海上风力机锥体结构抗振分析

为降低海冰与海上风力机撞击作用下的结构非线性动力响应,提出锥体结构防振模型并将其安置于风力机与海平面交界处。通过开发海冰载荷计算模块并与风力机多体动力学气动-水动-伺服-弹性仿真软件FAST结合,建立风-冰-结构多物理场耦合下的海上风力机动力学仿真模型。基于Croasdale与Karna方法计算海冰与结构碰撞,对比5组不同锥角下的结构动力学响应,研究锥体结构对海冰碰撞的减振降载效果。结果表明:未安装锥体结构时,海冰载荷、塔顶位移与塔顶加速度的幅值较大,且频率易与风力机发生共振;安装锥体结构后,随着锥角由70°减至40°,动态响应减弱,幅值分别减小79%、71. 8%与30. 8%,且频率均远离风力机固有频率,避免发生共振;塔基剪切力的最大值与标准差也因安装锥体而减小,其中最大值减小26. 9%,标准差减小67. 8%,降低风力机所受的疲劳载荷。     

基于混沌理论的海上风力机锥体结构抗冰研究

为分析在风载-冰载联合作用下海上风力机塔架动力响应非线性特性,以多体动力学仿真开源软件FAST为平台,建立冰-构耦合模型,通过自编程序开发风力机海冰碰撞模块,计算NREL 5 MW风力机在安装不同锥体角度的锥体结构及未安装锥体时受海冰激励作用下的塔顶振动特性,并基于混沌理论,采用相图法及最大Lyapunov指数法从定性与定量两个角度研究了塔顶振动信号的非线性特征。结果表明:未安装锥体及70°锥体结构时,塔顶振动具有明显的混沌特征,最大Lyapunov指数大于零,表现出非周期性的非平稳特征;随着锥体角度的降低,混沌特性减弱并消失,当锥角为40°与50°时,最大Lyapunov指数小于零,混沌特性消失,该结果与塔顶位移时域分析结果相吻合,表明锥体结构能有效减弱塔顶振动,增加风力机稳定性。     

海冰作用下近海桩柱式风力机动力学响应研究

高纬度低温海域海平面存在大量运动状态的海冰,位于此处的近海桩柱式风力机容易受到不规则的海冰载荷作用,风力机平台、塔架和叶片等结构部件的动力学响应均受其影响.为定性及定量分析海冰载荷对叶片和塔架的结构动力学响应的影响程度,以NREL5 MW近海4桩柱式风力机为研究对象,耦合风载荷、波浪载荷及海冰载荷,通过Kane方法建立风力机动力学模型,其中海冰载荷通过冰力函数定义.对比分析了在IEC Lock in冰力函数、Mttnen海冰模型和无海冰作用三种工况下叶片和塔架的结构动力学响应,结果表明:海冰载荷使塔顶位移增加,在Mttnen海冰模型作用下塔顶位移增加了24.1%,在IEC Lock in模型作用下则增加了16%;两种海冰模型均不同程度地使叶片挥舞振动的频率增大,其中在Mttnen海冰模型中变化更加剧烈,这极大地增加了叶片的疲劳载荷.     

海冰载荷作用下海上风力机TMD减振研究

为保证桩柱式海上风力机塔架结构稳定和系统运行安全,提出安装于机舱内的调谐质量阻尼器(Tuned Mass Damper,TMD),以减弱海冰与湍流风联合作用环境下的风力机振动。基于多体动力学开源仿真软件(FAST),通过计算并分析NREL 5 MW海上风力机风-冰联合作用下塔顶振动特性,发现TMD控制对前后向的塔顶位移及塔基剪切力影响较小,但可以有效降低侧向的塔顶位移及塔基剪切力,降低幅度分别达39%与52%。同时,塔架一阶固有频率处的响应降低64%与90%,说明TMD装置能有效减弱风力机振动,保护风力机安全。     

