共查询到19条相似文献,搜索用时 187 毫秒
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碳纤维传动轴胶接联接在传递载荷时,会出现端部胶层应力大、中间应力小的现象,这种现象会使胶接接头的胶层首先从端部破坏,影响联接性能。从应变角度阐述胶接胶层应力曲线规律,说明了影响胶层应力分布的因素有胶层内、外周向变形量和胶层厚度,提出几种胶接胶层应力均匀化方法,并用有限元分析方法进行了验证。结果表明:(1)增加胶层厚度可以使胶层应力均匀化,但均匀化程度不明显,且在工程中会增加胶层缺陷;(2)采用变胶层厚度的鼓形结构胶接能够使胶层应力均匀化明显,最后指出影响鼓形胶接胶层应力均匀化的因素有变厚度胶层长度L、胶层的最大厚度H。 相似文献
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在各种温度下,研究初始厚度为0.4mm(±0.03)的YSZ流延膜片薄层热风干燥的一般规律。干燥受风速的影响都较大,风速越高,干燥速度越快;风速越低,干燥速度越慢;在干燥后期,三个不同的风速水平对干燥过程的影响几乎没有明显差异。流延膜片越厚,干燥速度越慢;而流延膜片厚度越小,干燥速度越大;过高的风温风速会使流延膜片性能质量降低;热风干燥的参数必须考虑实际生产中产品的质量要求设定;所求得的Page模型能够正确反映水溶胶胶层薄层干燥规律,可用于实际生产工艺的基础参考数据。 相似文献
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0 前言
镀铬层特别是枪管镀铬层对厚度均匀性有着严格的要求.由于镀铬液分散能力差,对大工件镀铬,尤其是施镀时间长、电流大的镀硬铬,铬层沉积越厚,越容易造成电流分布不均匀,产生诸如锥度、椭圆度、"狗骨"形态等缺陷.本文介绍了阳极、内电阻、三价铬等因素对镀铬层厚度均匀性的影响. 相似文献
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共挤出技术可使产品同时具有阻隔性、透明性、印刷性、热封性等特殊性能,并使其成本费用得到大幅度的降低,因而其应用价值得到了越来越广泛的关注。以LDPE/HDPE/LDPE三层共挤出薄膜为例,确定了三层共挤出吹膜机头的流道结构和狭缝流道结构,对三层共挤出吹膜机头的流道进行全六面体网格划分,采用有限元方法对流体在共挤出流道内的等温流动过程进行了求解,分析了狭缝初始高度对机头流道的压力场、速度场以及界面位置的影响。研究表明,随着狭缝初始高度的增大,第一、二和三层的层分配流道压力降减小,共挤出流道压力降变化较小,出口速度分布越来越不均匀;减小狭缝初始高度有利于各层出口速度分布的均匀性,降低界面波动,有利于第一、三层层厚分布的均匀性。 相似文献
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不同干燥因素对天然橡胶微波干燥过程的影响 总被引:1,自引:0,他引:1
使用动态称量微波干燥设备研究了不同微波功率密度、不同胶样厚度和不同初始含水率3种因素对湿天然橡胶微波干燥过程及表观质量的影响。结果表明,3种因素对湿天然橡胶微波干燥过程和胶样表观质量的影响较大;微波功率密度越大,失水速率就越大,干燥时间就越短,胶样易出现干燥发粘现象;胶样厚度越厚,失水速率越小,干燥时间就越长,易出现部分夹生和发粘现象;初始含水率越高,失水速率就越大,干燥时间就越长,胶样易出现部分发粘现象。微波干燥湿天然橡胶较为合适的微波功率密度、胶样厚度和初始含水率分别为30.14-34.2W/dm3,5~15mm和10%-20%。 相似文献
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对已有的螺旋流道辊模型进行合理简化,运用流场仿真软件Fluent对流道辊的温度场进行了仿真分析,得到了流道辊的温度场,从而得到了流道辊内流体速率、流体温度场、辊筒表面温度场等。通过分析模拟仿真结果,得到了辊筒外表面温度不均匀的原因,并在此基础上,以提高辊筒外表面的温度分布均匀性为目标,对流道结构进行多次改进,找出一种最佳方案,明显改善了辊筒端部的温度分布均匀性,使辊面的有效利用长度延长了约50 mm。 相似文献
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采用CFD数值模拟方法研究热风循环隧道烘箱的内部温度及流场分布,提出了6种结构优化方案,考察了不同方案下的气流分布特性。结果表明,烘箱出口面局部温差在1 K以内,温度分布较均匀;气流速度分布是影响烘干品质的主要因素,原始结构下出口气流分布极不均匀,出口面角落位置出现局部高速区,最大速度达3.48 m/s,平均速度为0.94 m/s,相对均方根值为0.73;相比原始结构,6种改进方案中,弯头三隔板结构出口面的相对均方根值最低,最大速度降低51.4%,最佳风速区域占比提升至75.17%,整流效果最明显;弯头内设置三块隔板后,风罩内再设置隔板对气流均匀性的改进作用不大。 相似文献
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《Drying Technology》2007,25(12):1949-1958
A mathematical model for through drying of paper at constant pressure drop was developed. The model is based on physical properties; hence, basis weight, pressure drop, drying air temperature, pore size distribution, initial gas fraction, and tortuosity are important input parameters to the model. The model was solved for different combinations of the variables basis weight, drying air temperature, and pressure drop corresponding to industrial conditions and the results were compared with data from bench-scale experiments. The simulations show that the drying rate curve is very sensitive to the air flow rate and that correctly modeling the correlation between pressure drop and air flow rate is the most important factor for a successful model for through drying. The model was tuned by adjusting the parameters initial gas fraction and tortuosity in order to give the best possible fit to