新型渐增燃烧球形发射药的燃烧性能

提出了含微气孔结构分层球形药(LPBP)的燃烧物理模型,进而给出数学模型,模拟其定容燃烧时的燃气生成规律.最后使用密闭爆发器测试LPBP的燃烧性能,并与模拟结果进行了对比讨论.结果表明,特殊的壳芯结构有效地改善了球形发射药燃烧时的产气规律,调整分层厚度、壳层芯层密度之比可得到不同渐增燃烧性能的发射药,但壳层厚度比例大于60％时,发射药渐增效果不再明显.     

稀燃条件下主动预燃室式直喷汽油机燃烧和排放特性研究

为明晰不同点火方式对汽油机稀薄燃烧特性的影响规律,在一款排量为0.5 L的研究型单缸机上试验研究了传统火花塞和主动预燃室两种不同点火方式下发动机燃烧及排放特性,探索主动预燃室拓展稀薄燃烧极限的多种影响因素.研究结果表明,稀薄燃烧可有效降低油耗,提高发动机热效率.传统点火线圈的稀燃极限处于过量空气系数1.5附近,最高指示...     

主动预燃室式直喷汽油机稀薄燃烧性能研究

为明晰不同点火方式对汽油机稀薄燃烧特性的影响规律,在一款排量为0.5L的研究型单缸机上试验研究了传统火花塞和主动预燃室两种不同点火方式下发动机燃烧及排放特性,探索主动预燃室拓展稀薄燃烧极限的多种影响因素。研究结果表明,稀薄燃烧可有效降低油耗,提高发动机热效率。传统点火线圈的稀燃极限处于过量空气系数1.5附近,最高指示热效率为45.0%,而采用主动预燃室系统后,稀燃极限可进一步拓展,过量空气系数可达2.0,指示热效率提升至46.5%,氮氧化物排放比采用传统火花塞点火技术时降低约88%;主动预燃室匹配高压缩比14.80的燃烧系统,可进一步拓展稀燃极限至过量空气系数2.1,指示热效率可达48.0%,氮氧化物排放继续降低,在过量空气系数采用2.1时NOx排放最低可达58×10-6。     

无烟煤与贫煤混煤燃烧和NO_x排放特性的实验研究

利用热天平和小型煤粉燃烧实验台对无烟煤、贫煤及其三种配比混煤的燃烧特性、不同配风下NOx的生成规律和燃尽特性进行了实验研究。通过对试验数据的整理和分析,认为无烟煤与贫煤在燃烧性能上略有差异,混煤的燃烧特性介于两者之间,合适的选取过量空气系数可实现不同掺烧比无烟煤与贫煤混煤高效低NO燃烧。并针对三种掺烧比的混煤提出了其高效低污染燃烧的过量空气系数范围,为燃用上述混煤的电厂经济清洁运行提供一些参考数据。     

利用火花点火式快速压缩装置进行天然气直喷分层燃烧可行性的研究

利用快速压缩装置进行了天然气直喷分层燃烧可行性的研究。结果表明 :天然气分层燃烧具有短的初期火焰发展期和主燃期以及高的燃烧压力。分层燃烧可使稀燃极限延伸到很小的当量比。由于过度分层 ,CO在当量比大于 0 .8时急剧增加 ,而 NOx 的峰值也因充量分层而出现在小当量比处。燃烧效率在当量比处于0 .1～ 0 .9范围时高于 0 .92 ,在极小当量比时由于未燃混合气淬熄 ,在当量比时由于过度分层而使燃烧效率降低。根据燃烧产物计算的燃烧效率与根据放热分析获得的燃烧效率一致。因此 ,天然气直喷分层燃烧在宽广的当量比范围内可望实现高效燃烧火花助燃发动机的宽广的高效燃烧。     

液化石油气与汽油燃烧特性的对比试验研究

在点燃式发动机上分别燃用液化石油气和汽油,通过采集示功图并进行放热规律计算,对两种燃料在相似工况、相同过量空气系数下的燃烧特性进行对比分析。结果表明,在不改变样机结构和点火提前角的情况下,燃用液化石油气造成样机最大输出功率下降了7.64%。标定工况下,过量空气系数的变化对样机燃用汽油时的功率影响较大。两种燃料标定工况下的比热耗均随过量空气系数的增大而降低,但液化石油气降低的幅度较小。相似工况、相同过量空气系数下,相对于汽油,液化石油气的滞燃期短,燃烧持续期短,燃烧速度快。     

二甲醚—空气—N2/CO2混合气燃烧特性研究

在定容燃烧弹中系统地研究了常温常压下,不同稀释气、不同稀释系数、不同燃空当量比时二甲醚-0空气-稀释气混合气的燃烧特性.基于容弹计算的准维双区模型和实测的燃烧压力数据,计算了燃烧温度及规范化质量燃烧速率.研究结果表明:随着稀释系数的增加,最大燃烧压力值、最高燃烧温度值以及规范化质量燃烧速率均降低,而火焰发展期和快速燃烧期随稀释系数的增加而增加.研究发现,CO2作为稀释气体时对燃烧温度降低的效果较N2作为稀释气体时更加明显.     

