基于集合卡尔曼滤波的实时校正技术在流域洪水预报中的应用

为提高金华江流域实时洪水预报精度，建立了耦合MIKE 11 NAM与MIKE 11 HD的流域洪水预报模型和基于集合卡尔曼滤波的实时校正模型，实现了金华江流域洪水预报实时校正。流域洪水预报模型对流域内主要站点的模拟效果较好，洪水流量和洪水水位模拟精度较高；实时校正模型在预见期10 h以内，校正效果随预见期增加而降低，在预见期前期可有效降低预报误差。整体上，建立的流域洪水预报模型和基于集合卡尔曼滤波的实时校正模型能够满足金华江流域洪水预报应用要求。     

无调控小水库群对寿昌江流域洪水预报的影响

为研究小型水库群对流域洪水过程的影响程度,在三水源新安江模型的基础上,引入自溢式虚拟水库对产汇流环节进行改进,构建了受无调控小水库群影响的流域洪水预报模型。将改进的新安江模型应用于流域模拟中,对比分析改进、无改进新安江模型模拟结果表明,改进的新安江模型对于寿昌江流域具有良好的适应性,并能显著提高洪水模拟精度。研究成果可为无调控小水库群影响的流域洪水预报提供参考。     

考虑参数线型优选的俄罗斯洪水模拟模型应用研究

基于俄罗斯洪水随机模拟模型,采用线型优化技术,选用淮河流域上游的息县站构建模型模拟,统计检验了建模参数、时段量,并与传统季节性自回归一阶模型进行模拟比较.结果表明,线型优选后的俄罗斯模型模拟效果好、精度高、适用性强,在模拟多场洪水方面优于传统模型.     

洪水随机模拟中模型不确定性的影响研究

依据漳河流域岳城水库汛期日流量过程资料,分别建立了反映洪水随机变化特性的自回归模型和解集模型,应用统计试验的方法研究了随机模拟中模型不确定性对模拟入库洪水的影响,并通过综合分析影响模拟精度的原因,给出了未来洪水随机模拟时模型选择的建议.结果表明,典型解集模型的模拟效果明显优于自回归模型.     

考虑人类活动影响的改进新安江模型水文预报

为定量描述小水库和小塘坝等人造水利工程对流域产汇流过程的影响,以白山流域为例,引入自由虚拟水库的概念,建立了改进的三水源新安江模型,并应用于八场洪水的预报模拟,对原始和改进的新安江模型的模拟结果进行对比分析。结果表明,小水库和小塘坝对洪峰流量具有滞后作用,改进的新安江模型对白山流域产汇流的模拟较原始三水源新安江模型效果好。     

HSPF模型在渌水流域洪水预报中的应用

近年来,流域暴雨洪水灾害事件频发,准确、可靠的洪水预报是有效预防和抵御山洪灾害的重要措施。以渌水流域为研究区域,构建HSPF半分布式模型,选取流域2013～2020年洪水资料中代表性较好的场次洪水完成模型参数的率定和验证,并采用确定性系数、相对误差等指标进行洪水模拟精度评价。结果表明,该模型在渌水流域场次洪水模拟中表现良好,15场洪水模拟的峰现时间、洪峰流量合格率分别为100.0%、80.0%,洪量及径流深的模拟合格率均为93.3%,确定性系数均值为0.80,总体预报精度达到乙级,说明构建的HSPF洪水预报模型在渌水流域具有较好的适用性,可为该地区的洪水预报提供依据。     

Tank模型在中小河流洪水气象风险预警中的应用

结合蒲河流域的气候条件和洪水特性，利用Tank模型模拟了该流域2019～2020年10次暴雨洪水过程，构建了适用于该流域的概念性暴雨致洪气象风险预警模型，并进行仿真模拟和精度评定。结果表明，改进后的水箱模型能直观地模拟出石角水文站不同时间尺度、不同基础水位条件下的水位变化过程曲线，能减少面雨量阈值的不确定性，预报精度为乙等；根据模拟结果逐级发布气象风险预警，技巧评分和命中率为100%;平均预警发布时间提前3 h以上，可代入预测降水进一步延长洪水预报预见期。     

