短间隙下不同避雷针接闪性能试验研究

为探究不同避雷针在短间隙下的接闪特性,采用-250/2 500μs冲击电压波分别对全尺寸和缩小比例的可控放电避雷针、传统避雷针、普通避雷针进行间隙距离分别为0.3、0.6、0.9、1.2m的放电特性试验,采用升降法获取了不同避雷针的间隙放电电压参数和光学影像。结果表明,间隙距离为1.2m时,避雷针的50%放电电压的大小关系为普通避雷针传统避雷针可控放电避雷针,即在相同试验条件下可控放电避雷针更易于发生接闪。此外,为更加直观地比较不同避雷针在放电能力上的差异性,设计了双避雷针选择性放电试验,每组试验放电40次,发现可控放电避雷针的接闪概率分别为传统避雷针、普通避雷针的1.86、4.00倍。     

复古还是创新？——徕卡M-Monochrom

黑白照片给人一种时光的沧桑感，好像可以把人带回到回忆中的某个节点，而徕卡最新推出的M－Monochrom相机所带来的改变，恰能给人这样的感觉。M-Monochrom可以看做是徕卡M-9的黑白版，除采用与M-9不同的单色传感外，其它的配置基本相同，仅这一改变，所带来的效果就截然不同。由于取消了色彩滤镜，无需进行马克处理，从而获得了极其锐利的单像素锐度和飞跃般的感光度提升，同时，也带来了难以掌控的高光动态，对拍摄者提出了更高的要求。     

光伏组件两种Ⅰ-Ⅴ特性修正公式的比较

该文分别依据IEC 60891—2009和ASTM 1036—93标准中I-V特性修正公式的要求,对户外条件下同一光伏组件的I-V特性曲线进行修正,并对修正参数的结果进行比对和误差分析,得出两组修正公式的差异性。分析结果表明:ASTM 1036—93的修正公式更适于在与STC条件有较大辐照度差异的环境(如户外自然环境)中进行组件性能检测,而IEC 60891—2009的修正公式更适用于在接近STC条件的辐照度环境(如室内模拟环境)下进行检测。     

光伏组件加速试验应用现状及发展趋势

通过分析各种环境因素对光伏组件性能的影响及光伏组件在户外环境中出现的失效现象,回顾近几年来加速试验在光伏组件寿命预测、户外失效现象分析以及加速试验与计算机数值仿真相结合等发展方向的最新研究和技术进展,认为现有的标准加速试验程序并不能有效地预测光伏组件的寿命及失效现象,需发展更贴切现实环境的加速试验程序对组件寿命进行预测,尤其是需结合长期的户外监测数据和计算机仿真模拟技术对光伏组件进行寿命预测和失效分析。     

基于紫外成像的电晕放电参数变化特性及距离修正方法研究

鉴于光斑面积是紫外成像检测电晕放电的一种有效量化参数,以棒-板模型交流放电为例,研究了不同交流放电强度下光斑面积随紫外成像仪的增益与观测距离的变化而变化的特性,并进行了拟合分析。结果表明,光斑面积与紫外成像仪的增益近似呈指数关系变化,与观测距离之间近似呈幂函数关系。在此基础上,为了将不同距离下的观测结果归一到同一距离上以便提出可行的应用判据,根据试验获得的样本数据,建立了自适应模糊逻辑推理模型(ANFIS),实现了对观测结果的归一化处理,测试结果表明该模型具有较高的精度。     

低温热水地板辐射供暖间歇运行研究

建立了低温热水地板辐射供暖系统间歇运行时室内热环境数学模型，利用模型计算了不同运行方式、内围护结构和内热源作用下室内热环境变化规律。发现此类供暖系统采用适当间歇运行即可满足室内热环境要求，运行时间主要受室外温度和内热源变化规律影响。当系统按冬季室外供暖计算温度设计时，在冬季室外平均条件下，系统夜间运行半天左右即可基本保证全天室内热环境要求。     

