Experiments on a same opaque multilayer component were run with both facilities and the comparison of the obtained results are given; the good agreement of the efficiency values and the analysis of the most important working parameters of the tested component points out the effectiveness and the peculiarity of both methodologies.     

Facile synthesis of N,P-doped hierarchical porous carbon framework catalysts based on gelatin/phytic acid supermolecules for electrocatalytic oxygen reduction

The design of porous carbon frameworks with high-density distributions of dopant sites, especially those derived from renewable biomaterials, is highly desirable to improve the activity of nonprecious porous carbon catalysts for oxygen reduction reaction (ORR). In this paper, we prepared N, P-doped hierarchical porous carbon catalysts via a direct pyrolysis of a gelatin/phytic acid supermolecular aggregate without extra activation processes. The optimal catalyst materials (NPC1000) showed not only the highest N and P contents but also the highest specific surface area, total pore volume and mesoporous pore volume, which are also higher than those of the contrast sample prepared with a chitosan/phytic acid supermolecular aggregate. Thus, the sample NPC1000 had the best electrocatalytic activity compared with the Pt/C catalyst, which was nearly a direct four-electron reaction. The sample also had higher stability and methanol tolerance than Pt/C. This work provides a simple, economical and environmentally friendly method to prepare nonprecious porous carbon catalysts with the desired properties.     

Preparation and performance of form-stable polyethylene glycol/silicon dioxide composites as solid–liquid phase change materials

This work mainly involved the preparation and characterization of form-stable polyethylene glycol (PEG)/silicon dioxide (SiO₂) composite as a novel solid–liquid phase change material (PCM). In this study, the polyethylene glycol/silicon dioxide composites as form-stable, solid–liquid phase change material (PCM) was prepared. In this new material, the polyethylene glycol acts as the latent heat storage material and silicon dioxide serves as the supporting material, which provides structural strength and prevents the leakage of the melted polyethylene glycol. Results indicated that the composite remained solid when the weight percentage of silicon dioxide was higher than 15%. Moreover, the polyethylene glycol was observed to disperse into the network of the solid silicon dioxide by investigation of the structure of the composite PCMs using a scanning electronic microscope (SEM). The properties of the porous materials and phase change materials were characterized using Fourier transformation infrared spectroscope (FTIR). The transition process was observed using polarizing optical microscope (POM) and dynamic thermo mechanic analysis (DMA). The melting temperatures and latent heats of the form-stable PEG/SiO₂ composite PCMs were determined using differential scanning calorimeter (DSC).     

基于小波分析与神经网络的气阀机构故障诊断研究

运用小波分析对柴油机缸盖振动信号进行分析与讨论,计算二进小汉分解后尺度1信号在各个时间段内的能量百分比;将能量百分比作为神经网络的输入进行训练和故障识别,用BP网络及自组织聚类算法实现了气阀机构的故障诊断,取得了较好的效果。     

Energy System Selection for Small Underwater Vehicles

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Mechanical strength of porous nickel plates containing lithium and their performance as the cathode for MCFC

To improve the mechanical properties of MCFC cathode materials, pre-lithiated porous nickel plates containing 1–5 mol% of lithium were fabricated by the tape casting method, and the microstructures, mechanical properties, and performance was examined. The microstructure and pore distribution was not changed until the lithum content reached 3 mol%. The sample containing 5 mol% of lithium had patch structure on the skeleton and a smaller volume of primary pores. XRD analysis showed that lithium-containing porous nickel plates can easily form solid solutions without any undesirable byproducts after the oxidation. Both the bending strength and Young’s modulus of the porous plates increased with the increase of lithium content. The average bending strengths of the samples containing 1, 3, and 5 mol% of lithium were 1.29, 1.33, and 1.49 kgf/mm² which were 2.9, 3.0, and 3.4 times higher than that of pure porous nickel plate. The Young’s modulus increased up to 1.35 kgf/mm in the case of the 5 mol% lithium containing sample that is 5.4 times higher than that of pure porous nickel plate. The OCV of single cells using pre-lithiated cathodes were between 1.065 and 1.067 V, and comparable cell performance was obtained for 500 h of single cell operation.