基于小波包与神经网络的柴油机故障诊断

针对柴油机缸盖振动信号的非平稳时变特点,提出应用小波包能量法提取故障特征向量,并将提取的特征向量作为BP神经网络的输入向量进行学习训练。训练后的神经网络可以利用测量的振动信号判断柴油机的气阀机构故障状况。实践证明该方法在柴油机振动诊断中是有效可行的,对其他设备的故障诊断也具有借鉴意义。     

基于小波包与神经网络的柴油机故障诊断

针对柴油机缸盖振动信号的非平稳时变特点，提出应用小波包能量法提取故障特征向量，并将提取的特征向量作为BP神经网络的输入向量进行学习训练。训练后的神经网络可以利用测量的振动信号判断柴油机的气阀机构故障状况。实践证明该方法在柴油机振动诊断中是有效可行的，对其他设备的故障诊断也具有借鉴意义。     

小波降噪在柴油机振动诊断中的应用研究

基于小波分析与神经网络的振动信号故障诊断方法，本文提出在小波包特征提取前对原始信号进行小波降噪处理，并以295柴油机进排气系统故障诊断为例验证采用小波降噪处理方法的必要性。结果表明：进行小波降噪处理的故障识别率较未经小波降噪处理的有较大提高。     

基于小波分析的柴油机故障信号特征的提取

本文提出了一种新的柴油机表面振动信号的故障特征的提取方法，利用柴油机表面振动信号经过小波降噪处理，有效地剔除柴油机表面振动信号的噪声干扰，提高信号的信噪比。用小波包提取降噪后振动信号的能量特征参数。以表征柴油机故障特征，建立起能量到柴油机故障的映射关系。实际研究表明这一特征提取方法是有效的。     

基于小波包分析和神经网络柴油机故障诊断研究

对于柴油机而言,及时的对其实施故障诊断是十分必要的.小波包分析能有效的对柴油机缸体振动信号进行消噪处理,并提取表征柴油机故障的振动信号能量特征向量作为BP神经网络的输入值.本文中,对4100QB柴油机缸盖振动信号实验数据采用单隐层BP网络进行训练,并对不同故障模式进行分类识别,实验验证表明这一方法是非常有效的.     

小波神经理论在风力机齿轮箱故障诊断系统中的应用

风力机齿轮箱振动信号是一种时频特性复杂的非平稳信号,常规的时域和频域分析方法难以有效的分析齿轮箱故障及提取故障特征。提出一种基于小波分析和神经网络的风力机齿轮箱故障诊断方法,该方法采用小波时频分析技术对风力发电机故障振动信号进行消噪滤波,通过小波包分解系数求取频带能量,根据各个频带能量的变化提取故障特征,为实现智能诊断提供故障特征值。应用BP神经网络进行故障识别,并采用LabVIEW和matlab软件予以实现。结果表明,该方法能有效提高风力发电机组齿轮箱故障诊断的准确性。     

小波包改进算法及其在柴油机振动诊断中的应用

针对柴油机缸盖表面振动信号的非平稳时变特点,提出了基于小波包分析的柴油机振动诊断方法。给出了小波包变换的一种改进算法,通过移频处理,克服了原算法中的频率混叠现象,使分解序列的排列顺序与频带的线性划分顺序一一对应。通过对完整工作循环内的缸盖信号进行小波包分解,实现了整循环诊断特征向量的快速提取。试验结果表明,该方法在柴油机振动诊断中是有效可行的,对其它复杂机械的振动诊断同样具有参考价值。     

柴油机动态振声信号实用采集技术的研究及在故障诊断中的应用

在利用振声方法对190柴油机进行故障诊断与状态监测的可行性研究中,笔者发现内燃机设计与试验研究中,把其工作循环作为平稳时间过程的思维模式难以有效地从振声信号中提取所需要的特征信息,试验证明柴油机的振声特性服从于弱非平稳随机过程.文中详细叙述了从这一新的思维模式出发、通过同步锁相技术所解决的内燃机振声信号的正确采样问题,以及由此取得的极有价值的试验结果和适用于包括柴油机在内的所有往复机的故障诊断与状态监测的有益振声技术.     

柴油机动态振声信号实用采集技术的研究及在故障诊断中的应用

在利用振声方法对 1 90柴油机进行故障诊断与状态监测的可行性研究中 ,笔者发现内燃机设计与试验研究中 ,把其工作循环作为平稳时间过程的思维模式难以有效地从振声信号中提取所需要的特征信息 ,试验证明柴油机的振声特性服从于弱非平稳随机过程。文中详细叙述了从这一新的思维模式出发、通过同步锁相技术所解决的内燃机振声信号的正确采样问题 ,以及由此取得的极有价值的试验结果和适用于包括柴油机在内的所有往复机的故障诊断与状态监测的有益振声技术     

柴油机气缸盖振动信号特征提取方法的研究

研究了基于短时AR分析、小波多分辨率分析和小波包分析的故障特征提取和识别方法,分析了柴油机气缸盖振动信号特征提取方法。得出了两条重要结论:基于短时AR分析的柴油机气缸盖振动信号整循环特征提取方法特别适合于短序列数据的分析;利用小波多分辨率分析和小波包分析以及Kllback-Leibler信息量最小,对柴油机表面振动信号进行分解与分析,确定各故障状态的特征频带,进而可用频带的时间序列的时序模型作为特征矢量,实现对柴油机运行状态故障的诊断。     

Aerodynamic performance effects of leading-edge geometry in gas-turbine blades

The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°,   −5°,   +5°,   +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods.     

