基于Modelica语言的燃气涡轮建模及应用

为了对燃气涡轮的性能进行更好的仿真研究，利用模块化建模的方法，并根据质量和能量守恒的原理，把燃气涡轮分为流动模块和容积模块两部分。其中．容积模块看作是质量和能量的集聚，流动模块看作是质量和能量的流动。采用新型的、面向对象的仿真软件Modelica编制了燃气涡轮的仿真模型，建立了可扩展的燃气涡轮程序库，并利用该程序库与其它模型库结合，搭建了单轴燃气涡轮发动机模型，得到了合理的仿真结果，验证了该方法可行及推广应用价值。图11参8     

航空发动机涡轮流场仿真与涡轮功计算

针对航空发动机涡轮功热力分析法的不足，将计算机流场仿真与力学分析相结合，推导出了单位时间内燃气对涡轮做功的计算公式，并进行了仿真计算。结果表明，该公式不仅与燃气流场参数有关，还与涡轮转速、几何结构等有关，更适合于涡轮特性分析与结构设计。     

轴流涡轮变工况性能模拟

给出了计算涡轮平均 S2流场分布和总性能的计算方法 ,并给出了计算叶片排中非设计点的损失和落后角模型 ,计算中考虑了变比热、冷气掺混的影响。针对单级和两级涡轮进行了计算分析 ,结果表明该方法可为预测已有的涡轮性能及其调试、改进提供分析工具。图 3表 1参 6     

轴流涡轮变T况性能模拟

给出了计算涡轮平均S2流场分布和总性能的计算方法,并给出了计算叶片排中非设计点的损失和落后角模型,计算中考虑了变比热、冷气掺混的影响.针对单级和两级涡轮进行了计算分析,结果表明该方法可为预测已有的涡轮性能及其调试、改进提供分析工具.图3表1参6     

轴流涡轮变工况生能模拟

给出了计算涡轮平均S2流场分布和总性能的计算分析,并给出了计算叶片排中非设计点的损失和落后角模型,计算了中考虑了变比热,冷气掺混的影响,针对单级和两级涡轮进行了计算分析,结果表明该方法可为预测已有的涡轮性及其调试,改进提供分析工具。图3表1参6。     

工质加湿后简单燃气涡轮循环的动态响应

在传统燃气轮机循环的动态仿真研究中，对涡轮部件的处理一般都采用涡轮特性图或曲线的方法来完成；但如果进入涡轮的工质发生变化，由纯燃气变成高温高压高湿的燃气，那么涡轮特性图或曲线在无法获得的情况下要建立湿工质循环的动态仿真模型，对涡轮部件需作特殊处理。本文根据涡轮的工作原理建立了基于逐级计算的涡轮部件性能仿真模块：利用此涡轮模块，搭建完成了发电用简单燃气轮机循环动态仿真模型，同时燃烧室考虑注湿，计算在不同注湿情况下涡轮部件的性能变化以及整个循环的动态响应过程。     

用于估算燃气轮机出口温度的列线图

此图可根据涡轮给定的效率值、膨胀比和入口温度提供一个快速估算燃气轮机排气温度的方法。对于涡轮中燃气的绝热膨胀,温降可按下列方程进行计算:由该方程得到:式中:T_1=初始绝对温度T_2=最后绝对温度r=膨胀比e=涡轮效率K=比热比,K=C_P/C_V此列线图可解上述方程式。为了方便起     

熵函数法在航空发动机涡轮效率计算中的应用

为提高涡轮效率计算精度,将熵函数法引入到涡轮效率计算过程中,借助变比热法等熵绝热过程基本方程,准确求解涡轮进出口截面理想等熵焓差,进而得到涡轮效率。利用该方法,对某型核心机的变比热涡轮效率进行计算,得到不同因素对涡轮效率的影响规律,并完成敏感性分析。分析结果表明：熵函数法能够将涡轮效率计算误差减小到1%～2%之间;压气机引气量的增加会导致涡轮效率计算值偏高,而压气机出口漏气量越小、高压轴效率越高,涡轮效率计算值越低;压气机出口漏气量对涡轮效率的影响最大,而高压轴效率敏感度最低。     

基于Dymola/Mbdelica的航空燃气涡轮访真研究

设计开发新的航空发动机是一项复杂耗时的工程．而计算机仿真是一种有效的解决办法，因此开发比较通用的仿真模型已成为一种发展趋势。本文利用模块化建模的方法．把航空燃气涡轮分为流动模块和容积模块两部分．并采用新型仿真软件Dymola／Modelica编制了相关仿真程序库。该模型库具有层次化的结构，以及可扩展、标准化的特点。以涡轮为例建立了可扩展的航空燃气涡轮程序库，并利用该程序库与其它模型库结合．搭建了一个带开关磁阻电机的混合排气航空发动机模型，得到了合理的仿真结果．验证了该方法的可行性及推广应用价值。     

采用热-流耦合方法对火焰筒壁温三维数值模拟

考虑了流场变化对换热的影响,使用热-流耦合方法,对某型燃烧室整个流场、温度场进行完全的数值模拟。该方法对流场和固壁内换热进行耦合计算,得出了三维燃烧室壁温分布。计算中,对完全发展的湍流燃气采用了标准“k-ε”湍流模型,运用DO模型计算了燃气的热辐射,燃烧模型使用涡-耗散模型来计算化学反应速度,固壁材料使用了变比热和变导热系数。数值模拟结果表明流场与固壁相互作用得更充分,能更精确地反映流场和温度场的整个形态,可以模拟出较为合理的流场和温度场分布以及相应的流动换热特性。     

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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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.     

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.