共轨轨压和进气压力对柴油机燃烧和排放的影响

运用CFD商用软件FIRE对不同轨压与不同进气压力下燃烧室内油气混合特性进行了仿真计算分析。研究了高速直喷柴油机的混合气形成规律,通过与试验值的对比可知,计算结果有效反映了这种混合气形成特性对燃烧过程及排放特性的影响。结果表明：通过对缩口直喷燃烧室内气流特性和轨压、进气压力的优化匹配,可以有效地控制燃烧过程的滞燃期、预混合燃烧比例和扩散燃烧过程,从而控制高温燃烧持续期,在保证经济性的前提下,可以有效地降低NOx和烟度排放。     

喷油提前角对柴油机燃烧特性的影响

为了研究柴油机在不同喷油提前角下的燃烧特性,采用三维流体数值分析软件AVLFIRE建立了某型柴油机燃烧计算模型.在不同喷油提前角下,对燃烧滞燃期、油气混合程度、温度、燃空当量比、放热率和压力进行分析,得出:随着喷油提前角的增大,滞燃期延长,着火时刻形成的可燃混合气增多,缸内最高燃烧压力和最高温度也随之升高同时放热规律相...     

发动机缸内自燃着火与火焰传播的调控

在一台轻型光学发动机上对比了部分预混压燃(PPC)和燃料活性控制压燃(RCCI)两种燃烧模式的着火及燃烧发展过程,并分别探究了不同喷射策略对两种燃烧方式的影响.研究发现,对于PPC燃烧模式,混合气浓度分层越小,燃烧过程中自燃占比越高;混合气浓度分层越大,燃烧过程中火焰传播占比越高.对于RCCI燃烧模式,缸内直喷高活性燃料比例较高时,燃烧是从高活性区到低活性区分阶段顺序自燃;缸内直喷高活性燃料比例较低时,燃烧是火焰传播与自燃共同主导的过程.从而阐明了PPC和RCCI相较于均质压燃(HCCI)能够实现更高负荷高效清洁燃烧的本质是,燃烧发展历程从单纯的多点自燃燃烧转变为火焰传播与自燃共存.     

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.     

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.     

Wind power for pumping: The development of the ITP windpump

Water pumping has been one of the main applications for wind power in the past and despite the spread of mains-electric pumps, more than a million windpumps remain in regular use. This paper reviews the general technical and economic requirements for pumping water using wind energy and by way of example gives an overview of the development of the new ITP wind-pump. It then considers the future prospects for this kind of technology.     

Methods of creating solar-reflective nonwhite surfaces and their application to residential roofing materials

We describe methods for creating solar-reflective nonwhite surfaces and their application to a wide variety of residential roofing materials, including metal, clay tile, concrete tile, wood, and asphalt shingle. Reflectance in the near-infrared (NIR) spectrum (0.7–2.5 μm) is maximized by coloring a topcoat with pigments that weakly absorb and (optionally) strongly backscatter NIR radiation, and by adding an NIR-reflective basecoat (e.g., one colored with titanium dioxide rutile white) if both the topcoat and the substrate weakly reflect NIR radiation. Coated steel and glazed clay-tile roofing products achieved NIR reflectances of up to 0.50 and 0.75, respectively, using only cool topcoats. Gray-cement concrete tiles achieved NIR reflectances as high as 0.60 with coatings colored by NIR-scattering pigments. Such tiles could attain NIR reflectances of up to 0.85 by overlaying a white basecoat with a topcoat colored by NIR-transparent organic pigments. Granule-surfaced asphalt shingles achieved NIR reflectances as high as 0.45 when the granules were covered with a white basecoat and a cool color topcoat.     

Thermal decay of an initially hot isothermal water body with application to thermal energy storage

The thermal decay of an initially hot isothermal water body contained in a tank was studied. Analytical solutions (including a group-theoretic solution) were obtained for the one-dimensional heat conduction equation with heat loss from the sides of the tank. The convective heat transfer coefficient was assumed not to be constant over the surface of the tank but to vary with space and time. A very good agreement was obtained between the group-theoretic solution and a numerical solution using the Crank-Nicholson finite difference scheme. The analytical results are discussed in terms of the underlying physical mechanisms.     

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.     

秸秆燃烧中温度对钾转化与释放的影响

通过对稻秆原料进行常规特性分析和EDX元素含量分析,发现钾在稻秆无机元素中占有重要地位。参考原料化学分馏法和土壤中钾的分类与测试方法,给出了对生物质原料及其燃烧产物中钾的定性与定量简易方法。通过程序控温型固定床对稻秆先进行缓慢氧化,然后以100℃为间隔从400～900℃进行成灰,并分别测试其成灰率、有效钾和全钾的份额。结合稻秆原料及其灰中钾的份额分析,进行了稻秆灰中有效钾转化与释放的计算,发现有效钾在700～800℃之间有快速的释放和形态转变。稻秆灰的XRD分析结果表明秸秆灰中钾主要以KCl、K_2SO_4形式存在,得到了钾以盐的形式进行转化与释放的机理。该文中燃烧温度对钾转化与释放的影响规律对设计秸秆电厂时的炉型选择和燃烧参数确定有一定参考价值。