汽轮机中压进汽导流环温度场及变形分析

中压进汽导流环是汽轮机中的关键部件,在设计过程中必须分析其温度场及变形。针对某亚临界600MW汽轮机导流环,建立了有限元模型,介绍了导流环表面不同区域的传热系数计算方法,用有限元法分析了导流环的温度场和变形,得出了在稳态运行工况的详细温度和变形分布。结果表明,导流环温度梯度以径向为主,导流环的最下部径向变形为1.611 3mm,导流环安装汽封处径向变形为2.063 6mm。所采用的分析方法可以用于分析亚临界、超临界和超超临界汽轮机导流环的温度场和变形,为导流环螺栓分析和冷却结构设计打下基础。     

双流给水泵机组汽缸的结构性能研究

与二次再热主机配套的给水泵汽轮机,相比于与一次再热主机配套的给水泵机组,其进汽参数有大幅提升。以某一电厂1 000MW等级全容量双流给水泵汽轮机的汽缸为例,通过三维有限元分析手段,研究了1 000MW等级全容量双流给水泵汽轮机汽缸在不同参数下的结构适应性。研究结果显示,相比于工作压力,工作温度对双流给水泵机组汽缸的结构影响更明显。进排汽温差越大,蒸汽室与进汽缸法兰接合面的密封性越差,排汽缸靠近垂直法兰处的斜撑板强度也越差;排汽温度越高,动静部件偏心越严重。从强度、密封及部件偏心的角度出发,论述了不同的汽缸结构可适用的工作参数范围,为1 000MW全容量双流给水泵汽轮机的开发设计提供参考。     

某汽轮机喷嘴阀箱结构强度的计算方法分析

采用有限元法对汽轮机喷嘴阀箱结构强度进行了计算,同时根据结构强度计算结果来验证汽轮机进汽阀箱设计的安全性和合理性.     

空冷135MW机组低压进汽导流环流动损失分析

以135MW机组的低压进汽部分吹风试验结果为依据,进行了低压进汽导流环在不同型线下流动损失的研究分析,检验了空冷135MW机组低压进汽导流环的结构设计合理性,并提出了湿冷135MW机组低压进汽部分的改进方案.     

新型非道路卧式柴油机龙门机体结构的设计与分析

针对非道路卧式柴油机结构特点,分析了现有卧式柴油机隧道式机体存在的技术问题,自主创新设计开发了卧式柴油机龙门机体结构。结合自由模态试验,建立了机体组件有限元分析模型,计算分析了机体结构刚度和强度状况。研究结果表明:新型卧式柴油机龙门机体结构紧凑、润滑油道短、冷却效果好、铸造和加工方便;其低阶固有频率较高,整体刚性较好,各阶模态固有频率均大于500Hz;在计算的预紧工况、最大扭矩工况下第1缸爆发和第2缸爆发3种情况下机体没有出现很高的应力集中现象和较大的变形,计算得到的安全系数均在1.5以上;其结构刚度和强度满足非道路柴油机使用工况要求。     

四缸内燃机机体结构模态分析

以某直立四缸柴油机为例 ,用 Pro/ Engineer软件在建立底部被约束的机体三维实体模型的基础上 ,对机体结构进行了约束模态的有限元分析 ,得出了机体结构的前 2 0阶约束模态的固有频率及相应振型 ,并与机体自由模态分析结果进行了比较。结果显示出了机体各部分结构振动的强弱分布以及抗振薄弱区 ,揭示了不同频率范围内机体结构振动模态的特点。同时 ,分析结果表明 :约束模态的固有频率及振型都与自由模态有显著的差别 ,因此考虑约束边界条件的机体模态分析对揭示机体结构的动力学特性是非常有必要的。     

汽轮机排汽通道内导流元件对其性能影响的数值研究

考虑到单独模拟与排汽通道耦合模拟结果的差异性,利用数值计算软件模拟汽轮机排汽缸和凝汽器喉部耦合流动,得到更加精确的通道流场,在此基础上通过添加导流板优化排汽通道性能。计算结果表明,无论排汽通道进口汽流是直流还是旋流,在排汽通道上游(排汽缸缸顶)、中游(排汽缸出口)、下游(喉部)适当加装导流板均能有效改善通道内流场,但直流进汽时的改造效果更加明显,同时,越靠近上游,汽阻优化效果越明显,而在下游添加挡板则更有利于提高出口流场的均匀度。     

工业汽轮机不同进汽结构的气动特性数值研究

高压进汽结构是影响工业汽轮机安全高效运行的关键部件之一。采用数值模拟方法对比和分析了优化前后两种不同进汽结构的气动性能。研究结果表明:在相同的进汽压力和温度下,新型进汽结构的总压损失明显减小,且与原始进汽结构之间的总压损失差异随着流量的增加而增加,证明新型进汽结构对不同蒸汽过热度的适应性更为出色;此外,也考虑了轴向制造偏差对不同进汽结构所产生的影响。本研究将为新型流道在工业汽轮机上的应用提供参考。     

超大型自平衡一体式高中压内缸研究

为减少部件接合面漏汽,同时配合机组取消阀门到外缸间的导汽管,提高机组效率,上海汽轮机厂新型超临界350MW汽轮机采用超大型自平衡一体式高中压内缸。新型内缸将传统高中压合缸机组中的内缸、持环、蒸汽室、平衡活塞汽封体等分散部件整合为一体,设有高压排汽腔室,并设置上半缸竖直高压进汽管和下半缸左右高压进汽管。采用软件ABAQUS计算分析一体式内缸的密封、刚度及蠕变强度,结果表明其满足汽轮机全寿命周期的要求。一体式内缸能够降低外缸设计难度,平衡轴向推力,降低应力水平,减少机组安装和检修时间,并配合机组实现无导管进汽,提高了机组运行的经济性。     

低压缸进汽蜗壳气动性能试验研究

为了研究汽轮机低压缸进汽蜗壳气动性能,将某机组低压进汽蜗壳进行吹风实验研究。分析发现周向速度在三维速度矢量中占据主导,带导流结构出口速度更均匀,不带导流气流角更均匀,进汽蜗壳的流动损失随流量增加而上升,横置导叶全周进口流场不均匀,且随着流量的增大而增强。     

Contents in Volume 23,2014

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Performance assessment of some ice TES systems

In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efficiencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working fluid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efficiencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efficiencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efficiencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

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.     

Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions

Natural gas is a fossil fuel that has been used and investigated extensively for use in spark-ignition (SI) and compression-ignition (CI) engines. Compared with conventional gasoline engines, SI engines using natural gas can run at higher compression ratios, thus producing higher thermal efficiencies but also increased nitrogen oxide (NO_x) emissions, while producing lower emissions of carbon dioxide (CO₂), unburned hydrocarbons (HC) and carbon monoxide (CO). These engines also produce relatively less power than gasoline-fueled engines because of the convergence of one or more of three factors: a reduction in volumetric efficiency due to natural-gas injection in the intake manifold; the lower stoichiometric fuel/air ratio of natural gas compared to gasoline; and the lower equivalence ratio at which these engines may be run in order to reduce NO_x emissions. High NO_x emissions, especially at high loads, reduce with exhaust gas recirculation (EGR). However, EGR rates above a maximum value result in misfire and erratic engine operation. Hydrogen gas addition increases this EGR threshold significantly. In addition, hydrogen increases the flame speed of the natural gas-hydrogen mixture. Power levels can be increased with supercharging or turbocharging and intercooling. Natural gas is used to power CI engines via the dual-fuel mode, where a high-cetane fuel is injected along with the natural gas in order to provide a source of ignition for the charge. Thermal efficiency levels compared with normal diesel-fueled CI-engine operation are generally maintained with dual-fuel operation, and smoke levels are reduced significantly. At the same time, lower NO_x and CO₂ emissions, as well as higher HC and CO emissions compared with normal CI-engine operation at low and intermediate loads are recorded. These trends are caused by the low charge temperature and increased ignition delay, resulting in low combustion temperatures. Another factor is insufficient penetration and distribution of the pilot fuel in the charge, resulting in a lack of ignition centers. EGR admission at low and intermediate loads increases combustion temperatures, lowering unburned HC and CO emissions. Larger pilot fuel quantities at these load levels and hydrogen gas addition can also help increase combustion efficiency. Power output is lower at certain conditions than diesel-fueled engines, for reasons similar to those affecting power output of SI engines. In both cases the power output can be maintained with direct injection. Overall, natural gas can be used in both engine types; however further refinement and optimization of engines and fuel-injection systems is needed.     

Exergetic evaluation of 5 biowastes-to-biofuels routes via gasification

This paper presents the exergy analysis results for the production of several biofuels, i.e., SNG (synthetic natural gas), methanol, Fischer–Tropsch fuels, hydrogen, as well as heat and electricity, from several biowastes generated in the Dutch province of Friesland, selected as one of the typical European regions. Biowastes have been classified in 5 virtual streams according to their ultimate and proximate analysis. All production chains have been modeled in Aspen Plus in order to analyze their technical performance. The common steps for all the production chains are: pre-treatment, gasification, gas cleaning, water–gas-shift reactions, catalytic reactors, final gas separation and upgrading. Optionally a gas turbine and steam turbines are used to produce heat and electricity from unconverted gas and heat removal, respectively. The results show that, in terms of mass conversion, methanol production seems to be the most efficient process for all the biowastes. SNG synthesis is preferred when exergetic efficiency is the objective parameter, but hydrogen process is more efficient when the performance is analyzed by means of the 1st Law of Thermodynamics. The main exergy losses account for the gasification section, except in the electricity and heat production chain, where the combined cycle is less efficient.     

Controls on the Karaha–Telaga Bodas geothermal reservoir,Indonesia

Karaha–Telaga Bodas is a partially vapor-dominated, fracture-controlled geothermal system located adjacent to Galunggung Volcano in western Java, Indonesia. The geothermal system consists of: (1) a caprock, ranging from several hundred to 1600 m in thickness, and characterized by a steep, conductive temperature gradient and low permeability; (2) an underlying vapor-dominated zone that extends below sea level; and (3) a deep liquid-dominated zone with measured temperatures up to 353 °C. Heat is provided by a tabular granodiorite stock encountered at about 3 km depth. A structural analysis of the geothermal system shows that the effective base of the reservoir is controlled either by the boundary between brittle and ductile deformational regimes or by the closure and collapse of fractures within volcanic rocks located above the brittle/ductile transition. The base of the caprock is determined by the distribution of initially low-permeability lithologies above the reservoir; the extent of pervasive clay alteration that has significantly reduced primary rock permeabilities; the distribution of secondary minerals deposited by descending waters; and, locally, by a downward change from a strike-slip to an extensional stress regime. Fluid-producing zones are controlled by both matrix and fracture permeabilities. High matrix permeabilities are associated with lacustrine, pyroclastic, and epiclastic deposits. Productive fractures are those showing the greatest tendency to slip and dilate under the present-day stress conditions. Although the reservoir appears to be in pressure communication across its length, fluid, and gas chemistries vary laterally, suggesting the presence of isolated convection cells.     

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.     

液压系统常见的故障诊断及处理

任何工程机械式液压设备使用时出现故障是不可避免的。但是怎样确定故障的原因及找到好的解决方法,这是使用者最关心的问题。讲述了液压系统常见的故障及其排除方法。     

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。