薄膜透气性测试装置3层密封结构的研究

基于压差法的薄膜透气性测试装置,在压力和温度检测器的检测性能给定和环境温度相对稳定的情况下,影响测试结果的主要因素是测试装置的密封性能。为了同时提高测试装置的密封性能和测试精度,提出了3层密封结构设计的模型,建立了相应的数学模型,并给出了因泄漏而引起压强变化的特性和仿真结果。为3层密封结构薄膜透气性测试装置的实际应用提供了理论依据。     

基于压差法的薄膜透气性测试装置研究现状

分析了国内外基于压差法的塑料薄膜透气性测试装置的研究现状,总结了影响满足国家标准要求的透气性测试装置测试性能的主要因素。指出了单密封结构的测试装置难以满足高阻隔性薄膜透气性的测试要求,提出了合理处理高阻隔性薄膜透气性测试问题的途径。     

载人航天器舱内气体泄漏数值模拟分析

针对载人航天器舱内气体在太空中的泄漏问题,提出内外舱同时升压法来进行数值模拟计算,引入无量纲参数气体泄漏因子来判定气体泄漏量。采用基于Simple算法的有限体积法,对载人航天器舱内气体泄漏状态进行仿真,并分析了气体泄漏过程中影响参数。结果表明:增加镀铝薄膜层厚度和减小镀铝薄膜层材料孔隙率都能同时减弱气体泄漏因子,使气体泄漏量降至最小。     

典型双密封结构泄漏机理研究

使用氦质谱吸枪检漏法检测航天器管路双密封结构螺接头漏率时,常会发生漏率随时间变化的情况。为了从理论上分析该问题的实质,本文建立了两种双密封结构泄漏过程的数学模型,分别考虑了分子流和粘滞流两种状态,并求解了数学模型的方程解析解,编制程序进行数值模拟仿真,形象地显示了双密封结构系统正压泄漏情况下,漏率、压力与泄漏时间关系的规律,及其影响泄漏时间长短的因素。并计算了不同初始条件下,双密封结构的漏率稳定时间。这些研究结果可直接应用于航天器管路双密封结构螺接头漏率测试候检时间评估计算,并对双密封结构系统的设计和泄漏安全评估,从理论上提供指导意义。     

科学看待压力差与材料透气性的关系

本文详细分析了认为在压差法中气体压力差的存在会影响透气性测试结果这种观点的错误之处，并通过大量实测数据证明了在压差法透气性测试中施加在试样两侧的压力差不会对材料的透气性（透气量和透气系数）带来影响。     

气体渗透镀铝薄膜机理研究

用氧气（O2）、氮气（N2）和二氧化碳（CO2）在20－40℃的环境温度下，对2种不同的镀铝薄膜及其叠层和底层分别进行了透气性测试，来阐明金属覆膜对降低聚烯烃薄膜透气量所起到的作用，由试验结果分析可得：气体分子能渗透镀铝薄膜是由于铝层中可渗透的孔状结构以及薄膜表面上有均布的微孔。     

真空热沉积过程中有机薄膜生长的模拟研究

利用Monte Carlo方法对真空蒸发系统下的有机薄膜生长过程进行了模拟.在该系统模型中,Ns个点蒸发源均匀分布在半径为R的圆周上,基板相对蒸发源所在平面距离为d.利用该模型分析了膜厚分布以及点蒸发源个数Ns、蒸发源与基板的相对位置R和d对薄膜厚度均匀性的影响,并通过实验对仿真结果进行了验证.结果显示,增加蒸发源个数、增大相对基板位置均可以有效提高薄膜的均匀性,测试发现薄膜样品的精度MaX-Min均保持在5%左右.     

重型液压凿岩机双缓冲系统特性分析与实验

针对当前双缓冲系统特性研究不足,严重制约凿岩机冲击功率提高的现状,考虑岩石动力学特性和应力波的透射与反射,建立以冲击为输入的应力波传递模型,获取了钎头凿入位移和缓冲活塞回弹速度。考虑油液压缩、油液泄漏、阀口压降等因素,建立了包含缓冲活塞、缓冲阀、缓冲蓄能器以及连接管路的双缓冲系统耦合模型。设计现场凿岩实验,同步测试了冲击系统和双缓冲系统腔内压力,验证了数值仿真模型的正确性。在此基础上,分析了双缓冲间隙对缓冲活塞运动规律和一、二级缓冲腔压力变化规律的影响。仿真结果表明,双缓冲间隙存在最优范围,如若设计不当,会影响系统的响应速度,引起极高的压力峰值,甚至造成系统空蚀的发生。     

基于LabVIEW的液压缸密封件泄漏试验测试系统设计

设计了一种基于LabVIEW的液压缸密封件泄漏试验测试系统,方便有效地实现了对密封件泄漏的测试并利用电子天平称重法对泄漏进行检测,同时通过RS232与计算机通讯实现上位机对泄漏量的数据采集、曲线绘制和结果分析等。该系统具有测试精度高、自动化程度高,测试效率高等特点,可为密封件密封性能测试提供实验支持。     

