INFLUENCE OF MIMIC CARDIAC RATE ON HYDRODYNAMICS OF DIFFERENT MECHANICAL PROSTHETIC CARDIAC VALVES IN VITRO

Objective To assess the influence of mimic cardiac rate on hydrodynamics of different mechanical prosthetic cardiac valves. Methods US-made CarboMedics bileaflet valve, China-made Jiuling bileaflet valve and C-L tilting disc valve were tested via a pulsatile flow simulator in the aortic position. Testing conditions were set at mimic cardiac rates of 55 bpm, 75 bpm, 100 bpm with a constant mimic cardiac output of 4 L/min. The mean pressure differences (ΔP), leakage volumes (LEV) and closing volumes (CLV) across each valve, and effective orifice areas (EOA) were analyzed. Results Within physiological range, ΔP, LEV, and CLV decreased as mimic cardiac rate increased, with a large extent of variance. EOA increased along with an increase in mimic cardiac rate. It was a different response in terms of cardiac rate alteration for different types of mechanical prosthetic cardiac valves. Conclusion Mimic cardiac rate change affects hydrodynamics of mechanical prosthetic cardiac valves. Within physiological range, the hydrodynamic of prosthetic bileaflet valve is better than that of tilting disc valve.

Modeling of fluid-induced vibrations and identification of hydrodynamic forces on flow control valves

Dynamics and vibration of control valves under flow-induced vibration are analyzed. Hydrodynamic load characteristics and structural response under flow-induced vibration are mainly influenced by inertia, damping, elastic, geometric characteristics and hydraulic parameters. The purpose of this work is to investigate the dynamic behavior of control valves in the response to self-excited fluid flow. An analytical and numerical method is developed to simulate the dynamic and vibrational behavior of sliding dam valves, in response to flow excitation. In order to demonstrate the effectiveness of proposed model, the simulation results are validated with experimental ones. Finally, to achieve the optimal valve geometry, numerical results for various shapes of valves are compared. Rounded valve with the least amount of flow turbulence obtains lower fluctuations and vibration amplitude compared with the flat and steep valves. Simulation results demonstrate that with the optimal design requirements of valves, vibration amplitude can be reduced by an average to 30%.

Dynamic characteristics of the high-flow water three-way valve

Operating principle of water three-way valve with high flow for individual hydraulic prop in coal was presented in this paper, its strict and precise mathematical model was established, its flow field was simulated numerically by software Fluent, and its dynamic characteristics were analyzed during the work process such as raising leg, loading and overflow, the influence of the related parameters on high-flow water three-way valve was determined. The results as follows： during the raising leg stage and early raising leg stage, when the damping ratio increases, the overshoot of system decreases and the setting time reduces, and the dynamic response performance has a significant improvement. During the loading stage and the overflow stage, the pressure in plunger chamber of single hydraulic prop, the output flow and the displacement of the high-flow water three-way valve decrease with the decreasing of the external load. The spring stiffness of the safety valve directs the flow and the spool＇s displacement of the safety valve, and it can be used to control the high-flow three-way valve＇s sensitivity.

In Vitro Study of Hydrodynam ics at DifferentSimulated Cardiac Output for a Newly JiulingBileaflet Heart Valve Prostheses

Objective:To assess the hydrodynamic function of a newly China-made Jiuling bileaflet heart valve prosthesis at different simulated cardiac output.Methods:Jiuling valve,CarboMedics valve and C-L tilting disc valve have been tested in the aortic position of the pulsatile flow simulator.The testing condition is set at the simulated cardiac output of 2.0,3.0,4.0,and 5.0 L/min and a constant pulsatile frequency of 75 beats/min.The mean pressure difference(ΔP),leakage volume(LEV)and closing volume(CLV)across each valve,and the effective orifice area(EOA)have been analyzed.Results:The mean ΔP of all the Jiuling valves is in the range of below 10 mmHg and decreases with increasing the tissue annulus diameter.The ΔP of 25 mm CarboMedics is about 1.5 times of the same sized Jiuling valve and 27mm C-L tilting disc valve is about 71.8% higher than the same sized Jiuling valve.The EOA of the Jiuling mechanical valves increases with increasing the given cardiac output or the tissue annulus diameter,but 25 mm CarboMedics and 27 mm C-L tilting disc valve is similar to 21 mm and 23 mm Jiuling heart valve.The CLV of the Jiuling prosthetic cardiac valve is in the range of below 11%(normalized by stroke volume),25 mm Jiuling valve is about 56.4% lower than 25 mm CarboMedics and 27 mm Jiuling valve is about 11.4% higher than 27 mm C-L tilting disc valve.The LEV of the Jiuling prosthetic cardiac valves is in the range of below 28.9% (normalized by stroke volume),25 mm Jiuling prosthetic valve is about lower 27.3% than 25 mm CarboMedics and 27 mm Jiuling valve is about lower 11.2% than 27 mm C-L tilting disc valve.Conclusion:For a given tissue diameter,the newly Jiuling heart valve prostheses show more satisfactory hemodynamic characteristics at different cardiac output.

