带有放气阀的二级增压系统的设计与试验

二级增压系统在重型柴油机和高性能轿车柴油机上均有良好的应用前景.为获得结构更为紧凑的二级增压系统,提出了将调节阀集成在高压级涡轮壳内部的二级增压系统结构方案,进行了增压系统与柴油机的匹配计算、两个涡轮壳的设计计算、调节阀计算以及流动分析,并对所设计的二级增压系统进行了试验研究.调节阀流通性能试验结果表明:高压级涡轮膨胀比在1.2到2的变化范围时,调节阀的流量调节范围达30%以上.紧凑型二级增压系统的联合运行性能试验结果表明:系统可以有效工作,且运行在高效率区.     

蝶阀在可调二级增压柴油机中的调节特性计算研究

建立了以蝶阀作为调节阀的可调二级增压柴油机的平均参数模型,包括发动机本体模型、进排气系统模型、涡轮增压器模型和调节阀模型,其中蝶阀模型以工程上常用的流量系数为基础,针对柴油机排气的可压缩性进行了修正.利用该模型对调节阀的调节特性进行了计算研究.研究结果表明:蝶阀用作可调二级增压系统的调节阀在90°-60°开度区间内几乎无调节能力;在60°-0°开度区间内,能够近似地呈线性调节排气流量在阀门和高压级涡轮间的分配,同时也能实现对总增压压力的连续调节.     

间冷循环燃气轮机低压工作线及影响因素分析

为详细掌握间冷循环燃气轮机的工作特性及实际运行过程中低压工作线的变动,考虑空气系统引 气、压气机出口漏气对流量连续的影响,引人压气机与涡轮及相邻涡轮间的流量比例系数,理论推导间冷循 环燃气轮机低压工作线方程,得到影响低压工作线的典型因素。开展间冷循环燃气轮机低压工作线在典型 影响因素下的变动机理分析,不同于高压工作线变动分析采用等换算转速条件,低压工作线变动分析采用等 高压转子增压比条件更为合理。依据间冷循环燃气轮机长期运行后典型影响因素的变化,获得间冷循环燃 气轮机低压工作线的具体变动结果,即高压压气机效率降低、高压涡轮效率降低、高压涡轮导向器面积增加、 间冷器性能衰减及二次水温度升高等会导致低压工作线升高,低压压气机效率降低、低压涡轮效率降低、低 压涡轮导向器面积增加、低压出口漏气量增加及大气温度增加等会导致低压工作线降低。     

注蒸汽对涡轮增压器的影响

水蒸气与燃气混合后的混合气体注入涡轮后,涡轮增压器会出现运行状态的变化。经对注蒸汽后的涡轮增压器进行了热力学的分拆,认为：汽气比的增大使增压器的转速、压气机空气流量和压气机压比增高;注汽温度对压气机压比有较小影响;低工况时,水蒸气的注入使涡轮的折合流量、膨胀比皆增大;在高工况时,膨胀比、折合流量能够增大的幅度减小：不同的汽气比对涡轮效率特性曲线影响较小。     

船用增压器大膨胀比轴流涡轮气动技术研究进展

宽流量范围、高效、高压比设计是现代船用涡轮增压器的发展趋势,而轴流涡轮作为主要部件,其膨胀比和变工况效率要求亦将随之增加,加之特殊的通流形式与进排气环境,使得涡轮内部流动异常复杂,严重限制了大膨胀比涡轮气动性能的提高。本文从大膨胀比涡轮气动设计、大膨胀比涡轮中的复杂流动现象和流动机理,以及大膨胀比涡轮气动研究存在的问题3个方面对船用增压器大膨胀比轴流涡轮气动技术的研究进展进行综述,并指出未来应在宽工况大膨胀比涡轮激波主导非对称流动机理及调控方法方面深入开展研究,以期把涡轮气动设计参数与其内部复杂流动相关联,进而探求能显著改善大膨胀比涡轮全工况气动性能的设计策略和方案,从而为高效船用增压器涡轮研发提供技术支撑。     