Hydrogen production by steam-gasification of carbonaceous materials using concentrated solar energy – V. Reactor modeling,optimization, and scale-up

A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified.     

汽轮机数字电液调节系统挂闸异常的技术完善

分析了200MW汽轮机数字电液调节系统在运行中存在的挂闸异常问题,采取了相应的技术处理措施,且运行实践效果良好。     

新型高压共轨ECU升压模块的数字化开发与优化

为了提高喷油器电磁阀的响应速率,提出了一种基于CPLD(复杂可编程逻辑器件)应用于高压共轨ECU的数字升压模块。鉴于该升压电路结构参数多,其升压电压的恢复响应要求高等特征,基于Pspice建立了升压电路的仿真模型,研究了不同电路参数下升压模块的输出特性,全面优化了该升压模块的性能。结果显示,该升压模块的最大转换效率可以达90%以上。在柴油发动机上对ECU的试验表明,升压电压最大波动不超过10%,其恢复时间仅为1.3ms,功率管最大温升仅为41℃,满足整机运行范围内ECU的需求。     

Trace metal chemistry and silicification of microorganisms in geothermal sinter, Taupo Volcanic Zone, New Zealand

As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied.     

Wind power for pumping: The development of the ITP windpump

Water pumping has been one of the main applications for wind power in the past and despite the spread of mains-electric pumps, more than a million windpumps remain in regular use. This paper reviews the general technical and economic requirements for pumping water using wind energy and by way of example gives an overview of the development of the new ITP wind-pump. It then considers the future prospects for this kind of technology.     

Methods of creating solar-reflective nonwhite surfaces and their application to residential roofing materials

We describe methods for creating solar-reflective nonwhite surfaces and their application to a wide variety of residential roofing materials, including metal, clay tile, concrete tile, wood, and asphalt shingle. Reflectance in the near-infrared (NIR) spectrum (0.7–2.5 μm) is maximized by coloring a topcoat with pigments that weakly absorb and (optionally) strongly backscatter NIR radiation, and by adding an NIR-reflective basecoat (e.g., one colored with titanium dioxide rutile white) if both the topcoat and the substrate weakly reflect NIR radiation. Coated steel and glazed clay-tile roofing products achieved NIR reflectances of up to 0.50 and 0.75, respectively, using only cool topcoats. Gray-cement concrete tiles achieved NIR reflectances as high as 0.60 with coatings colored by NIR-scattering pigments. Such tiles could attain NIR reflectances of up to 0.85 by overlaying a white basecoat with a topcoat colored by NIR-transparent organic pigments. Granule-surfaced asphalt shingles achieved NIR reflectances as high as 0.45 when the granules were covered with a white basecoat and a cool color topcoat.     

Thermal decay of an initially hot isothermal water body with application to thermal energy storage

The thermal decay of an initially hot isothermal water body contained in a tank was studied. Analytical solutions (including a group-theoretic solution) were obtained for the one-dimensional heat conduction equation with heat loss from the sides of the tank. The convective heat transfer coefficient was assumed not to be constant over the surface of the tank but to vary with space and time. A very good agreement was obtained between the group-theoretic solution and a numerical solution using the Crank-Nicholson finite difference scheme. The analytical results are discussed in terms of the underlying physical mechanisms.     

Ash-forming elements in four Scandinavian wood species. Part 1: Summer harvest

Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden.     

秸秆燃烧中温度对钾转化与释放的影响

通过对稻秆原料进行常规特性分析和EDX元素含量分析,发现钾在稻秆无机元素中占有重要地位。参考原料化学分馏法和土壤中钾的分类与测试方法,给出了对生物质原料及其燃烧产物中钾的定性与定量简易方法。通过程序控温型固定床对稻秆先进行缓慢氧化,然后以100℃为间隔从400～900℃进行成灰,并分别测试其成灰率、有效钾和全钾的份额。结合稻秆原料及其灰中钾的份额分析,进行了稻秆灰中有效钾转化与释放的计算,发现有效钾在700～800℃之间有快速的释放和形态转变。稻秆灰的XRD分析结果表明秸秆灰中钾主要以KCl、K_2SO_4形式存在,得到了钾以盐的形式进行转化与释放的机理。该文中燃烧温度对钾转化与释放的影响规律对设计秸秆电厂时的炉型选择和燃烧参数确定有一定参考价值。