Novel bulk modulus model to estimate stiffness in fluid power systems

A precise evaluation of the bulk modulus is essential for the efficient simulation and accurate design of hydraulic circuits. The compression and dissolution of air bubbles in hydraulic oil can affect the density as well as the effective bulk modulus during corresponding operation. To address this phenomenon, this study presents a novel model for the bulk modulus. The representation does not rely on the tangent or the secant definition of the bulk modulus, but on the assumption of compression as a polytropic process. The results are compared to various experimental studies, showing that the new model can properly reproduce the experimental data. In addition, a model based on new bulk modulus and a model based on a commercial software are used for the simulation of four-chamber cylinder in digital fluid power circuits. These simulations verify that the LMS model can be reliable though a discrepancy exists in reproducing the position of piston, which will be increased by time.     

Novel transcatheter aortic heart valves exhibiting excellent hemodynamic performance and low-fouling property

Transcatheter aortic heart valves (TAHVs) have been widely used for aortic valve replacements, with less trauma and lower clinical risk compared with traditional surgical heart valve replacements. In the present study, composites of poly(ethylene glycol) diacrylate (PEGDA) hydrogels and anisotropic high-shrinkage polyethylene terephthalate/polyamide6 (PET-PA6) fabric (PEGDA/PET-PA6) were fabricated as artificial heart valve leaflets. Dynamic mechanical analyses (DMA) indicated that PEGDA/PET-PA6 composites possessed anisotropic mechanical properties (i.e., storage moduli ～23.30 ± 1.36 MPa parallel to the aligned fabric fibers and ～9.68 ± 0.90 MPa perpendicular to the aligned fibers at 1 Hz) that were comparable to aortic valve leaflets. The PEGDA/PET-PA6 composites with smooth surfaces were highly hydrophilic (contact angle ～41.6° ± 3.8°) and had low-fouling properties without platelet adhesion, suggesting a low risk of thrombogenicity when they interacted with blood. Furthermore, transcatheter aortic heart valves were fabricated using nitinol self-expanding frames and PEGDA/PET-PA6 composites as artificial leaflets, which presented excellent hemodynamic performance with a large orifice area (1.75 cm²) and low regurgitation (3.41%), thus meeting the requirements of ISO 5840-3 standard. Therefore, PEGDA/PET-PA6 composites had suitable mechanical properties, good biocompatibility, and low-fouling properties, indicating that they might be used for TAHVs in the future.     

基于最小平方误差逼近的线性阀体的设计

针对线性阀体的内孔筒设计问题,建立了一个以过流面积和其逼近直线之间的平方误差最小为目标的泛函优化模型.     

便携式安全阀在线校验仪的研制

目前,安全阀在线校验系统普遍存在精度低、安全性和便携性差等缺点.提出了以STC12C5A单片机为核心,基于阀瓣微动技术的便携式安全阀自动校验仪的设计方案,并完成了对该压力校准系统的研制.工程应用表明,该仪器具有精度高、功耗低等特点,能实现数据共享,操作灵活,易于携带,在行业中具有很高的推广价值.     

高速电磁阀的动态特性

高速电磁阀是重要的液压执行元件,因此其响应速度尤为重要.首先分析高速电磁阀的原理结构,再对电学、磁学、运动学进行建模,研究不同参数下系统的响应速度与时间的关系.研究结果表明:采用的控制变量仿真法可以清晰地看出不同参数对系统动态参数的影响,其中起励电压、线圈匝数与占空比对响应的影响比较明显,为项目研究提供参考.     

基于SPI通信的便携式电子膨胀阀控制器设计

研究了一种基于SPI通信的便携式电子膨胀阀控制器设计.该设计采用主控制板和按键显示板两个独立单片机系统的架构,且两个单片机系统之间应用SPI通信进行实时数据交换.详细介绍了SPI通信技术以及Atmega16单片机的SPI通信接口,并给出该便携式电子膨胀阀控制器的SPI通信部分的软件流程图.     

特种电动机高压阀门准确制动的仿真计算

对于特种异步电动机拖动的高压阀门 ,切断电动机交流供电电源后 ,在电机的定子绕组中通入适当的直流电流 ,产生直流磁场 ,使电机进行能耗制动 ,让阀心和电机转子的能量 ,包括动能消耗在转子的绕组中 ,达到准确停车的目的。介绍了这一过程的计算机仿真计算     

新型自封带旁通阀回油过滤器基本模型介绍

针对箱侧、箱底回油过滤器的特点,提出一种较传统结构更简单、使用起来更方便的结构模型。     

低压长袋脉冲袋式除尘器设计与应用

以工业原料尤里卡沥青(EP)为对象，详细论述了低压长袋脉冲袋式除尘器的主要设计环节，着重分析了新型脉冲阀技术。指出了该技术在化肥行业原料干燥、风扫制备等方面的推广应用和发展趋势。     

大埌水库高低放水涵洞二洞合一的处理方法

介绍了大埌水库的工程概况及放水设施存在的问题.论述了新建放水设施将高低放水涵洞二洞合一的处理方案,说明了采用龙翘尾型式的放水涵洞同时解决高低渠道放水问题的操作方法.