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以空气,水为工质,利用马尔文粒度分析仪对气液两相流雾化器喷嘴的雾化特性进行了详细的实验研究。测量了气,液两相流不同入口压力比条件下通过喷嘴后形成的液体雾化粒子的粒径分布,详细讨论分析了气,液两相压力及进气,进液方式对喷雾效果的影响,得出了喷嘴雾化过程中气液两相流量与气液两相压力之间的规律和 化原则,并对喷嘴的雾化机理进行了探讨。 相似文献
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使用激光相位多普勒分析仪PDA对旋转型气-液雾化喷嘴的雾化特性进行了实验研究。使用水代替油作为被雾化的液体,采用压缩空气作为雾化介质,测量了不同工况下的喷雾特性参数,如:喷雾液滴粒子的索太尔平均直径SMD和粒子速度等。实验测量结果表明,喷嘴在较小的气液比条件下可以达到较好的雾化状态,中心的液滴平均SMD可以达到40μm。随着压力和气液比的增加,雾化水平也随之提高,但是受喷嘴结构的影响很小。本文的研究为喷嘴的实际设计提供了基础依据。 相似文献
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内混式气液雾化喷嘴雾滴粒径的实验研究 总被引:1,自引:0,他引:1
雾滴粒径是衡量喷嘴雾化性能的一个重要指标,为了提高喷嘴的雾化效果,对一种新型的内混式气液雾化喷嘴进行了测试。实验采用4组不同几何结构参数的喷头,研究了气孔直径、气孔数、气液流交角和喷孔直径等喷嘴结构及气压、气液比、混合室压力等工况参数对MMD(质量中值粒径)的影响;并且进一步对实验结果进行了定性和定量分析,得出具有较好雾化性能的喷嘴结构和工况参数,为喷嘴的结构优化和使用提供了依据。 相似文献
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溶气对不同燃油喷雾特性的影响 总被引:1,自引:0,他引:1
对溶有甲烷(CH4)的煤油和柴油稳态喷雾特性进行了试验研究,并对两者的试验结果进行了对比分析。结果表明,溶气对燃油的雾化有正反两方面的影响,它与CH4的浓度、喷嘴的L/D值、燃油的性质有关;柴油和煤油试验结果的规律相似,但促进雾化的临界浓度值不同;由于溶气的膨胀作用,在喷嘴出口处形成均匀的喷雾,喷雾锥角急剧增大;CH4的浓度较大时,燃油雾化粒子分布规律向小粒径方向移动,浓度较小时,向大粒径方向移动;低粘度的燃油有助于增强溶气对燃油雾化的促进作用。 相似文献
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在一种内置拉法尔气体喷管两相流“液包气”喷嘴的设计基础上,搭建了多相雾化实验台,进行了喷嘴雾化性能实验,研究了气液质量比(训)对喷嘴雾化颗粒粒径分布均匀性、索特尔平均雾化直径、雾化角等性能指标的影响,推导出“液包气”喷嘴液气压力比和气液质量比的经验公式及适用范围,得到了内置拉法尔喷管两相流“液包气”喷嘴气液质量比的临界点为0.057.结果表明:液气压力比随着硼的增大而减小;当w=0.057时,液气压力比为0.92;气体流量系数与气液质量比呈反比关系;“液包气”喷嘴单相雾化效果远差于两相时的雾化效果,且随着喷嘴液相压力的提高,雾化效果变好,但压力对雾化效果的影响越来越弱. 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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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
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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