The parametric optimum design of a new combined system of semiconductor thermoelectric devices

By introducing an internal structure parameter, the characteristic curve of a new combined system consisting of a semiconductor thermoelectric cooler and a semiconductor thermoelectric generator is obtained. The maximum coefficient of performance and rate of refrigeration of the system and the corresponding values of other important parameters are calculated. Moreover, the optimal operating region of the system and the optimal range of the internal structure parameter of thermoelectric devices are determined. The results obtained here may provide theoretical guidance for the optimal design and operation of such a new combined system.     

Performance analysis and parametric optimum criteria of an irreversible Atkinson heat-engine

Multi-irreversibilities, mainly resulting from the adiabatic processes, finite-time processes and heat loss through the cylinder wall, are considered in the cycle model of an Atkinson heat engine. The power output and efficiency of the cycle are derived by introducing the pressure ratio and the compression and expansion efficiencies. The performance characteristic curves of the cycle are presented. The bounds of the power output and efficiency are determined. The optimum criteria of some important parameters, such as the power output, efficiency and pressure ratio are given. The influences of the various design parameters on the performance of the cycle are analyzed in detail. The results obtained may provide a theoretical basis for both the optimal design and operation of real Atkinson heat engines.     

Effect of heat transfer on stability and transition characteristics of boundary-layers

Stability and transition problems of two dimensional boundary-layers with heated walls have been studied numerically using the linear stability theory. Incompressible stability equations have been modified to account for the variation of temperature dependent fluid properties across the layer. The equations obtained have been solved with an efficient shoot-search technique. Low speed flows of air and water have been analyzed with a wide range of heat transfer rates. In addition to the mean velocity profile characteristics, variable viscosity and density terms in the stability equations also have considerable influence on the results of the stability and transition analysis.     

Effect of Mg-doping on the structural and electronic properties of LiCoO2: A first-principles investigation

The electronic structures of Mg-doped LiCoO₂ have been investigated by the first-principle pseudopotential method. The effect of Mg-doping content on the band structure and structural stability of LiCoO₂ is presented. The results obtained via a full relaxation of the crystalline structure show that a rational amount of Mg-doping in LiCoO₂ is helpful to enhance its electronic conductivity. However, the doping magnitude should be controlled within 15 mol% of LiCoO₂ in order to keep its crystalline structure unchanged. By combining total energy calculations with basic thermodynamics, the average intercalation voltages of this doped system have been predicted.     

柴油机试车能源回收系统

分析目前柴油机试车过程中能源回收的可行性，提出两种柴油机试车回收能源的方案、并对设计能源回收系统应遵循的原则及未来的发展趋势进行探讨。     

Optimization of the power,efficiency and ecological function for an air-standard irreversible Dual-Miller cycle

This paper establishes an irreversible Dual-Miller cycle (DMC) model with the heat transfer (HT) loss, friction loss (FL) and other internal irreversible losses. To analyze the effects of the cut-off ratio (ρ) and Miller cycle ratio (r_M) on the power output (P), thermal efficiency (η) and ecological function (E), obtain the optimal ρ_opt and optimal r_Mopt, and compare the performance characteristics of DMC with its simplified cycles and with different optimization objective functions, the P, η and E of irreversible DMC are analyzed and optimized by applying the finite time thermodynamic (FTT) theory. Expressions of P, η and E are derived. The relationships among P, η, E and compression ratio (ε) are obtained by numerical examples. The effects of ρ and r_M on P, η, E, maximum power output (MP), maximum efficiency (MEF) and maximum ecological function (ME) are analyzed. Performance differences among the DMC, the Otto cycle (OC), the Dual cycle (DDC), and the Otto-Miller cycle (OMC) are compared for fixed design parameters. Performance characteristics of irreversible DMC with the choice of P, η and E as optimization objective functions are analyzed and compared. The results show that the irreversible DMC engine can reach a twice-maximum power, a twice-maximum efficiency, and a twice-maximum ecological function, respectively. Moreover, when choosing E as the optimization objective, there is a 5.2% of improvement in η while there is a drop of only 2.7% in P compared to choosing P as the optimization objective. However, there is a 5.6% of improvement in P while there is a drop of only 1.3% in η compared to choosing as the optimization objective.     

