超声波场强化解吸的机理分析

在定域吸附的假定条件下，从能量的角色出发，由统计热力学理论得到了有外场作用的吸附平衡关系式。由此进一步讨论了超声波场强化解吸的机理，得到了在超声波场中吸附相分子比基准态分子获得更多的能量是导致吸附平衡等温线降低，即强化解吸的主要原因，由于超声波的“聚能效应”使得吸附相分子比基准态分子能够获得更多的能量，这正是超声波对固液吸附系统能够强化解吸的本质所在，其理论研究与实验结果一致，研究结果还表明，吸附相分子在超声波场中只要获得可与kT 比拟或更高的能量，解吸效果就会明显，这体现了强化解吸中超声波场与温度场之间的协同作用。     

碱金属离子交换Y型分子筛CO分子吸附量子化学研究

应用量子化学方法,从微观角度了解一氧化碳（CO）分子吸附在碱金属离子（Li⁺、Na^+、K⁺、Rb⁺、Cs⁺）交换Y型分子筛上的机理,详细研究了吸附时红外光谱的变化情况。研究发现,CO分子能与碱金属离子交换Y型分子筛发生多分子吸附,且其吸附行为和结构相类似。CO发生单分子和双分子吸附后,其红外光谱均会发生蓝移。当CO双分子吸附时,其红外光谱会出现两个新的吸附带,且其振动频率比单分子吸附时有所降低。当CO在Li-Y、Na-Y分子筛上发生双分子吸附时,其振动频率与单分子吸附时有较大差别;而CO在K-Y、Rb-Y、Cs-Y分子筛上发生双分子吸附时,其吸附前后的振动频率变化较小,且两个CO分子的振动频率很接近。能量计算结果显示,CO分子吸附强度会随着离子半径的增加而减弱。     

超声波对苯酚在NKAⅡ树脂上吸附平衡的影响

本文以苯酚水溶液／NKAⅡ树脂吸附体系为实验对象,研究超声波对液固吸附平衡的影响。分别测定了在超声场和无超声场条件下,苯酚在NKAⅡ树脂上的吸附等温线,报道了在超声场条件下苯酚在高聚物吸附剂上的吸附等温线。研究结果表明：超声场作用下的吸附平衡等温线要低于在常规条件下的吸附等温线,超声场强度越大,苯酚在吸附剂上的吸附容量就越小。向吸附体系施加超声场,会导致吸附体系的温度升高。超声场对吸附平衡的影响是由超声场的热效应和非热效应所引起的,而后者的影响要大于前者。向液固吸附体系添加乙醇或乙酸乙酯作为第三组分,能进一步使体系的相平衡关系朝着吸附量减少的方向移动,这种变化在超声波场条件下更为明显。     

基于非局部理论的纳米复相陶瓷超声磨削试验研究

基于非局部理论,建立了纳米复相陶瓷材料在超声振动下的非局部本构模型,通过对超声振动条件下纳米复相陶瓷磨削试验研究,获得超声频率对磨削力的影响规律以及非局部衰减率的变化规律,并对磨削表面三维微观轮廓特征进行观测分析.试验结果表明,试件在所研究超声振动频率范围内磨削力出现衰减现象,且随频率的增大更为明显,超声振动大大减小了磨削力,表面质量得到明显改善,更容易实现延性域加工.     

超声波应用于吸附/脱附过程的研究进展

从热力学和动力学两方面介绍了近年来超声波应用于吸附/脱附过程的研究结果。比较了非超声波/超声波作用下吸附等温线的变化,分析了超声波强度、频率、第三组分的加入等因素对吸附/脱附相平衡影响;以及非超声波/超声波作用下吸附/脱附动力学的变化,并对温度、超声功率、初始浓度和颗粒大小等因素对吸附/脱附速率的影响及其原因进行分析。     

超声波对活性炭吸附苯酚相平衡的影响

研究了超声波条件下的苯酚水溶液 +活性炭体系的相平衡以及超声波强度和第三组分的加入对这种相平衡关系的影响。研究结果表明 :与无超声波同温度下的常规脱附过程相比 ,超声波能够通过空化作用将能量施加于体系的分子上 ,使体系的相平衡明显向固相吸附量减少的方向移动 ;将乙醇或乙酸乙酯作为第三组分加入苯酚水溶液 +活性炭吸附体系 ,也可改变原有的吸附相平衡关系 ,使体系的相平衡向固相吸附量减少的方向移动 ,在超声场的同时作用下 ,这种相平衡关系的变化更为明显     