INVESTIGATION ON THE DYNAMIC RESPONSE PERFORMANCE OF A NOVEL THREE-WAY SOLENOID VALVE

Objective A novel high-speed three-way solenoid valve is developed, which is used for the common-rail injection system equipped on DME powered engine. In order to improve the dynamic response performance of the three-way solenoid. Methods Experimental studies have been conducted to investigate the effects of spool stroke, drive voltage, negative demagnetizing pulse and two drive schemes on the dynamic response performance of the three-way solenoid valve. Results The results show that the dynamic response performance of the three-way solenoid valve can be remarkably improved by shortening the spool stroke and increasing the drive voltage. Simultaneously, the difference between the response time of closing valve and that of opening valve decreases. At each different drive voltage, there exists an optimal negative demagnetizing pulse corresponding to the same positive exciting pulse. At this optimal pulse, the dynamic response performance of the three-way solenoid valve is the best. In addition, the high drive voltage can lead to the smaller optimal negative demagnetizing pulse. It is also indicated from the experiments that the dynamic response performance of the three-way solenoid valve is better when the NO.1 drive scheme is adopted. The lower drive voltage results in the larger difference between the dynamic response performances for the two drive schemes. Conclusion The dynamic response performance of a novel three-way solenoid valve is good.

A Novel SiC Foam Valve Tray for Distillation Columns

The novel SiC foam valve tray was made of thin slices of SiC foam material with a high specific surfacearea. Hydrodynamic performances of the novel SiC foam valve tray were studied with air-water system at atmos-pheric pressure. These performance parameters included pressure drop, entrainment, weeping and clear liquidheight. The mass transfer efficiency of the SiC foam valve tray was measured in laboratory plate column. Comparedwith the F1 float valve tray, the dry pressure drop was decreased about 25%, the entrainment rate was about 70%lower at high gas load, the weeping was much better, and the mass transfer efficiency was far higher. Thus, theoverall performance of the novel SiC foam valve tray was better than that of F1 float valve tray.

COMPARISON OF ALLOGRAFT AORTIC VALVE ORIFICE AREA ESTIMATED BY GORLIN FORMULA AND THE CONTINUITY EQUATION IN A PULSATILE DUPLICATOR

During the hydrodynamic characteristic testing of aortic valve allograft (AVA),the testing condition was adjusted to obtain the best hydraulic performance of AVA.The testing condition,the character of the circulation duplicator,is regarded as to beconsistent with the human circulation in vivo.Then the comparison among the re-sults of AVA orifice area (AVA) estimated by Gorlin formula,the continuity equa-tion and their modified types,respectively,was performed.

COMPARISON OF THE DUPLICATOR'S CARDIAC CYCLE WITH THAT OF HUMAN LEFT HEART CIRCULATION WHEN AORTIC VALVE ALLOGRAFT TESTED

By adjusting the testing condition,we obtained the best pulse hydrodynamic per-formance of aortic valve allograft tested in the duplicator made by Chengdu Universi-ty of Science and Technology.Meanwhile,we regarded the condition of the duplicatoras the consilience of human left circulation.By comparing the results(comparison)ofthe different periods of the cardiac cycle including beat to beat interval(RR),systolictime(ST),left ventricular eject time(LVET)and the relationship between them,which got from the observation on volunteers with normal or prostheses aortic valveby using two dimensional Doppler echocardiography,with that of the testing condi-

平面阀门启门初期与闭门末期数值水动力及负载特性模拟研究

文中采用标准k-ε模型结合动网格技术,通过单向流固耦合方法对阀门启门初期及闭门末期阀门水动力及负载特性进行数值模拟研究;同时将仿真结果与物理缩比试验结果对比,验证了数值模拟的可行性。结果表明:阀门速度曲线变化对0~4 s的顺水流作用力及15~20 s的垂直水流方向作用力影响较小,主要影响4~9 s的顺水流方向作用力以及2.5~8.5 s的垂直方向作用力;闭门末期阀门速度曲线变化对顺水流方向作用力的影响较小,主要影响垂直水流方向作用力,其中工况6条件下的垂直水流方向作用力降低幅度约为44%;相较于正常工况,启门初期4种不同工况下阀门最大启门力均有所降低,工况1在0~14s时的启门力降低幅度最大;闭门末期控制阀门运行加速度由小变大可以明显降低闭门力。