experimental data. For a given basis weight and pressure drop, different drying air temperatures resulted in relatively constant values of the fitted parameters. This means that the model can well predict the effects of changes in drying air temperature based on a tuning of the model performed at the same basis weight and pressure drop. However, for a given basis weight, an increase in pressure drop yielded fitted parameters that were somewhat different; i.e., a lower initial gas fraction and a higher tortuosity, a change that increases the resistance to air flow. This implies that the correlation between pressure drop and air flow rate in the model does not quite capture the nonlinear relationship shown by the experiments. 相似文献
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A mathematical model for through drying of paper at constant pressure drop was developed. The model is based on physical properties; hence, basis weight, pressure drop, drying air temperature, pore size distribution, initial gas fraction, and tortuosity are important input parameters to the model. The model was solved for different combinations of the variables basis weight, drying air temperature, and pressure drop corresponding to industrial conditions and the results were compared with data from bench-scale experiments. The simulations show that the drying rate curve is very sensitive to the air flow rate and that correctly modeling the correlation between pressure drop and air flow rate is the most important factor for a successful model for through drying. The model was tuned by adjusting the parameters initial gas fraction and tortuosity in order to give the best possible fit to experimental data. For a given basis weight and pressure drop, different drying air temperatures resulted in relatively constant values of the fitted parameters. This means that the model can well predict the effects of changes in drying air temperature based on a tuning of the model performed at the same basis weight and pressure drop. However, for a given basis weight, an increase in pressure drop yielded fitted parameters that were somewhat different; i.e., a lower initial gas fraction and a higher tortuosity, a change that increases the resistance to air flow. This implies that the correlation between pressure drop and air flow rate in the model does not quite capture the nonlinear relationship shown by the experiments. 相似文献
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The objectives of this research were to investigate empirical and diffusion models for thin-layer crumb rubber drying for producing STR20 rubber using hot air temperatures of 110–130°C and to study the effect of drying parameters such as inlet drying temperature, volumetric flow rate, and initial moisture content on the quality of dried rubber. Finally, a mathematical drying model for predicting the drying kinetics of crumb rubber was developed using inlet air flow rates of 300–600 m3/min-m3 of crumb rubber (equivalent to 1.8–5.0 m/s) with the crumb rubber thickness fixed at 0.25 m. The average initial moisture content of samples was in the ranges of 40 and 50% dry basis while the