变化环境下非一致性极端水文事件的模拟及预测

在气候变化与高强度人类活动综合作用下,洪水事件的时空格局发生了变异,洪水序列的不一致性导致流域洪水设计值难以界定,应对难度加大。为研究变化环境下洪水特征的非一致性,更好地估计洪水特征变化,以汉江流域为例,运用GAMLSS模型,以时间、气象因素(气温和降水)和人类活动(水库指标)为协变量,对汉江流域1951～2005年的最大洪峰流量序列进行非一致性频率分析,并基于CMIP5模式下两种典型浓度路径RCP2.6、RCP4.5情景下的输出数据,利用率定好的最优非一致模型模拟未来变化环境对汉江流域最大洪峰流量的影响。结果表明,构建的具有物理意义的非一致性模型可较好地模拟汉江流域洪水过程的非一致性特征,且该模型在一定程度上能适应环境变化;在RCP2.6、RCP4.5两种情景下,汉江流域的年总降水和年均气温在2006～2100年呈上升趋势;在不考虑汉江流域未来水利工程继续建设的情况下,气候变化在未来将会导致流域洪水风险进一步增加。     

基于改进双超模型的采空区特殊下垫面径流模拟

针对长期大规模开采煤炭资源导致许多地区形成了煤矿采空区,改变了传统的水文过程的问题,通过室内试验,将采空区对径流过程的影响参数化,并将参数引入传统双超模型,建立适用于采空区特殊下垫面改进的双超模型,并以静乐水文站控制流域为例,选取了该区域23场次洪水,分别用改进前传统双超模型与改进后的双超模型进行模拟。结果表明,在采空区出现前,传统双超模型的模拟结果较好,模拟合格率达90.9%;采空区出现后,如果暴雨中心位于煤矿采空区附近,那么采空区将会严重影响降雨径流的产生过程,从而导致传统双超模型的模拟精度大大降低,模拟合格率为0。采用改进后的双超模型模拟采空区出现后的12场次洪水的精度得到了显著提升,模拟合格率达75%。     

改进的TOPMODEL在流域洪水模拟中的应用研究

将具有流域分布特征的Green-Ampt下渗曲线引入TOPMODEL中,并在TOPMODEL的结构中增加超渗产流模块,将TOPMODEL结构中的一层蒸发模块改进为二层蒸发模块。根据Internet提供的土壤组成和土地覆盖资料,提出了计算植被根系层最大持水量参数的方法。分别用原始的、改进后的TOPMODEL和三水源新安江模型对黄河渭河流域的秦渡镇流域洪水资料进行了验证和应用。计算结果表明,参数植被根系层最大持水量在流域分布上是不均匀的,改进后的TOPMODEL可取得更好的洪水模拟结果。     

Performance assessment of some ice TES systems

In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efficiencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working fluid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efficiencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efficiencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efficiencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

Exergetic evaluation of 5 biowastes-to-biofuels routes via gasification

This paper presents the exergy analysis results for the production of several biofuels, i.e., SNG (synthetic natural gas), methanol, Fischer–Tropsch fuels, hydrogen, as well as heat and electricity, from several biowastes generated in the Dutch province of Friesland, selected as one of the typical European regions. Biowastes have been classified in 5 virtual streams according to their ultimate and proximate analysis. All production chains have been modeled in Aspen Plus in order to analyze their technical performance. The common steps for all the production chains are: pre-treatment, gasification, gas cleaning, water–gas-shift reactions, catalytic reactors, final gas separation and upgrading. Optionally a gas turbine and steam turbines are used to produce heat and electricity from unconverted gas and heat removal, respectively. The results show that, in terms of mass conversion, methanol production seems to be the most efficient process for all the biowastes. SNG synthesis is preferred when exergetic efficiency is the objective parameter, but hydrogen process is more efficient when the performance is analyzed by means of the 1st Law of Thermodynamics. The main exergy losses account for the gasification section, except in the electricity and heat production chain, where the combined cycle is less efficient.     

