内压式超滤换向流反洗技术优势

根据电力行业的水质特点,电厂广泛采用中水作为除盐水的来水水源,水质相对于地表水而言水质较差,从而需要进行深度预处理。目前深度预处理工艺主要是全膜法工艺流程UF超滤 + 两级反渗透 + 混床工艺,而超滤在系统中发挥着重要的作用,也是保证反渗透稳定运行的关键设备。很多工程大部分采用的外压式超滤,而外压式进水口与反洗口方向固定不能调换,运行周期时间相对较短,且膜污染较严重,经多次反洗后不能完全达到初始状态,对此进行彻底展开分析试验比对,根据水质及工艺系统要求选择适宜的内压式超滤膜,在工艺设计方面通过增加适当的管路与阀门来实现超滤膜进水口与反洗口相互切换(即换向流运行),分析此系统运行的状况,延长超滤系统运行周期使用时间,减少膜反洗的频次从而提高系统制水率,从而达到节约用水的目的。According to the water quality characteristics of the power industry, power plants widely use reclaimed water as a source of desalinated water. The water quality is relatively poor compared to surface water, so deep pretreatment is needed. Currently, the main deep pretreatment process is the full membrane process UF ultrafiltration + two-stage reverse osmosis + mixed bed process. Ultrafiltration plays an important role in the system and is also a key equipment to ensure the stable operation of reverse osmosis. Many projects use external pressure ultrafiltration, and the direction of the external pressure inlet and backwash outlet is fixed and cannot be changed. The operating cycle time is relatively short, and the membrane pollution is severe. After multiple backwashing, it cannot fully reach the initial state. Therefore, a thorough analysis and experimental comparison are carried out, and suitable choices are selected based on water quality and process system requirements. Internal pressure ultrafiltration membrane, In terms of process design, appropriate pipelines and valves are added to achieve mutual switching between the ultrafiltration membrane inlet and backwash port (i.e. reversing flow operation), analyze the operation status of the system, extend the operating cycle of the ultrafiltration system, reduce the frequency of membrane backwashing, and improve the water production rate of the system, thereby achieving the goal of water conservation.

多段换向穿流干燥过程的分析和设计

基于物料特性干燥曲线的数学表达式开发了多段换向穿流干燥过程的通用数学模型。可用于采用该类干燥方法的任何物料干燥过程的分析和干燥机的设计计算。讨论了若干因素的影响,阐述了操作条件、设计参数的决策和分析计算方法。

气液联合驱动式冲击器换向系统参数研究

为了研究换向系统结构参数对液压冲击器工作性能的影响,根据气液联合驱动式液压冲击器,采用高速开关电磁阀作为先导阀和二通插装阀作为主阀的配流换向组合,替代了传统液压换向阀配流换向系统,构建了配流换向系统数学模型,在多领域建模仿真软件AMESim平台下,构建液压冲击器的整体仿真模型,获得了不同主阀芯质量、弹簧刚度下的活塞的速度和位移曲线。结果表明:主阀芯质量越轻,弹簧刚度越大,冲击活塞到达最大冲击速度和最大位移所需的时间越短,冲击效率越高。仿真结果对提升冲击器的品质有一定的指导。

CCC在直流输电系统中的运行特性分析

在串联电容换流装置中CCC与传统的换相换流器相比,有一些优点。当运用高压直流输电技术连接两个大型非同步电力系统时,所连接电网的短路容量与额定直流功率相比可能降低,尤其当系统运行在逆变侧系统为弱交流故障的情况下,这可能导致高压直流系统发生严重的次同步振荡。本文采用暂态仿真软件PSCAD对CCC的运行特性进行了评估。

新型压力反馈高频液压配流系统设计研究

采用以配流换向阀、高速开关阀及电子控制模块组成的新型压力反馈高频液压配流系统,其中换向阀为执行元件,高速开关阀起先导控制作用,而电子控制模块起着信号分析、处理及发布的作用,这种柔性高频配流换向系统能很好地实现对目标执行器工作性能的控制。

Simulation and Design Optimization of Ammonia Synthesis Converter

One-dimensional pseudo-homogeneous model of an axial flow converter and one-dimensional heteroge-neous model of a horizontal converter have been presented, which describe the distribution of gaseous composition,temperature and pressure along the height in the two converters, respectively. Design optimization methods of the two converters have been proposed, by which the minimum catalyst volume can be obtained to satisfy the productive capacity of 1000 tons per day, when the operating pressure is 15.0, 10.0 and 7.5 MPa, respectively.

Modeling of a Reverse Flow Reactor for Methanol Synthesis Modeling of a Reverse Flow Reactor for Methanol Synthesis

An accurate one-dimensional, heterogeneous model taking account of axial dispersion and heat transfer to the reactor wall, and heat conduction through the reactor wall for methanol synthesis in a bench scale reactor under periodic reversal of flow direction is presented. Adjustable parameters in this model are the effectiveness factors for each of the three reactions occurring in the synthesis and a factor for the bed to wall heat transfer coefficient correlation. Experimental data were used to evaluate these parameters and reasonable values of these parameters were obtained. The model was found to closely predict the reactor performance under a wide range of operating conditions, such as carbon oxide concentrations, volumetric flow rate, and cyclic period.