desired final moisture content was below 5% dry basis. The results showed that the drying equation of crumb rubber was highly related to the inlet air temperature, while the drying constant value was not proportional to the initial moisture content. Consequently, the experimental data were formulated using nine empirical models and the analytical solution of moisture ratio equation was developed by Fick's law of diffusion. The result showed that the simulated data best fitted the logarithmic model and was in reasonable agreement to the experimental data. The effective diffusion coefficient of crumb rubber was in the range of 1.0 × 10?9 to 2.15 × 10?5 m2/s corresponding to drying temperatures between 40 and 150°C, respectively. The effects of air recirculation, inlet drying temperature, initial moisture contents, air flow rate, and drying strategies on specific energy consumption and quality of samples were reported. The experiments were conducted using two different drying strategies as follows: one-stage and two-stage drying conditions. The results showed that initial moisture content and air flow rates significantly affected the specific energy consumption and quality of rubber, while the volumetric air flow rate acted as dominant effect to the specific energy consumption. The simulated results concluded that the percentage of recycled air between 90 and 95% provided the lowest specific energy consumption as compared to the others. 相似文献
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干气密封流体膜与密封环间传热模型的合理选取对于准确求解密封温压分布和稳态性能至关重要。在CO2近临界工况下,对比研究了密封环等温模型、绝热模型和共轭热传递模型对超临界CO2干气密封端面温度、压力分布和开启力、泄漏率等稳态性能的影响,探讨了不同膜厚和转速条件下密封环等温模型和绝热模型的适用性,并基于共轭热传递模型研究了超临界CO2和空气介质干气密封的温压分布和稳态性能差异。结果表明:以共轭热传递模型计算结果为基准,密封环等温模型假设适用于小膜厚低速流动工况,不过开启力偏低而泄漏率偏高,绝热模型假设适用于大膜厚高速流动工况;相较于空气介质干气密封,超临界CO2干气密封在小膜厚下的温度分布和大膜厚下的压力分布基本接近,不过小膜厚下的温度更低,而在大膜厚下的压力更高。 相似文献
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在Fluent软件中选用标准的k-ε模型对分级机送料筒内气流分布进行模拟,得到两种不同进风口时的气流分布情况。分级机采用对侧进风口时,送料筒内气流运动属于对冲、挤压、压扁与转向的过程,气流分布不均。分级机采用环面进风口时,送料筒内气流运动是一个汇集、分散、转向的过程,气流分布相对均匀,有利于提高分级精度。实验研究中,保持喂料速度、系统风量、分级机转速一定的条件下,通过改变进风口面积,分别测试了两种风口在不同进口风速时的切割粒径、分级精度的变化。实验结果表明,随着风口面积的减小,进口风速增大,两种风口的分级机的分级粒径基本不变,分级精度先增大后减小。通过分级精度的对比,说明环面进风对于颗粒的分散性能较对侧面进风更为优越。 相似文献
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为解决侧进风盐泥干燥室内干燥不均匀问题,采用数值模拟、实验研究的方法进行结构改进。基于标准k-ε模型和多孔介质模型对干燥室流场进行数值模拟,测量了风速及干燥后盐泥的含水率,根据结果对干燥室结构进行改进。结果表明:原结构干燥室内热风流动的动力来源主要依靠初速度,在干燥室内流动扩散并产生各种扰动,气流不均匀系数较大,干燥后的盐泥含水率较高且不均匀;改进结构后的干燥室内部形成的压力梯度成为热风流动的驱动力,使热风穿过盐泥层向上运动,气流不均匀系数小,干燥后的盐泥含水率低且较为均匀。对比原结构,改进结构后的干燥室内部气流不均匀系数至少下降27.6%,干燥后的盐泥含水率下降4.48%,含水率不均匀系数下降8.4%。 相似文献
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为解决实际工业中除雾器在高气速时分离效率明显降低的问题,利用除雾器分离实验装置,以水为实验介质,采用电火花线切割技术在叶片表面构建仿生微结构实现表面疏水化,考察了表面润湿性对除雾器分离效率和压降的影响。结果表明,仿生微结构的疏水功能和减阻效应良好,表面液膜的排液速率明显加快。当气速超过5 m/s时,其液膜厚度相对较薄,可有效抑制液滴的二次夹带,提升分离效率。同时,疏水型梯形除雾器内的流场分布较平缓,流动阻力小,总压降约为带钩型梯形除雾器的一半。因此,疏水型梯形除雾器兼具高效率和低阻力特性,综合分离性能最佳。 相似文献
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随着经济的飞速发展,空气质量存在着严重的问题,而清洁能源天然气是当前最合适的汽车替代燃料。应用分输站或城镇管网预留接口的天然气,经调压、计量、脱水干燥后进入压缩机,经压缩机增压至20 MPa后直接为高压气体半挂车充气,为CNG加气子站提供天然气气源,在一定程度上缓解了环境污染问题。阐述了压缩天然气加气母站的主工艺流程、安全泄压保护流程、加臭流程,压缩机、脱水装置等主要设备的选型以及自控仪表等方面的工艺设计方案。 相似文献