基于变热量等效热降的混合发电系统通用矩阵模型

以定热量等效热降法为基础,建立了混合发电系统的变热量等效热降通用矩阵模型。以某600 MW机组的混合发电系统为例,利用矩阵通用模型计算了该机组采用混合发电的热经济性,分析了混合发电系统的优越性。研究表明,系统效率、节煤量、CO2减排量与辅助热源系统作用位置及流量分配系数密切相关,辅助热源系统作用于高压级加热器时系统的节能潜力及经济效益总体好于作用于低压级时,辅助热源系统作用于各低压级加热器时,各高压级和除氧器级的抽汽效率均有提高。     

两级涡轮增压

本文叙述了在何时何处采用两级涡轮增压的问题。一般是在单个增压器不能满足压气机的高压比或总效率时才使用两级涡轮增压。文章提供了在采用降低压缩比提高平均有效压力而使用两级增压的实例。文章讨论了两级涡轮增压系统的优缺点。缺点包括成本、装置体积和部分负荷时的运转问题等。除涡轮增压器匹配的某些问题以外,文章还讨论了在柴油机上装两级涡轮增压器的灵活性。本文所提出的这种紧凑布置是今后的方向。目前,由于两级涡轮增压的缺点,使其不如单级涡轮增压那样具有引吸力。这或许是因为单级涡轮增压器将继续朝高压比和高效率发展的原因。因此,必须采用两级涡轮增压才能获得更高压比的观点将发生变化。     

带有超高负荷高压级的1+1/2对转涡轮低压涡轮的设计与分析

开展了带有超高负荷高压级的1 +1/2对转涡轮低压级设计与研究.首先对该超高负荷涡轮进行特性分析,提出了1 +1/2对转涡轮低压涡轮的设计目标,并进行了低压涡轮的详细设计与分析.研究结果表明,所设计的1+ 1/2对转涡轮低压级基本达到设计要求;1+1/2对转涡轮出口背压的变化,对低压级流场产生直接显著的影响,但对高压级流场的影响较弱.     

气冷涡轮转子变叶尖间距性能试验及数值研究

为量化评估工程应用的气冷低压涡轮带冠转子叶片的叶尖间距大小对涡轮气动性能的影响,综合现有涡轮部件试验能力,以单级轴流低压涡轮性能试验件为基础,通过控制圆度的机加方式磨削转子外环内壁以实现叶尖间距的变化,采用控制冷气流量比的方法,开展5次不同叶尖间距大小的涡轮级性能试验,得到多工况下涡轮效率、换算流量和换算功率等特性参数。采用加载冷气及考虑转子叶冠结构的数值模型进行三维仿真计算,并与试验结果对比分析。研究表明：叶尖间距由0.6 mm增加至3.2 mm,低压涡轮流通能力增大1%,叶冠泄漏量增多3.4%,但做功能力下降2.3%。涡轮效率变化与叶尖间距大小近似呈线性关系,叶尖间距每增加1 mm,效率约降低0.7%,同时,叶尖间距的增加导致了叶冠腔的旋涡结构、气流掺混及主流入侵强度逐渐增大,引起动叶总压损失的增大,叶尖间距增加至3.2 mm导致叶间位置总压损失由0.88增至2.3。     

车用增压器涡轮内部脉动流场仿真研究

为了解车用增压器涡轮在脉冲进气条件下的性能,改善涡轮与发动机的匹配,采用数值模拟方法研究了径流有叶涡轮内部脉动流场。针对涡轮瞬时效率的计算,特别采用了相位平移方法。研究结果表明:由于涡轮级进口脉动气流的影响,涡轮流量和效率变化相对于压比均出现了滞后现象;脉动周期内转子进口攻角变化对叶轮内部速度场起主要影响作用;转子功率变化规律与涡轮级进口压力变化一致;适当提高涡轮设计流量能够增加涡轮有效利用发动机废气能量的能力。     

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.