海上风力机锥体结构抗冰性能分析

为降低海冰对结构碰撞造成的损伤,提出在风力机与海平面交界处安置抗冰锥体。基于Matlock与Ralston方法建立海冰与结构碰撞载荷计算模型,通过开发海冰载荷计算模块并将其与开源软件FAST结合,建立海上风力机在湍流风与海冰实时耦合下的动力学仿真模型。结果表明:未安装锥体时,塔基剪切力最大值、均值和标准差均随海冰厚度和海冰移速的增加而增大,其中海冰厚度对最大值和均值的影响较为显著,而海冰移速对标准差的影响较大;安装锥体后,塔基剪切力最大值与均值分别减小67.8%与41.6%,其标准差显著减小并趋于稳定,从而使得结构疲劳载荷降低。     

基于土基-结构耦合作用的风力机塔架地震时频特性分析

为研究不同土质时地震载荷对大型风力机结构动力学响应的影响,基于Wolf方法建立风力机基础平台与土体的耦合模型,通过FAST软件仿真Wind PACT 1.5 MW风力机在不同土质和不同地震强度时塔架的动力学响应。通过分析不同工况下风力机的结构动力学响应,发现地震载荷对塔顶位移和塔基弯矩的影响不可忽略,尤其是塔顶侧向位移和塔基俯仰力矩。在九级设防烈度地震作用下,相比无地震工况,软土、硬黏土和岩土地质风力机塔顶侧向位移分别增大925%、785%和771%。且由于软土阻尼最小,能量耗散小,所以地震后塔架响应降低的速率最慢。     

基于土-结构耦合作用的风力机塔架地震动力学响应分析

风力机塔架在地震激励下的动力学响应研究对保证风力机安全运行具有重要意义。基于有限元软件ANSYS和Wolf土-构耦合理论对Vestas1.65 MW风力机建立较高精度有限元模型,对是否考虑土-结构耦合(Soil-Structure Interaction,SSI)效应两种条件下进行瞬态动力学分析。选用摩根希尔(Morgan Hill)地震运动,土体选用软土物性参数。结果表明:考虑SSI效应会降低风力机塔架自振频率,塔架在地震激励下的塔顶位移响应、塔顶加速度响应、塔架Mises等效应力响应和塔架剪应力响应频率有较明显下降,塔顶加速度峰值减小6.7%,塔基承受剪应力增加73.5 MPa,增幅98.9%。因此,研究风力机结构抗震设计应考虑SSI效应。     

大型风力机地震动力响应研究

为研究地震载荷与风载荷联合作用下的大型风力机结构动力学响应,本文研究分别以Wind PACT 1.5 MW和NREL 5 MW风力机为研究对象,采用EI Centro 6.9级地震为输入激励,通过改进版的开源软件FAST(风电载荷仿真软件)计算风力机在正常运行、紧急停机和一直停机3种运行方式下的塔顶振动和塔架结构荷载情况,结果表明:地震载荷极大加剧了塔顶振动,机舱加速度峰值增大2倍以上。紧急停机操作可减小塔尖位移,一定程度上可以保护风力机结构安全。地震载荷主要增大了塔架一阶固有频率及其二倍频的振动。6.9级地震与额定风载荷联合作用下,NREL 5MW风力机塔基弯矩设计需求为159 MN·m,略大于极限风载荷作用。说明地震常发地区,塔架结构强度设计必须考虑地震载荷作用。     

异步冰载荷作用下风力机动力学响应分析

为研究与结构接触表面不平整浮冰导致的冰激振动对风力机影响,建立风力机Kane多体动力学模型,采用异步Matlock模型模拟冰激振动,由Kaimal风速谱、指数风廓线模型和空间相干模型模拟来流风场,结合叶素动力学计算风力机非定常气动载荷,分析湍流风载荷和异步冰激振动模型作用下塔架动力学响应。研究结果表明：异步Matlock模型冰载荷峰值低于同步模型;塔顶前后位移受冰激振动影响较侧向更为显著,幅值和标准差均大幅提高;冰激振动导致塔顶前后位置破碎频率及其靠近叶片2阶挥舞频率倍频处幅值大幅提高,且异步Matlock增幅小于同步模型;异步Matlock模型对塔顶侧向位移影响较小。     

