碳化硅烧成窑内烟气温度测量装置的研究

烟气温度是影响碳化硅制品烧结的重要因素之一,对制品的质量、产量以及设备的使用寿命等均有重要意义。针对烧成窑内烟气具有温度高,不易测量的特点,提出了一种以热电偶为测温元件的温度测量装置,深入窑内测量的部分均采用碳化硅耐火材料制成,在窑外使用不锈钢水冷套管对烟气进行冷却,两段用法兰连接,使用双层遮热罩和风机抽气的方式来提高测量的精度,并可通过该装置实现对烟气的取样和窑内压力的测量。     

SiC电热元件的发展动向

碳化硅电热元件的开发、应用已有70年的历史。作为工业炉用加热元件广泛用于大气气氛下1300℃的高温加热领域。近年来随着高新技术的发展,可满足各种环境条件的SiC电热元件相继得到开发。概述了SiC电热元件的制造方。重点介绍了SE,SA,SGE等各种类型SiC电热元件的研究开发及其性能、     

水泥和石墨组成的新型非金属电热元件的研究

本文较为详细地介绍了由水泥、石墨和耐火材料等制成导电混凝土及其两种非金属电热元件,以及它们的配方和制作过程,并对它们的一些性能进行了测试和分析。结果发现:由水泥、石墨和耐火材料等制成的非金属电热元件具有原料便宜、制作简便、成本低、抗过电流过电压能力强、使用寿命较长,节省贵重金属稀有金属和有色金属、散热快且均匀、使用安全等优点,有可能成为一种新型的电热元件。     

硅碳棒制造中几项新工艺

碳化硅电热元件,因为多作成空心棒状,故一般均称之为硅碳棒,它是高温箱式电炉和实验室用高温电炉的主要电热元件。硅碳棒的制作工艺比较简单,但对工艺的要求较高,因为加工工艺对硅碳棒的性能影响很大。 制作硅碳棒的原产是焦碳与石英砂。将焦碳与石英砂粉碎后,经电炉在高温2000℃以上焙烧后,即得碳化硅生料。一般电热元件制造厂,不直接烧制碳化硅生料,而是由专门厂家供应,故所谓硅碳棒的制作工艺,均指从碳化硅生料开始,到硅碳棒成品出厂这一过程的加工方法。     

二硅化钼发热体

电阻炉具有清洁、操作方便、易控制等优点。在电阻发热元件中能在氧化气氛下使用的除贵金属铂、铑外,以碳化硅发热体温度最高,一般1450℃左右。随着科学技术事业的发展需要解决更高温的抗氧化电热材料。 1958年瑞典KANTHAU公司开始制造一种叫做:KANTHAL SUPER的电热元件。这种元件是以MoSi_2为主体的,最高使用温度为1700℃。 在党的总路线光辉照耀下,随着我国科学技术事业飞速发展,迫切需要解决高温电热材     

改性材料电热元件应用于电热锅炉的研究

本文对用一种新型改性材料作为电热锅炉的加热元件进行了研究 ,并对影响该电热元件热力性能的各类因素作了较详尽的分析和探讨 ,提出了优化设计方案 ,旨在为电热锅炉电热元件的研究和设计提供理论依据。     

电阻炉电热元件使用寿命问题的热工方案的研究

以电阻炉中的电热元件和被加热元件为研究对象,经过简化提出简化模型,运用辐射换热理论对其进行了热工方面的理论计算和分析,在被加热元件热负荷一定的情况下,得出了影响电热元件温度的几大要点,提出了延长电热元件使用寿命的热工技术方案。     

固体电热储能装置热工与储能性能测试平台设计北大核心CSCD

该平台以GB/T39288—2020《蓄热型电加热装置》中提出有关固体电热储能装置的热工性能测试方法及流程为蓝本,参考了国内外标准,专门针对固体电热储能装置,进行纯储热工况、纯放热工况、边储边放工况全工况测试,改善并补充了固体电热储能装置热工与储能性能测试。该平台改进了GB/T 39288—2020的试验流程,结合非制热状态下的放热测试和制热状态下的放热测试,能够进行固体电热储能装置热工与储能性能标准测试。为了验证该平台可靠性,对某固体电热储热装置进行一次标准测试,记录其试验时的电量、时间、温度等参数,画出试验时温度曲线、加热丝电流电压曲线、热输出负荷曲线,通过改进、补充的公式计算了固体电热储能的热工与储能性能;利用计算结果画出了在额定热输出功率下的储能性能图。该图清晰展示了固体电热储能装置的有效释放的温度范围,储能能力,以及能量利用情况。本次测试结果与理论值、经验值相近,证明该平台可以作为设备商自检或教学使用的测试平台。该平台还留有自定义热负荷曲线功能,可以帮助教学者和学习者在真实的工况下,对固体电热储能装置进行研究和学习。     

SiC电热元件用高温防氧化涂料的研制

通过比较研制的不同配比,自愈合型高温防氧化涂料对SiC电热元件抗氧化性、电气性能、使用寿命等性能的综合影响,认为能产生SiO2保护膜的配方最适宜。通过在1650℃试验电炉上的试验验证表明：该涂料能很好地解决SiC电热元件,在高温使用条件下易产生强烈氧化之弊端,使SiC元件最高使用温度的上限提高了300℃,从而创新性地解决并扩大了其在高温使用条件下的使用范围和寿命。实施方法简单、经济实用,具有极高的推广应用价值和社会经济效益。     

再谈电锅炉用管状电热元件的应用

针对少数厂家对电热锅炉配套使用的金属管状电热元件了解不深,甚至在使用过程中出现一些误区等问题,介绍相关计算公式、产品系列,结合笔者工作经验,分析使用中出现误区的因果关系,从而使电热元件在应用中更加发挥其特有功能,提高电热锅炉的整体产品性能.     

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%.     

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.     

Contents in Volume 23,2014

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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.