球型调节阀液动力矩特性仿真及优化设计

为了获得液体火箭发动机调节阀的液动力矩特性,采用kubota空化模型和标准k-ε湍流模型针对某型调节阀在发动机运行工况下的空化流动开展了数值仿真研究,通过与液流实验数据的对比验证模型准确性,并定量分析了阀芯液动力矩的影响因素、分布特性和演化规律。研究结果表明:阀芯液动力矩大小取决于开度、压差和阀芯流道直径。相同压差下,开度由10°增加至80°,液动力矩单调增加,方向均为使阀芯关闭。相同开度下,压差分别增至3倍和5倍,液动力矩分别变化为原来的3倍和5倍左右。液动力矩分布主要由密封面力矩和主流道力矩两部分组成。随着开度的增加,密封面力矩先减小后增加,主流道力矩先增加后减小。阀芯流道直径由70 mm减小为60 mm,液动力矩最大值增加了24.5 N·m。这是因为相同发动机工况下,减小流道直径使得阀芯开度增加,主流道力矩增加数值大于密封面力矩减小数值,所以总液动力矩呈增加特征。提出了削去原始模型主流道下壁面区域的优化方案,优化模型在100%工况时液动力矩仅为13.2 N·m,且优化模型的流通面积保持不变。与降低流道直径的优化方案相比,所提出的针对主流道下壁面优化方案液动力矩最大值减小了94.4 N·m,大大减轻了控制电机的负荷,已成功经过多次发动机试车考核,提高了液体火箭发动机的可靠性,并为实现发动机轻量化提供了重要参考。

船用阀门流场数值模拟及水动力噪声特性研究

船用阀门是用于控制船舶管路内流体的压力、流量和流动方向的设备,往往由于其内部流道结构相对复杂,易产生较大的湍流噪声,属于管路噪声重点关注的对象。本文选取几款常见的船用阀门,利用CFD数值模拟技术对其内部流场进行了仿真计算,并在此基础上研究其水动力噪声,最终揭示了流场、声场分布特征以及流阻系数、声压级随流速的变化规律。研究结论可用于指导低噪声船用阀门优化设计。

ADV微分浮阀塔板的研究和应用

应用空气－水物系，在直径为６００ ｍ ｍ 的塔内，对ＡＤＶ微分浮阀塔板的流体力学进行了试验研究，测定了临界孔速、塔板压降、雾沫夹带率和液体泄漏率。应用空气－水－氧气物系，测定了ＡＤＶ 微分浮阀塔板的传质效率，并与Ｆ１ 型浮阀塔板进行了对比试验研究。试验结果表明，ＡＤＶ微分浮阀塔板比Ｆ１型浮阀塔板具有更好的流体力学和传质性能。通过对试验数据进行回归，获得了计算临界孔速、塔板压降、雾沫夹带率和泄漏点孔速的关联式，用于ＡＤＶ 微分浮阀塔板的水力学计算。并介绍了ＡＤＶ 微分浮阀塔板的工业应用情况。

新型浮阀塔板研究进展

介绍了在传统圆盘形浮阀、条形浮阀及固定阀塔板基础上研究开发的新型浮阀塔板。分析了各种新型浮阀塔板的结构特点、流体力学性能和传质性能,并比较了各种新型浮阀塔板的优缺点,概述了在不同生产工况下浮阀塔板的选择。

3种微灌砂过滤器水动三向阀性能比较试验研究

为了研究不同水动三向阀对砂石过滤器进行过滤和反冲洗过程切换的影响,通过对市场上常用的2种进口水动三向阀和国内自主生产的水动三向阀进行试验对比,测试了3种阀门过滤和反冲洗条件的水头损失、启闭时间、最小切换压力等参数.测试结果表明:不同阀门过滤和反冲洗条件下的水头损失差异具有统计学意义,建立了3种阀门正向过滤和反向反冲洗过程的水头损失和流量的回归模型,符合幂函数关系;国产阀门在水损控制上与进口阀门差异不大;在60~350 k Pa条件下进行3种阀门启闭时间和最小切换压力试验,测得3种阀门正向切换时间均长于反向切换时间,且单腔结构三向阀的启闭时间要长于双腔结构阀门,而国产三向阀在材料和精度上的不足导致阀门在启闭时间和最小切换压力两方面均落后于进口阀门.试验数据对实际应用中阀门选型及灌溉规划设计能够提供一定的数据参考.

