共查询到19条相似文献,搜索用时 115 毫秒
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基于单颗粒消溶的缩核模型,建立了酸消溶石灰石反应在液膜传质和化学反应共同控制条件下的颗粒群的液固反应模型。实验研究了五种石灰石样品在不同温度、不同pH值和不同粒径分布下的消溶过程,模型理论计算与实验进行了验证,得到了不同种类的石灰石在不同反应条件下的平均整体反应常数k_m,且k_m是一个与反应条件相关的特征数。通过实验数据和理论模型对反应过程中的整体反应常数进行反推,发现同一反应条件下k_m随时间不断缩小并趋于常数,但粒度分布不同和产地不同的样品在相同反应条件下的整体反应常数相差不大。 相似文献
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为探究闪蒸喷雾冷却的微观机理, 设计并搭建了液滴悬挂式真空闪蒸实验装置, 利用可视化窗口探究Tween20 液滴闪蒸过程中的闪蒸特性及气泡生长机理. 液滴在快速降压过程中形态会经历气泡成核、气泡生长、伴随气泡生长、爆裂这四个阶段的变化, 并反复循环这一过程直至液滴稳定蒸发. 对于液滴温度的变化, 闪蒸室的终态压力起到了决定性的作用, 并且其终态温度随压力的升高明显上升. 同时通过液滴闪蒸过程形态图分析发现, 液滴在剧烈爆炸阶段其温度也发生明显下降; 在稳定蒸发阶段, 其温度也将开始稳定不变. 因此可知液滴的剧烈爆炸会带走其自身的大量热量. 而 Tween20 浓度对液滴温度的影响微乎其微, 但其会使液滴内气泡的初始成核时间发生明显滞后, 并抑制液滴内的气泡发生破裂. 相似文献
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炉内喷钙脱硫过程数值模拟 总被引:4,自引:0,他引:4
建立了一套较为完整的对炉内喷钙脱硫过程进行模拟的方法,获得了炉内气固两相流动、温度分布、石灰石颗粒脱硫化学反应和SO2浓度分布的详细情况。石灰石颗粒的硫化反应主要发生在颗粒与烟气均匀混合之前。 相似文献
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柠檬渣吸附污水中Hg~(2+)的动力学研究 总被引:2,自引:0,他引:2
由于农业废弃物价格低廉,改性后吸附性能优越等优点,目前利用农业废弃物制作吸附剂吸附污水中的重金属逐渐成为研究热点。为了研究柠檬渣对污水中Hg2+的吸附动力学,利用15%硫酸对柠檬渣进行了改性,测试了吸附剂的孔容与孔径等性能,并利用差热分析、红外光谱、电镜和能谱对样品进行了表征。结果表明改性柠檬渣吸附Hg2+的吸附速率由膜扩散控制,符合膜扩散中Lagergren一级动力学方程,该吸附过程主要为物理吸附。改性后的柠檬渣吸附性能有较大改善,孔径分布主要是中孔;有三个失重过程,在66℃左右有一个吸热峰,在316和494℃左右有两个放热峰。吸附前后并柠檬渣的基本框架没改变;样品属于无定型结构。改性柠檬渣表面疏松、多孔,能有效吸附Hg2+。 相似文献
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基于同时降低柴油机中的NOx和微粒的想法,作者提出混合闪蒸喷雾的设想,井建立了混合闪蒸试验台,以证实这种设想在喷雾阶段是否能实现.试验证实了混合闪蒸雾化改善柴油雾化的机理.文中分析了水油比、水的温度、压力对雾束形状、油滴平均直径的影响,对混合闪蒸用于实际柴油机的潜力做了估计. 相似文献
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Xue Dong Jie Yang David L.S. Hung Xuesong Li Min Xu 《Proceedings of the Combustion Institute》2019,37(4):4921-4928
Higher engine efficiency and ever stringent pollutant emission regulations are considered as the most important challenges for today's automotive industry. Fast evaporation and combustion technique has caused unprecedented attention due to its potential to solve both of the above challenges. Flash boiling, which features a two-phase flow that constantly generates vapor bubbles inside the liquid spray is ideal to achieve fast evaporation and combustion inside direct-injection (DI) gasoline engines. In this study, three spray conditions, including liquid, transitional flash boiling and flare flash boiling spray were studied for comparison under cold start condition in a spark-ignition direct-injection (SIDI) optical gasoline engine. Optical access into the combustion chamber includes a quartz linear and a quartz insert on the piston. In separate experiments, we recorded the crank angle resolved spray morphology using laser scattering technique, and distribution of fuel before ignition employing laser induced fluorescence technology, as well as time-resolved color images of flame with high-speed camera. The spray morphology during the intake stroke shows stronger plume-plume and plume-air interaction under flash boiling condition, as well as smaller penetration. Then around the end of compression (before ignition), the fuel distribution is also shown to be more homogeneous with less cyclic variation under flash boiling. Finally, from the color images of the flame, it was found that with the increase of superheat degree, the diffusion rate of blue flame (generated by excited molecules) is higher, which is considered to be related with the larger fractal dimension of the flame front. Also, the combustion is more complete with less yellow flame under flash boiling. 相似文献
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低压闪蒸液滴形态和温度变化的研究 总被引:5,自引:0,他引:5
将液滴在常压下突然置于低压环境中,液滴由最初的平衡状态变成过热状态,发生闪蒸.本文实验研究了低压闪蒸液滴内部形态和温度的变化,系统描述了液滴闪蒸过程中的各种形态变化,总结了稳态闪蒸和稳态结冰过程中环境压力和初始温度对温度变化的影响.实验结果表明液滴闪蒸分六种形态.稳态闪蒸中环境压力越低,液滴的最终温度也越低;液滴的初始温度越高,降到最低温度的时间越长.稳态结冰过程中,液滴初始温度增加,液滴结冰温度和结冰回升最高温度也随之增加;液滴的结冰温度和回升最高温度随环境压力的增高而减小. 相似文献
