一种微型传感器的研制与应用

文中针对反应堆中一种具有小间隙窄长叠层薄板结构形式的堆芯元件（简称板型元件）在高速流场中流体诱发振动和动态失稳等问题研制出了一种微型传感器以适应电磁法的要求，这种微型传感器具有体积小，制作简单，几乎不干扰“流场”等优点，文章详细阐述了这种传感器的制作原理和相应的电气设备的技术参数。通过对板型元件流致振动试验的综合动态测试，结果表明这种微型传感器可靠而有效。     

电磁发射电源叠层母排设计

瞬变电磁法是地质探测中广泛应用的有效方法。利用瞬变电磁法通过阶跃电流产生一次磁场,分析地下导体感应的二次磁场的频谱进而实现地质探测。通过仿真并实物搭建了电磁发射系统的整流、逆变电路,完成了双极性脉冲电流的输出,并分析了开关器件关断时刻电压尖峰的产生过程。通过更换直流母线测试了开关器件关断时其两端电压尖峰的变化,通过实验数据分析不同连接方式对尖峰的影响。由于叠层母排具有低电感特性,通过研究不同因素对叠层母排杂散电感的影响,设计了一套叠层母排来实现开关管电压尖峰的抑制。为了进一步提高发射源功率密度、降低缓冲吸收电路的要求,研究直流母线的设计与优化,具有良好的应用价值。     

单相永磁力矩马达的力矩转角特性

现有的2D阀用电-机械转换器从磁路原理和结构而言均较为复杂,本文设计了一种单相励磁的轴向不对称磁路,并根据该磁路提出了一种新型的单相永磁力矩马达。首先通过磁路解析法推导了马达的力矩转角特性方程,随后建立有限元模型分析了该马达的磁场分布和力矩转角特性。基于数值模拟结果加工了样机,建立了测试台架对其作了力矩转角特性的测试。测试结果与模拟结果较为符合,表明该马达的电磁力矩较大,其力矩-转角特性曲线呈上升的线性关系,力矩幅值随励磁电流而增加,适合作为2D三通阀及其他类似元件的电-机械转换器。     

吊篮振动特性分析研究

反应堆结构的流致振动问题与核安全直接相关。为了完成反应堆堆内构件的流致振动分析,需要先对反应堆堆内构件振动特性进行分析。文中建立吊篮及其主要附属结构在空气和安装于反应堆压力容器内水下环境中的三维有限元模型,并分别进行了振动特性分析,使用ANSYS软件得到其梁式模态和壳式模态。     

负载敏感系统煤矿用防爆三联电磁换向阀组的设计研究

遥控操作煤机装备负载敏感液压系统采用负载敏感电比例多路阀控制执行元件存在过度设计问题。通过分析煤矿用负载敏感液压系统的特点及压流特性，进而确定负载敏感用防爆电磁换向阀组的设计要求，设计了三联防爆电磁换向阀组元件原理图和整个负载敏感系统原理图；然后对阀组进行三维建模设计、元件选型；最后对制造的三联电磁换向阀组的应用情况进行了介绍。结果表明，该阀组的设计研究为矿用负载敏感系统控制提供了新的解决方案。     

一种核电主设备内管路流致振动分析

核电一回路主设备,如反应堆压力容器、蒸发器等内部管束或管路区处于一个高速横向流的流场中。在流场作用下会产生明显的由漩涡分离及流体弹性失稳引起的流致振动现象。根据管束的结构特点及在横向流作用下的振动行为特性,并根据ASME规范对某套管组件结构进行流致振动分析,结果表明:套管组件新结构可有效避免流致振动发生,而且该套管组件的设计流程可为其他核电厂主设备管束结构的设计提供参考。     

基于动态特性研究的堆内测量格架组件试验件优化设计

作为一种新的设计,CAP1400堆内测量格架组件的流致振动需要进行试验验证。研究过程中,分析了堆内测量格架组件的振动特性,通过湍流随机振动分析发现堆测导管响应最大,在此基础上分析各阶模态对堆内测量格架组件流致振动的贡献,提取出其主要模态,作为试验件模型优化的依据。随后共提出了四种简化模型,通过对比简化模型和实际结构的模态频率和振动响应,确认了简化模型的合理性;综合考虑经济型和准确性,选择了一种最优的简化模型,为CAP1400堆内测量格架组件流致振动试验件的设计提供支持。     

电磁辅助支承非线性系统的稳定性分析

对电磁执行器直接安装在主支承上的一种新型支承结构--电磁辅助支承系统的稳定性进行研究.首先分析一模拟的单自由度电磁辅助支承系统,建立非线性运动方程,采用相平面法进行分析;然后采用数值分析方法分析多自由度电磁辅助支承系统.分析结果表明, 在电磁执行器作用期间,转子系统处于一种局部稳定状态,其振动不能超过所允许的最大振动值.而该转子系统允许的最大振动值受静态励磁电流Ib的影响较大,受P控制参数的影响较小.     