三用阀阀芯微造型的动压润滑性能

以煤矿三用阀中的安全阀阀芯的密封面为研究对象,通过在阀芯表面开设微造型以改善其润滑及抗磨损性能。建立阀芯微造型的数学模型,采用基于N-S方程的计算流体力学方法对微造型区域进行流场分析。通过得到不同结构参数及速度参数下的阀芯表面压力分布曲线及阀芯承载力曲线,探究在阀芯表面开设微造型对改善其动压润滑性能的影响效果。分析结果表明:在水压三用阀阀芯表面开设的微造型能产生良好的动压润滑效果;动压润滑性能随壁面间隙的增大,先略有下降然后再逐渐增强;随微造型深度的加深,先提高而后再逐渐下降;而不断增大微造型半径及壁面移动速度均能使动压润滑性能不断提升。

C-L短柱瓣体外流体动力学评价

目的:评价C-L短柱瓣体外流体动力学性能。方法:以C-L标准瓣、Medtronic-Hall瓣作对照,对C-L短柱瓣进行了静态泄漏、定常流及脉动流测试。结果:C-L短柱瓣静态泄漏率为(298±66)ml/min,符合临床应用要求。C-L短柱瓣定常流跨瓣压差明显低于C-L标准瓣(P<0.01),流场模型显示其瓣后流场涡流明显小于C-L标准瓣,且大瓣口层流清晰,小瓣口基本保持层流。脉动流测试表明C-L短柱瓣与Medtronic-Hall瓣跨压差相近,每搏返流量相近。结论:C-L短柱瓣体外流体动力学性能优良,明显优于第一代C-L侧倾碟瓣,并与国外同类产品相近,是一种有希望的新一代国产人工心脏瓣膜。

安全阀水动力特性的CFD模拟和研究

运用计算流体动力学方法(CFD)对安全阀从开启到排放过程进行数值模拟,研究了安全阀的动态特性。通过动网格的生成与消亡,较好地解决了因阀瓣运动所导致计算区域瞬时变化问题。并以弹簧直接载荷式安全阀为对象,研究了不同阀前静压力下的弹簧开度、泄流量及阀芯所受轴向力变化等特性,获得了安全阀内部流场分布。模拟结果表明,应用CFD技术对安全阀动态过程的模拟,将为研究安全阀水动力特性提供一种有力工具。

CTST-F1复合塔板的实验研究

结合CTST和F1浮阀各自的优点,在CTST塔板的基础上组合得到了新型的CTST-F1复合塔板。以空气-水为物系,在直径为570 mm的有机玻璃冷模实验塔内,对CTST-F1复合塔板的清液层高度、板压降、雾沫夹带、漏液量等流体力学性能进行了实验测定,并与CTST塔板和F1浮阀塔板的性能进行了比较。由实验数据关联得到了复合塔板的干板压降、湿板压降和雾沫夹带的经验公式。实验结果表明:CTST-F1复合塔板通量大、效率高、板压降比F1浮阀低,气相负荷上限高于F1浮阀,下限比CTST塔板和F1塔板都低,操作弹性大且接近于CTST,是一种具有广泛应用前景的新型塔板。

导向筛板-导向浮阀塔板流体力学及传质性能

设计了一种高分离效率、高操作弹性的新型导向筛板-导向浮阀塔板(FGS-VT)。并在直径为600 mm的有机玻璃塔内,以空气-水-氧气为物系,测定了3种结构不同的FGS-VT的流体力学性能和传质性能,包括干板压降、湿板压降、漏液量、雾沫夹带率和塔板效率等。通过与筛孔、导向孔大小和排布方式相当的导向筛板在相同条件下的实验数据对比得出结论,带有14个浮阀的导向筛板-导向浮阀(FGS-VT-14-8)具有更低的干板压降和湿板压降,更大的操作弹性(更低的漏液和雾沫夹带)和更高的塔板效率。

直驱阀用音圈电机的模糊非线性PID控制

针对基于音圈电机的直驱阀系统中存在液动力负载扰动对系统的稳、动态性能有较大影响的问题,以及经典PID控制所存在的不足,在建立基于音圈电机的直驱阀系统数学模型的基础上,提出一种位置环/电流环的双闭环控制结构。位置环采用非线性PID(Nonlinear PID,NLPID)控制,给出了位置环模糊NLPID控制器的具体设计方法,并通过与模糊控制相结合,实现控制参数的自整定。仿真及实验结果表明,在相同的扰动情况下,该控制策略具有比经典PID控制器及模糊PID控制器更好的抗干扰性和鲁棒性,稳、动态性能也更优。