基于紫外成像法的绝缘子电晕放电影响因素试验研究

绝缘子局部电晕放电的紫外检测是判定在线运行绝缘子绝缘性能的重要手段之一。采用光子型紫外探测器检测降雨量、污秽、均压环布置方式等不同试验条件下绝缘子的局部电晕放电程度,统计了检测到的光子数均值,进而分析不同因素对绝缘子电晕放电的影响。结果表明,污秽加剧了绝缘子的局部电晕放电程度;降雨量与绝缘子局部电晕放电程度具有复杂关系;绝缘子局部电晕放电程度与外施电压幅值呈指数增长关系;高压端均压环对绝缘子串的局部电晕放电具有关键作用。     

干式结构地板采暖运行模式的实验研究

探讨分析了一种将热盘管置于封闭夹层空间的干式结构的地板采暖方式。实验测试了不同地面盘管间距、不同室外条件和不同供热工况下，采暖开启时的预热阶段、间歇采暖和连续采暖时地板表面和诸壁面温度分布以及室内热环境变化的规律，为在满足室内热环境条件下，提供节能运行的方式。     

这里的景色生机无限奥林巴斯E—M5长白山体验记

对于户外摄影爱好者来说，好的相机和好的风景总是缺一不可。在很多极端的环境下，一款能够抵御风雨的装备，往往可以陪伴他们前往更加入迹罕至的拍摄地点，收录意想不到的精彩画面。奥林巴斯（Olympus）E—M5作为今年单电相机中的旗舰机型，拥有着同类徽单中最为出色的三防性能。     

介质特性对介质阻挡放电脱除NO影响试验研究

在介质阻挡气体放电等离子体条件下,研究阻挡介质特性对NO脱除的影响规律。首先建立了介质阻挡放电等离子体脱硝试验系统,实验研究了Al2O3、CaO、MgO和玻璃等不同介质阻挡下NO的脱除效果,并对此影响规律进行了理论分析。实验结果及理论分析表明,不同阻挡介质所形成的气体放电的电场强度不同,提供给活性粒子的能量也不同,从而对NO的脱除效果具有不同的影响。     

带电作业用绝缘遮蔽用具组合沿面放电试验研究

在配网带电作业中,为了提高绝缘防护面积,常将多个绝缘遮蔽用具组合使用,此时不同遮蔽用具之间的重叠部分就成为绝缘防护的薄弱区域。针对几种常用的绝缘遮蔽用具开展了组合使用时的沿面放电试验,采用球-棒电极模拟现场作业工况,并使用高速摄像机观察放电路径。结果表明,绝缘遮蔽用具的材料类型对其沿面绝缘性能影响较大,橡胶类和塑料类遮蔽用具的沿面绝缘性能接近,树脂类遮蔽用具的沿面绝缘性能较低;树脂绝缘毯在组合使用时,重叠部位贴合更加紧密;当重叠长度为15cm时,树脂绝缘毯重叠区域的沿面放电电压与橡胶毯接近;考虑10kV配网线路最大工频电压为24kV时,绝缘遮蔽用具组合使用时的重叠部位的长度不小于15cm。     

基于多重分形的SF6替代气体击穿特性研究

为探究干燥空气作为SF_6替代气体的可能性并深入理解短间隙气体放电流注的放电特性,搭建冲击电压放电试验平台,施加雷电冲击电压和快速暂态过电压,在极不均匀电场下探究干燥空气和SF_6气体的绝缘水平。为进一步研究流注形态特性受气体种类、电压极性等外界条件的影响,利用ICCD相机捕获二维流注图像分析了流注发展速度和流注通道长度的关系,并基于多重分形理论对流注整体形态的复杂性进行了解释。结果表明,在0.4MPa的气压下,干燥空气的脉冲击穿电压(V50%)满足24kV C-GIS的基本脉冲绝缘水平;在负极性下分形谱最大值相对较大,流注发展速度更快;与SF_6气体下的流注形态相比,空气下的流注形态的分形谱最大值较大,流注发展速度更快;多重分形谱谱宽不随外界条件变化而变化,说明流注光电离在二维图像空间分布上具有一定的相似性。     

