600MW汽轮机组高压联合进汽阀变工况内部流场的特性分析

采用数值模拟方法对某600 MW汽轮机高压联合进汽阀的内部流动进行了分析.通过求解全三维N-S方程和k-ε湍流模型,得到了阀门内部的流场特性.在3种不同负荷下对主汽阀全开、调节阀阀门不同开启顺序时的流场进行模拟,并分析了流动损失产生的机理.结果表明:调节阀B的流量比调节阀A大,流动状态比调节阀A好;先开启调节阀B后开启调节阀A时,各截面的压损小,各阀门的流动状态好.     

上下游结构对喷嘴调节给水泵汽轮机调节阀组流动特性的影响

针对某喷嘴调节给水泵汽轮机调节阀组在额定工况时的三维蒸汽流动,采用计算流体力学方法对其进行数值模拟分析,以获取各调节阀均全开时阀组上下游结构对阀组管道内部稳态蒸汽流场的影响.计算中采用剪切应力输运模型(SST)来封闭湍流模型控制方程组,并采用多重参考坐标系法(MRF)计算获取调节级内动叶排通道区域的三维蒸汽流场.重点分析了各阀门通道内的压力损失水平、流量分配情况和过热蒸汽在调节阀组系统中的流动特性,以及多阀腔室、阀门出口下游扩压管路和弯管等部件内部的复杂三维流动特征.结果表明:调节阀流量主要由阀门下游喷嘴数量决定;调节阀距离阀组系统进口的距离对调节阀通流能力具有较大影响.     

600MW超超临界汽轮机高压主汽调节联合阀内部流场的数值模拟分析

采用非结构化四面体网格,对某600MW超超临界汽轮机组高压主汽调节联合阀的额定工况进行了数值模拟.针对3种不同结构的模型分别进行了计算,分析研究了阀门内部流场的流动特性,以及在主汽阀内加置挡板和滤网对内部流场和阀门损失的影响.     

1000MW超临界汽轮机主调阀内流动和噪声计算分析

针对某1000 MW超临界汽轮机主调阀系统(主汽阀和调节阀)内的蒸汽流动和噪声辐射,进行了全三维计算分析.通过求解全三维N-S方程和к-ε湍流模型,并考虑水蒸汽热力性质参数,得到了阀门流道中的蒸汽流场参数;然后采用基于FW-H方程的剪切流噪声模型,求解了蒸汽流场内的噪声源幅度分布.计算结果表明:主调阀流道内的压力损失为1.38%,其中调节阀部件的压损占主调阀总压损的66%;主汽阀和调节阀的喉口位置和阀腔流动死区等位置处的涡量很强,从而成为主要的气动噪声辐射源.     

调节阀内部流场数值模拟及能量损失分析

针对小流量单座调节阀,首先应用三维建模软件对其该阀进行宾体建模与造型,其次基于计算流体力学技术对阀门内部三维粘性流场进行数值模拟,从而获得了调节阀的流动特性参数,并对数值模拟计算结果进行了分析,得到了调节阀流道内能量损失的原因,最后以降低流动损失为目的,对能量损失严重的部位进行流道优化,并对优化后流道进行模拟计算.计算结果表明,与优化前的流道相比较,在满足原有调节性能的同时流动得到改善,能量损失明显降低.     

调节阀内部流场的动态模拟及优化分析

运用动网格技术对调节阀关闭过程中不同开度的内部流场进行了动态数值模拟,基于数值模拟结果分析了阀门的流动特性,并与试验结果进行比较,结果表明与试验数据十分吻合。此外,对流场中的流线、漩涡和压力分布等参数进行分析,从考虑减小流场中漩涡的范围和减小能量损失为目的对阀门流道进行优化构思,为调节阀的优化设计提供可靠的依据。     

核电主汽阀关闭流场的二维动态模拟

为了研究核电主汽阀关闭时流场的变化情况及阀板的受力情况,利用计算流体力学软件FLUENT对主汽阀二维简化模型的流场进行了稳态和不同关闭速度的动态数值模拟,得到了阀门的动态流场信息及阀板的受力分布曲线。通过分析可知,阀板两侧的压力差产生的摩擦力是决定阀门能否正常关闭的关键因素,关闭速度越快所受到的摩擦力越大。     

某汽轮机补汽阀流场数值模拟及改进

对某汽轮机补汽阀进行流场数值模拟计算,对比分析不同开度下阀门内部流场结构及壁面压力脉动,并通过改进阀门结构来改善流体的流动特性.结果表明:结构改进前,在中大开度下,流场蒸汽压力呈周期性剧烈变化,压力脉动的频率成分非常复杂;结构改进后,流场内涡流区域减小,压力脉动幅值显著下降,流动稳定性提高,压损减小,阀门通流能力得到提...     

600MW汽轮机主汽调节阀流动特性的数值研究

对某600MW亚临界汽轮机主调阀在全开度下的流动特性进行了数值模拟。给出了阀门内流动总压损、压损沿流程分布情况以及调节阀门的流量分配。分析了蒸汽在阀门中的流动特点及流动损失产生的机理。为进一步研究阀门的流场特性及结构改进提供了参考。     

超超临界百万千瓦汽轮机主调阀流场非稳态数值研究

采用计算流体力学商用Fluent软件,对某百万千瓦超超临界汽轮机主调阀系统(主汽阀和调节汽阀组成的进汽系统)正常运行时的蒸汽稳态流场和快速关闭时的非稳态流场进行了全三维数值计算及分析.结果表明:稳定工作状态下,阀门全开时的阀组总压损失约为进口总压的1.23%,其中调节汽阀损失占总损失的57.52%;主汽阀、调节汽阀都为快开特性的阀,它们的相对升程大于30%时流量基本不可调.采用Fluent中的动网格技术,计算分析了调节汽阀从全开到快速关闭的非稳态过程中蒸汽的流动特性,并给出了调节汽阀快速关闭时的行程、流量及阀后压力与关闭时间的动态曲线.     

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。     

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.     

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.