Simulation and experiment of six-bed PSA process for air separation with rotating distribution valve

In this work,a six-bed pressure swing adsorption(PSA)process was investigated to produce medical oxygen from air,which uses the combination of six-way rotating distribution valve and PSA and has the main advantage of effectively saving space compared to the traditional two-bed or four-bed PSA process and can obtain greater productivity.The mathematical model of adsorption beds was developed based on the separation mechanism and the interaction among different equipment.Moreover,a pilot-scale device has been constructed to verify the accuracy of mathematical model by experiment.The oxygen product conformed to the medical standard(>93%(vol))with a recovery of over 57%.Some related parameters were also discussed in detail,such as step time,ratio of length to the diameter,flow rate of product.

Partitioning of Water Distribution Network into District Metered Areas Using Existing Valves

Water distribution network(WDN)leakage management has received increased attention in recent years.One of the most successful leakage-control strategies is to divide the network into District Metered Areas(DMAs).As a multi-staged technique,the generation of DMAs is a difficult task in design and implementation(i.e.,clustering,sectorization,and performance evaluation).Previous studies on DMAs implementation did not consider the potential use of existing valves in achieving the objective.In this work,a methodology is proposed for detecting clusters and reducing the cost of additional valves and DMA sectorization by considering existing valves as much as possible.The procedure of DMAs identification has been divided into three stages,i.e.,a)clusters identification;b)sectorization or boundaries optimization and c)performance evaluation of the partitioned network.The proposed methodology is evaluated on a simple network and a real-world water network with the findings provided and compared to the DMAs,established for a raw water network with no existing valves.It is found that there is an adequate difference in cost of strategy implementation in both the cases for the network under consideration and the existing valve system achieved better network performance in terms of resilience index.

Red cell distribution width in anemic patients undergoing transcatheter aortic valve implantation

AIM: To determine the impact of red blood cell distribution width on outcome in anemic patients undergoing transcatheter aortic valve implantation(TAVI).METHODS: In a retrospective single center cohort study we determined the impact of baseline red cell distribution width(RDW) and anemia on outcome in 376 patients with aortic stenosis undergoing TAVI. All patients were discussed in the institutional heart team and declined for surgical aortic valve replacement due to high operative risk. Collected data included patient characteristics, imaging findings, periprocedural in hospital data, laboratory results and follow up data. Blood samples for hematology and biochemistry analysis were taken from every patient before and at fixed intervals up to 72 h after TAVI including blood count and creatinine. Descriptive statistics were used for patient's characteristics. KaplanMeier survival curves were used for time to event outcomes. A recursive partitioning regression and classification was used to investigate the association between potential risk factors and outcome variables.RESULTS: Mean age in our study population was 81 ± 6.1 years. Anemia was prevalent in 63.6%(n = 239) of our patients. Age and creatinine were identified as risk factors for anemia. In our study population, anemia per se did influence 30-d mortality but did not predict longterm mortality. In contrast, a RDW > 14% showed to be highly predictable for a reduced short- and longterm survival in patients with aortic valve disease after TAVI procedure.CONCLUSION: Age and kidney function determine the degree of anemia. The anisocytosis of red blood cells in anemic patients supplements prognostic information in addition to that derived from the WHO-based definition of anemia.

Equilibrating Pressure with Auto-Control Valve in Water Distribution Networks

This paper probes into the feasibility of equilibrating pressure of water distribution network through (using auto-control valves) in theory and in the economy. An optimal valve control model is designed to minimize the sum of squares of residual pressure in the network. Such an analog simulation has been performed on the year 2003 programming network of a certain littoral district in North China, through which this paper confirms that it is feasible to equilibrate pressure with auto-control valves in theory. The research work has brought about a discovery of applicable conditions of valves in economic feasibility, which avoids a great economic loss due to the wild use of auto-control valve. In addition, simulated annealing algorithm is applied to optimize valve settings and shown to identify global optimum or near-optimum.

Design of a New Type of Distribution Valve for Hydraulic Breaker and Analysis of Energy Consumption

Energy consumed by distribution valves causes an energy loss for the output energy of hydraulic breakers, which has a significant influence on its efficiency. A new type of distribution valve used for hydraulic breakers, de- signed to reduce energy consumption, is analyzed on the basis of the operating principle and energy loss of the current distribution valve. The new distribution valve adopts a cone valve and the optimization technique of unequal open de- gree for the valve port. Theoretical calculations and analyses have proven that the new distribution valve can reduce en- ergy loss by 9.0127J, or energy consumption by 31%, during an impact cycle and the efficiency of the hydraulic breaker can be raised by 4.5%. It has the following characteristics: little leakage, little pressure loss and low energy consump- tion.