Investigation on the optimal performance and design parameters of an irreversible solar-driven Braysson heat engine

An irreversible solar-driven Braysson thermal engine has been investigated, in which finite rate heat transfer with the radiation–convection mode from the high-temperature reservoir to the heat engine and the convection mode from the heat engine to the heat sink, and irreversible adiabatic processes are taken into account. Based on the thermodynamic analysis method, the analytic expressions of the power output and efficiency of the Braysson heat engine are derived. By using numerical value calculation, the effects of the isobaric temperature ratio, internal irreversibility parameter, temperature ratio of the thermal reservoirs as well as the allocation parameters involving the heat-transfer coefficients, and areas on the performance characteristics of the Braysson heat engine are analysed and discussed in detail. The results obtained in this paper are more general than the related conclusions published in the literature and may provide some parameter design reference for solar-driven heat engines.     

Optimization of hydrogen charging process parameters for an advanced complex hydride reactor concept

Complex hydrides are identified as promising hydrogen storage media with gravimetric capacities up to 10 wt.%. However, the high temperatures required for the initiation of their hydrogen charging process and their slow kinetics prevent their integration in many practical applications. This paper discusses the challenge of addressing these issues by combining this kind of materials with the appropriate metal hydrides. For this purpose, the complex hydride, 2LiNH₂–1.1MgH₂–0.1LiBH₄–3 wt.% ZrCoH₃ (CxH) and the metal hydride, LaNi_4.3Al_0.4Mn_0.3 (MeH) have been selected as reference materials. The studied configuration corresponds to a tubular reactor where the metal hydride and the complex hydride, separated by a gas permeable layer, are embedded respectively in the centre and the annular ring of the reactor. A 1-dimensional finite element model and a dimensionless number comparing the dominance of the kinetics and the heat transfer processes have been developed to optimize the charging process for different thicknesses and volumetric ratios of the studied materials. For the selected cases, the influence of the thermal properties of the complex hydride and the operating conditions on the charging process is assessed. A sensitivity study has shown that the thermal conductivity of the CxH is the most important parameter influencing the hydrogen storage rate if thick MeH and CxH beds are considered. In contrast, the hydrogen loading time is significantly improved by increasing the coolant temperature for small thicknesses of the two storage media. Thereafter, the gravimetric and volumetric capacities resulting from the scale up of the optimized configurations to store 1 kg of hydrogen are calculated and results are discussed taking into account the interdependence of the different studied parameters.     

A new method for optimal parameters identification of a PEMFC using an improved version of Monarch Butterfly Optimization Algorithm

In this paper, a circuit-based model of proton exchange membrane fuel cell (PEMFC) is developed for optimal selection of the model parameters. The optimization is based on using an improved version of Monarch Butterfly Optimization (IMBO) algorithm for minimizing the Integral Time Absolute Error between the measured output voltage and the output voltage of the achieved model. For validation of the proposed method, two different case studies including 6 kW NedSstack PS6 and 2 kW Nexa FC PEMFC stacks have been employed and the results have been compared with the experimental data and some well-known metaheuristics including Chaotic Grasshopper Optimization Algorithm (CGOA), Grass Fibrous Root Optimization Algorithm (GRA), and basic Monarch Butterfly Optimization (MBO) to indicate the superiority of the proposed method against the compared methods. Final results show a satisfying agreement between the proposed IMBO and the experimental data.     

多联产配置是推进我国IGCC系统发展的重要途径

分析了IGCC电站在我国及世界的发展形势,并从经济和技术角度分析了影响其发展的主要因素,重点对多联产系统相对IGCC电站具有更好的经济性和操作灵活性进行分析。提出通过多联产系统来推进IGCC这种清洁煤发电技术发展的观点。     

Hydrogen fuel as an important element of the energy storage needs for future smart cities

A considerable amount of non-dispatchable photovoltaic and wind power have always been planned in smart cities, however, the problem of massive energy storage has not yet been solved which limits the use of green energy on larger scale. At present the only battery energy storage is available, and it is effective only for storing modest quantities of energy for short periods of time. The other storage technology options are not often commercially available items; rather, they are just good concepts that need to be tested for viability. Currently, the only alternative options for turning an urban development into one that exclusively uses green energy is to use that energy to generate hydrogen through electrolyzers, then use this fuel to generate the required electricity in order to stabilize the grid. Even more appealing is the idea of using wind and photovoltaic energy to transform smart communities into a centre for producing hydrogen in addition to a city that solely uses renewable energy. The most likely solution, absent an urgent debate inside the science establishment, will be to import electricity from the burning of hydrocarbons while continuing to pay carbon offsets, which is incompatible with the goal of using only renewables. The smart city has not officially accepted this issue, just like the science establishment.     