船用轴流压气机推力轴承特性计算及试验研究

为获得某新型推力轴承在某船用轴流压气机中的工作特性并进行试验验证,基于ARMD Bearings软件及自编程序对推力轴承特性进行了模拟计算,在全尺寸高速大推力滑动轴承试验台上进行了轴承特性试验研究,并在实机台架试验中对轴瓦温度进行了监测。计算分析了15种工作条件下油膜的压力、厚度、温度、刚度、阻尼及能量损失与推力和转速关系。轴承特性试验主要包括9种稳定工况下的性能试验,以及轴承超载、超速试验中每块轴瓦表面温度及油膜压力的测量。结果表明：模拟计算结果及试验测试得到的油膜温度、压力随推力及转速变化规律基本一致;轴瓦表面最大油膜压力位于支承块背部附近,与推力基本呈线性关系;转子转速越低、推力越大,则油膜厚度越小、油膜刚度及阻尼越大;转子转速越高、推力越大,则油膜温度越高、能量损失越大;在设计点轴承运行参数均有一定安全裕度,该推力轴承可以满足机组使用要求。     

Visualisation of jet fires from hydrogen release

Hydrogen release tests with defined ignition represent one important aspect of hydrogen combustion in a potential accident. This paper shows the application of high-speed cinematography in combination with image processing techniques, the background-oriented-schlieren (BOS) and a difference method to visualise the shape of hydrogen jet. In addition, these methods were also used to observe the ignition and combustion zone on defined initiation. In addition the combustion zone was recorded by a high-speed IR camera. The IR camera was synchronized with a rotating filter wheel to generate four different motion pictures at 100 Hz each on a defined spectral range. The results provide some detailed information that might be used for improving model predictions.     

Test standards for thermosyphon-type solar domestic hot water system: review and experimental evaluation

This communication presents a review of test standards based on steady-state methods and applicable to thermosyphon-type solar domestic hot water systems (TSDHWS). The theoretical basis, the technique of parameter estimation and the test procedure of each standard have been reviewed and compared. Three standards concerning solar-only systems have been evaluated experimentally in detail. Extensive studies have been carried out under a wide range of weather and operating conditions. Two commercially available TSDHWS (having two different collector technologies) have been used in the investigation. The tests were carried out at the same location under similar conditions. The characteristic parameters of the TSDHWS have been obtained on the basis of each procedure/standard. A sensitivity study has also been carried out in order to examine the effect of measurement errors on the values of the estimated parameters from different standards. There are no significant effects on CNS parameters. JIS is the simplest one to implement. The normalizing factor of 20 930 kJ/m² day for the quantity of heat collected in this standard is not very clear. The ISO (part-2) is a very stringent standard as far as the operating and weather conditions are concerned. The combination of CNS parameters along with the overnight loss factor of ISO (part-2) forms an ideal set for comparing different TSDHWS.     

Influence of laser ignition on characteristics of an engine for hydrogen enriched CNG and iso-octane usage

The study has focused on determining the laser plug effects on engine characteristics and the laser plug usage results have compared with spark plug usage. The laser ignition technique is a type of new ignition technique and an important solution that can make combustion systems more efficient. The testing of an engine with a laser plug is the novelty of the study and the tests were carried out with reference to equivalence ratio and plug power ranges. The behaviors of the engine at full load were examined so experimentally for both ignition techniques at hydrogen enriched CNG and iso-octane mixture usage. The tests were carried out for variations of 0.4–2.0 equivalence ratio and 20–120 W plug power. A mixture that 90% iso-octane and 10% HCNG in mass was used at two ignition modes in tests for 3300 rpm maximum engine torque speed. Also, the flame formation and propagation for both ignition techniques were detected via a high-speed camera. The tests have shown the laser ignition leads to more energy consumption in the rich mixture conditions and also, less energy is required in the lean conditions. The laser ignition discharge has extended the engine's lean combustion limits via a small energy input at the tests. The high-speed camera images have shown that the laser ignition reduces the Kernel flame formation and propagation time. The laser ignition technique was produced less NO_x than the conventional spark ignition method.     

