贯流机组两种弹簧连杆结构分析比较

导叶安全保护装置是贯流机导水机构的重要组成部分,其动作的可靠性、对于电站的日常运行至关重要。导叶安全保护装置主要包括：破坏性结构,剪断销、拉断销;半破坏结构,弯曲连杆;自动回复结构,弹簧连杆。其中弹簧连杆结构可靠性与前两种相当,动作后自动回复是其最显著的特点。目前弹簧连杆结构主要有两种：拉伸式弹簧连杆、压缩式弹簧连杆。从两种弹簧连杆结构的工作原理、结构设计、安装调整、弹簧选择几方面分析比较其各自的优缺点。     

某汽油机连杆失效分析与优化验证

通过使用故障树FTA分析,主要运用AVLEXCITE进行连杆系统动力学分析、Nastran应力恢复评估连杆应力状况,同时校核螺栓拧紧方式,改善连杆涨断工艺等手段,解决了涨断连杆在试验中出现的多次连杆断裂问题,并通过了相关的可靠性试验,取得了良好的市场表现。     

DF_7型机车柴油机连杆瓦失效故障分析与预防

针对DF7型机车柴油机发生多起连杆瓦失效,柴油机遭受重大损失的故障,搜集该机型连杆瓦故障信息并进行分析。分析表明:轴瓦失效的主要形式是微动磨损引起的磨损失效;分析了轴瓦产生微动磨损的主要原因,并提出了预防措施。     

连杆锻坯的主要缺陷分析

连杆是柴油机中重要的传动件之一,要求其具有良好的综合机械性能,对于年产量数十万根的大型企业,连杆的锻造质量无疑起着举足轻重的作用,为使连杆锻坯减少次品、杜绝废品而作了多次的金相分析,初步归纳出以下几种主要的缺陷;原材料裂缝;锻造折迭;因锻造参数控制不当而引起的锻裂、淬裂等。文中还提出了防止这些缺陷的预防措施。     

东风135柴油机讲座(4)

<正> 5 连杆连杆是活塞和曲轴之间的连接件,它主要起着传递力的作用。它由连杆体、连杆盖、连杆螺钉、小头铜套、连杆大头轴瓦、定位套筒组成。为了减少连杆小头孔内活塞销的磨损,在小头孔内压入铅青铜套。     

基于有限元的某机型连杆结构分析

以某机型连杆为分析对象,对连杆的稳定性和疲劳强度进行分析。首先建立连杆有限元模型,对连杆进行非线性屈曲分析;然后以连杆动力学结果为力学边界,计算了连杆的疲劳强度。计算结果表明:连杆在轴线方向上所受到的最大载荷为43.5 kN,小于屈曲载荷65kN;该连杆高周疲劳最小安全系数为1.53,高于安全系数1.5的评判标准。根据以上结果可以判定,该连杆结构能够满足此发动机的使用要求。     

浅谈某柴油机连杆瓦烧瓦原因分析

我们基于某型柴油机连杆瓦烧瓦问题,针对曲轴的制造质量、润滑油压力及润滑系统、连杆刚性、配瓦间隙及连杆瓦自身参数等方面进行分析,结果表明:连杆瓦自身参数半径高偏大是导致连杆瓦烧瓦的主要原因。同时,通过优化半径高,并进行有关的试验验证,成功解决了连杆瓦烧瓦问题。     

典型零件的设计结构特点与加工工艺过程分析

连杆组件是柴油机中的关键运动、传力构件,四方机车车辆厂柴油机分厂与奥地利AVL联合开发的轻型、高速、大功率12V180ZJC柴油机用的连杆又有许多特殊之处.本文主要介绍该连杆的特殊设计结构特点和加工工艺过程分析.通过该方法的使用,不仅极大的改善了连杆的加工质量,而且大大提高了连杆的生产效率.实践证明,此方法不失为特殊连杆的良好加工工艺方法.     

发动机连杆材料及工艺

连杆轻量化的途径主要是制造工艺和材料的改进.本文对发动机连杆工艺和材料进行了较全面的分析论述,指出了今后连杆工艺和材料的应用发展趋势.     

轿车发动机高强度连杆开发

采用计算机辅助设计(CAE)方法设计了轿车发动机用轻量化、高强度连杆;通过有限元计算分析,该连杆不存在失稳危险,并符合强度要求;用液压伺服疲劳试验系统进行疲劳试验,连杆安全系数满足设计要求;通过严格控制生产加工工艺,提高制造加工质量,实现了该连杆的批量生产.     

