A wind tunnel simulation of the dynamic processes involved in sand dune formation on the western coast of Hainan Island

The western coast of Hainan Island exhibits a savanna landscape. Many types of sand dunes, including transverse dune ridges, longitudinal dune ridges, elliptical dunes, coppice dunes, and climbing dunes, are widely distributed in the coastal zone. In winter, high-frequency and high-energy NE winds （dominant winds） are prevalent, with a resultant drift direction （RDD） of S35.6°W. In spring, low-frequency and low-energy SW secondary winds prevail, with a RDD of N25.1°E. Wind tunnel simulations revealed that the airflow over the dune surface is the main factor controlling the erosion and deposition patterns of dune surfaces and the morphological development of dunes. In the region＇s bidirectional wind environment, with two seasonally distinct energy levels, the airflow over the surface of elliptical dunes, barchan dunes, and transverse dune ridges will exhibit a transverse pattern, whereas the airflow over longitudinal dunes ridges exhibits a lateral pattern and that over climbing dunes exhibits a climbing-circumfluent pattern. These patterns represent different dynamic processes. The coastal dunes on the western coast of Hainan Island are influenced by factors such as onshore winds, sand sources, coastal slopes, rivers, and forest shelter belts. The source of the sand that supplements these dunes particularly influences the development pattern： when there is more sand, the pattern shows positive equilibrium deposition between dune ridges and dunes; otherwise, it shows negative equilibrium deposition. The presence or absence of forest shelter belts also influences deposition and dune development patterns and transformation of dune forms. Coastal dunes and inland desert dunes experience similar dynamic processes, but the former have more diversified shapes and more complex formation mechanisms.

Development of Optimal Maintenance Policies for Offshore Wind Turbine Gearboxes Based on the Non-homogeneous Continuous-Time Markov Process

Gearbox in offshore wind turbines is a component with the highest failure rates during operation. Analysis of gearbox repair policy that includes economic considerations is important for the effective operation of offshore wind farms. From their initial perfect working states, gearboxes degrade with time, which leads to decreased working efficiency. Thus, offshore wind turbine gearboxes can be considered to be multi-state systems with the various levels of productivity for different working states. To efficiently compute the time-dependent distribution of this multi-state system and analyze its reliability, application of the nonhomogeneous continuous-time Markov process(NHCTMP) is appropriate for this type of object. To determine the relationship between operation time and maintenance cost, many factors must be taken into account, including maintenance processes and vessel requirements. Finally, an optimal repair policy can be formulated based on this relationship.

Integrated Design of D.D.I., Filament Winding and Curing Processes for Manufacturing the High Pressure Vessel(Type Ⅱ)

As energy crisis and environment pollution all around the world threaten the widespread use of fossil fuels,compressed natural gas(CNG)vehicles are explored as an alternative to the conventional gasoline powered vehicles.Because of the limited space available for the car,the composite pressure vessel(TypeⅡ)has been applied to the CNG vehicles to reach large capacity and weight lightening vehicles.High pressure vessel(TypeⅡ)is composed of a composite layer and a metal liner.The metal liner is formed by the deep drawing and ironing(D.D.I.)process,which is a complex process of deep drawing and ironing.The cylinder part is reinforced by composite layer wrapped through the filament winding process and is bonded to the liner by the curing process.In this study,an integrated design method was presented by establishing the techniques for FE analysis of entire processes(D.D.I.,filament winding and curing processes)to manufacture the CNG composite pressure vessel(TypeⅡ).Dimensions of the dies and the punches of the 1 st(cup drawing),2 nd(redrawing-ironing 1-ironing 2)and 3 rd(redrawing-ironing)stages were calculated theoretically,and shape of tractrix die to be satisfied with the minimum forming load was suggested for life improvement and manufacturing costs in the D.D.I.process.Thickness of the composite material was determined in the filament winding process,finally,conditions of the curing process(number of heating stage,curing temperature,heating rate and time)were proposed to reinforce adhesive strength between the composite layers.

Numerical simulation of non-gaussian process of wind waves

In this paper further mathematical analysis on 'correlation transfer technique' by Polge el al. is carried out, the tenable conditions and the extent of suitability for the said method are proved as well. In consideration of the influence of skewness of the sea surface elevation on spectral shape, a 'quasi-correlation transfer techique' is developed by the modification of the simulated target spectrum. Meanwhile, the numerical simulation of the non-Gaussian process of wind waves is carried out in view of the two conditions of the surface elevation probability distribution and the spectrum. By using its simulated results, the influence of skewness of the sea surface elevation on two parameters in the distribution of wave heights (which had been fitted by using the Weibull distribution) is analysed. The 'quasi- correlation tranfer technique' is verified and compared with the selection wave data observed in the Jiaozhou Bay in the period of 1980 to 1981. Results make clear (hat, as far as the statistical distribution of the wave heights and the distribution of the maximum (minimum) values of the sea surface elevation are concerned, the said method is obviously superior to the conventional mothed of the linear wave superposition, and that the simulated results are closer to the observation data.

