最大功率跟踪控制下大型风电机组的轴系扭振分析及抑制

随着风电机组向大型化和轻量化发展,机组传动轴扭振现象加剧,风机轴系扭振的研究变得越来越重要。该文分析了3种常用的风机最大功率跟踪控制方法下系统轴系扭振模态,发现利用发电机转速反馈的不同控制方法,都能够提升传动轴阻尼。据此提出了一种最大功率跟踪控制的改进方法,该方法在原有转矩指令的基础上叠加了传动轴扭振抑制指令,在保证最大功率跟踪的同时抑制了风机传动轴扭振。通过软件仿真,验证了上述理论分析以及改进方法的有效性。     

海上浮式风电机组变桨距自抗扰控制策略研究

为有效抑制由随机风、浪载荷引起的海上浮式风电机组发电功率波动,提出了变桨距线性自抗扰控制(LADRC)策略。综合考虑气动力、水动力、结构弹性和变桨距控制等影响因素,建立5 MW级海上浮式风电机组气弹水控耦合系统动力学模型,基于恒转矩控制目标设计变桨距线性自抗扰控制器,分别采用带宽整定法和BP神经网络整定法对控制器参数进行整定,对比分析变桨距线性自抗扰控制对发电功率波动的抑制效果。研究结果表明:采用带宽整定和BP神经网络整定的变桨距线性自抗扰控制可以有效地改善海上浮式风电机组变桨距灵敏度,抑制发电功率波动。     

随机风载下兆瓦级风电机组传动链系统的动态响应分析

以MW级风电机组传动链系统为研究对象,利用集中质量法对其纯扭转耦合非线性动力学模型的建立与动态响应规律进行探讨.在应用达朗贝尔原理建立传动链系统的质量-弹簧-阻尼模型和考虑部件间相互耦合影响的动力学方程组基础上,根据威布尔风速法建立西北酒泉地区的风速模型,并据此得到了一种作为传动链系统输入的随机时变转矩.在考虑增速箱中各齿轮副间的时变啮合刚度、啮合阻尼和时变误差激励影响的前提下,利用Matlab编写程序对建立的动力学方程组进行数值仿真计算,获得传动链系统的固有频率,以及各部件的扭转振动角位移、角速度、齿轮啮合力的响应情况.本研究对揭示随机风速作用下风力机组传动链系统的扭转振动响应规律,为传动链系统结构的动态性能优化设计提供了理论参考依据.     

基于发动机轴系扭振抑制的扭弯减振器分析

扭弯复合减振器能同时抑制扭转振动和弯曲振动,降低发动机噪声.以发动机轴系扭转振幅最小化为目标,研究了扭弯复合减振器的设计方法,并分析扭振减振器或弯振减振器参数偏离对扭转振幅曲线的影响.分析表明:增大扭振减振器惯量比、降低弯振减振器惯量比,能减小扭转振幅曲线的共振峰值;弯振减振器阻尼比和刚度偏离最佳参数后,能增大曲线共振峰值,但影响程度很小;扭振减振器阻尼比和扭转刚度的偏离能显著增大峰值.     

驱动半轴扭转刚度对车内噪声影响研究

针对一款前置后驱车型传动系统扭振引起车内噪声的问题,分析了"驱动桥——后悬架"路径耦合点的作用机理,然后应用AMESim软件建立仿真分析模型并用测试结果进行校验。基于仿真模型分析半轴扭转刚度对驱动桥2个耦合点扭振的影响规律,使用相干分析方法分离了主减输入与车轮扭振对车内噪声的影响程度,提出了半轴扭转刚度的优化方向。实车验证结果表明,提高半轴扭转刚度后,车内噪声明显降低,车内噪声降幅最大可达6 dB,后排噪声改善好于前排。该项研究为解决同类问题提供了参考。     

旋转机械轴系扭振频率微弱信号的混沌检测方法

利用Duffing随机方程的混沌特性,提出了应用于旋转机械正常扭振频率微弱信号检测的方案.分析了应用Duffing随机方程的检测原理,给出了一种将旋转机械正常运转条件下的扭振响应传感器信号作为Duffing方程周期策动力的摄动,使信号中包含的旋转机械扭振频率在幅值较小时也能得到检测分离的方法.该方法对非检测频率的噪声信号具有免疫力,仿真分析结果表明了所提方法的可行性.     

兆瓦级风电机组传动链振动远程在线测试

传动链作为风力发电机组的主要部分,工作在柔性塔架支撑、风向和载荷多变等恶劣的环境下,其振动特性好坏直接影响风机可靠性和使用寿命,成为风电机组最薄弱环节。论文基于SKF的WindCon智能采集系统,以某兆瓦级风力发电机组为例,在正常运行和启、停工况下对传动链的振动进行远程在线检测,得到传动链在各运行工况下的振动特性,并揭示其动态特性变化规律。测试结果表明传动链振动较为复杂,主要表现为系统低频扭转振动和弯、扭、摆构成的复合振动,传动链中主轴、齿轮箱等振动频率主要由转频和各级齿轮啮合频率尤其是高速级齿轮啮合频率构成,并存在被转频调制现象。     

旋转机械轴系扭振频率微弱信号的混沌检测方法

利用Duffing随机方程的混沌特性,提出了应用于旋转机械正常扭振频率微弱信号检测的方案。分析了应用Duffing随机方程的检测原理,给出了一种将旋转机械正常运转条件下的扭振响应传感器信号作为Duffing方程周期策动力的摄动,使信号中包含的旋转机械扭振频率在幅值较小时也能得到检测分离的方法。该方法对非检测频率的噪声信号具有免疫力,仿真分析结果表明了所提方法的可行性。     

高转速汽油机扭振计算问题

目前，汽油机正朝着高转速，大功率，低噪声，轻型化方向发展。因此，对汽油机扭转振动特性的研究变得越来越重要。曲轴扭振过大，不仅会引起曲轴扭转疲劳破坏，而且也是产生发动机噪声的主要原因之一。在曲轴前端安装扭振减振器是减低曲轴系扭振的有效方法。本文结合４８６Ｑ型汽油机的扭振测试分析和计算对其扭振特性及橡胶减振器参数进行了研究，并提出一种减振器的优化设计方法。     

基于高阶滑模观测器的风机改进反演滑模控制

针对风电机组风速波动幅度大、发电机转矩抖振大、功率无法平滑输出等问题,同时考虑风电机组中部分状态参数难以准确测量的问题,设计一种基于高阶滑模观测器的改进反演滑模控制策略。通过在反演设计中引进积分项来实现系统的有效控制和全局调节。采用高阶滑模观测器来实现时估计系统的状态,避免了直接测量会引入高频噪声的问题,使系统在外界扰动干扰的情况下具有较强的鲁棒性。为了验证算法的优越性在MATLAB中进行控制器仿真实验。最后通过仿真证明了所提方法的正确性,可行性。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Jane Eyre——A Feminist In The 19th Century

In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-