微薄膜多场耦合非线性振动分析

将微谐振压力传感器谐振薄膜简化为微薄膜多场耦合系统,给出考虑分子力作用时微薄膜多场耦合动力学方程,利用Linz Ted-Poincaré方法求得其非线性振动固有频率与振型方程,研究了分子力对薄膜非线性固有频率及自由振动的影响规律,利用微加工技术制作出谐振薄膜,利用静电激励-电容检测方法对薄膜非线性固有频率进行了测试。结果表明:当薄膜尺寸较小时,分子力对于微薄膜多场耦合非线性振动的固有频率具有较大影响。研究结果对于压力传感器进一步微型化具有指导意义。     

打坑BOPP薄膜的透湿性能研究

打坑薄膜通过对薄膜进行打坑微处理,可提高其透氧性能及透湿性能。打坑BOPP薄膜在食品包装中得到了广泛的应用,但使用过程中其透湿性不好的问题较为突出,包装内易出现结露问题。以透湿性能为试验指标,选用2种不同透氧系数的打坑BOPP薄膜和未打坑BOPP薄膜进行了对比试验。结果表明,透氧系数大的打坑BOPP薄膜的透湿量也相对较大;同时,透氧系数相同的打坑BOPP薄膜的反面透湿量要大于其正面透湿量;对于不同透氧系数规格的薄膜,反面的透湿性增加量要大于正面的。可见,在实际应用中,不仅需要根据透氧系数来选择合适的包装用BOPP薄膜,且在应用时还需调整薄膜正反面的选择。     

Nichtlineare,inverse Parameteridentifikation zur TEHD-Simulation von geschmierten Kontakten bei hohen Druckgradienten

For the evaluation of lubricated contacts with high pressure gradients and temperatures, it is necessary to perform a FEM simulation under thermo-elastohydrodynamic (TEHL) conditions. For this purpose, a TEHL-simulation model of a micro gap test rig was built. This model can show elastic interactions between the housing and the lubricating film as well as the influence of the temperature on the thermal expansion of the housing and on the viscosity changes. The consideration of the temperature effects increases the simulation accuracy, but also makes it necessary to define specific model input parameters more accurate. For the comparison of measurement and simulation results of the test rig, a nonlinear, inverse parameter identification method was used to adjust the unknown specific input parameters of such a tribological system and the influences of them.The comparison of the results of pressures and temperatures in the lubricated gap as well as the leakage shows a very good accordance of measurement and simulation. Furthermore, the results show the need to consider temperature effects in the simulation of lubricated contacts with high pressure gradients and temperatures.     

Procedure to determine the impact of the surface film resistance on the hygric properties of composite clay/fibre plasters

The experimental determination of dynamic mass transfer properties of porous materials such as eco-efficient clay plasters is greatly influenced by the convective conditions at the surface of the material during the test. The measurement of the intrinsic vapour permeability of highly porous materials has shown to present wide discrepancies when the surface film resistance is not known. Therefore, a proper assessment of the hygric properties of clay plasters requires the determination of such resistance to vapour flow. An adapted experimental procedure was used to determine intrinsic water vapour permeability taking into account the influence of the surface film resistance. The moisture buffering test was used to measure dynamic exchange behaviour. The results gave evidence on the thickness of the active layer in the material and the impact of surface resistance on the exchange behaviour. A 1D mass transfer model was used to verify the validity of corrected vapour permeability by the surface film resistance and discuss its nature and influence on dynamic results.     

改性二氧化硅对SiO2/PLA复合膜性能的影响

目的研究改性二氧化硅对聚乳酸力学性能、氧气透过性能和水蒸气透过性能的影响。方法选择粒径为50nm的工业级二氧化硅为添加剂,使用KH570硅烷偶联剂对其进行改性,然后通过溶液浇铸法将改性后的二氧化硅与聚乳酸共混制备成膜。测试分析拉伸性能、透氧性能和透水蒸气性能,表征复合膜的力学性和阻隔性能。结果与纯PLA膜相比,改性复合膜的拉伸强度和弹性模量分别提高了18.65%和19.91%;玻璃化转变温度比纯PLA膜高11℃左右,热稳定性得到增强。与纯PLA膜相比,改性复合膜的氧气透过系数和水蒸气透过系数分别降低了29.89%和43.76%,阻隔性明显提高。结论经KH570硅烷偶联剂改性的二氧化硅对聚乳酸材料性能的增强效果更佳,为聚乳酸材料在包装领域的应用提供了依据。     

预测相融共混膜氧气透过率的分形渝渗模型

目的 预测相融体系共混膜氧气透过率,为高阻氧共混膜的生产和设计提供理论依据.方法 应用分形与渝渗理论提出一种氧气透过率预测模型,该模型能够在高阻氧材料体积分数条件下更准确地估算相融体系共混膜的氧气透过率.以聚酯/聚萘二甲酸乙二醇酯(PET/PEN)共混膜为例,通过扫描电镜分析共混膜微观形貌,确定PET/PEN共混膜中氧气渗透维数,并根据渗透维数结合文中提出的预测模型计算PET/PEN共混膜氧气透过率,最后通过实验数据验证该模型的有效性.结果 氧气在PET/PEN混合膜中的渗透可以简化为二维渗透.在低PEN体积分数条件下,现有模型和文中提出的预测模型均与实验结果高度吻合.该模型在高PEN体积分数条件下展现出了现有其他模型所没有的曲线趋势,能够更准确地描述高阻氧材料在共混膜体系中对氧气的阻隔作用.结论 文中提出的预测模型能够用于预测相融体系共混膜的氧气透过率.     