Multivariate stationary non-Gaussian process simulation for wind pressure fields

Stochastic simulation is an important means of acquiring fluctuating wind pressures for wind induced response analyses in structural engineering. The wind pressure acting on a large-span space structure can be characterized as a stationary non-Gaussian field. This paper reviews several simulation algorithms related to the Spectral Representation Method （SRM） and the Static Transformation Method （STM）. Polynomial and Exponential transformation functions （PSTM and ESTM） are discussed. Deficiencies in current algorithms, with respect to accuracy, stability and efficiency, are analyzed, and the algorithms are improved for better practical application. In order to verify the improved algorithm, wind pressure fields on a large-span roof are simulated and compared with wind tunnel data. The simulation results fit well with the wind tunnel data, and the algorithm accuracy, stability and efficiency are shown to be better than those of current algorithms.

多因素下风力发电机组系统可靠性分配方法的研究

针对目前可靠性分配结果较为主观的问题,以串联系统的可靠性分配方法为基础,提出了一种基于改进模糊层次分析法的可靠性分配方法。采用三标度法对多个系统可靠性影响因素进行专家评判,通过模糊层次分析法初步确定可靠性分配权重,然后对分配权重初值进行熵权法处理,建立综合分配权重计算模型,最终确定各子系统的可靠性分配权重,进而实现对机械系统可靠度分配模型的建立。以风力发电机组系统为例,将该方法应用在风力发电机组可靠性分配中。通过改进模糊层次分析法与传统的模糊层次分析法以及其它方法对该风力发电机组系统的可靠性分配结果,进行对比分析。结果表明:该方法不仅有效;而且相比于文献中的分配结果有所降低,更符合机组的实际运行情况,验证了该方法的合理性。

基于OPC UA的纤维缠绕机信息模型开发和应用

为实现对复合材料纤维缠绕机生产过程的监测,以缠绕机及其辅助设备为研究对象,针对实际加工设备的多样性造成的加工数据采集的异构性,基于OPC UA建立缠绕机的信息模型架构。根据OPC基金会发布的OPC UA规范和相关的行业标准,建立纤维缠绕机系统的信息模型和实例化。基于开源项目open62541,导入编译后的缠绕机的信息模型代码,自定义开发出符合使用规范的OPC UA服务器,然后利用UA客户端实现对服务器的连接,客户端能够通过服务器查询系统的加工数据,解决加工数据的异构性问题以达到监测缠绕机生产加工过程的目的;最后验证了建立的纤维缠绕机信息模型能够正确导入到开源项目open62541中,实现了加工数据监测。

基于未知风荷载作用下拉索振动位移的拉索MR阻尼器失效破坏的原位识别方法

MR阻尼器在长期服役过程中可能由于各种因素导致阻尼器失效破坏。现有的对MR阻尼器的性能识别多为离线方法,需将阻尼器从斜拉索上拆卸下来后进行人工检测。该文提出一种基于斜拉索在未知风荷载作用下振动位移,对在役失效无模型的MR阻尼器作用力进行原位在线识别的方法。首先,建立模态坐标下斜拉索-阻尼器系统运动方程及观测方程,并进行模态截断以减少未知变量的数量。然后,将模态风荷载建模为随机游走过程并加入系统的增广状态中,并视MR阻尼器的作用力视为作用在斜拉索上的‘附加未知输入’,采用最近提出的无直接反馈的平滑最小方差无偏Bayesian滤波,对结构增广状态和MR阻尼器作用力进行识别。通过识别数值模拟的MR阻尼器三种典型的失效破坏模式,验证所提方法的有效性。

低温试验室内小型风洞设计及结冰过程试验

在低温试验室中利用自搭建风洞设备提供水结冰所需的风速和温度条件,研究了极区风速、温度对水结冰速率的影响.结果表明:结冰池经历了整体快速降温和结冰两个阶段.在前一阶段对流换热占主体换热地位,风速影响大于温度影响;后一阶段随冰厚增加热传导占比逐渐上升,温度的影响也逐渐上升.结合温度变化与冰厚生长数据,计算得出降温速度与结冰速度,结合温度与风速分别进行曲面拟合,得到降温速度、结冰速度关于温度、风速的关系式.