PMN-PZT多层厚膜微致动器的制作与分析

研制了一种用于计算机磁头精确定位的"U"形压电微致动器。该致动器由流延法在不锈钢(SUS304)基体上制备镁铌酸铅一锆钛酸铅(PMN-PZT)多层膜,并由丝网印刷工艺制作Ag／Pd内电极。在此基础上,在多普勒干涉仪(LDV)上对封装了压电元件的"U"形微致动器进行了测试。结果表明,该致动器具有优异的位移／电压灵敏度、谐振频率等特点。此外,有限元仿真进一步验证了多层结构的压电元件可以有效地提高压电微致动器的驱动能力。     

蒸汽发生器传热管流致振动的数值研究

基于计算流体力学和计算结构动力学,同时考虑流体-结构两个物理场之间的相互作用,利用有限体积法及LES方法离散非稳态、粘性、不可压缩湍流流场的N-S方程,用有限元方法离散结构动力学方程,结合动网格控制技术,建立了横向流体作用下传热管流致振动计算的三维仿真模型。基于建立的模型,首先得到了横流作用下传热管的振动响应,并与已有的实验数据比较,证明了模型的合理性;其次,研究了来流速度和频率比对传热管流致振动特性与流场结构的影响。     

用概率分析研究克服流体诱发调节阀振动

按流体诱发振动的流体力学理论 ,应用概率分析和数理统计方法 ,研制了异径多束流调节阀。使用表明 ,其克服流体诱发调节阀的振动效果十分显著     

三维转子密封系统气流激振的研究

提出了分析三维转子密封系统气流激振流固耦合作用的数值计算方法。首先建立三维转子密封流固耦合模型,然后直接数值求解密封流场的非线性气动力,形成了考虑流固耦合效应的转子密封气流激振问题的分析方法。数值计算表明,对应于不同的转速、压比和预旋,转子振动的各个频率成分的幅值不同,但始终存在着转子一阶临界转速频率成分,而且该成分的幅值随着转速、气流进口压力和正向进气预旋的增高而增大,与工程和试验中的密封气流激振现象有较好的一致性,捕捉到了密封气流激振的基本特性。     

被动式电磁阻尼器对转子振动进行控制的机理探讨和实验研究

设计了一种新型的被动式电磁阻尼器，其采用直流稳压电源供电，无需控制。本文对该阻尼器用于转子振动控制的机理进行了探讨，实验研究了该阻尼器的减振、增稳效果。结果表明，该阻尼器减振效果明显，结构简单，性能可靠，成本低，有推广应用价值。     

稀醋酸酐冷凝器的振动分析

原子能工业与化工工艺过程中广泛应用的管壳式换热器、诸如冷凝器、蒸发器以及原子能蒸汽发生器，实际上一半以上都是在两相流状态下操作的。但是目前研究有关两相流诱发振动的资料仍然较少。持续的振动，由于疲劳与磨损将导致管子的破坏。根据两相流诱发振动的机理与有关文献中的实验数据，笔者推荐的振动分析方法可用来预测稀醋酸酐冷凝器的振动。     

基于拉索振动特征的索力检测与评估方法

基于拉索振动力学模型,建立了频率与索力的数学关系.提出运用实测振动频率推算索力及频率点所对应振动阶数的计算公式,给出采用相邻频率值推算出的频率阶数偏离整数程度来评价索力测量结果可靠性、合理性的方法.针对拉索振动特点及索力检测应用环境开发出一款新型索力检测仪,其实用性、合理性已在实际工程应用中获得验证.     

Experimental investigation on the flow-induced noise under variable conditions for centrifugal pumps

With extensively using of centrifugal pumps,noise generation in these pumps is increasingly receiving research attention in recent years.The noise sources in centrifugal pumps are mainly composed of mechanical noise and flow-induced noise.And the study of flow-induced noise has become a hotspot and important domain in the field.The flow-induced noise closely related to the inner pressure pulses and vibration of volute in pumps,therefore,it is necessary to research the interaction and mechanism among them.To investigate the relationships,a test system is designed which includes a test loop and a measurement system.The hydrophones and pressure sensors are installed on the outlet of the pump and vibration acceleration sensors are disposed on the pump body.Via these instruments,the signals of noise,pressure pulses and vibration are collected and analyzed.The results show that the level of flow-induced noise becomes smaller as the flow increment during low flow rate operations,and it is steadily close to the design point,then it increases with the growing of flow rate in high flow rate conditions.Furthermore,there are some similar peak points in the power spectrum charts of noise,pressure pulses and vibration.The broadband noise at low flow rate is mostly focused on the region of 0-40 times shaft frequency,which is mostly made by rotating stall and vortex;while the noise at high flow rate conditions is focused on the region of 60-100 times shaft frequency,which may be mostly made by cavitations.The proposed research is of practical and academic significance to the study of noise reduction for centrifugal pumps.     

