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利用相界面追踪的耦合水平集-流体体积(CLSVOF)方法,对液滴撞击超疏水管状壁面的动态特性展开研究,主要讨论粘性系数和表面张力系数对撞击过程的影响。研究结果表明:液滴粘性系数越小,液膜的铺展速度越快,回缩速度也越快,同时越早发生反弹,反弹高度也越大;随着表面张力系数的增大,液膜达到最大铺展所需时间减少,会阻碍液膜的铺展,但会促进其回缩,当表面张力系数为0.01 N/m时,液膜外边缘出现飞溅且液膜主体不发生反弹;还对液滴撞击超疏水管壁后出现的反弹、飞溅现象的机理展开分析。 相似文献
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利用相界面追踪的CLSVOF(coupled level set and volume of fluid)方法,对液滴在不同速度下撞击超疏水管状壁面的演化过程展开研究。研究结果表明,不同初速度会对液滴在管壁上的动态特性产生较大影响。当撞击速度较小时,液膜会以整体的形态反弹;继续增大撞击速度后,由于受到外缘液膜的牵扯,液膜内部开始出现断裂;撞击速度足够大时,液膜发生解体破碎。同时给出了对于初速度在2.00m/s以内、直径为2.58mm的水滴撞击管径为8.00mm的超疏水壁面时运动状态发生转变的临界条件。 相似文献
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采用界面追踪法(front-tracking method)对液滴撞击液膜动力学特性进行数值模拟,通过撞击后的形态演变及内部物理场信息分析,研究了韦伯数和无量纲液膜厚度对界面运动过程的影响,并阐述了撞击过程中形成卷吸现象的机理。研究表明,液滴撞击之后,会在颈部区域产生小射流,该射流是后期水花形成的基础;水平方向上,在撞击影响不到的区域压力不变化,而在射流形成处的颈部附近存在局部压差;液滴撞击液膜时其间的气体层被压缩,在流体黏性和剪切力的作用下,压力高的气层中的气体逃逸速度减慢,从而形成卷吸现象。 相似文献
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本文针对液滴撞击固体表面后出现的反弹和黏附两种运动状态,通过引入基于连续温度函数的能量方程,建立了用于计算液滴运动、传热和相变过程的数值模型,并与实验结果对比,验证了数值模型的准确性。进而模拟了具有不同韦伯数We和奥内佐格数Oh的液滴撞击低温超疏水表面的运动、传热和相变过程。结果表明:液滴撞击后的运动状态主要取决于奥内佐格数Oh,临界范围是0.022-0.026,而基本不受韦伯数We的影响。当液滴撞击后的运动状态为反弹时,韦伯数We越大的液滴,最大铺展直径越大。而当韦伯数相同时,随着奥内佐格数Oh的增大,液滴与表面的接触时间越大。 相似文献
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基于两相格子Boltzmann模型,对大密度比下有一定水平间距的双液滴冲击液膜的流动过程进行了仿真,模拟了不同液滴初始间距和不同雷诺数下液滴冲击液膜的动态过程,重点分析了不同液滴初始间距和雷诺数下产生不同冲击和溅射现象的原因,以及不同参数对冲击和溅射行为的影响.总结了中心位置水花溅射高度随时间的变化规律,并论述了冲击和溅射过程中的内在作用机理.结果表明:在一定范围内,初始间距和雷诺数越大,中心位置水花溅射高度上升越快;随着雷诺数的增大,冲击、碰撞的程度越剧烈,中心位置水花顶端有液滴飞出. 相似文献
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液滴撞击高温壁面的运动特性 总被引:1,自引:0,他引:1
《燃烧科学与技术》2017,(5)
利用相界面追踪复合Level Set-VOF方法,综合考虑液滴蒸发传热及接触热阻作用,对单液滴撞击高温壁面运动及影响因素进行了研究.研究表明,由于液滴蒸发传热作用,液滴撞击高温壁面会发生Leidenfrost现象;撞击速度较小时,液滴撞壁后发生铺展反弹,随着撞击速度的增大,液滴撞壁后会发生破碎现象;壁面温度的升高利于液滴破碎发生;液滴初始直径的减小有利于液滴撞壁后的反弹,而液滴直径的增大有利于液滴撞壁后破碎.通过数值模拟,给出了一定条件下柴油液滴撞击高温壁面反弹及破碎的临界条件. 相似文献
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采用CLSVOF(coupled level set and volume of fluid)方法,对低We情况下液滴撞击不同固体表面的过程进行了数值模拟研究。分析了液滴撞击平板表面的动态过程,构建了液滴衰减振荡的数学模型,探究了不同的表面润湿性、撞击速度及表面微尺度结构对液滴动态特性的影响。结果表明:液滴撞击固体表面的过程包含铺展、回缩、振荡等多个现象,其最大铺展因子及振荡周期随着表面接触角的增大而减小,随着撞击速度的增大而增大;撞击表面的微尺度结构会对液滴的动态特性产生影响,微尺度结构会对液滴的铺展及回缩运动产生阻碍作用,导致液滴的振荡特性减弱;液滴在矩形沟槽表面达到最大铺展因子的用时最短,在三角形沟槽表面的最大铺展因子最小。 相似文献
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Andreas Sumper Oriol Boix-Aragonès Roberto Villafáfila-Robles Joan Bergas-Jané Rodrigo Ramírez-Pisco 《Energy Policy》2010
This paper presents a methodology for the assessment of the impact of existing high voltage lines in urban areas. This methodology is based on the numeric evaluation of several impacts which are combined with weight factors. The novelty is that it opens up the possibility of citizen participation, basically in the way in which impacts and weighting factors are determined. The proposed methodology has been applied first in the municipality of Rubí, a mid-sized town near Barcelona, and later on in several municipalities in the Catalonia region in Spain. The results were used to prioritise mitigation action in the Catalonia Energy Plan. 相似文献
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Across Europe, CO2 emission allowances represent one of the main policy instruments to comply with the goals of the Kyoto Protocol. In this paper we use microdata to address two issues regarding the impact of the European Carbon Market (EU ETS). First, we analyze the sectoral effects of the EU ETS in Portugal. The goal is to study the distributive consequences of imbalances, with the novelty of taking into account firm financial data to put values into context. We show that a large majority of installations in most sectors had surpluses and the opportunity to raise remarkable revenues in some cases. We also look at the regional impact, since the pre-existing specialization of different regions in the production of different goods and services might lead to an uneven economic impact of the allowance market. In particular, Portuguese data indicate a distribution of revenue from low income to high income regions, or rather, between installations located in those regions. We focus on the first phase of the EU ETS, using data for each one of the 244 Portuguese installations in the market as well as financial data for 80% of these installations, although we also present data for 2008 and 2009. 相似文献
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A.S. Silitonga A.E. Atabani T.M.I. Mahlia H.H. Masjuki Irfan Anjum Badruddin S. Mekhilef 《Renewable & Sustainable Energy Reviews》2011,15(8):3733-3756