An Optoelectronic High-voltage Probe for Measuring Impulse Voltage Distribution of HVDC Converter Valve

A high-voltage optoelectronic probe is developed for measuring impulse voltage distribution along thyristor units in the HVDC converter valve.The dimension of the resistive voltage divider is optimized by means of numerical computation of electric field.A pulse frequency modulation(PFM) mode is adopted for the data transmission link because of its immunity to high-intensity electromagnetic interference.Experimental results indicate that the linearity deviation for the whole measuring system is within ±0.15%,and therefore it can meet requirements specified by IEC60700-1.

Improving the Performance of an Electro-Hydraulic Load-Sensing Proportional Control Valve

The paper deals with the simulation and the experimental verification of the hydraulic behavior of an electro-hydraulic load-sensing proportional control valve. An innovative CAE （computer aided engineering） methodology, developed combining CFD （computational fluid dynamics） simulations with lumped and distributed numerical modeling, is firstly introduced and tailored by comparing the numerical results with measurements coming from an experimental campaign performed for a wide range of pressure loads and metered flow rates. Then, both the reliability and the limits of the numerical approach are highlighted through a detailed numerical vs. experimental comparison, involving the pressure of the main hydraulic lines, the flow rate through the first section and the local compensator displacement. Finally, the CAE methodology has been applied for assessing the internal ducts hydraulic permeability and the local compensator spring pre-load influence on the control valve metering curves. At the end of this analysis, an optimized design configuration, featuring a maximum controlled volumetric flow rate increased of more than 25%, has been proposed.

高温高压Y型截止阀组内流特性及流道结构改进研究

流动性能是高温高压Y型截止阀组的关键性能指标,对截止阀组的运行具有重要意义。流速与流量的降低都会导致整体系统的工作效率下降。针对该问题,对全开工况下的DN15高温高压Y型截止阀组进行了研究。首先,以入口200 MPa、2000℃、出口常温真空为边界条件,对截止阀组内的流场进行了数值模拟,全面分析了截止阀组内部截止阀、球阀、喷管区域的流动特性,重点研究了阀组内流速的变化;然后,识别了流道中流动受限的区域,并提取了相应的特征结构参数,如喷管扩张段过渡角度数等;最后,采用非支配排序遗传算法,根据阀组的出口流速与出口流量这两项流动性能指标,对阀组内的流道局部结构参数进行了优化。研究结果表明:根据最优结构参数所得模拟结果与优化前的数据进行对比,出口流量提升了8.13%,出口速度提升了3.52%。该研究结论揭示了特定结构参数对截止阀组流动特性的影响机制,结合遗传算法与数值模拟方法,实现了特种阀门的流动性能升级目的,可对后续类似阀门的设计与性能优化工作提供一定的参考。

纵向风下大间距排烟阀集中排烟模式温度及烟气蔓延研究

为研究盾构隧道组合排烟模式下火灾时烟气流动特性,采用数值模拟方法研究了盾构隧道在纵向通风与集中排烟协同作用下的隧道温度分布和烟气蔓延长度。选取火源功率50 MW,分析不同纵向风速、排烟口间距及排烟量作用下隧道内温度分布和烟气蔓延长度。结果表明:大间距排烟阀组合排烟隧道火源下游的顶板下方纵向温度分布符合双指数衰减模型,隧道内温度分布情况主要受纵向风速和火源热释放速率主导,集中排烟量对隧道纵向温度分布影响不大;大间距排烟阀组合排烟模式下,火源下游的烟气蔓延长度随热释放速率的增大而增大,随排烟量的增大而减小,随纵向风速的增大而增大。对于大间距排烟阀集中排烟模式,具体设计应考虑三项原则:(1)纵向风速达到临界风速来抑制烟气向火源上游回流;(2)兼顾人员安全和漏风量的设计标准,在满足漏风量的设计前提下尽量缩短排烟阀间距;(3)排烟量达到一定量来控制烟气在两个排烟阀范围内。通过量纲分析,得到大间距排烟阀组合排烟模式下火源下游烟气蔓延长度预测模型。

A parametric bootstrap approach for one-way classification model with skew-normal random effects

In this paper,several properties of one-way classification model with skew-normal random effects are obtained,such as moment generating function,density function and noncentral skew chi-square distribution,etc.Based on the EM algorithm,we discuss the maximum likelihood(ML)estimation of unknown parameters.For testing problem of fixed effect,a parametric bootstrap(PB)approach is developed.Finally,some simulation results on the Type I error rates and powers of the PB approach are obtained,which show that the PB approach provides satisfactory performances on the Type I error rates and powers,even for small samples.For illustration,our main results are applied to a real data problem.

