W型火焰分级燃烧的热态试验研究

针对东方锅炉厂引进的FW公司300MW的W型火焰锅炉，设计搭建了1MW的W型火焰热态试验台，依据冷态空气动力场的试验结果设计了W型锅炉贫煤燃烧试验，研究了分级燃烧时炉膛中心温度分布规律及排放特性．实验结果表明，良好的组织W型火焰，其炉膛最高温度点应在F层中心线下部．合理的分级配风比是降低飞灰含碳量和NOx的关键，分级程度过大会引起不完全燃烧损失大幅增加，并破坏燃烧稳定性．     

旋流及直流燃烧方式超临界W火焰锅炉特性对比

以2台采用旋流和直流燃烧方式的600 MW超临界W火焰锅炉为研究对象,对比了其炉膛结构以及冷、热态特性的差异,并对原因进行了分析。结果表明:2台锅炉为适应的不同燃烧方式,采用了不一样的炉膛设计思路,并在冷态特性方面存在很大不同,但热态性能并没有显著的区别,相对于亚临界W火焰锅炉都有了十分突出的进步,说明我国对此类炉型的运用日趋势成熟。     

过量空气系数对W型火焰锅炉燃烧影响的数值模拟研究

过量空气系数是影响W型火焰锅炉燃烧的重要因素.利用数值模拟技术对某电厂300MW"W"型火焰锅炉炉内燃烧进行了4个工况的计算.通过分析各个工况下炉内流场、温度场、NO排放量以及炉膛出口处飞灰含碳量,得出过量空气系数增大时,炉内流场变化不大,炉内温度水平降低,火焰中心上移,NO排放量增大,飞灰含碳量减少.     

W型火焰锅炉炉膛温度场的可视化试验研究

使用火焰辐射图像探测系统探测炉膛空间发射到镜头各像素的辐射能量，然后从能量传递和平衡的角度，由所得图像重建空间的温度场。在300MW机组W型火焰炉进行了炉膛二维断面温度场可视化重建试验。试验在炉膛壁面布置4个CCD火焰探测器，采用计算机图像采集处理技术获取炉膛火焰辐射图像，通过对火焰辐射图像的处理以厦相关算法，重建炉膛断面温度分布、可动态反映火焰断面温度水平、火焰中心的偏穆和火焰刷墙等燃烧异常工况。断面温度场可视化结果刷新一次的时间不超过5S，满足在线监测的要求。     

二次风下倾对W火焰锅炉燃烧特性影响的试验研究

针对FW型W火焰锅炉高负荷下飞灰含碳量高、运行稳定性差等问题,在某厂300 MW机组的W火焰锅炉上进行了F层二次风的下倾改造,将导流板下倾角度固定为30°.改造后对锅炉进行了冷态空气动力场试验和热态调整试验.结果表明：F层二次风下倾后炉膛火焰中心下移,炉膛燃尽区内烟气温度下降;高负荷加风困难的问题得到了有效解决,烟气中CO体积分数下降为0,飞灰可燃物降低,锅炉效率提高了4.37%;F层二次风下倾改造后,锅炉的稳定性和经济性都得到了提升.     

北巴600MW“W”锅炉水冷壁结焦问题防治分析

北巴600MW超临界W型火焰锅炉运行中炉膛结焦严重,掉焦频繁发生,影响锅炉安全运行。本文介绍了北巴W火焰燃烧技术特点和卫燃带敷设情况,从炉膛温度、空气动力厂、还原性气氛等因素分析了结焦的原因,对炉膛具体结焦位置进行了描述。根据卫燃带改造后锅炉运行情况,提出了防治结焦对策。     

600MW亚临界锅炉低氮改造后汽温特性研究

以某台600MW亚临界锅炉为例,分析了低氮改造对其汽温静态特性和动态特性的影响.结果表明:低氮改造后炉内温度场、受热面结渣情况和锅炉运行模式均发生较大变化,对锅炉汽温特性产生较大影响;高负荷时锅炉汽温主要受分级燃烧导致的炉膛出口烟气温度上升和受热面结渣改善导致的炉膛出口烟气温度下降的综合影响;低负荷时锅炉汽温主要受分级燃烧导致的炉膛火焰中心高度降低和炉膛出口氧量的影响;快速降负荷过程中,炉膛火焰中心高度降低与汽轮机高压缸排汽温度下降对再热汽温的叠加影响是导致再热汽温易超跌的主要原因.     

燃尽风配风率对炉膛出口烟气温度的影响

以某1000 MW超超临界双切圆燃煤锅炉为模型,利用Fluent软件对烟煤分级燃烧后炉膛出口烟气温度进行了数值计算和分析,并将计算结果与实际改造后的数据进行比较.结果表明:在一定燃尽风配风率下,该锅炉燃烧烟煤时燃尽风配风率提高会导致燃烧中心升高,使分离燃尽风(SOFA)层以上的烟气冷却段缩短,进而导致炉膛出口烟气温度升高.通过对炉膛出口烟气温度公式中的火焰中心系数M进行修正,计算结果基本能满足实际工程改造的需要,具有一定的工程应用价值.     

W火焰锅炉炉膛动态数学模型

建立了W火焰锅炉炉膛动态数学模型，模型中对碳的反应速度计算式进行了修正。考虑了烟气质量和能量的动态特性及炉膛压力对反应速度的影响。仿真试验表明，模型正确反映了W火焰锅炉的燃烧特点，模型可用于W火焰锅炉的仿真工程分析。     

消除炉膛出口残余旋转的试验研究

四角切圆燃烧锅炉炉膛出口气流的残余旋转，是形成水平烟道两侧烟气温度偏差的主要原因之一。作者通过冷态模化试验，研究了RG670／140－10型锅炉残余旋转的成因，探讨了消除残余旋转的方祛，并提出了一个判定反吹风消旋能力的W判据，可作为消除残余旋转的综合性指标。     

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%.     

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.     

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.     

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.     

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.     

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.     

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.     

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。