Energy is fundamental to the quality of life in the earth. Meeting the growing demand for energy sustainably is one of the major challenges of the 21st century. Indonesia is a developing country and the world's fourth most populous nation. Total annual energy consumption increased from 300,147 GWh in 1980, 625,500 GWh in 1990, 1,123,928 in 2000 and to 1,490,892 in 2009 at an average annual increase of 2.9%. Presently, fossil-fuel-based energies are the major sources of energy in Indonesia. During the last 12 years, Indonesia has recorded the most severe reduction in fossil fuel supplies in the entire Asia-Pacific region. This reduction has stimulated promoting the usage of renewable energy resources capable of simultaneously balancing economic and social development with environmental protection. Biodiesel is an alternative and environmentally friendly fuel that will participate in increasing renewable energy supply. Jatropha curcas is one of biodiesel resources that offer immediate and sustained greenhouse gas advantages over other biodiesel resources. Globally, J. curcas has created an interest for researchers because it is non-edible oil, does not create a food versus fuel conflict and can be used to produce biodiesel with same or better performance results when testing in diesel engines.The present study is concerned with the prospect of biodiesel produced from J. curcas in Indonesia. The first part gives a summary and overview of energy resources and consumption in the country, second part discusses the potential of biodiesel as a powerful renewable energy resource and third part investigates the potential of J. curcas as a feedstock for biodiesel in Indonesia. The final part discusses the development of biodiesel market in Indonesia. The paper found out that the production of biodiesel from J. curcas offers many social, economical and environmental benefits for the country and can play a great role to solve the problem of energy crisis in Indonesia. 相似文献
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The determination of optimum thickness of insulation is often applied to energy technologies and building projects. In this study, the energy, economic and environmental evaluations of thermal insulation in district heating pipeline are discussed. The optimum insulation thickness, energy saving over a lifetime of 10 years, payback period and emissions of CO2, CO and SO2 are calculated for nominal pipe sizes and fuel types based on heating loads in Afyonkarahisar/Turkey. The life cycle cost analysis is used to determine the optimum thickness of the pipeline material in order to take into account the change in inflation that directly affect both the cost of pipeline material and fuels depending on fuel type. The results show that the highest value of optimum insulation thickness, energy savings, emissions and the lowest payback period are reached for a nominal pipe size of 200 mm. About three times more energy saving results by making 200 mm nominal pipe instead of 50 mm. Considering the economical and environmental advantages, the geothermal energy is a better choice and then fuel-oil. When thermal insulation is done in a district heating pipeline, there will be a significant reduction of 21% in the amount of CO2 emitted to the atmosphere. 相似文献
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Gas–solid separator, a key component of a circulating fluidized bed boiler, controls the recirculation of solids around this type of boiler. As the technology matures, the drive is to have smaller size units handling a greater amount of solids. The impact separator is well suited to meet these demands with a low pressure drop from operating at low gas velocities. Complex hydrodynamics are encountered in an impact separator, where a staggered array of collection elements separates solids from an incoming mixture of gas and solid particles. The research was to examine the performance of this separator experimentally in a scale model, built to provide benchmark data. At an inlet gas velocity of 4.0 m s?1, an overall collection efficiency of 87.5% of particles with a mean particle diameter of 125 µm was realized. The results were compared with those from a similar study. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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《动力工程》2012,32(1)
对650℃时效500 h、1 000 h、3 000 h和10 000 h的P92钢以及时效后经过760℃回火处理的试样进行了冲击吸收能量、冲击断口和微观组织的试验,并定量分析了Laves相对P92钢冲击性能的影响程度.结果表明:冲击吸收能量、冲击断口的晶状断面率与组织中的Laves相含量之间的变化趋势一致,存在对应关系;Laves相对P92钢热脆化的影响程度取决于时效时间,在短时时效下,Laves相的析出和长大占主导地位,随着时效时间的增加,其影响份额逐渐降低,组织中的其他变化变得逐渐重要,但Laves相的析出和长大仍是主要影响因素;760℃回火可使Laves相发生回溶,并改善了冲击韧性,短期时效试样的冲击韧性可完全恢复到正、回火状态,但冲击吸收能量的组成比例却发生了变化. 相似文献
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建设项目环境影响评价与规划环境影响评价均遵循《中华人民共和国环境影响评价法》的要求,分析了两者之间存在的差异以及联系,得出,建设项目环境影响评价与规划环境影响评价虽然存在不同,但两者总体评价目的相同,他们之间存在个体服从整体的必然联系,存在环境影响评价结论及相关要求的一致性。 相似文献