低温等离子体对柴油机排气微粒数量和质量影响的试验研究

基于电晕放电理论设计了低温等离子体(non-thermal plasma,NTP)发生器,由柴油机、低温等离子体处理器和静电低压冲击仪组成试验系统和测试系统,测试低温等离子体对柴油机排气微粒粒径、数量及其分布的影响。以试验为基础,对柴油机排气微粒经过低温等离子体后的物理性质进行了研究和分析,为聚集体的清除提供了理论基础。试验结果表明:低温等离子体通过氧化和捕集的方式降低柴油机排气微粒的数量浓度和质量浓度,排气微粒总数量下降了40%,排气微粒总质量减小了76.9%,随着低温等离子体强度的增大降低作用增强。     

模拟柴油机排气微粒的试验研究

为了改善柴油机排气微粒袋滤器性能试验的可控性及经济性，本文研制了一种微粒模拟装置，用以模拟柴油机的排气微粒。并采用气溶胶粒度电分析仪、扫描电镜、透射电镜等对模拟微粒影响柴油机微粒袋滤器性能的主要物理特性进行了测试，并与柴油机微粒的相应特性做了对比分析，证明所模拟的微粒具有与柴油机微粒相似的物理特性。因此可用本文研制的微粒模拟装置代替柴油机进行柴油机排气微粒袋滤器的性能试验。     

柴油机排气碳烟微粒稀释采样系统的研究

本文介绍了一种小型稀释采样系统和相应的试验结果。1.柴油机排放微粒的稀释采样系统柴油机排放微粒是以较高浓度随高温气体排入大气的。当高温排气受到环境大气冷却时,排气中的挥发性物质会发生冷凝,微粒间的碰撞也会产生相互粘连而聚合。为尽量真实地测出微粒排放参数,对排气进行稀释可以有效地防止测量过程中发生微粒的聚合和凝聚。     

柴油机排气微粒物理特性及生成机理研究

设计了柴油机排气微粒测量装置,对Ｓ１９５非直喷式柴油机的排气微粒数量浓度、表面积浓度、体积浓度进行了测量,发现了非直喷式柴油机排气微粒数量浓度呈双峰分布的特性。通过研究柴油机排气微粒在不同转速和负荷下的物理分布特性,对微粒的生成机理进行了探讨。     

柴油机排气微粒旋流净化技术的初步研究

根据柴油机排气微粒净化的要求,研制了一台柴油机排气微粒轴流直流式旋流净化器,并对旋流净化器的净化特性进行了初步的理论分析和试验研究,研究结果表明,排气微粒旋流净化技术对净化柴油机排气微粒是有效的;柴油机运行工况及旋流子结构参数对排气微粒净化效率有一定影响;排气微粒的凝聚是微粒旋流分离净化的前提。通过对净化器结构的优化以及采取必要的微粒凝聚措施,相信会显地提高柴油机排气微粒旋流净化器的净化效率,利     

柴油机排气中碳烟微粒的测量和特性

作者使用各种方法,包括悬浮粒子电子分析仪,冷凝核计数仪,快速-容积串联惯性冲击收集器,滤纸称重法对一台分开式燃烧室,自然吸气小轿车用柴油机排气中的碳烟微粒进行测量和分析。对柴油机排气中碳烟微粒进行取样和研究,以确定微粒的数量浓度、表面积浓度、体积浓度、质量浓度及其分布。该柴油机排气中微粒的数量浓度为(5～6)×10~7/cm~3,表面积浓度为1.51m~2/m~3,体积浓度为4.35×10~(-2)cm~3/m~3,质量浓度为47.5mgm~(-3)。碳烟微粒大小按质量区分,90%在1.2μm以下的范围内。本文对实验方法和结果进行了详细讨论。     

柴油机微粒袋滤器的模拟试验研究

本文利用微粒模拟装置建立了考察柴油机微粒袋滤器性能的无发动机模拟试验台架，并对一单袋过滤器模型进行了试验考察。结果表明，袋滤器在正常工作时，对柴油机排气微粒的捕集以筛滤机理为主，且效率高达９０％以上；在本文考察滤速范围内，过滤效率受滤速影响很小，随微粒质量浓度增大而增高；袋滤器阻力时间线性增大，阻力增长率与微粒质量浓度成正比，还随虑速增大而增大。本文还进行了多种方案的清灰试验，为柴油机微粒袋滤器选     

柴油机排气微粒过滤体选型试验研究

在分析了各类柴油机排气微粒过滤材料的优缺点的基础上，在气道试验台上测试了常用的壁流式蜂窝陶瓷过滤体和泡沫陶瓷过滤体的排气阻力，得到了一些定性的规律，从而为柴油机排气微粒过滤器的过滤材料选型提供了依据。     

柴油机排气微粒捕捉器燃气再生技术的研究

提出了一种新的柴油机排气微粒捕捉器的加热再生技术 ,即利用燃气与排气中的氧气燃烧清除微粒捕捉器中沉积的微粒 ;根据液化石油气的物化特性和排气中的含氧量 ,对这种方法的可行性进行了理论分析和试验验证 ;研制了一种以液化石油气为再生燃料的柴油机排气微粒捕捉器 ,并对燃气流量、过滤体内的微粒沉积量以及再生时间等影响因素进行了台架试验研究。     

柴油机微粒过滤器滤芯结构设计

本文设计了两种内部有曲折气流通道的柴油机排气微粒过滤器滤芯结构,并进行了柴油机台架实验。结果表明:改进过滤器滤芯的几何结构可以大大降低过滤器的排气背压,减小过滤器对发动机输出功率的影响,改善微粒在滤芯内部分布的均匀性,提高滤芯的有效过滤体积。     

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。