Suppression of flow-induced vibration of a circular cylinder by means of a flexible sheet

In this study, the suppression of flow-induced vibration of an elastically supported circular cylinder by attachment of a flexible sheet was investigated experimentally. In particular, the dependence of flow-induced vibration characteristics of the circular cylinder upon the flow velocity was investigated in detail by axially attaching the flexible poly-ethylene sheet to the cylinder surface. The characteristics of the flow-induced vibration of the cylinder were investigated by changing the attachment angle ?? and the length l of the flexible sheet (rectangular type) as experimental parameters in various combinations. The angle ?? was set at five different angles, 90°, 45°, 0°, ?45° and ?90°. The angle??s base point was the back side stagnation point of the cylinder. The length l of the flexible sheet varied from 0.5 to 3.0 times of the cylinder??s diameter at the interval of 0.5 times. The width T of the flexible sheet along the span of the cylinder also varied in 7 cases from 1.0L to 0.4L (L is the length of the cylinder) in order to discover the minimum width of the sheet necessary to effectively suppress the flow-induced vibration of the cylinder. Furthermore, the flexible sheet of the minimum width was split into 2 to 5 pieces and attached to the cylinder, and changes in the flow-induced vibration characteristics were investigated. Also, vibration characteristics were investigated for a flexible sheet in the shape of an isosceles triangle. As a result, the optimal length l and minimum width T of the flexible rectangular sheet were found to be 2??2.5D and 0.7L, respectively, to suppress the flow-induced vibration of the cylinder. Most importantly, it was found that the sheet located at the back side stagnation point can suppress the flow-induced vibration generated by any directional flow to strike the front surface of the cylinder.     

Divergent vibration of a test cylinder with a control cylinder at the rear

The objective of this study was to experimentally investigate flow-induced vibration occurring in a test cylinder capable of free vibration when there was a control cylinder with a diameter half of that of the test cylinder behind the test cylinder. This paper intensively investigated divergent vibration among flow-induced vibration characteristics of the test cylinder. The mechanism for generating divergent vibration was also determined. To clarify the mechanism, flow-induced vibration characteristics of the test cylinder and wakes were investigated when the control cylinder was located closely to the rear of the test cylinder. Among tests for investigating wakes, a visualization test was also conducted using hydrogen bubble as a dye in a water channel. As a result, it was found that when the control cylinder was in close proximity to the rear of the test cylinder, the divergent vibration that appeared in the test cylinder was divided into three patterns based on vibration amplitude characteristics. Results of wake investigation revealed that the presence of the control cylinder affected the emission frequency, shape, and intensity of the vortex discharged from the test cylinder, which in turn affected vibration characteristics of the test cylinder. As a result of investigating flow-induced vibration characteristics of the test cylinder using different methods by changing the flow velocity, vibration inertia was found to one cause for the divergent vibration of the cylinder.

     

Mechanisms of fluid-flow-induced matrix production in bone tissue engineering

Matrix production by tissue-engineered bone is enhanced when the growing tissue is subjected to mechanical forces and/or fluid flow in bioreactor culture. Cells deposit collagen and mineral, depending upon the mechanical loading that they receive. However, the molecular mechanisms of flow-induced signal transduction in bone are poorly understood. The hyaluronan (HA) glycocalyx has been proposed as a potential mediator of mechanical forces in bone. Using a parallel-plate flow chamber the effects of removal of HA on flow-induced collagen production and NF-kappaB activation in MLO-A5 osteoid osteocytes were investigated. Short periods of fluid flow significantly increased collagen production and induced translocation of the NF-kappaB subunit p65 to the cell's nuclei in 65 per cent of the cell population. Enzymatic removal of the HA coat and antibody blocking of CD44 (a transmembrane protein that binds to HA) eliminated the fluid-flow-induced increase in collagen production but had no effect on the translocation of p65. HA and CD44 appear to play roles in transducing the flow signals that modulate collagen production over long-term culture but not in the short-term flow-induced activation of NF-kappaB, implying that multiple signalling events are initiated from the commencement of flow. Understanding the mechanotransduction events that enable fluid flow to stimulate bone matrix production will allow the optimization of bioreactor design and flow profiles for bone tissue engineering.