Fracture mechanics approach for failure of adhesive joints in wind turbine blades

Composite components of wind turbine blade are assembled with adhesive. In order to assess structural integrity of blades it is needed to investigate fracture of joints. In this study, finite element analysis based on fracture mechanics was conducted to characterize failure of adhesive joint for wind turbine blade. The cohesive zone model as proposed fracture mechanics approach was verified through the comparison of numerical results with experimental data. Finite element models of wind turbine were developed to predict damage initiation and propagation. Numerical results based on fracture mechanics showed that failure was initiated in the edge of the adhesive bond line due to high level of shear stress prior to reaching the extreme design loading and propagated progressively.     

黑龙江省新林—呼中地区水系沉积物地球化学特征及找矿意义

在新林—呼中地区森林沼泽-冻土景观区,开展1∶50 000水系沉积物测量,探讨该区水系沉积物中元素含量分布、元素组合特征和区域地球化学异常特征,为下一步划分成矿远景区,开展地球化学找矿提供依据。结果显示:该区具备中高温热液型Cu、Pb、Mo、Au多金属矿成矿条件;早白垩世二长花岗岩区和白音高老组火山岩区Cu、Pb、Zn、Mo、Au显著富集,强烈分异,是寻找Pb、Cu、Mo、Au多金属矿化(床)的有利地段;区域异常与燕山早期酸性侵入体密切相关,应是晚侏罗世—早白垩世岩浆侵入、喷发以及构造运动强烈作用的结果。     

Transient performances of the gas turbine recuperating waste heat through hydrogen rich fuels

Operational rules and control strategies of the chemically recuperated gas turbine (CRGT) in the marine propulsion are investigated in this paper. The Minimization of Gibbs free energy method is used to calculate the diesel-steam reforming reaction which products synthetic hydrogen rich fuels, and a universal model of the chemical regenerator which is easily applied to different application environments is created. The hydrogen production and hydrogen molar fraction are investigated to verify that the CRGT improve the combustion performances under low working conditions. Off-design calculations are performed to derive proper operational rules, and transient calculations are performed to investigate the best control strategies for the systems. The modelling approach of the chemical regenerator can be generally used in the chemically recuperated gas turbine. The elaborate operational rules can greatly improve the thermal efficiencies under every working condition. The system using synchronous control strategies have better regulation speed and operation stability than that using asynchronous control strategies.     

An experimental investigation on hydroxy (HHO) enriched ammonia as alternative fuel in gas turbine

Today, the important challenges with the utilization of hydrogen in power-producing applications (internal combustion engines and fuel cells) are its delivery and storage and these create a big hesitation regarding the application safety. Ammonia, which can be regarded as the most promising alternative fuel to hydrogen, provides the possibility of storage in liquid form at low pressures and high temperatures. This study was carried out to investigate how to compensate the drawbacks of using ammonia as the main fuel in a gas turbine by hydrogen and hydroxy-gas enrichment. During the experiments, propane that is standard working fuel of the gas turbine, neat ammonia, as well as a 10 L/min ammonia fuel enriched with 3 L/min, 5 L/min, and 7 L/min hydroxy gas, were utilized. The results show that hydroxy enrichments cause improvements in the performance data as well as emission values due to the absence of any carbon emissions. When the performance outputs are examined, it has been shown that the power values of NH₃ + 3 HHO and NH₃ + 5 HHO fuels are 10.98% and 3.65% lower than propane, whereas NH₃ + 7 HHO fuel produces 4.12% more power, and the desired performance values are reached. It has been also fund that NO_x emissions should be kept under control in addition to the increase in the performance and elimination of the carbon emissions.     

Generated output increase control with consideration of the influence of wake for wind farm

Presently, many wind turbine generators (WTGs) are connected to the power grid. While the penetration of wind power to the power system is increasing, FIT price is decreasing. Therefore, wind generation companies want to increase the electric power output from wind farms (WFs). In this article, we propose a control technique to reduce the influence of the wake by changing a power coefficient of each WTG in a WF for the purpose of improving electric power output of WFs. We showed the optimization technique of a power coefficient of each WTG and the effect of reducing the influence of the wake using measurement data from WFs. In addition, we formulated the wake effect as a function of distance between WTGs. We verified 1% improvement of generated energy in a year compared to the conventional control method by simulation. Furthermore, we quantified the improvement of generated energy output, using the distance between WTGs and the occurrence rate of the direction of the wind as a variable.     