漂浮式风力机多频调谐质量阻尼器控制及其参数优化设计

以ITI Barge型漂浮式风力机为研究对象,在机舱和塔架中配置参数不同的调谐质量阻尼器(TMD),组成多频调谐质量阻尼器(MTMD)系统。基于多岛遗传算法,对MTMD系统进行参数优化,并比较了无控制、无优化MTMD控制及优化MTMD控制下风力机的稳定性。结果表明:MTMD对塔顶纵向位移和平台横摇角有很好的抑制效果;风力机塔顶纵向位移和平台横摇角均随机舱TMD质量和塔架TMD质量的增大而减小,随TMD阻尼的增大而增大;优化MTMD控制后,风力机稳定性进一步提升,其塔顶纵向位移和平台横摇稳定性分别提升了80.4%和83.8%。     

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.     

NEXT GENERATION ENGINEERED MATERIALS FOR ULTRA SUPERCRITICAL STEAM TURBINES

正1 ABSTRACT To reduce the effect of global warming on our climate,the levels of CO2emissions should be reduced.One way to do this is to increase the efficiency of electricity production from fossil fuels.This will in turn reduce the amount of CO2emissions for a given power output.Using US practice for efficiency calculations,then a move from a typical US plant running at 37%efficiency to a 760℃/38.5 MPa(1 400/5 580 psi)plant running at 48%efficiency would reduce CO2emissions by 170kg/MW.hr or 25%.     

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。     

Assessment methods of material ageing using Sdobyrev''s creep rupture model

The physical aspects of the activation energy, in higher and high temperatures, of the metal creep process were examined. The research results of creep-rupture in a uniaxial stress state and the criterion of creep-rupture in biaxial stress states, at two temperatures, are then presented. For these studies creep-rupture, taking case iron as an example the energy and pseudoenergy activation was determined. For complex stress states the criterion of creep-rupture was taken to be Sdobyrev's, i.e. σ_red = σ₁ β + (1 − β)σ_i, where: σ₁-maximal principal stress, σ_i-stress intensity, β-material constant (at variable temperature β = β(T)). The methods of assessment of the material ageing grade are given in percentages of ageing of new material in the following mechanical properties: 1) creep strength in uniaxial stress state, 2) activation energy in uniaxial stress state, 3) criterion creep strength in complex stress states, 4) activation pseudoenergy in complex stress states. The methods 1) and 3) are the relatively simplest because they result from experimental investigations only at nominal temperature of the structure work, however, for methods 2) and 4) it is necessary to perform the experimental investigations at least at two temperatures.     

Production of hydrogen from sewage biosolids in a continuously fed bioreactor: Effect of hydraulic retention time and sparging

Hydrogen was produced from primary sewage biosolids via mesophilic anaerobic fermentation in a continuously fed bioreactor. Prior to fermentation the sewage biosolids were heated to 70 °C for 1 h to inactivate methanogens and during fermentation a cellulose degrading enzyme was added to improve substrate availability. Hydraulic retention times (HRT) of 18, 24, 36 and 48 h were evaluated for the duration of hydrogen production. Without sparging a hydraulic retention time of 24 h resulted in the longest period of hydrogen production (3 days), during which a hydrogen yield of 21.9 L H₂ kg⁻¹ VS added to the bioreactor was achieved. Methods of preventing the decline of hydrogen production during continuous fermentation were evaluated. Of the techniques evaluated using nitrogen gas to sparge the bioreactor contents proved to be more effective than flushing just the headspace of the bioreactor. Sparging at 0.06 L L min⁻¹ successfully prevented a decline in hydrogen production and resulted in a yield of 27.0  L H₂ kg⁻¹ VS added, over a period of greater than 12 days or 12 HRT. The use of sparging also delayed the build up of acetic acid in the bioreactor, suggesting that it serves to inhibit homoacetogenesis and thus maintain hydrogen production.     

Contents in Volume 23,2014

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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.