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Negative photoconductance or optical quenching has been observed in thin InSb films, fabricated by vacuum evaporation on glass substrates. An electronic flash was used as the light source. The time constant of the photocurrent measured on several samples ranges from 30 sec to 3 min. Whereas bulktraps localised in the narrow band gap of InSb (0.18 eV) can hardly be responsible for the high time constants, it is believed that slow surface traps or traps inside an In2O3 layer, covering the InSb film, are responsible for the optical quenching. 相似文献
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Carbon foams are being developed as a new class of thermal management materials. These foams are produced with a wide variety of thermo-mechanical properties; however, very few studies of the properties of carbon foams have been reported in literature. This article reports on an experimental study that was conducted to determine the thermal conductivity of various forms of graphitic carbon foam by using the flash diffusivity and guarded hot plate method. To reduce errors introduced by porous specimen, the test samples were vacuum infiltrated with epoxy. The thermal diffusivity results from the flash diffusivity instrument were used to determine the thermal conductivity of the samples. Some foam samples were determined to have large variations in thermal properties within the sample block. A theoretical and numerical model has been used to examine the effect of the filler epoxy on the experimental results and the influence of pore characteristics on the thermal conductivity of these foams. It was determined that accurate measurement of thermal properties of graphitic foam samples requires careful selection of sample size and measurement technique. 相似文献
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A study of the optical properties and adhesion of zinc sulfide anti-reflection thin film coated on a germanium substrate 总被引:1,自引:0,他引:1
S.A.R. FiroozifarA. Behjat E. KadivarS.M.B. Ghorashi M. Borhani Zarandi 《Applied Surface Science》2011,258(2):818-821
To conduct this study, zinc sulfide (ZnS) thin films deposited on germanium (Ge) substrates were prepared by an evaporation method. The effects of deposition rate and annealing on the optical properties and adhesion of the ZnS thin films were investigated. The transmission intensity and the X-ray diffraction (XRD) pattern of the samples showed that the transmittance of the samples decreases by increasing the evaporation rates. However, with the increase of the annealing temperature, crystallinity of the thin films improves which, in turn, results in the enhancement of the transmission intensity in a far infrared region. The maximum grain size was obtained at the annealing temperature of 225 °C. Our experimental results also show that evaporation rate and annealing influences the adhesion of ZnS thin films to Ge substrates. 相似文献
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《Journal of Physics and Chemistry of Solids》2003,64(9-10):1821-1824
Ce-doped CaGa2S4 and SrGa2S4 thin films were prepared for the first time by the flash evaporation method. The films were characterized before and after annealing in H2S(10%)+Ar gas stream by measuring photoluminescence and absorption spectra, X-ray diffraction and electron probe micro analyses. X-ray diffraction curves and absorption spectra before annealing show amorphous behaviour, whereas the annealing leads to a significant crystallization and improves the stoichiometry of the films. Based on the performance data obtained from dispersive type EL cells using CaGa2S4:Eu powder together with photoluminescence property comparison between CaGa2S4:Eu and CaGa2S4:Ce powders, the annealed films prepared by flash evaporation can be considered to become one of the candidates for TFEL flat panel devices. 相似文献