Development of a novel two-stage proportional valve with a pilot digital flow distribution

Pilot two-stage proportional valves are widely used in high-power hydraulic systems. For the purpose of improving the dynamic performance, reliability, and digitization of the traditional proportional valve, a novel two-stage proportional valve with a pilot digital flow distribution is proposed from the viewpoint of the dual nozzle-flapper valve’s working principle. In particular, the dual nozzle-flapper is decoupled by two high-speed on/off valves (HSVs). First, the working principle and mathematical model of the proposed valve are determined. Then, the influences of the control parameters (duty cycle and switching frequency) and structural parameters (fixed orifice’s diameter and main valve’s spring) on the main valve’s motion are analyzed on the basis of theory, simulation, and experiment. In addition, in optimizing the value of the fixed orifice’s diameter, a new design criterion that considers the maximum pressure sensitivity, flow controllability, and flow linearization is proposed to improve the balance between the effective displacement and the displacement fluctuation of the main valve. The new scheme is verified by simulations and experiments. Experimental results of the closed-loop displacement tracking have demonstrated that the delay time of the main valve is always within 3.5 ms under different working conditions, and the tracking error can be significantly reduced using the higher switching frequency. The amplitude–frequency experiments indicate that a −3 dB-frequency of the proposed valve can reach 9.5 Hz in the case of ±50% full scale and 15 Hz in the case of 0%–50% full scale. The values can be further improved by increasing the flow rate of the pilot HSV.

Using Excel to Explore the Effects of Assumption Violations on One-Way Analysis of Variance (ANOVA) Statistical Procedures

To understand any statistical tool requires not only an understanding of the relevant computational procedures but also an awareness of the assumptions upon which the procedures are based, and the effects of violations of these assumptions. In our earlier articles (Laverty, Miket, & Kelly [1]) and (Laverty & Kelly, [2] [3]) we used Microsoft Excel to simulate both a Hidden Markov model and heteroskedastic models showing different realizations of these models and the performance of the techniques for identifying the underlying hidden states using simulated data. The advantage of using Excel is that the simulations are regenerated when the spreadsheet is recalculated allowing the user to observe the performance of the statistical technique under different realizations of the data. In this article we will show how to use Excel to generate data from a one-way ANOVA (Analysis of Variance) model and how the statistical methods behave both when the fundamental assumptions of the model hold and when these assumptions are violated. The purpose of this article is to provide tools for individuals to gain an intuitive understanding of these violations using this readily available program.

高速电磁阀能量分布和动态响应耦合关系仿真

为研究高速电磁阀内部的能量分布及能量参数与动态响应之间的耦合关系,对高速电磁阀性能进行优化.首先,基于有限元法建立高速电磁阀动态模型,并通过实验数据验证模型的准确性;其次,利用D最优实验设计方法和最小二乘法,构建以能量参数为因素的电磁阀动态响应特性响应面预测模型;最后,使用元效应分析法开展了高速电磁阀动态响应显著能量参数及参数交互作用的仿真分析.研究结果表明:单参数中涡流能量E_(1)是影响高速电磁阀开启响应时间T_(o)的较敏感参数,T_(o)随着E_(1)的增加相应地增加了约25%,涡流能量分别与阻尼能量(E_(3))和焦耳能量(E_(4))之间的交互是影响T_(o)的高敏感参数,同时涡流能量与焦耳能量之间的交互也是影响关闭响应时间T_(c)的高敏感参数;交互参数中起主导作用的因素会随取值范围而改变.

电磁阀异步启闭的PWM喷雾系统设计与试验

PWM变量喷雾是国内外精准农业领域的研究热点,但PWM变量喷雾过程中电磁阀的快速启闭在管路内易形成压力脉冲,致使喷头喷雾压力发生变化,导致喷雾质量下降。为了降低压力脉冲,设计了一种相邻电磁阀异步启闭的PWM喷雾系统,由移动底盘、药箱、隔膜泵、稳压罐、PWM控制器、电磁阀及压力表等组成,通过延时控制,实现电磁阀异步启闭。在室内无风环境条件下,探究了喷雾系统电磁阀前管路内压力波动特性和沉积量分布均匀性。试验表明:与电磁阀同步启闭的PWM喷雾系统相比,电磁阀异步启闭可有效降低管路内压力峰值,不同PWM频率工况条件下,50%占空比时降幅最大,降幅最高为14%;20Hz频率条件下,异步启闭PWM喷雾的沉积量分布均匀性变异系数略高于常规连续喷雾,但均小于15%。上述结果符合喷杆喷雾机技术性能国家标准。

