安装倾角对热声发动机性能影响的试验研究

为充分利用太阳能作为驱动热源,开展了驻波型热声发动机在不同安装倾角下热力性能的试验研究.试验结果表明,热声发动机的安装倾角对热声系统的起振温度、消振温度以及起振时板叠中的温度梯度等参数有着显著的影响,当系统中氮气压力为1.3MPa时,在试验的7种角度下.最高起振温度484℃,最低起振温度428℃,该特性为选择合适角度以降低系统起振温度提供了试验依据;而当系统稳定振荡时,安装倾角的变化对系统的压比和压力振幅等热力特性的影响较小,该特性为利用自动跟踪太阳能集热器在不同角度下驱动稳定振荡的热声发动机创造了有利条件.试验结果为设计太阳能驱动的热声发动机提供了试验依据.     

以氦气为工质的行波热声发动机研究

随着对热声热机研究的深入，特别是行波热声发动机概念的提出，热声发动机效率得到了质的提高。为了实现热声发动机与制冷机的良好匹配，以氦气为工质时热声发动机需具有较低的起振温度、较大的压力波强度、较好的单频率特性。本文对自行研制的新型热声发动机进行了深入研究，以氦气为工质，在充气压力为2．0MPa时获得了1．19的压比，系统频率稳定在约73Hz，为利用新型热声发动机驱动脉管制冷机或其它热声制冷机创造了有利条件。此外，该热声发动机起振温度较低，初步具备了利用工业废热等低品位能源驱动的条件。     

纯环路型和混合型行波热声发动机的对比实验

研制了以陶瓷为板叠的行波热声发动机实验装置,进行了纯环路型与混合型行波热声发动机热力性能的对比实验研究,分析了系统的起振和消振过程及机理,研究了加热端温度、冷却端温度和回热器对系统性能的影响。结果表明,混合型行波热声发动机比纯环路型行波热声发动机具有更低的起振温度;且随着冷却端温度的升高,系统的起振温度也随着升高;回热器孔径对系统的性能有较大的影响,本实验中回热器孔径为0.8mm时系统起振温度最低;实验过程中还发现了"二次起振"现象。     

非对称双级环路行波热声热机的实验研究*

对于双级环路行波热声热机,两个热声核的相对位置直接影响到其起振温度,而热声热机的起振温差决定了其可利用的热源品位。基于线性热声理论分析,通过改变两个热声核的相对位置,研究了两个热声核的相对位置改变对其起振温差、压力振幅和压比等的影响。结果表明,双级环路行波热声热机的起振温度随着两个热声核从中心对称位置逐步靠近时先下降再上升,当两个热声核之间的谐振管长度比例为1:3.5时,系统获得最小的起振温差为59.6℃（工质为N₂,充气压力为2.5 MPa）。在相同温差下,该系统在谐振管长度比例为1:3.5的位置相较于其他位置具有较大的压力振幅和压比。     

可利用低品位热源的热声驱动脉管制冷机

针对原有热声驱动脉管制冷机实验装置,改进了板叠冷端夹套式水冷却器内部的丝网填料,进一步优化了小孔阀和双向进气阀的开度,获得了116．4K的最低制冷温度。通过操作脉管制冷机双向进气阀,使系统的起振温度从560℃降低为370℃,为低品位能源的利用创造了条件。     

二甲醚与柴油互溶性实验研究

利用高精度热物性测量系统对二甲醚与柴油的互溶性进行了实验研究。实验系统中温度覆盖范围为-80~300℃,测量不确定度小于±0.002℃;压力测量范围为0~2 MPa,测量不确定度小于±0.7 kPa。测量了10%、20%、30%的二甲醚/柴油混合燃料的饱和蒸气压力和临界互溶温度。研究表明:二甲醚与柴油互溶性良好。混合燃料的饱和蒸气压力低于纯二甲醚蒸气压,并且随柴油所占混合组分的增加而减小,混合燃料蒸气压的降低有利于避免发动机燃油供给系统中的气阻;此外,混合燃料的临界互溶温度随二甲醚所占混合比的增加而降低,有利于燃用混合燃料的发动机在更低的环境温度下正常运行。     

丝网热声板叠的最佳填充率

自行研制了热声驱动脉管制冷机实验台,着重研究了热声机械中热声转换的关键部件丝网板叠的填充率对热声驱动脉管制冷机起振温度,制冷温度和加热功率等的影响,并通过实验发现了丝网板叠的最佳填充率,以氮和氮作工质,分别获得了196K和138K的无负荷制冷制度,达到国际先进水平,为热声机械的实用化奠定了基础。     

回热器热功转换特性的实验研究

搭建一个实验测试平台,对回热器热声转换特性进行实验研究。实验系统由分别充当压缩机和发电机的多台直线电机及被测的回热器、换热器、热缓冲管等组成。实验对不同加热温度与声场条件下回热器的热声转换特性进行系统的研究。在平均压力为4 MPa时,实验获得的最大净输出声功为688 W,最大热声效率为34.2%。实验结果表明,在同等条件下,回热器加热温度越高,其输出声功越大,同时热声转换效率越高;回热器工作存在最优的声场条件,使其净输出声功与热声效率分别达到最大。     

热分层对HCCI燃烧过程的影响

在一台经改装的单缸光学发动机上进行不同热分层下均质压燃燃烧过程实验研究.保证每循环供油量一定,燃料为正庚烷,转速为600 r/min,进气压力为0.1 MPa,进气温度分别为95℃和125℃;循环冷却水温度分别为55℃、65℃和85℃.研究结果表明,冷却水温度和进气温度的变化,改变了缸内温度分布,对HCCI这种受控于化学反应动力学的燃烧过程有很大影响,引起微弱自燃着火、局部燃烧淬熄和相对均匀燃烧等不同燃烧过程;缸内热分层越大,自燃着火传播速度越慢,燃烧的不均匀性越大;增大缸内热分层,可以降低燃烧反应速率,具有拓宽HCCI运转工况范围的潜力.     

燃煤电厂尾部烟气热能梯级利用技术研究

由于设计、运行方式及燃用煤质等因素,目前国内燃煤机组空预器排烟温度普遍在120～160℃,排烟热损失严重,对于湿法脱硫机组来说也因入口温度较高耗费了大量宝贵的水资源。低温省煤器技术起到了回收烟气余热、降低供电煤耗、提高电除尘效率、降低脱硫水耗的功效,目前已得到推广应用,但热能利用水平较低。为在保证现有环保效果的情况下进一步提高余热利用水平,结合空预器旁路烟气热能梯级利用技术,通过能量置换获得高品位的热能,可以进一步地降低供电煤耗。通过研究旁路烟气比例,空气预热升温幅度等对能效提高,一、二次风温和排烟温度的影响,优化系统设计参数。进一步研究了系统改造对锅炉、汽机的影响,以及热能梯级利用技术对空预器低温腐蚀、硫酸氢铵黏附堵塞问题的改善功能。     

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%.     

Contents in Volume 23,2014

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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.     

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.