Optimization of the polypyrrole-coating parameters for proton exchange membrane fuel cell bipolar plates using the Taguchi method

In order to overcome the high price, weight and volume of non-porous graphite bipolar plates, metallic bipolar plates are being investigated as a substitute material. However, metallic materials can corrode under proton exchange membrane fuel cell (PEMFC) working conditions, leading to a degradation in the performance of the membrane. Previous work had shown that a polypyrrole coating on SS316L can significantly increase the corrosion resistance of the base material. In this study, a Taguchi design of experiment method was used to optimize the process parameters for the polypyrrole coating so as to produce the maximum corrosion resistance. Potentiodynamic and potentiostatic tests were used to determine the corrosion resistance of the polypyrrole-coated SS316L. Scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) was used to characterize the coating thickness and coating appearance. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to determine the metal ion concentration in the solution after corrosion. The interfacial contact resistance of SS316L with carbon paper was measured both before and after coating with polypyrrole.     

A Thermal Analysis of Characteristic Parameters in the Electrode—Region for Tubular Plasma Generators

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某超超临界锅炉低NOX燃烧优化对高温腐蚀的影响

为了评估低NOX燃烧器升级后水冷壁高温腐蚀的可能性,对某超超临界锅炉炉内燃烧进行了数值模拟,并对SOFA上摆的燃烧优化工况做了水冷壁贴壁气氛测试。结果表明,主燃烧区的上部和COFA、SOFA之间的还原区发生高温腐蚀的可能性较大;SOFA上摆扩大了还原区,增加了高温腐蚀的可能性,还原区贴壁H2S平均浓度沿着炉膛高度的增加而升高,为180-400μl/L;SOFA摆角的偏差使得局部H2S浓度达到了800μl/L,进一步加剧了局部区域高温腐蚀的风险;强氧化⇌强还原交替变动,使得SOFA以上区域(43.3m-46.1m)的高温腐蚀风险较典型还原区更为严重。在锅炉实际运行中,应尽可能权衡降低NOX排放和控制高温腐蚀风险。     

给定通流部分形状时多级轴流压气机效率优化

用一维理论对轴流压气机的初步设计作进一步的研究。导出了多级轴流压气机特性关系，建立了在给定通流部分形状时最优化设计的数学模型，得到了解析关系，并以某三级压气机为例进行了数值计算，所得结论具有一定的普适性，对多级轴流压气机的初步设计有一定的指导作用。     

内燃机消声器特性试验装置的研制及应用

研制了一种用于消声器声学性能研究的试验装置，该装置可研究在气流条件下内燃机进气消声器和在热气流条件下排气消声器的声学性能，为研究和分析消声器声学性能提供了坚实的试验基础。初步的试验结果表明：该装置能向试验管道内提供稳定的流动气体，对管内气流的加热温度能达到设计要求，能很好地模拟内燃机消声器内的声学条件。     

Evaluation of Tafel-Volmer kinetic parameters for the hydrogen oxidation reaction on Pt(1 1 0) electrodes

Modelling of PEM fuel cells has long been an active research area to improve understanding of cell and stack operation, facilitate design improvements and support simulation studies. The prediction of activation polarization in most PEM models has concentrated on the cathode losses since anode losses are commonly much smaller and tend to be ignored. Further development of the anode activation polarization term is being undertaken to broaden the application and usefulness of PEM models in general.Published work on the kinetics of the hydrogen oxidation reaction (HOR) using Pt(h k l) electrodes in dilute H₂SO₄ has been recently reassessed and published. Correlations for diffusion-free exchange current densities were developed and empirical predictive equations for the anode activation polarization were proposed for the experimental conditions of the previously published work: Pt(1 0 0), Pt(1 1 0) and Pt(1 1 1) electrodes, pH₂ of 1 atm, and temperatures of 1, 30 and 60 °C. It was concluded that the HOR on Pt(1 1 0) electrodes followed a Tafel-Volmer reaction sequence.The aim of the present paper is to generalize these Tafel-Volmer correlations, apply them to published data for Pt(1 1 0) electrodes and further develop the modelling of anode activation polarization over the range of operating conditions found in PEMFC operation.     

基于面向对象的透平级设计优化专家系统的研究

基于面向对象的设计方法,研究开发了透平级设计优化专家系统。本系统具有模块化程度高,良好的人机界面等优点,它为透平级设计带来了新的设计思想和实现方法,从而推动了人工智能技术在透平机构械设计领域中的进一步应用。