脉冲电晕对气调包装薄膜透气性能影响研究

采用脉冲电晕对非极性的食品包装薄膜聚乙烯(PE)和聚丙烯(PP)进行表面处理,研究了电晕处理时的4 种因素(即放电功率、电极与薄膜间的距离、走膜速率和导辊温度)对薄膜透气率的影响,探讨了电晕处理后薄膜的透气率和薄膜的表面张力值之间的关系,建立了电晕处理对薄膜透气率的影响规律。结果表明,电晕处理对薄膜的表面张力和薄膜的透气率有明显的影响,为建立电晕处理与薄膜透气率之间的数学模型和气调包装设计提供了可靠的薄膜透气率数值计算。     

Flow of Newtonian fluid in non-uniform tubes with variable wall permeability with application to flow in renal tubules

Summary The hydrodynamical aspects of flow through proximal renal tubule have been investigated. Assuming renal fluid as Newtonian fluid, flow through diverging/converging tubes with variable wall permeability has been considered. Solutions have been obtained for approximate Navier-Stokes equations with boundary conditions which include a dynamic condition, i.e., leakage flux at the wall depends on variable wall permeability and transboundary pressure drop. Numerical solutions, using fourth order Runge-Kutta method, and approximate analytic solutions, using perturbation method, have been obtained. A comparison of the numerical solution with approximate analytic solution, shows a good agreement (difference less than 4%) between the two solutions for small values of ||, a tube non-uniformity parameter. The velocity profiles at different positions along the axis, the axial distribution of wall shear stress, flow rate and leakage flux have been obtained. For a given value of wall permeability, in diverging (converging) tubes the fractional reabsorption FR is more (less) than its corresponding value in uniform tubes. Further, FR increases (decreases) as the wall permeability increases (decreases) as a linear function of axial distance. The results for flow with constant/variable permeability through uniform tubes and for flow through diverging/converging tubes with constant permeability can be obtained as special cases of this analysis. It is shown that by considering the divergent tube model with linear increase of wall permeability along the axis, an improvement of about 20% in total reabsorption can be achieved over the uniform tube model with constant wall permeability. It is concluded that the approach of using a dynamic boundary condition for leakage flux at the wall has an advantage over the method of prescribing the leakage flux at the wall for this physical problem. Using a set of data, relevant to a physiological situation, implications of the results on glomerular tubular balance have been briefly discussed.     

PMSM馈能系统硬件在环仿真研究

为对电动汽车动力电机馈能效率进行研究,方便馈能效率的测量,提出一种基于滑模控制算法的PMSM(permanent magnet synchronous motor)馈能研究方法,即通过控制电动机的输入电压与电流来驱动相同性能的电动机发电。首先以馈能理论为基础,建立包含滑模变结构控制、空间矢量、PMSM等模块的PMSM馈能系统仿真模型,并进行离线仿真分析。结果表明:采用所提出的馈能方法可达到70%左右的馈能效率,具有一定的可行性。同时,建立PMSM馈能系统dSPACE硬件在环试验平台,对其进行硬件在环试验验证。试验结果表明:电动机馈能效率在60%~80%的范围内,与离线仿真所得结果较为接近。这不仅验证了所建立的馈能仿真模型的正确性,且进一步证明了纯电动汽车动力电机自身馈能在节能方面的可行性。所提出的馈能方法能够为目前现有馈能方式提供更多选择,硬件在环试验研究也能够为后续的PMSM台架和实车试验研究提供一些技术支持。     

Measurement of transverse permeability using gaseous and liquid flow

Accurate measurement of transverse permeability is important for processes such as resin film infusion and vacuum-assisted resin transfer molding. In these liquid composite molding processes the out-of-plane flow is dominant and thus the transverse permeability is needed for flow prediction. This paper introduces an apparatus to measure saturated permeability for fibrous preforms using both gaseous and liquid flow. The setup creates a uniform one-dimensional flow through-the-thickness of the reinforcement by integrating a high permeability layer on the mold surfaces. A wide range of permeability as a function of fiber volume fraction can be measured in one experiment while applying a known load under a hydraulic testing machine. The system has been designed using process simulation. The measurements using the gaseous medium are comparable to the saturated fluid flow results. The measurement system can also be used to measure changes in dry fabric permeability prior to infusion due to debulking or application of binders on the fabric surface.