带有热障涂层的涡轮叶片前缘气热耦合数值研究

采用气热耦合的数值计算方法以及考虑转捩的湍流模型,对采用热障涂层技术的某型气冷涡轮叶片前缘传热进行了数值研究.结果表明,由于热障涂层的高绝热性,热障涂层一方面大幅提高叶片的抗氧化和抗热腐蚀的能力,另一方面配合高效的冷却技术,可以降低金属叶片的工作温度和叶片内的温度梯度.     

基于机器视觉的热障涂层内部裂纹在线检测方法及传热特性研究

燃气轮机服役过程中,热障涂层(以下简称涂层)内部裂纹萌生和扩展是导致涂层失效的主要原因。通过数值重构方法获得了含不同长度裂纹的热障涂层（TBCs）微结构,基于耦合双分布格子波尔兹曼方法（DDF-LBM）建立了热障涂层与冷却气膜流动传热模型,研究了热障涂层内部和表面温度分布特性。结果表明：出现裂纹会极大地改变涂层的温度分布情况,增加涂层温度不均匀性,造成局部烧结,进一步产生应力集中,极易导致涂层分层断裂,从而影响其耐久性。同时,基于耦合检测算法（GEMSS）通过大量机器学习训练,提出了热障涂层内裂纹定位和长度估算的在线检测评估方法。该方法能有效确定裂纹位置,高精度估算裂纹长度,为高温叶片在线健康度评估和寿命预测提供理论基础和技术支撑。     

高温半透明涂层的辐射特性研究

在先进燃气轮机技术领域,具有半透明辐射特性的高温热防护涂层被广泛应用以降低高温环境下金属部件的温度。以具有氧化锆涂层的燃气轮机热端金属表面为研究对象,基于半透明涂层的多波段吸收和散射特性谱带模型,采用蒙特卡罗法和控制容积法对半透明涂层内部的辐射-导热耦合传热进行模拟计算,获得了涂层内部的温度场分布规律,进一步研究了不同光谱波段、散射特性以及涂层厚度变化对涂层表观辐射特性的影响。为特定响应波段内的辐射温度与热流测量提供基础的应用数据。     

涡轮叶片综合冷却效率实验的缩尺效应

基于简化叶片的传热实验,研究缩尺模化对综合冷却效率的影响,得到缩尺效应随主流雷诺数和流量比的变化情况,以及毕渥数和热障涂层厚度对综合冷效缩尺效应的影响规律。采用一维传热模型,量化分析了缩尺模化对综合冷却效率的影响,并在实验中得到验证。结果表明：缩尺比例为1.5时,缩尺叶片综合冷却效率相对基准叶片增加10%,且增幅随主流雷诺数和流量比增加;基准叶片导热系数由17 W/(m·K)增加至50 W/(m·K),缩尺叶片平均综合冷却效率差异由13.71%降至0.34%;热胀涂层厚度等比例缩尺可减小缩尺效应的影响,使缩尺叶片综合冷却效率差异由13.07%降至2.98%。     

碳纳米管堆积床导热及热松弛

运用热线法测量了碳纳米管堆积床在120 K-370 K温度范围内的导热系数和传热松弛时间。测量数据表明:碳纳米管床导热系数极低,其在低温段随温度升高呈线性增加,在高于室温的范围趋于稳定。测量过程中碳纳米管床表现出的传热松弛时间,较已有文献报道的最大的碳纳米管床传热松弛时间大一个数量级。基于此数据并结合经典的(CV双曲型热传导)模型分析单个碳纳米管接触节点上的瞬态导热及热电特性,分析认为:利用纳米多孔材料的传热延迟特性可提高瞬态热电转换效率。     

回流式冷却叶片流热耦合数值分析

建立了某型回流式涡轮冷却叶片流热耦合分析模型,采用P-1辐射模型将辐射热流作为源项加入到方程中,对未考虑辐射和考虑辐射的不带热障涂层冷却的叶片进行了流热耦合分析,结果发现,占总燃气质量流量3.76%的冷却气体可以使回流式冷却结构对叶片的降温达到200 K。在入口最高温度为1 655和1 555 K时,通过对两种计算模型下叶片温度分布的比较,发现辐射对叶片壁面温度的影响具有显著性,回流式冷却叶片较易在尾缘叶尖位置形成最高温度点。     

保护法瞬态辐射热流计原理及瞬态响应特性

提出一种用于真空环境下辐射热流测量的保护法瞬态辐射热流计,通过热保护环使得中心热敏感片侧面绝热,根据其结构和瞬态传热方程建立测量原理的理论模型。红外热像仪的测量结果表明其中心热敏感片温度分布均匀,符合理论模型要求。经黑体炉和氙灯瞬态辐射热流测试,该热流计具有较高的测量精度和良好的瞬态响应特性。     

陶瓷发动机燃烧室不稳定传热的数值分析

本文提出了一个在瞬态对流和热辐射边界条件下,陶瓷发动机燃烧室不稳定传热二维数值分析模型。其中,燃烧室零件的不稳定热传导采用了轴对称有限(?)法,瞬态对流和热辐射边界条件由发动机循环模拟模型得到。该模型可以用来预测陶瓷燃烧室表面薄层的温度波分布、瞬态温度场以及瞬态热流分布等。本文还讨论了陶瓷镀层厚度和发功机转速对温度波动现象的影响,并以活塞和缸套为例,介绍了在陶瓷燃烧室内所发生的瞬态传热过程。     

低散热发动机表面传热研究的一种新方法

本文探索了一种低散热发动机陶瓷涂层表面传热的实验研究方法─—表面温度法。通过实测低散热发动机燃烧室陶瓷涂层表面的瞬态温度与平均热流，可较准确地计算低散热发动机陶瓷涂层表面的局部瞬态热流。文中着重介绍了陶瓷涂层表面瞬态热流的具体求解方法。     

基于热流固耦合分析的重型燃气轮机透平高压叶片寿命研究

先进高效的重型燃气轮机透平高压叶片工作在高温、高压、高转速的严苛环境中,为了评估其安全可靠性,本文基于三维稳态粘性Navier-Stokes方程,考虑气动与热物理场的耦合,运用共轭计算技术和SST湍流模型建立了具有完整内外冷却结构的某燃气轮机高压透平叶片热流固耦合分析模型和寿命分析模型,获得了叶片温度分布及相应的应变应力场,并详细分析了叶片上热障涂层和金属基底的寿命状况。研究结果对理解和掌握先进的燃气轮机透平叶片设计技术具有重要参考意义。     

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%.     

Contents in Volume 23,2014

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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.     

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.