燃气轮机燃料轴向分级燃烧室的数值分析

为改善燃气轮机燃烧室的火焰筒壁温较高以及污染物排放等问题,提出了在火焰筒的壁面增加二次燃料喷口的轴向分级燃烧模式。利用ANSYS CFX软件并根据化学反应机理计算和分析了燃气轮机轴向分级燃烧室的流场和温度场,并与非分级燃烧室的结果进行了比较。结果表明:增大二次燃料比例可以使火焰筒壁面温度降低、出口污染物质量分数及出口不均匀系数减小,但出口平均温度会随之降低,导致做功能力减小。过量空气系数会影响火焰筒壁温、出口平均温度与NO质量分数。合理的二次燃料比例区间取决于多个条件。     

复合式燃烧室壁面温度的变化规律及其对燃烧过程影响的研究

本文介绍了用接触法测量X2105柴油机燃烧室壁面温度的试验结果。研究了复合式燃烧室壁面温度随发动机负荷、转速、燃油喷射正时和冷却水温度等的变化规律以及燃烧室壁面温度对复合式燃烧过程的影响。研究结果表明,适当提高X105系列柴油机在低负荷时燃烧室壁面温度,并避免高负荷时燃烧室壁面温度过高,将有利于提高柴油机的经济性和降低有害排放物质。     

旋流角度对燃料掺混特性影响研究

为了研究工业燃气轮机燃烧室旋流器旋流角度对燃料/空气混合均匀度以及NOx排放的影响,针对某型燃烧室的中心分级双级轴向旋流器,应用Fluent软件,选择Realizable k-ε和Species Transport模型,在燃气轮机的设计工况下对不同旋流角度回流区形态、甲烷的体积分数分布、温度场和污染物的排放进行了数值模拟。研究表明：随着内旋流角度从30°增加到50°,燃烧室内流场形成的回流区尺寸有减小的趋势,燃料的分布趋于均匀,主燃区最高温度从2 304 K降低到2 180 K, NOx排放呈先增大后减少的趋势,旋流角度为50°时NOx排放质量浓度为501.045 mg/m3。     

大气温度对某型燃气轮机燃烧稳定性和 NOx排放影响的数值研究

为了对比扩散和预混两种不同燃烧模式下大气温度对燃气轮机燃烧稳定性和NO_x排放的影响规律,针对某重型燃气轮机燃烧室,对多旋流喷嘴燃烧室的燃烧稳定性和NO_x排放进行了数值研究。结果表明:对于扩散燃烧,大气温度升高,燃烧室内高频脉动增强,燃烧稳定性变差;对于预混燃烧,大气温度升高,有利于提高燃烧的稳定性;在扩散燃烧模式下燃烧室燃料喷嘴下游回流区的温度最高,NO_x生成量最大;预混燃烧下燃烧室头部温度分布较均匀,燃烧室NO_x生成主要集中在驻涡回流区和燃烧室中下游位置,燃料喷嘴下游回流区NO_x生成量很小;随着大气温度的升高,扩散燃烧和预混燃烧下燃烧室内NO_x的生成量均增加。研究结果可为指导燃气轮机运行提供参考。     

乙醇微型燃烧室燃烧特性的数值模拟研究

为了解决化石燃料储备不足与环境污染问题,生物质燃料作为石油替代能源得到大力提倡,如何合理地将化石燃料替换为生物质燃料且维持设备正常运行成为工程上亟待解决的问题。本文采用CFD软件研究了车载5 kW生物乙醇微型燃烧室的燃烧特性,对比分析了不同功率（0.5~5 kW）和出口温度（840~960 K）时的回流区长度与宽度、回流量、出口温度分布系数（OTDF）、出口NO体积分数等特征参数。结果表明：随着出口温度升高,回流区长度逐渐缩短,回流量减少,出口温度均匀性逐渐变差,出口NO体积分数明显增加;随着燃烧室功率增大,回流区长度变长,回流量增加,OTDF先增大后减小,NO体积分数随着功率的降低而显著升高,最大值出现在1 kW时,达到满负荷时的7倍。因此,为了实现稳定燃烧和减少污染物排放,该乙醇微型燃烧室应在较高的空燃比（即较低的出口温度）和功率下运行。     