超声解吸柠檬酸盐溶液中SO2的影响因素

研究了用超声波解吸柠檬酸盐溶液中SO2的影响因素. 重点考察了温度、电流强度、搅拌强度、初始SO2浓度及柠檬酸盐浓度对SO2解吸率、柠檬酸盐溶液稳定性和硫酸根浓度的影响,并与无超声时作了对比. 结果表明,应用超声可提高SO2解吸率,但不改变解吸反应机理,且解吸过程中柠檬酸盐保持稳定,无硫酸根生成. 确定了在超声波频率为40 kHz时,超声解吸SO2的最佳温度为50℃,最佳电流强度为1.4 A.     

超声波强化HCl-NaCl浸出高铅锑吹渣

对高铅锑吹渣进行HCl-NaCl常规浸出,并在其最佳工艺条件下引入超声波强化浸出. 实验表明,超声波强化浸出15 min,Sb的浸出率可达到常规浸出45 min的值. 超声波强化浸出高铅锑吹渣可大大提高Sb, Pb的浸出速率,缩短浸出时间. 超声波功率增大,浸出率提高. 在浸出率相同时,高功率比低功率的超声波强化浸出所需的时间少. 但由于Sb, Pb的最大浸出率是由其物相组成决定的,超声的能量并没有为常规下不能发生的反应开辟新的化学反应通道,因而Sb, Pb的最大浸出率与超声场的引入几乎无关.     

超声场对栀子甙提取过程的强化

测定了在栀子果实中栀子甙在水溶液中浸取的固液平衡关系,不同强度超声场作用下栀子甙相平衡关系,研究比较了机械搅拌法和超声场介人下栀子甙的浸取率和浸取速率。实验结果表明：超声场可以改变浸取相平衡,超声场强度越大,固体中栀子甙吸附容量越小：超声场作用下使浸取率达到最高、浸取速率达到最大。超声场可有效强化液膜传质、粒内扩散,提高浸取率、加快浸取速率,能达到机械搅拌无法达到强化传质的效果。     

超声塑化生热及其参数对温度特性的影响

超声熔融塑化注射成型是一种新型的聚合物塑化方式,而聚合物超声熔融塑化过程中温度场分布、超声波频率和振幅对聚合物塑化的影响规律等问题有待进一步的研究。本文针对这些问题,通过仿真计算、实验验证的方法,研究了超声工具头端面和外圆柱面振动对聚合物的熔融塑化效果和不同超声波参数对聚合物的熔融塑化的影响。结果表明:熔池从工具头端面中心部位开始形成,并向轴向和径向扩展;工具头轴向振动的塑化作用为聚合物熔融塑化的主要能量来源,其效果远远大于径向振动的塑化作用;超声波振幅对聚合物的塑化效率比超声波频率影响更大。     

沉浸式换热器超声强化传热影响因素

以沉浸式换热器为研究对象,通过壁面加载超声波,比较了超声波振幅、换热器入口流速和管外压力对超声波效应及强化传热效果的影响。结果表明：超声波振幅由20μm增大至35μm时,表面对流传热系数增幅由15.67%增至26.71%;管外压力由0.1MPa增大至1.0MPa时,表面对流传热系数增幅由20.95%增至48.43%;入口流速由1.0m/s降低至0.05m/s时,表面对流传热系数增幅由1.76%增至39.01%。增大超声波振幅、环境压力和减小介质流速均能增强超声波声流现象和空化效应,有效提高超声波强化传热效果;高压环境会使同振幅、同频率超声振动作用下声功率呈指数增长,高流速会降低流体介质的声能密度,两种情况都需要匹配合适的超声波以保证强化传热最佳效果。     