Review on Malaysia's national energy developments: Key policies,agencies, programmes and international involvements

This paper aims to present a review on Malaysia's national energy developments by looking at various angles in terms of renewable energy and energy efficiency. Energy demand and consumption by sectors are presented as well as the fuel mix in electricity generation. Key energy policies implemented from the incorporation of Malaysia's national oil company, Petronas in 1974 until the National Green Technology Policy 2009 and a future policy will be addressed. The roles of key players as well as important agencies in energy development are briefly presented. Key programmes in energy development such as Malaysian Industrial Energy Efficiency Improvement Project, Small Renewable Energy Power Programme and Building Energy Efficiency Programme are discussed as well as successful initiatives from the programmes. Malaysia's international involvements towards reduction of greenhouse gas emissions and carbon emissions especially Montreal Protocol and Kyoto Protocol are highlighted. As a conclusion, Malaysia is aware of its role in formulating its national energy development policies, sensitive towards the country's development towards the environment and utilization of energy resources as well as conscientious and responsive towards the call for sustainable development in promoting renewable energy and energy efficiency.     

Performance characteristics of refrigeration cycle with parallel compression economization

Thermodynamic analyses and economizer pressure optimizations of ammonia, propane and isobutane‐based refrigeration cycles with parallel compression economization are presented in this article. Energetic and exergetic performance comparisons with transcritical CO₂ cycle are presented as well. Results show that the optimum economizer mass fraction as well as COP improvement increase with increase in cycle temperature lift. The expression for optimum economizer pressure has been developed. Study shows that the performance improvements using parallel compression economization are strongly dependent on the refrigerant properties as well as the operating conditions. Using parallel compression economization, carbon dioxide yields maximum COP improvement of 31.9% followed by propane (29.8%), isobutane (27.2%) and ammonia (11.3%) for studies ranges. In spite of higher COP improvement, the cooling COP as well as second low efficiency for carbon dioxide is still significantly lower than that for others. Component‐wise irreversibility distributions show the similar trends for all refrigerants except CO₂. Employing parallel compression economization in refrigeration cycle not only improves the cooling COP but also increase the compactness of evaporator. Copyright © 2010 John Wiley & Sons, Ltd.     

Magnetic field aligned nanocomposite proton exchange membranes based on sulfonated poly (ether sulfone) and Fe2O3 nanoparticles for direct methanol fuel cell application

Sulfonated poly (ether sulfone) (SP-ES) are prepared and optimized considering the transport properties and physicochemical stability. Afterward, nanocomposite membranes composed of SP-ES containing various loading weights of γ-Fe₂O₃ nanoparticles are fabricated. Nanoparticles assembled into an aligned form across the membrane by applying magnetic field during solvent casting. The effect of nanoparticles orientation is studied by consideration of the water uptake, membrane ionic conductivity, and activation energy as well as methanol permeability. Aligned membranes have a higher proton conductivity and also lower activation energy for proton migration as well as lower water uptake and methanol permeability. It is also noted that nanocomposite membranes have sufficient thermal stability and high electrochemical performance. Consequently, the anisotropic nanocomposite membranes with oriented nanoparticles demonstrate the ability to have potential application in fuel cells as well as ionic actuators.     

RENEWABLE ENERGIES AND ENERGY CONSERVATION TECHNOLOGIES FOR BUILDINGS IN SOUTHERN EUROPE

The characteristics of the building's energy consumption in Southern Europe are analysed. The energy potential of solar energy for heating and lighting purposes as well as the potential of passive cooling techniques are investigated. The ecological impact of the energy saving technologies as well as the market opportunities of the alternative technologies are discussed.     

Exploring the application of AlN graphyne in calcium ion batteries

Destiny functional theory (DFT) calculations are undertaken in order to scrutinize the electrochemical and calcium (Ca) storage characteristics of a graphyne-like aluminum nitride monolayer (G-AlNyen) as an electrode material for Ca-ion batteries (CIBs). The results show that the change in internal energy as well as the cell voltage values for the CIB with the G-AlNyen anode are comparable to others with two-dimensional 2D nano-materials. It is shown that Ca is adsorbed primarily onto the center of a hexagonal and triangular ring of G-AlNyen with absorption energies of ?2.06 and ?0.42 eV. After increasing the concentration of Ca atoms on G-AlNyen, the adsorption energy as well as the cell voltage decreases. Lower values of 0.15–0.32 eV related to the diffusion barrier confirm that the diffusion of Ca in the 2D nano-sheets is rapid. G-AlNyen shows a maximum theoretical capacity of approximately 869.23 mAh h g^?1. The results are evaluated in terms of charge transfer, structure, energy as well as electronic characteristics and provide insight into the construction of better anode materials with higher capacity for the CIB.     

