基于前馈补偿的模糊自适应解耦控制在单元机组协调控制系统研究

针对单元机组负荷控制对象延迟性、非线性和强耦合的特点,提出一种基于前馈补偿的模糊自适应解耦控制方案,以提高控制系统的调节能力。在300MW直流锅炉单元机组负荷控制对象动态数学模型基础上进行了动态特性研究和关联度分析。采用前馈补偿法设计了单元机组协调系统的解耦补偿器。仿真结果表明,前馈补偿解耦控制在单元机组协调控制系统中取得满意的效果;并且与常规PID控制相比,模糊自适应PID控制系统超调量降低,调节时间缩短,具有良好的控制性能。     

单元机组协调控制系统模糊自适应控制研究

单元机组协调控制系统的负荷控制对象存在耦合性和时变性,常规PID控制方案在负荷大范围变化时控制效果变差.为了提高协调控制系统的调节性能,采用了一种模糊自适应控制方案.基于300MW直流锅炉单元机组不同工况下采集的数据,建立了机组在210MW和270MW工况下的负荷控制对象动态数学模型,并进行了动态特性分析;基于常规PID协调控制方案,设计了一种模糊自适应PID控制器,可以自动调整控制器参数以适应工况的变化.锅炉控制器和汽轮机控制器均采用模糊自适应PID控制器.仿真结果表明,单元机组协调控制系统模糊自适应控制与常规PID控制相比,超调量降低,调节时间缩短,抗干扰能力和负荷适应能力增强.     

基于动态论域的循环流化床锅炉燃烧系统的模糊自适应PID控制

基于循环流化床(CFB)锅炉燃烧系统非线性、强耦合、大滞后等特点,针对床温与主蒸汽压力强耦合控制难点,设计前馈补偿解耦控制器降低二者耦合度,在对解耦后的独立回路采用模糊自适应PID控制的基础上,引入动态论域的思想,利用随工况自适应变化的伸缩因子调整模糊论域范围,对PID参数Kp、Ki、Kd进行更精准的在线整定.以某CFB锅炉燃烧系统为研究对象,进行动态论域模糊自适应PID控制仿真试验.结果 表明:相比传统模糊PID控制,燃烧系统主要参数通过动态论域模糊自适应PID控制的动态超调量减小5％～10％,动态响应速度提高近30％;动态论域模糊自适应PID控制方法自适应性和鲁棒性良好,可满足实际热工现场需求.     

风电机组模糊PI控制与前馈控制相结合的变桨控制

针对经典PID变桨距控制器超调量大、波动剧烈等缺陷,提出了一种采用模糊PI控制与前馈控制相结合的控制器来控制浆距角,进而使机组功率稳定在额定功率附近的控制思路。通过对某1.5MW风力发电机组进行仿真,结果表明,该控制器控制效果优于经典PID变桨距控制器。     

采用神经网络改善式循环柴油机的供氧控制

在氧气反馈调节的基础上,不依赖系统模型,借助神经网络的构成前馈控制器,以反馈输出引导网络权值及输出的调整,使网络逐步学成前馈补偿功能,并最在控制中占据主导地位,实现对负荷扰动的补偿。仿真结果表明,采用这一复合控制系统能有效地改善氧气控制的动态特性。     

火力单元机组的前馈模糊神经非模型协调控制

提出了一种前馈模糊神经非模型协调控制方法。使用该方法设计的非模型控制器由模糊控制器和神经元控制器复合构成 ,针对某单元机组进行了实例仿真试验。结果表明 :这种新的控制方法不仅具有满意的控制性能 ,而且具有强鲁棒性和抗干扰性能 ,它显著地提高了协调控制系统在机组负荷及工况变化时的鲁棒性和控制品质。这种新的控制系统设计方法非常简单 ,不需要解耦补偿 ,而且控制器参数选择不严格 ,可方便地用于工业控制。图 7参 9     

基于模型的发动机空燃比控制策略研究与仿真

空燃比的精确控制是现代车用汽油机控制最为关键的技术。发动机平均值模型由于其模型简单、计算时间短、使用方便,且能满足控制设计的要求而被广泛应用。基于模型的空燃比控制技术是当前国内外研究的热点。在建立某型汽油发动机空燃比平均值数学模型的基础上设计了稳态工况下模糊自适应PID控制器,并与传统的PID控制器空燃比控制效果进行了对比。设计了瞬态工况下燃油前馈补偿控制器并进行仿真。仿真结果表明在稳态工况下模糊自适应PID控制策略不仅能够满足实际控制需要,而且比传统的PID控制策略控制效果更好。前馈补偿控制策略能满足瞬态工况下空燃比的控制要求。     

基于CMAC神经网络前馈控制的柴油发电机组转速控制研究

提出了一种小脑模型神经网络(CMAC)前馈负荷控制的柴油机调速策略,利用传统PID来实现反馈控制,保证船用柴油发电机组调速系统的稳定性并抑制扰动,在CMAC神经网络输入信号中加入负荷电流和转速指令,实现对控制器的前馈控制,确保系统的控制响应速度,提高控制精度。经过仿真后,使用MicroAutoBox控制器进行了D6114发电机组配机试验。试验结果表明:机组具有良好的动静态特性,标定负载突变超调6.2%,稳定时间2.8s,完全满足二级电站对柴油机调速系统的要求。     

为力单元机组的前馈模糊神经非模型协调控制

提出了一种前馈模糊神经非模型协调控制方法。使用该方法设计的非模型控制器由模糊控制器和神经元控制器复合构成，针对某单元机组进行了实例仿真试验。结果表明：这种新的控制方法不仅具有满意的控制性能，而且具有强鲁棒性和抗干扰性能，它显著地提高了协调控制系统在机组负荷及工况变化时的鲁棒性和控制品质。这种新的控制系统设计方法非常简单，不需要解耦补偿，而且控制器参数选择不严格，可方便地用于工业控制。图７参９     

电站锅炉汽包水位的CMAC神经网络与PID复合控制

提出了电站锅炉汽包水位系统的CMAC神经网络与PID的复合控制策略。将蒸汽流量信号引入到CMAC神经网络中，考虑负荷变化对汽包水位的影响，使其具有前馈补偿能力，以消除“虚假水位”现象。总的控制输出由CMAC神经网络的输出和一个常规PID控制器的输出通过变参数加权综合后作用于被控对象，这样保证在控制初期以及对象特性变化的情况下系统仍然具有良好的调节品质。仿真试验结果表明了该控制策略的有效性和实用性。图6参6     

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.