基于超声技术的沉浸式换热器强化传热研究

针对沉浸式换热器管外强化传热的问题,采用振动壁面的方式向换热器内输入超声波,研究了超声外场对沉浸式换热器内的管外流动、空化现象以及传热强化的作用。超声作用在流体中能够产生空化现象和声流的传播。其空化作用使得邻近振动面的流体发生液气相变,在远离振子的区域发生微小气泡的膨胀,换热器管外流体区域的平均气体体积分数由未加载超声时的0.01302最大增至0.01359。声流现象使得换热器管外流体的流速具有和超声波相同的脉动变化特性,呈高低速相间分布流向换热器两侧,最低速度接近0,最高速度4.93 m·s^-1,平均流速由0.0248 m·s^-1增至0.102 m·s^-1,超声作用效果显著。在空化和声流的双重作用下,换热管外表面湍动能均值由2.090×10^-4 m²·s^-2增大至0.01847 m²·s^-2,表明换热管外表面流体受到扰动增强,换热管外表面对流传热系数由1634.533 W·m^-2·K^-1增大至2031.069 W·m^-2·K^-1,传热强化比率达24.26%。本研究对超声技术在沉浸式换热器内的应用具有重要意义。     

三角槽道低 Reynolds 数脉动流与柔性壁耦合特性研究

以水为工质对三角槽道低 Reynolds 数脉动流与柔性壁耦合特性进行了实验研究。通过传热与流动实验,分析了脉动频率(W)、脉动振幅(A)、柔性壁特性对脉动流传热及流动的影响。同时,通过可视化实验,研究了柔性壁与脉动流之间的响应特性,解析了柔性壁形变与振频对脉动流传热及流动的作用机制及分离贡献。研究结果表明,柔性流道脉动流可以实现强化传热与流动减阻双重效果,但强化传热效果相对较弱(传热效率提升0~50%),适用于以减阻为主要目的的换热场合;柔性壁减阻与削弱强化传热效率,源于柔性壁形变造成时均流通截面积增大(流体流速下降)、W与A的增大减弱脉动能量;W的增加将使得柔性壁振动对脉动流强化传热效率的削减逐步趋于主导地位,而A的增加将使得柔性壁变形对脉动流强化传热效率的削减逐步趋于主导地位;脉动流阻力的削减主要来自于柔性壁的变形(D₁>70%),而柔性壁振频对于脉动流能量耗散的抑制作用较为次要。     

Enhanced nanoflow behaviors of polymer melts using dispersed nanoparticles and ultrasonic vibration

In the micro/nano fabrication of polymer nanostructures, a key factor is the favorable nanoflow behavior of polymer melts. Compared with the fluidic hydrodynamics of simple liquids through micro- or macrochannels, the nanoflow behavior of polymer melts, however, is affected much more by nanoscale effects and surface interactions. Therefore, achieving a favorable nanoflow of polymer melts in nanochannels is the key to fabricate high quality polymer nanoproducts. In this paper, the improved nanoflow behaviors of polystyrene melts in ordered porous alumina templates with the addition of nanoparticles and ultrasonic vibration were reported for the first time. Compared with bulk polystyrene (PS), the nanoflow rate of PS melts was enhanced when nanoparticles, such as surface-modified nano-silica (nano-SiO(2)) or β-cyclodextrin (β-CD), were added in a dispersed phase into a polystyrene matrix due to the decrease of the melts' viscosity caused by interactions between nanoparticles and PS segments. The enhancement action of β-CD was observed to be more significant than that of nano-SiO(2) based on the adsorption and the supramolecular self-assembly interactions between PS segments and β-CD. The enhanced nanoflow rate has shown to be more pronounced under ultrasonic vibration than those of the static condition and the low frequency vibration attributed to the synergetic effects of mechanical vibration and ultrasonic oscillation. The nanoflow rate of polymer melts increases with the gradual increase of vibration frequency. The optimal nanoflow behavior can be obtained by simultaneously adding β-CD as dispersed phase into PS matrix and applying ultrasonic vibration in one nanoflow system. These new findings will help the preparation of polymer-based functional nanocomposites, ultrasonic vibration-assisted nanofluidics, and micro/nano injection molding etc.     