卷烟工艺风力负压波动分析与对策

目前国内大多数卷烟厂采用模块化扁布袋除尘器实现集中工艺风力与除尘,除尘器配置的脉冲喷吹清灰系统周期性的喷射压缩空气进入除尘布袋,造成卷烟工艺风力负压规律性波动,影响烟支卷制质量。为了解决以上不足,通过优化改造,实现独立控制每列喷吹电磁阀的脉冲信号通断,使得两列同序号的电磁阀不同时工作,分时喷吹,每次喷吹时减少一半的压缩空气流量,从而降低脉冲喷吹对负压的波动幅度,保障烟支卷制质量的一致性。

基于KA-SRCN-pSTAP的低空风切变风速估计方法

针对由于独立同分布(IID)样本严重不足,导致极化空时自适应(pSTAP)处理性能下降,进而导致低空风切变风速估计不准确的问题,本文提出了一种基于知识辅助的稀疏表示杂波零陷极化空时自适应(KA-SRCN-pSTAP)的低空风切变风速估计方法。该方法首先利用杂波脊的先验知识辅助构造极化空时稀疏字典,然后利用极化空时稀疏字典,通过SRCN算法挑选原子并对到杂波线性子空间补空间上的投影矩阵进行估计,从而得到pSTAP权矢量,最后构造pSTAP滤波器对地杂波进行抑制,准确估计低空风切变风速。该方法仅使用少量IID样本,将SRCN算法与极化-空时域相结合,完成对风切变风速的有效估计。仿真实验结果证明该方法可以有效实现少样本情况下的风速准确估计。

基于特征选择的风机检修流程预测性监控方法

针对风机检修业务流程中存在的操作失误和工作延期等问题,应用业务流程预测性监控方法,预测业务的下一事件、下一事件执行时间和剩余时间,以提醒工作人员预防和避免风险的发生。首先,针对不同预测任务,提出一种基于优先级的特征自选取策略,并使用LightGBM(Light Gradient Boosting Machine)算法作为特征选择策略的依托预测模型,得到对预测结果有积极影响的输入特征;然后,针对不同预测任务分别采用LightGBM算法和LSTM(Long Short Term Memory)神经网络构建预测模型;最后,经实验评估和分析,在风机检修业务流程中,特征选择策略能够为不同的预测任务提供有效特征,确保预测的准确率,具有实际应用价值。对于不同预测任务而言,LightGBM算法更适用于下一事件任务预测,LSTM模型更适用于时间方面的任务预测。

基于非平稳高斯过程的高空风场偏差建模方法

高空风场偏差建模方法对运载火箭气动载荷计算和总体性能优化具有显著影响。目前工程常用方法未考虑不同高度层风速相关性,所得样本与实际风场特征存在差异,难以精确预示火箭气动载荷。提出将U/V风速分量建模为关于高度的非平稳高斯过程,基于大量历史风场样本统计分析实际风场在不同高度层的特征参数,利用扩展最优线性估计方法生成与实际风场具有相同分布的子样。结果表明提出的方法相比传统手段能够从形态上更加准确表征真实风场剖面。基于真实飞行器仿真程序对风致载荷进行计算,结果显示该方法对气动载荷裕度的预示误差远小于目前工程方法,对提升火箭运载效率和放行概率具有重要意义。

基于多源异构数据的风机多模态装配工艺知识图谱建模

风力发电机装配工艺信息通常分散于以三维模型、自然文本、图像等多模态信息构成的工艺文件中,导致数据维护和工艺知识获取成本高、效率低.针对这一问题,提出一种基于多源异构数据的风力发电机多模态装配工艺知识图谱建模方法.首先,分析工艺特点给出风力发电机多模态知识工艺图谱(MPKG-WT)中各类概念,完成图谱本体构建;其次,基于多源异构数据及各模态特点,利用数据分析、知识抽取和语义相似度计算等技术实现图谱的自动实例化;最后,以某风力发电机企业装配工艺数据为例,实现MPKG-WT构建,并开发辅助装配工艺设计系统进行验证.研究结果表明,MPKG-WT较单模态图谱蕴含更丰富的知识,且不同模态数据之间能够互补,显著提升装配工艺设计效率.

液体缠绕工艺用阻燃环氧树脂性能研究

针对液体缠绕工艺用环氧树脂进行阻燃改性,研究阻燃剂添加量对树脂与复合材料性能的影响。结果表明阻燃剂加入使树脂黏度略有降低,固化反应活性无明显改变。随着阻燃剂含量提高,环氧树脂拉伸强度基本稳定而冲击强度有所下降,其中30 phr阻燃剂添加的环氧树脂相比0 phr冲击强度下降44.1%。另外随着阻燃剂含量增加,树脂热分解稳定性提高,但过多添加阻燃成分不利于炭化层稳定形成。综合以上研究,20 phr阻燃剂添加量的树脂体系阻燃效果最优,50 W垂直燃烧测试结果达到V-0级,且力学性能具有较好保持率。改性后树脂与T700SC制备的复合材料NOL环拉伸强度达2790 MPa,层间剪切强度为50.7 MPa,树脂与纤维具有良好的结合界面。

