脉冲电流对6016-T4铝合金板材力学性能的影响

为研究在电流辅助成形时脉冲电流的电流密度、占空比和脉冲频率3个因素对6016-T4铝合金板材力学性能的影响规律,设计了3因素5水平的正交实验。实验表明,对6016-T4铝合金力学性能影响的主次因素是:电流密度>占空比>脉冲频率。在此基础上,选用主次2个因素,即电流密度和脉冲频率,使用控制变量法进行进一步的实验研究。实验结果表明,电流密度对6016-T4铝合金力学性能影响较大,改变电流密度的同时带来了明显的焦耳热效应,该效应对材料有明显的软化作用,降低了材料的流动应力,但是,同时也降低了铝合金板的伸长率,这是因为过大的电流密度加剧了试样的主应变演化,进而促进了试样的断裂。而脉冲频率的变化对6016-T4铝合金板材的力学性能影响很小,这也印证了正交实验的结论。     

高温烟气中煤焦气化行为

针对高温烟气中煤焦的气化行为，本文采用FactSage 6.1计算了煤焦在高温烟气下的高温反应特性，并利用热重分析仪分析了煤焦气化行为。通过沉降炉实验进一步研究了不同温度、气体配比、粒径条件下气体产物的动态析出特性，同时计算了评价指标α、β、LHV值。结果表明：随着温度的升高，气体产物H₂和CO的含量增加，β、α、LHV值增大，CH₄和CO₂的含量下降。在温度为1200℃时，β、α值分别由CO₂/CO比为10∶70时的10.80%、5.21%增加到CO₂/CO比为50∶30时的24.71%、41.06%。同时，随着CO₂/CO比值的增大，高温烟气对煤焦气化反应抑制减弱。通过对比反应温度和粒径对煤焦气化反应的影响，得出反应温度远大于粒径对煤焦气化反应的影响。通过实验验证了向高温烟气中喷吹煤焦制备高品质可燃气体方法的可行性。     

改进ILoG算子的故障检测方法

针对强背景噪声干扰下轮对轴承故障特征微弱、难以准确检测的问题,提出了一种自适应改进高斯拉普拉斯(improved Laplacian of Gaussian,简称ILoG)算子的微弱故障检测方法。ILoG算子滤波器具有优良的信号突变特征检测能力,将其用于轮对轴承故障信号的冲击特征检测,同时利用水循环算法(water cycle algorithm,简称WCA)的寻优特性,并行搜寻筛选最佳的ILoG算子影响参数,通过对参数优化后ILoG算子滤波后信号做进一步包络解调分析,提取出轮对轴承微弱的故障特征信息。对实际轮对轴承外圈和内圈故障信号分析的结果表明,该方法可以有效检测出轴承微弱故障特征频率,故障检测效果优于小波阈值和多尺度形态学差值滤波方法。     

高粘度流体横掠麻面管的传热与流动特性研究

采用三维数值模拟方法,研究不同Re(381、572、763、954、1144)下凹坑直径d(1.8、2.0和2.2 mm)、深度h(0.9、1.0和1.1 mm)、轴向距离p(10、12和14 mm)、周向距离l(5.236、6.283和7.854 mm)与布置型式(叉排、顺排)对高粘度润滑油横掠麻面管流动与传热的影响。结果表明:外壁周期性凹坑的存在使得麻面管油侧换热增强,同时减阻效果明显;相比于光管,当Re=381～1 144时,麻面管油侧Nu增加了28.6%～55.4%,阻力系数f减小了0.59%～26.9%,综合换热性能指标η为1.05～1.59。     

A comparative thermodynamic analysis of Kalina and organic Rankine cycles for hot dry rock: a prospect study in the Gonghe Basin

Hot dry rock is a new type of geothermal resource which has a promising application prospect in China. This paper conducted a comparative research on performance evaluation of two eligible bottoming cycles for a hot dry rock power plant in the Gonghe Basin. Based on the given heat production conditions, a Kalina cycle and three organic Rankine cycles were tested respectively with different ammonia-water mixtures of seven ammonia mass fractions and nine eco-friendly working fluids. The results show that the optimal ammonia mass fraction is 82% for the proposed bottoming Kalina cycle in view of maximum net power output. Thermodynamic analysis suggests that wet fluids should be supercritical while dry fluids should be saturated at the inlet of turbine, respectively. The maximum net power output of the organic Rankine cycle with dry fluids expanding from saturated state is higher than that of the other organic Rankine cycle combinations, and is far higher than the maximum net power output in all tested Kalina cycle cases. Under the given heat production conditions of hot dry rock resource in the Gonghe Basin, the saturated organic Rankine cycle with the dry fluid butane as working fluid generates the largest amount of net power.     