钛合金异形内螺旋线电解加工过程工艺优化

针对钛合金异形内螺旋线电解加工过程中间隙流场分布不均、工件表面易发生点蚀、加工质量差等问题,对加工工艺进行了优化。设计了一种顺流换向式新型阴极结构,通过加工间隙流场仿真对阴极过液孔直径进行了优化。开展了电解液基础试验,获得了一种适用于钛合金材料高效高质量电解加工的复合电解液配方:10%NaCl+8%NaNO3+3%Na2HPO4。并采用优化后的阴极与复合电解液完成了钛合金内螺旋线的稳定可靠加工,加工表面无点蚀现象出现,成形精度达到0.04mm,阴线表面粗糙度优于Ra0.8μm。

PRIMARY SIDE DETECTION AND PEAK CURRENT MODE CONTROL IN FLYBACK CONVERTER

A new cycle-by-cycle control flyback converter with primary side detection and peak current mode control is proposed and its dynamic characteristics are analyzed. The flyback converter is verified by the OrCAD simulator. The main advantages of this converter over the conventional one are simplicity, small size, rapid regulating and no sensing control signals over the isolation barrier. The circuit is suitable for digital control implementations.

EFFECTS OF THE HOE 694 ON TRANSIENT INWARD CURRENT AND NA^+- CA^(2+) EXCHANGE IN GUINEA PIG CARDIOMYOCYTES

To determine the effects of HOE 694, a new and potent Na＋- H＋ exchanger blocker, on transient inward current (Iti) and Na＋- Ca2＋ exchange during hypoxia- reoxygenation in guinea pig cardiomyocytes. Methods. Cardiomyocytes were isolated from adult guinea pig ventricle. Experiment was performed in an experimental chamber that allowed the cells to be exposed to a sufficiently low O2 pressure. The cells were subjected to hypoxia and reoxygenation. The ionic currents were studied with patch clamp technique. Results. In the absence of HOE 694, hypoxia- reoxygenation induced Iti in 12 of 15 experiments; but in cardiomyocytes pretreated with HOE 694 (10～ 50μ mol/L), the incidence of Iti observed during reoxygenation was reduced to 5 of 11 experiments and 3 of 10 experiments, P Conclusions. Blockade of the Na＋- H＋ exchange by HOE 694 could reduce Ca2＋ overload upon hypoxia- reoxygenation, and inhibition of Na＋- H＋ exchange may also indirectly decrease Na＋- Ca2＋ exchange activity during hypoxia.

Methodology for expressing the flow coefficients of coupled throttling grooves in a proportional–directional valve

Calculating the flow coefficient of a spool-valve is complicated due to the coupling–throttling effect in the throttling grooves of a proportional–directional valve.In this paper,a methodology for expressing the flow coefficient of coupled throttling grooves is proposed to resolve that difficulty.With this purpose,an approach of a 3 D numerical simulation and an experimental bench were introduced based on the prototype of a commercial proportional valve.The results show consistency between the numerical simulation and the bench test.Based on that,the concept of‘saturation limit’is introduced to describe the value gap between the current and saturated flows,so that the flow-coefficient saturation limit of the prototype in the process can be deducted.Accordingly,an approximate flow coefficient suitable for coupled throttling grooves within finite variable space,which is based on three typical throttling structures(i.e.O-shape,U-shape,and C-shape)of the coupled throttling grooves,is obtained based on an orthogonal test.The model results are consistent with the numerical and experimental results,with maximum errors of less than 5.29%and 5.34%,respectively.This suggests that the proposed method is effective in approximating the flow coefficient.

A Twin Unidirectional Impulse Turbine for Wave Energy Conversion

A twin unidirectional impulse turbine has been proposed in order to enhance the performance of wave energy plant. This turbine system uses two unidirectional impulse turbines and their flow direction is different from each other. However, the turbine characteristics have not been clarified to date. The performances of a unidirectional impulse turbine under steady flow conditions were investigated experimentaUy by using a wind tunnel with large piston/cylinder in this study. Then, efficiency of the twin impulse turbine have been estimated by a quasi-steady analysis using experimental results.

Local heat transfer enhancement induced by a piezoelectric fan in a channel with axial flow

The present work experimentally and numerically investigates the local heat transfer enhancement induced by a piezoelectric fan interacting with a cross flow in a local heated channel.The piezoelectric fan is placed along the flow direction and tested under different amplitudes and flow rates.In the simulations,a spring-based smoothing method and a local remeshing technique are used to handle the moving boundary problems.Hybrid mesh is used to reduce the size of dynamic mesh domain and to improve computational efficiency.The experimental and numerical values of the time-averaged mean Nusselt number are found to be in good agreement,with deviations of less than 10%.The experimental result shows that the heat transfer performance of the heated surfaces is substantially enhanced with a vibrating piezoelectric fan.The numerical result shows that the heat transfer enhancement comes from the strong longitudinal vortex pairs generated by the piezoelectric fan,which significantly promote heat exchange between the main flow and the near-wall flow.In the case of a=0.66(a is the dimensionless amplitude)and Re=1820,the enhancement ratio of the time-averaged mean Nusselt number reaches 119.9%.

Realization of band-pass and low-pass filters on a single chip in terahertz regime

In this paper, we present the design, simulation, fabrication and characterization of a terahertz(THz) filter based on metamaterial consisting of the periodical double symmetric splits ring resonator(DS-SRR) array. We can observe that the metamaterial-based filter possesses a band-pass transmission when the electrical field is along y direction, and it possesses a low-pass transmission when the electrical field is along x direction. Our results demonstrate that the proposed filter can realize the switching between band-pass effect and low-pass effect by only changing the polarization direction of the incident electromagnetic wave. Moreover, the calculated surface current distributions are also used to analyze the switchable mechanism of the THz metamatrial filter. Therefore, the proposed THz wave filter has a potential application in THz wave communication systems.