利用风电进行CO_(2)加氢制甲醇与天然气和煤路线对比的技术经济分析

将水电解､CO_(2)捕集､风力发电引入甲醇生产,在200 t/d的产能下,利用Aspen Plus对天然气重整､煤气化､CO_(2)直接加氢3种路线生产甲醇进行流程模拟,并依据模拟结果进行成本估算､碳排放分析和敏感性分析,分析引入电解水､CO_(2)捕集和风力发电的经济和环境效益。结果显示,在200 t/d的产能下,路线三(CO_(2)直接加氢)的成本高达9944.1元/t,远高于路线一(天然气重整,2595.2元/t)和路线二(煤气化,2266.5元/t),但路线三每t甲醇生产可减少CO_(2)排放0.57 t,相比另外2种方式的高额碳排放(0.67 t CO_(2)/t MeOH和2.29 t CO_(2)/t MeOH)具有巨大的优势。当电解水成本下降和高额碳税存在时,路线三有望实现商业应用。

基于图像处理的风电叶片损伤识别定位系统

设计一套基于图像处理的风电叶片损伤识别定位系统。首先,耦合图像滤波、分割和形态学处理等图像处理算法实现损伤区域的检测识别;然后,基于多边形拟合结果,结合质心定位算法和外接矩形的位置坐标实现叶片损伤的精确定位;最后,依据提取到的基础几何特征、形状因子和长短径之比等图像特征实现叶片损伤类型的准确判断;通过对比不同光照条件下的叶片损伤检测效果,验证了本系统具有一定的自适应能力。试验表明,本系统的平均检测准确率为90%,具备一定的可靠性和稳定性。

风电齿轮箱滑动轴承润滑性能及可靠性分析

风电齿轮箱采用滑动轴承代替滚动轴承是未来发展的主流趋势,然而由于复杂多变的服役工况,风机滑动轴承的润滑规律尚有待深入研究。为此,建立风电齿轮箱滑动轴承的润滑分析模型,仿真分析多种工况下滑动轴承的润滑状态,并拟合出滑动轴承的最小膜厚经验公式;结合润滑可靠性理论,基于最小膜厚公式建立润滑可靠性模型,并采用该模型研究风机在启动和停机工况下齿轮箱滑动轴承的润滑性能;提出一种风电齿轮箱滑动轴承的润滑可靠性分析方法,分析风电齿轮箱滑动轴承的润滑可靠性。结果表明:启动过程中滑动轴承的最小膜厚先快速增大,随后迅速下降直到稳定状态,而停机过程中最小膜厚则迅速降低;停机工况下滑动轴承的润滑失效时长要高于启动工况;外载荷方向对启动工况的润滑失效概率影响较大,对停机工况的影响较小。

强风下输电塔破坏分析与加固研究

为了提高服役输电塔抵抗极端荷载的能力,保障线路的安全稳定运行,结合输电塔的失效模式和破坏特点,提出了一种无损加固措施,通过加载试验和数值模拟验证了该加固措施的可行性.以220 kV典型输电塔为研究对象,运用多尺度分析手段,建立了加固前后输电塔精细有限元模型,模拟分析了输电塔动力特性,以及风荷载下输电塔的非线性响应和连续性倒塌模式,进而评估了无损加固措施对输电塔抗风性能的提升效果.结果表明,该加固措施能够有效降低输电塔风振响应和提高其抗风性能,临界倒塌风速由29.2 m/s提高至30.8 m/s,加固节间以及相邻节间的刚度得到了提升,且加固后节间内力分布更加均匀,该无损加固措施为提升服役输电塔抵抗极端荷载的能力提供参考.

考虑极端天气冲击过程的风电机组竞争失效可靠性评估

针对风电机组的运行可靠性易受极端天气影响的问题,提出了一种考虑极端天气冲击过程的风电机组竞争失效可靠性评估方法。同时考虑风电机组自然退化、极端天气冲击导致的瞬时退化以及极端天气持续过程产生的加速退化,构建极端天气下的风电机组综合退化模型;考虑风电机组退化过程对其耐冲击性能的影响,建立风电机组竞争失效可靠度模型以评估风电机组可靠性;基于我国北方某风电场工程数据和极端天气历史数据评估了某2 MW风电机组的可靠性并进行了参数灵敏度分析。结果显示,到第5年时,仅考虑自然退化的方法评估风电机组可靠度为0.84,而考虑极端天气冲击过程的方法评估风电机组可靠度为0.178,后者更加符合工程实际。通过模型参数的灵敏度分析发现,运行时间超过3年后,退化失效开始逐渐影响风电机组的可靠性。