换流阀用阳极饱和电抗器温升特性及优化

阳极饱和电抗器(anode saturable reactor,ASR)是换流阀的关键一次设备,其在运行中因电磁损耗引发的温升问题明显并威胁绝缘体热老化。因此,准确分析ASR温升特性并寻求优化方法,对其状态评估、产品设计具有重要意义。为此首先根据发热机理和散热路径建立等效热路模型,定性分析了ASR实际运行中的温升特性;然后,建立ASR三维等效模型,结合瞬态传热原理来设定固体传热和空气对流参数,进一步应用基于湍流和实时混合假设的水冷却简化模型来模拟水冷散热过程,在兼顾准确性和高效性下开展多物理场耦合有限元仿真,定量计算ASR温度的大小变化和空间分布;最后,结合温度分布规律,提出不同截面积铁芯组合的结构优化方案,仿真验证了在电气性能不变前提下,各铁芯之间最大温差减少了原温差的91.7%,环氧树脂的最高温度降低3℃,为ASR的性能校验和参数设计提供借鉴。

汽轮机当量配汽级组变工况计算方法

将汽轮机主汽阀至一段抽汽口视为当量配汽级组,建立不同总阀位指令下的当量配汽级组特性曲线,进而实现包含总阀位指令信息的汽轮机配汽端特性的变工况计算。经验证,当量配汽级组简化仿真计算与汽轮机配汽端全面仿真计算结果趋于一致。该方法计算简便,符合试验机组的实际特性,满足工程应用的要求。

大功率汽轮机故障工况下高调阀控制方式切换性能研究

无扰切换是当前主流大型汽轮机阀门管理实现的一个重要功能,目前的大部分无扰切换研究工作都集中在设备正常状态的无扰切换实现方法上,尤其是起机并网时的无扰切换实现。为了研究火电机组灵活性,本文以多台600 MW级别机组为研究对象,针对机组存在的阀门管理缺陷进行故障诊断并实施优化改造,使机组安全顺利地投运了顺序阀配汽方式。然后,在此基础上进行了2类非正常运行工况下的无扰切换试验研究,探讨了机组故障状态下的无扰切换快速反应能力和设备故障对无扰切换的影响。试验结果表明:进行阀门管理优化不仅能够提高机组应对故障的反应能力,而且还能够降低机组切换控制系统对辅机等设备故障的敏感性。这对提高机组故障状态下的安全稳定性具有一定的借鉴意义。

1000MW汽轮机中压阀门异常振动分析及治理

针对某型超超临界1000MW机组运行过程中出现中压阀门振动过大的异常现象,对中压阀门以及机组轴系振动进行测试及分析,得出中压阀门振动以50Hz分量为主,与机组转频、阀门固有频率比较接近,表明中压阀门存在结构共振现象,且激振源为中压转子。进一步分析表明:中压缸进汽阀门组弹簧支撑刚性不足、中压缸载荷不均,是诱发中压阀门结构共振的主要原因。在检修中,更换新的中压阀门支撑弹簧,并提高其预压紧量,提升其刚度及稳定性;对中压缸缸体进行载荷分配,提升缸体稳定性,从而降低中压转子振动对阀门的影响。处理后,1000MW机组中压阀门振动大幅降低,提高了机组的安全可靠性,具有很好的工程借鉴价值。

基于振动烈度的乳化液泵配流阀弹簧故障特征提取研究

针对乳化液泵配流阀弹簧故障识别难度大、故障特征提取困难等一系列问题,提出一种基于振动烈度的乳化液泵配流阀弹簧故障特征提取方法。基于AMESim软件搭建乳化液泵仿真模型,通过分别设置不同参数模拟吸、排液阀弹簧故障形式,得到正常和吸、排液阀弹簧故障状态下的出口压力信号;根据振动烈度理论,将泵出口压力信号转换成加速度信号,在频域上对出口压力信号进行烈度特征值的提取和分析。研究结果表明:当吸、排液阀分别发生故障时,对出口压力烈度特征值的影响规律不同,随着吸液阀弹簧故障程度的加深,出口压力烈度特征值由正常时的15.82 mm/s^(2)增大到20.58、28.18、34.85 mm/s^(2),且在断裂时达到最大值;随着排液阀弹簧故障程度的加深,出口压力烈度特征值由正常时的15.82 mm/s^(2)减小到15.77、14.88、9.28 mm/s^(2),且在断裂时达到最小值。该结果可为后续乳化液泵的故障诊断提供理论依据。