Thermal performance testing of flat-plate collectors

Existing standards for testing the performance of flat-plate solar collectors are documented in ASHRAE 93 [ANSI/ASHRAE Standard 93-2003, 2003. Methods of Testing to Determine Thermal Performance of Solar Collectors, ISSN: 1041-2336, ASHRAE, Inc., 1791 Tullie Circle, Ne, Atlanta, GA30329], ISO 9806-1 [ISO Standard 9806-1:1994(E), 1994. Test Methods for Solar Collectors – Part 1: Thermal Performance of Glazed Liquid Heating Collectors Including Pressure Drop, ISO, Case Postale 56, CH-1211 Geneve 20, Switzerland] and EN12975-2 [European Standard EN12975-2:2001, 2001. Thermal Solar Systems and Components – Solar Collectors – Part 2: Test Methods, CEN, Rue de Stasart, 36, B-1050, Brussels]. The ASHRAE 93 standard requires an experimental determination of the steady-state collector efficiency under prescribed environmental conditions for a range of collector fluid temperatures. Each test requires a minimum of 20 min and 22 tests are required to fully characterize a collector’s thermal performance. The ASHRAE 93 testing procedure is further complicated by the fact that the prescribed weather conditions do not often occur in some locations, which prolongs the time required to conduct the performance tests for a given collector. The EN12975-2 collector test procedure provides an alternative transient test method that can be conducted over a larger range of environmental conditions. This paper compares the results obtained by applying the EN12975-2 standard with results obtained from the ASHRAE 93 steady-state tests for a well-designed single-glazed selective surface flat-plate collector. The collector thermal parameters, F_R(τα)_e and F_RU_L obtained by the two test methods show good agreement. The incident angle modifier coefficient determined in the ASHRAE method, which uses a separate test for this purpose, was found to be more accurate than that determined in the transient method according to the EN12975-2 standard, which obtains this value and all other collector parameters in the same step. This transient method, however, uses a refined collector model that includes specific terms for the wind speed dependence and the collector thermal capacitance, which are absent in the ASHRAE model. The long-term collector thermal performance as a part of a water heating system was simulated using the efficiency curves derived from each of the test methods. The solar fractions obtained by simulation are within 7% for both cases.     

Theoretical and experimental analysis on efficiency factors and heat removal factors of Fresnel lens solar collector using different cavity receivers

The efficiency and heat removal factors are useful parameters for evaluating the thermal performance of concentrating solar collectors. In this work, the efficiency factors and heat removal factors of Fresnel lens solar collectors using different kinds of point-focus cavity receivers were obtained both theoretically and experimentally. An experimental unit was built, whereby eight kinds of cavity receivers, namely: conical, spherical, cylindrical, hemispherical, positive cone frustum, reverse cone frustum, heteroconical and domical, were tested and analyzed. It is found that the theoretical results agree well with the test results. For the point-focus Fresnel lens solar collector, the conical cavity receiver showed the best thermal performance, with a highest theoretical heat removal factor of 0.868. Effect of conical cavity parameters on the efficiency and heat removal factors were studied. Results showed that under given operation conditions, the optimum aperture diameter of the cavity, the optimum inside diameter of the receiver tube and the optimum vertex angle of the cross section through the symmetric axis of the receiver are 80 mm, 15 mm and 60°, respectively. For better thermal performance, the geometrical concentration ratio of the studied Fresnel lens solar collector should be more than 500.     

非均等配风下的风水冷选择性冷渣器冷态排渣特性

以某电厂450t/h CFB锅炉的风水冷选择性冷渣器为原型,通过冷态模化实验研究了各仓室在均等和非均等配风下的排渣特性,分析了各仓室的风量比关系对排渣速率的影响规律。实验结果表明,冷渣器的实际流化风量下限值高于设计值,在送风机总风量基本不变甚至减小的情况下,通过调配各仓室的风量比关系可明显提高冷渣器的排渣速率。所得实验数据对冷渣器的安全运行具有一定的指导意义和参考价值。     

New electronically controlled hydrogen-gas injector development and testing

The feasibility of high-pressure hydrogen-gas injection was investigated in a diesel engine with the help of an electronic control under microprocessor management. An injector prototype was developed with variable area orifice fitted with a solenoid actuator for lifting of the needle valve. A metering valve controlled by a digital actuator was installed at the injector's inlet to throttle the gas flow from the cylinder with compressed hydrogen. The injected fuel dose was therefore under double control: by the time of the injector's opening and by the metering valve flow area. This system was first investigated on a test set-up where the pressure in the injector, the needle lift and the gas dose were measured. A concentrated gas discharge rate characteristic of 3 ms duration was obtained. An attempt was also made to measure the gas discharge rate by recording the amplitude of the pressure wave created in a special long pipe. Ignition feasibility tests were finally conducted in a high speed diesel engine with spark ignition support.