振动圆管外对流换热特性的场协同机理

数值模拟了振动圆管外的对流换热,通过数据后处理分析了振动圆管外对流换热特性与场协同性能间的联系,从场协同原理的大值原则与匹配性原则上对振动圆体外表面传热的规律特性作了解释。振动圆管外的场协同角余弦值在面相位0°与180°处最大,在90°与270°处最小,并且随着时相位靠近平衡位置,其面上各点的场协同角余弦值逐渐变大。场协同匹配性能的分布规律与场协同角余弦值的分布基本相同。振动圆管外的对流传热系数分布规律与场协同余弦值及场协同匹配系数的分布规律一致,表明可以使用场协同原理阐述振动圆管外的对流换热规律。     

Phase morphology control of immiscible polymer blends under vibration force field

The formulas of polymer melt velocity, shearing rate, and shearing stress under vibration force field are established through simplifying coaxial cylinder circular flow into plane motional flow. On the basis of the concept of energy ratio model, the rate of energy dissipation and the energy ratio about blending systems are expressed, and the affected factors on phase morphology are studied theoretically. The calculated and analytical results of dynamic flow field and energy ratio show that with the increasing of vibration strength, the fluctuating shearing force field exerted on polymer melt and the negative pressure diffusion behavior of instantaneous impulse strengthen. The energy consumption for phase inversion of immiscible polymer blends under vibration force field is less than that of steady state. The parameter controllability of vibration force field provides a more effective method for realizing phase inversion of immiscible polymer blends. The analysis of transmission electron microcopy micrographs of ethylene–propylene–diene terpolymer/polypropylene blends verifies that the energy ratio model and its phase morphology controlling theory have a good coincidence in comparison with experimental results. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2299–2307, 2006     

Study on Energy Ratio Model for Phase Morphology of Immiscible Polymer Blends

The formulas of polymer melt velocity, shearing rate, and shearing stress in simple shearing flow under the vibration force field were established. Based on the concept of an energy ratio model, the rate of energy dissipation and the energy ratio for blending systems are expressed theoretically. The calculated and analytical results of both the dynamic flow field and energy ratio show that with the increasing of vibration strength the fluctuating shearing force field exerted on polymer melt and the negative pressure diffusion behavior of instantaneous impulse strengthen. The energy consumption for phase inversion of immiscible polymer blends under the vibration force field is less than that of steady state. The parameter controllability of the vibration force field provides a more effective method for realizing phase inversion of immiscible polymer blends.     

非稳定流体与U形管路耦合振动特性研究

针对采油用管道内流体引发管道振动问题,研究了U形管路在内流作用下的振动特性,利用非线性耦合方法分析非稳定流体与管道相互耦合规律.流固耦合模态结果与前人计算结果相近,验证了数据的可靠性.模拟结果发现,在周期性脉动流体的作用下,管道最大应力及位移振动呈周期性变化;流体频率与管道基频相近时,管道位移振动频谱既有流体诱发的高频又有较低的管路基频.流体速度增加,管道位移增加,管道最大应力增加,管道基频减小.另外,发现脉动流体频率增加,管路基频增加.     

Tensile fracture test of nanocomposite ceramics under ultrasonic vibration based on nonlocal theory

Based on non-local theory, the dispersion characteristics of ultrasonic vibration in Specimen tension are analyzed, and the effects of ultrasonic frequency and amplitude on the wave dispersion are obtained through theoretical analysis. Tensile tests were carried out using an ultrasonic vibration system and specimens, and the test process as well as test parts were observed and analyzed. The influence of the ultrasonic vibration on fracture properties and the change of grain micro-organization under different loading conditions were verified by experiments. The introduction of ultrasonic vibration changes the internal stress of the ceramic fracture, affects the hardness of the workpiece, and also leads to the scattering of particles, which leads to the aggravation of ultrasonic attenuation and phase velocity dispersion. SEM and XRD analyses showed that with the increase in ultrasonic frequency and amplitude，the trans-granular fracture was more obvious, the micro-cracks and dimples increased, and micro-pores increased in size and number. The tensile stress produced by ultrasonic vibration will induce the transformation from T-phase ZrO2 particles to M-phase ZrO2 particles and absorb strain, which greatly improves the plastic mechanical properties of nanocomposite ceramics. Due to the inherent phase transformation toughening mechanism, the material improves the plastic mechanical properties under the ultrasound excitation, and it is easier to achieve ductile domain processing.