Effect of load reduction mechanisms on loads and blade bearing movements of wind turbines

The power control of wind turbines is usually realized via a change in the pitch angle of the rotor blades. Pitching facilitates the exact control of the turbines and the reliable deceleration of the rotor when required. Pitch movements can moreover be used for load control. One of these methods is called individual pitch control (IPC). IPC controls the blades individually and brings about a significant reduction in the fatigue loads and extreme loads placed on the structural components, while at the same time reducing the yield of the turbine only slightly. The lower loads reduce material costs, and thus, the cost of energy (CoE) is reduced, despite the slight reduction in yield. The method is nevertheless not used everywhere since the additional movement cycles put the rotor blade bearings in particular under stress. Special attention must be paid to small amplitude oscillating movements, which carry a high risk of inducing surface damage in the rolling contacts of the blade bearings. This paper uses a cycle analysis of the IWT7.5‐164 reference turbine to illustrate the differences in the movement patterns of wind turbine blade bearings with and without IPC. Moreover, model calculations with single contacts are used to show which of the movement patterns carries a risk of inducing surface damage. The use of IPC leads to the expected load reduction at the blade root. In current literature, IPC is usually assumed to have a negative influence on the life expectancy of blade bearings, but the findings of this study contradict this. The summed blade bearing movement is increased, although the number of very small pitch angles occurring is reduced. This reduction reduces the risk of wear in the blade bearings.     

延长油田X油区长8储层孔隙结构特征研究

根据岩心、薄片及压汞资料,系统分析了长8储层的孔隙结构特征,并将其分为4种类型,其中Ⅰ类孔隙类型为优质储层。     

高效液相色谱-串联质谱法检测新鲜蔬菜中的氯酸盐残留

目的建立高效液相色谱-串联质谱(high performance liquid chromatography-tandem mass spectrometry,HPLC-MS/MS)检测新鲜蔬菜中氯酸盐的分析方法。方法称5 g样品,分别用5 mL乙腈提取2次,合并提取溶液,定容,无需净化步骤,选择Hypercarb多孔石墨化碳色谱柱作为固定相,1%乙酸-水溶液和1%乙酸-甲醇溶液作为流动相进行梯度洗脱色谱分离,然后采用电喷雾离子化三重四极杆串联质谱测定。结果氯酸盐在0.0025～0.2 mg/L范围内峰面积与质量浓度的线性关系良好,相关系数(r~2)大于0.999;平均回收率为72.9%～100.2%,相对标准偏差为1.8%～6.2%,氯酸盐的定量限为0.01 mg/kg。结论该方法简单快速、准确可靠、成本低廉,适合新鲜蔬菜中氯酸盐的测定。     

高湿黏性颗粒在聚四氟乙烯微孔膜滤料表面沉积特性的数值模拟

基于聚四氟乙烯(PTFE)微孔膜滤料扫描电镜(SEM)图像，建立PTFE微孔膜滤料微观结构模型，采用计算流体力学和离散单元法(CFD?DEM)耦合的方法对黏性颗粒在微孔膜滤料表面沉积特性进行模拟，引入液桥力模型，忽略范德华力的作用，统计计算域内颗粒的受力情况，分析了不同表面能条件下3~6 ?m粒径颗粒在微孔膜滤料表面的沉积特性，将模拟结果与黏附效率的经验公式进行对比。结果表明，黏附效率与经验值、颗粒受力与液桥力模型的相对误差均在6%以内，CFD?DEM耦合计算方法可用于模拟不同环境湿度条件下的颗粒沉积；过滤风速、粒径与黏性是影响沉积形态的重要因素，提高过滤风速及增大颗粒粒径与黏性，颗粒更易在滤料表面形成稳定的树突结构，黏附效率及含尘压降增加。环境相对湿度影响两物体间液桥体积，接触力影响颗粒沉积，当增加表面能与液桥体积时，接触力及液桥力均相应增加，根据受力平衡原理，环境相对湿度对颗粒沉积影响很大。     

Durable,Sensitive, and Wide‐Range Wearable Pressure Sensors Based on Wavy‐Structured Flexible Conductive Composite Film

Flexible pressure sensors have potential applications in human motion monitoring and electronic skins. To satisfy the practical applications, pressure sensors with a high sensitivity, a low detection limit, a broad response range, and an excellent stability are highly needed. Here, a piezoresistive pressure sensor based on wavy‐structured single‐walled carbon nanotube/graphite flake/thermoplastic polyurethane (SWCNT/GF/TPU) composite film is fabricated by a prestretching process. Due to the random wavy structure, high conductivity, and good flexibility, the prepared sensor displays a low detection limit of 2 Pa, a wide sensing range of 0–60 kPa, and a high sensitivity of 5.49 kPa^?1 for 0–50 Pa. Furthermore, the sensor shows a remarkable repeatability of over 1.1 × 10⁴, 9.0 × 10³, and 2.0 × 10³ pressure loading/unloading cycles at 50 Pa, 500 Pa, and 30 kPa, respectively, and a fast responsibility of 100–150 ms of loading response time and 400–600 ms of relaxation time. Therefore, the pressure sensor is successfully adopted to monitor both the large‐scale human activities (e.g., walk and jump) and the small‐scale signals (e.g., wrist pulse). Furthermore, a sensor array is assembled to map the weight and shape of an object, indicating its various potential applications including human–machine interactions, human health monitoring, and other wearable electronics.