Wind tunnel-based testing of a photoelectrochemical oxidative filter-based air purification unit in coronavirus and influenza aerosol removal and inactivation

Recirculating air purification technologies are employed as potential means of reducing exposure to aerosol particles and airborne viruses. Toward improved testing of recirculating air purification units, we developed and applied a medium-scale single-pass wind tunnel test to examine the size-dependent collection of particles and the collection and inactivation of viable bovine coronavirus (BCoV, a betacoronavirus), porcine respiratory coronavirus (PRCV, an alphacoronavirus), and influenza A virus (IAV), by a commercial air purification unit. The tested unit, the Molekule Air Mini, incorporates a MERV 16 filter as well as a photoelectrochemical oxidating layer. It was found to have a collection efficiency above 95.8% for all tested particle diameters and flow rates, with collection efficiencies above 99% for supermicrometer particles with the minimum collection efficiency for particles smaller than 100 nm. For all three tested viruses, the physical tracer-based log reduction was near 2.0 (99% removal). Conversely, the viable virus log reductions were found to be near 4.0 for IAV, 3.0 for BCoV, and 2.5 for PRCV, suggesting additional inactivation in a virus family- and genus-specific manner. In total, this work describes a suite of test methods which can be used to rigorously evaluate the efficacy of recirculating air purification technologies.     

论清康熙官窑瓷“仿明风”形成的条件与原因

清康熙中期时,御窑厂得到正式复兴。仿明是康熙官窑最鲜明的特色之一,从颜色釉至各类彩绘瓷均有显著的"仿明风"。康熙官窑"仿明风"是在各方面有利条件下形成的,其形成与当时政治与文化风气密切关联。     

Thermal–economic–environmental analysis and multi-objective optimization of an internal-reforming solid oxide fuel cell–gas turbine hybrid system

In this article, an internal-reforming solid oxide fuel cell–gas turbine (IRSOFC–GT) hybrid system is modeled and analyzed from thermal (energy and exergy), economic, and environmental points of view. The model is validated using available data in the literature. Utilizing the genetic algorithm optimization technique, multi-objective optimization of modeled system is carried out and the optimal values of system design parameters are obtained. In the multi-objective optimization procedure, the exergy efficiency and the total cost rate of the system (including the capital and maintenance costs, operational cost (fuel cost), and social cost of air pollution for CO, NO_x, and CO₂) are considered as objective functions. A sensitivity analysis is also performed in order to study the effect of variations of the fuel unit cost on the Pareto optimal solutions and their corresponding design parameters. The optimization results indicate that the final optimum design chosen from the Pareto front results in exergy efficiency of 65.60% while it leads to total cost of 3.28 million US$ year⁻¹. It is also demonstrated that the payback time of the chosen design is 6.14 years.     

Influence of blade deformation and yawed inflow on performance of a horizontal axis tidal stream turbine

For a better design of tidal stream turbines operated in off-design conditions, analyses considering the effects of blade deformation and yawed inflow conditions are necessary. The flow load causes deformation of the blade, and the deformation affects the turbine performance in return. Also, a yawed inflow influences the performance of the turbine. As a validation study, a computational fluid dynamics (CFD) simulation was carried out to predict the performance of a horizontal axis tidal stream turbine (HATST) with rigid blades. The numerical uncertainty for the turbine performance with blade deformation and a yawed inflow was evaluated using the concept of the grid convergence index (GCI). A fluid–structure interaction (FSI) analysis was carried out to estimate the performance of a turbine with flexible composite blades, with the results then compared to those of an analysis with rigid blades. The influence of yawed inflow conditions on the turbine performance was investigated and found to be important in relation to power predictions in the design stages.     

MDS与三边定位相结合的多点相对定位算法

结合当下导航系统对备份导航的需求,为了完善备份导航体系,针对拒止环境下网络集群定位算法开展相关研究,以MDS为基础研究相关的定位方法,推导了MDS用于集群定位的过程,分析了传统MDS用于网络集群定位的局限和不足,提出了一种MDS和三边定位相结合的网络定位方法,根据传统MDS对节点间距离的需求特性,用三边定位弥补缺失的距离信息,对相应的定位原理进行了论述,既减小了MDS中使用最短路径带来的观测误差,也减小了三边定位中的观测误差的传递层数,从而提高了定位精度。通过对不同分布环境条件下进行仿真验证了该方法的正确性与可行性,对比分析了该算法较之传统MDS定位的优越性,并从算法的复杂度和资源消耗等方面提出了该方法后续的优化方向。