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压气机特性的系数拟合法 总被引:3,自引:1,他引:2
本文提出了一种压气机特性的拟合方法,以利于燃机变工况性能计算。利用压气机特性曲线的形状相近性及各曲线位置和形状随转速渐进变化的规律,以先后两步一元拟合过程来构成特性参数(如压比或效率),以其它二特性参数(如转速和流量)表示的代数多项式,从而确立了特性参数之间的函数关系,使变工况计算得以简化和提高精度。方法实用,精度较高。本文还分析了拟合过程中若干应注意的问题。 相似文献
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为克服传统方法对压气机特性线内插与外推预测性能模拟精度不高的问题及准确实现压气机在变工况条件下基于部件特性线行为的燃气轮机的热力学仿真计算,一种基于蜜蜂采蜜行为的人工蜂群(Artificial Bee Colony, ABC)优化支持向量机 (Support Vector Machine, SVM)参数的方法被提出并用于压气机特性线的表达。从泛化精度及计算耗时的角度,与常用的BP算法、粒子群算法和网格寻优法的SVM模型相比较。同时,为验证训练样本容量对实验结果的影响,减少样本集数量,对比同一转速下不同算法的预测性能曲线及柱状残差图。应用分析表明,不同转速下基于ABC算法优化的SVM模型在压气机特性线的表达上具有更佳的预测精度和计算实时性,并且,该方法不随样本容量波动而精度失准,具有良好的鲁棒性。 相似文献
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主流预混式燃气发动机空燃比控制依赖混合燃气流量估计。为克服既有估计技术弊端,参考控制阀流量基本模型,将估计位置前移至节气门处,使混合燃气流量估计值更加准确、及时地反映转速或负荷调节需要。分析节气门工作条件和流经介质,依据控制阀标准定义简明的广义系数,并提出变量优选和数据拟合的广义系数标定方法,完善节气门混合燃气流量估计模型应用模式。通过预混式燃气发动机实测数据分析计算,验证节气门流量模型估计精度。通过在转速波动期间两种模型估计的混合燃气流量对比表明,节气门流量模型估计值与节气门开度是同步变化的,并超前于进气门均值模型估计值。 相似文献
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为了提升低转速工况下压气机的气动性能,采用人工神经网络与遗传算法相结合的优化方法对某单级离心压气机离心叶轮的弯特性进行优化计算。利用NUMECA软件对该离心压气机进行了不同转速的数值模拟,得到压气机不同工况下的气动性能。通过设置不同控制参数和曲线形式对离心叶轮叶片进行参数化拟合,以8个改变叶片弯特性的参数为自由参数进行了叶型优化设计,最终得到了优化后的叶轮叶片。结果表明:优化后在低转速的设计工况下离心压气机压比增加了4.69%,稳定裕度拓宽了17.41%。 相似文献
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为了实现对轴流压气机气动性能的准确预测,基于平均流线法建立了多级轴流压气机一维气动性能预测方法,编制了相应的Matlab程序,该方法允许针对不同类型压气机选择适用的经验模型。通过计算得到了某四级亚音速轴流压气机和某八级高速轴流压气机的气动性能,对比分析发现,一维性能预测结果与实验/三维CFD模拟结果吻合较好,效率与压比计算偏差均保持在较小范围内,预测结果精度较高。为进一步提高压气机气动性能预测的准确性,发展了一种经验模型自动校准方法,采用该方法对选取的四级亚音速轴流压气机和八级高速轴流压气机模型进行校准,校准后对各转速下气动性能的预测精度均有所提高。研究工作表明,所建立的多级轴流压气机一维气动性能预测方法以及模型自动校准方法具有一定的准确性和可靠性。 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