甲烷和氢气在亚毫米微燃烧室内燃烧的试验对比

在碳化硅材料的亚毫米尺度微燃烧室内,针对甲烷和氢气两种不同燃料进行了燃料与氧气预混合燃烧的试验。利用热电偶测出燃烧室壁面温度并进行了分析。结果表明:在燃料和氧气的总体积流量相同时,燃用甲烷时燃烧室的壁面平均温度更高,但氢气的燃烧室壁面温度更加均匀,梯度更小;氢气比甲烷有更宽的可燃范围,试验时甲烷/氧气在总体积流量为700mL/min、混合比为化学当量比时燃烧不能进行,而氢气和氧气在相同条件下能够燃烧。     

燃气轮机燃烧室点火位置及点火过程计算

采用Fluent软件模拟了某型燃气轮机燃烧室的点火位置及火焰传播过程,得到了燃烧室的最优点火位置和湍流火焰传播速度以及火焰传播特性。结果表明:可以通过逐渐减小火核半径的方法找到燃烧室的最佳点火位置;燃烧室的最佳点火位置为x=130 mm,y=85 mm,最优点火位置位于第二排冷却孔与第三排冷却孔之间;在最佳点火位置处,存在一个二次回流区,保证了点火的成功进行;主回流区起到了稳定火焰的作用;二次回流区和主回流区在燃烧室点火过程中起着不可替代的作用;油滴的蒸发导致了点火的延迟;湍流火焰传播速度约为6.5 m/s。     

初始条件对燃气轮机DLE燃烧室性能影响研究

以单头部中心分级旋流干式低排放(Dry Low Emission, DLE)燃烧室为研究对象,以天然气为燃料,针对不同的全局当量比、进口温度、进口压力条件开展试验测试和数值模拟,研究燃烧室的燃烧性能以及污染物排放的变化规律。研究发现：随全局当量比增大,中心回流区长度略有增大、宽度变窄、回流速度增大,燃料量的增加使得高温区面积明显扩大,燃烧室出口温升明显增大,出口温度分布系数变化不大,燃烧室出口CO和NO_x排放摩尔分数明显增大;随进口温度的增大,中心回流区长度先明显增大再减小、宽度变窄、回流速度先增大再减小,进口空气温度的升高使得反应速率加快从而导致燃烧室出口温度升高,但温升、出口温度分布系数变化不大,CO和NO_x排放摩尔分数增大;随进口压力的增大,中心回流区长度、宽度略有增大,回流速度增大,燃烧室内部和燃烧室出口温度无明显变化,出口温度分布系数减小,CO和NO_x排放摩尔分数受影响较小。     

低污染燃烧室预混喷嘴结构性能的数值研究

以某燃气轮机SAC(单环腔)燃烧室为原型,设计、研究了一种适用于甲烷燃料的低污染燃烧室,对燃烧室单喷嘴模型进行了数值模拟研究。就燃料喷孔位置、旋流器旋流数、叶片数目对流场和温度场进行了定性的分析。结果表明:(1)设计的喷嘴结构能形成明显的中心回流区和角回流区;(2)在有限预混长度情况下,燃料孔的位置对燃料空气预混效果有较大影响;(3)旋流器旋流数及叶片数目对燃烧室冷态流场有较大影响,且旋流数设计过大会导致回火现象,旋流数过低也会对燃料空气预混的均匀性产生一定影响;(4)结构优化后的喷嘴经计算得到NO_x排放量为7.01×10~(-6)(15%O_2浓度),CO为4.687×10~(-6)(15%O_2浓度),相比传统燃烧室降低了约80%,为形成与环境友好的燃烧室设计技术做了理论探索前期的研究工作。     

WZ003039燃烧室内燃料着火浓度界限区的研究——《тегчоэнергетика》

对燃料与空气混合物的着火浓度界限区和着火过程进行了数学描述和计算，对燃烧反应物和燃烧室结构参数的影响进行了研究。根据计算和测量结果做出了各因素影响的曲线图。从中可以看出，提高空气的温度和压力、增加燃烧室的直径，可增大界限区；增加雾化颗粒直径和单位面积上烧嘴的数目，会使着火浓度界限区变小。图7参7     

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.     

Contents in Volume 23,2014

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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.