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泡沫陶瓷过滤体微波再生过程的理论分析 总被引:2,自引:0,他引:2
建立了一个用于柴油机排气微粒泡沫陶瓷过滤体微波再生过程模拟计算的数学模型。通过模拟计算,对过滤体微波再生特性进行了数值预测,并对影响过滤体再生的几种主要因素进行了分析。计算结果表明,过滤体微波再生技术是可行的,再生持续时间为(10-15)min,再生效率一般可达到85%左右,但再生效率和再生速率受再生时间,过滤体积碳量,气流中氧含量以及气流速度大小等因素的影响。计算结果可以为再生系统的进一步优化提 相似文献
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通过台架试验,研究了二次空气对柴油机排气颗粒过滤体微波再生过程的影响。试验结果表明,二次空气能够明显提高再生效率、缩短再生时间,但其流量过大会导致过滤体烧熔和炸裂。为了获得理想的再生效果,选取适当的二次空气流量是很重要的。 相似文献
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气流特征对柴油机微粒捕集器微波再生的影响研究 总被引:4,自引:0,他引:4
柴油机微粒捕集器过滤体再生时,流过过滤体的气流特征对再生过程有重要影响.根据泡沫陶瓷过滤体微波再生的特点,建立了一个适用于圆柱形过滤体的二维微波再生数学模型.模型中考虑了过滤体微波再生时气流与过滤体、碳烟微粒之间的对流换热、微波能量在过滤体空间的再分布和衰减变化、碳烟颗粒在过滤体空间的分布不均匀性等主要因素.使用该数学模型研究了尾气中含氧量、流速、温度等物性参数对过滤体再生时间和再生效率等再生特性的影响,计算结果与试验结果吻合良好,说明所建立的数学模型合理,能满足工程应用要求.研究结果揭示了泡沫陶瓷过滤体微波再生过程中的一些重要特征和规律,为微粒捕集器的设计和优化提供了依据. 相似文献
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碳化硅泡沫陶瓷过滤器微波再生特性 总被引:1,自引:0,他引:1
利用所建立的柴油机排气微粒过滤器微波再生数学模型,对以新型过滤材料碳化硅为过滤体的微粒过滤系统进行了微波再生特性研究。并分析了几种主要因素对再生过程的影响。计算结果表明,碳化硅过滤材料具有良好的性能,基本满足微波再生要求。 相似文献
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微波能应用于柴油机排气微粒过滤体再生机理的研究 总被引:3,自引:3,他引:3
本文介绍了微波加热的基本原理及选择性加热的特性.实现了用微波对陶瓷过滤体进行再生的构想.通过对微粒及陶瓷过滤体的微波特性测量和计算,得出了过滤体上的微粒是微波选择性加热的主要对象的结论.文中描述了微波再生试验的结果,其再生效果也由过滤体的失重试验加以证实.此外还介绍了作者开发的一套微波再生试验系统,由此可以对过滤体的再生情况和规律进行分析研究. 相似文献
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柴油机排气微粒过滤器微波再生试验研究(1) 总被引:5,自引:1,他引:5
本对目前国内广泛采用的几种柴油机微粒过滤材料的微波特性进行了测量计算,并利用建立的柴油机微粒过滤及再生系统对过滤体的微波加热及再生特性了研究,结果表明,微波再生技术是比较成功的,它简单可靠,具有较广泛的应用价值,试验结果同时也表明,不同过滤材料的微波特性具有很大差异,需根据过滤材料垢特性合理地设计再生系统及组织再生过程。 相似文献
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根据柴油机排气微粒过滤体过滤及微波再生的要求,提出了一种多模箱式再生腔的结构设计。多模箱式再生系统中过滤体的尺寸可以不受安装空间的限制,并且可以采用多个微波源馈入功率以提高再生腔中的微波功率密度或改善加热均匀性。多模箱式再生系统适合于大功率柴油机排气微粒的过滤及过滤体的再生。文中建立了一个以过滤体为加热负载,由波导口激励的矩形微波多模箱式再生腔的分析模型,并采用FD-TD法对多模箱式再生腔中过滤体内部微波能量分布进行了计算,模拟计算结果与试验结果基本吻合。通过计算以改善加热均匀性为目的对再生腔结构进行了优化设计,结果表明优化后的过滤体内部能量分布得到明显改善。 相似文献
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柴油机排气微粒泡沫陶瓷过滤体微波再生过程的温度场研究 总被引:1,自引:1,他引:1
本文根据柴油机排气微粒过滤体微波加热的特点,在合理假 设的基础上建立了一个二维轴对称非稳态的泡沫陶瓷过滤体微波再生温度场数字模型,利用有限差 分法对该问题进行了数值计算,得出了与实际再生实验基本一致的计算结果,该研究为避免过滤体在微波再生时可能出现的局部烧熔和再生不均匀等现象提供了重要的理论指导。 相似文献
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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. 相似文献
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《热能动力工程》2014,(5)
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%. 相似文献
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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. 相似文献
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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. 相似文献
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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. 相似文献
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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. σred = σ1 β + (1 − β)σi, where: σ1-maximal principal stress, σi-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. 相似文献
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Jaime Massanet-Nicolau Alan Guwy Richard Dinsdale Giuliano Premier Sandra Esteves 《International Journal of Hydrogen Energy》2010
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. 相似文献