Design of grid connected PV systems considering electrical, economical and environmental aspects: A practical case

This paper presents the complete design of a photovoltaic installation that may be either used for internal electric consumption or for sale using the premium subsidy awarded by the Spanish Government. Electric optimization strategies are detailed in the project, as well as the sizing of the photovoltaic installation and economic and financial issues related to it. The project optimizes the electricity demand, improving reactive power and studying the convenience of hourly discrimination fees in addition to the design of the photovoltaic installation. A specific computer application for the automated calculation of all relevant parameters of the installation—physical, electrical, economical as well as ecological—has been developed to make the process of calculating photovoltaic installations easier and to reduce the design development time. Moreover, the budget of the photovoltaic installation is included, as well as its corresponding financial ratios and payback periods. Finally, the conclusions reached in the technical and economic design of the installation are shown.     

Multiple Ti and Li doped carbon nanoring for hydrogen storage

Multiple Ti and Li atom doped carbon nanorings are considered for hydrogen storage using density functional theory for the first time. There are five six membered carbon rings bonded through C–C bond in a carbon nanoring. Formation energy values show that both, Li as well as Ti atom doped carbon nanoring, are thermodynamically stable structures. Cohesive energy values indicate that Li and Ti atom doped carbon nanoring structures are more stable than undoped carbon nanoring. No clustering of metal atoms occurs in metal doped carbon nanorings which usually reduces the hydrogen storage capacity of a material. Li atom doped carbon nanoring is not suitable for hydrogen storage even at very low temperature at 1 atm pressure as well as at high pressure at room temperature. Ti atom doped carbon nanoring is suitable for hydrogen storage below 225 K and 1 atm pressure as well as at high pressure at room temperature. H₂ desorption temperature is found to be 113 and 450 K for Li and Ti atom doped carbon nanoring respectively. H₂ molecules interact strongly with Ti atom doped carbon nanoring than Li atom doped carbon nanoring that results in higher H₂ desorption temperature for the former than the latter.     

High temperature stability of larger aromatic compounds

This paper considers the rate constants for the following processes:where M is the collision partner and aromatic CH₃ is toluene, 1-methylnaphthalene or 1-methylphenanthrene. Rate constants are derived over a range of temperatures and pressures. Primary interest is focused on the effect of molecular size on temperature as well as pressure dependent rate constants. Results are based on the toluene system where comparisons can be made with experimental data and ab initio and RRKM calculations from the literature. A general strategy for deriving rate constants for chemical activated as well as thermal reactions, which is readily extendable to larger molecules, has been validated. The special feature of these reactions is the formation of resonance stabilized aromatic molecules. The results demonstrate the necessity of considering chemical activation processes in most of the cases where excited adducts are formed. These include oxygen addition to radicals as well as soot formation processes involved in ring growth. Chemical activation processes are intimately related to thermal process and their inclusion in current databases where thermal processes are properly represented is mandatory.     

Techno-economic evaluation of medium scale power to hydrogen to combined heat and power generation systems

The European Hydrogen Strategy and the new « Fit for 55 » package indicate the urgent need for the alignment of policy with the European Green Deal and European Union (EU) climate law for the decarbonization of the energy system and the use of hydrogen towards 2030 and 2050. The increasing carbon prices in EU Emission Trading System (ETS) as well as the lack of dispatchable thermal power generation as part of the Coal exit are expected to enhance the role of Combined Heat and Power (CHP) in the future energy system. In the present work, the use of renewable hydrogen for the decarbonization of CHP plants is investigated for various fossil fuel substitution ratios and the impact of the overall efficiency, the reduction of direct emissions and the carbon footprint of heat and power generation are reported. The analysis provides insights on efficient and decarbonized cogeneration linking the power with the heat sector via renewable hydrogen production and use. The levelized cost of hydrogen production as well as the levelized cost of electricity in the power to hydrogen to combined heat and power system are analyzed for various natural gas substitution scenarios as well as current and future projections of EU ETS carbon prices.     

The structure of premixed and stratified low turbulence flames

Practical combustion systems typically operate in stratified regimes to leverage the advantages of a spatially varying mixture fraction field. Although these benefits are well known in industry, the fundamental physics underpinning these effects are currently an area of active research. In this paper simultaneous Rayleigh–Raman–LIF measurements of temperature and major species concentrations along a line are used to investigate the structure of a weakly turbulent stratified flame. Concurrent cross-planar OH-PLIF enables the extraction of flame orientation relative to the measurement line, as well as flame front curvature. The behavior of major species concentrations with respect to temperature is found to agree well with laminar flames at the local mixture fraction, even in stratified flows. However, measurements of the surface density function, ∣∇c∣, and scalar dissipation, χ_c, suggest that both premixed and stratified flames are spatially thicker at the microscale than corresponding laminar flames.