液压系统常见的故障诊断及处理

任何工程机械式液压设备使用时出现故障是不可避免的。但是怎样确定故障的原因及找到好的解决方法，这是使用者最关心的问题。讲述了液压系统常见的故障及其排除方法。     

Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions

Natural gas is a fossil fuel that has been used and investigated extensively for use in spark-ignition (SI) and compression-ignition (CI) engines. Compared with conventional gasoline engines, SI engines using natural gas can run at higher compression ratios, thus producing higher thermal efficiencies but also increased nitrogen oxide (NO_x) emissions, while producing lower emissions of carbon dioxide (CO₂), unburned hydrocarbons (HC) and carbon monoxide (CO). These engines also produce relatively less power than gasoline-fueled engines because of the convergence of one or more of three factors: a reduction in volumetric efficiency due to natural-gas injection in the intake manifold; the lower stoichiometric fuel/air ratio of natural gas compared to gasoline; and the lower equivalence ratio at which these engines may be run in order to reduce NO_x emissions. High NO_x emissions, especially at high loads, reduce with exhaust gas recirculation (EGR). However, EGR rates above a maximum value result in misfire and erratic engine operation. Hydrogen gas addition increases this EGR threshold significantly. In addition, hydrogen increases the flame speed of the natural gas-hydrogen mixture. Power levels can be increased with supercharging or turbocharging and intercooling. Natural gas is used to power CI engines via the dual-fuel mode, where a high-cetane fuel is injected along with the natural gas in order to provide a source of ignition for the charge. Thermal efficiency levels compared with normal diesel-fueled CI-engine operation are generally maintained with dual-fuel operation, and smoke levels are reduced significantly. At the same time, lower NO_x and CO₂ emissions, as well as higher HC and CO emissions compared with normal CI-engine operation at low and intermediate loads are recorded. These trends are caused by the low charge temperature and increased ignition delay, resulting in low combustion temperatures. Another factor is insufficient penetration and distribution of the pilot fuel in the charge, resulting in a lack of ignition centers. EGR admission at low and intermediate loads increases combustion temperatures, lowering unburned HC and CO emissions. Larger pilot fuel quantities at these load levels and hydrogen gas addition can also help increase combustion efficiency. Power output is lower at certain conditions than diesel-fueled engines, for reasons similar to those affecting power output of SI engines. In both cases the power output can be maintained with direct injection. Overall, natural gas can be used in both engine types; however further refinement and optimization of engines and fuel-injection systems is needed.     

Economie d'énergie en trigénération

Trigeneration is defined as the production of three useful forms of energy—heat, cold and power—from a primary source of energy such as natural gas or oil. For instance, trigeneration systems typically produce electrical power via a reciprocating engine or gas turbine and recover a large percentage of the heat energy retained in the lubricating oil, exhaust gas and coolant water systems to maximize the utilization of the primary fuel. The heat produced can be totally or partially used to fuel absorption refrigerators. Therefore, trigeneration systems enjoy an inherently high efficiency and have the potential to significantly reduce the energy-related operation costs of facilities. In this paper, we describe a model of characterization of trigeneration systems trough the condition of primary energy saving and the quality index, compared to the separate production of heat, cold and power. The study highlights the importance of the choice of the separate production reference system on the level of primary energy saving and emissions reduction.     

Mineralogical characterization of the intraseam layers of Lofoi lignite deposits in Florina basin (western Makedonia,northwest Greece)

The mineralogical composition of intraseam layers from Lofoi lignite deposits (northwest Greece) is the subject of the present study. The samples were examined by means of X-ray diffraction (XRD), thermo-gravimetric (TG/DTG) and differential thermal analysis (DTA), and Fourier transform infrared (FT-IR) spectrometry. The clay minerals prevail in most samples, with illite-muscovite being the dominant phase, and kaolinite and chlorite being the other major clay components. No smectite was found. Quartz and feldspars, dominate in two cases. The studied materials are characterized as clays to clayey sands, showing significant similarities with the intraseam layers of the adjacent Achlada lignite deposits.     

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.     

Innovative methodologies in renewable energy: A review

This paper is concerned with innovative approaches to renewable energy sources computation methodologies, which provide more refined results than the classical alternatives. Such refinements provide additional improvements especially for replacement of fossil energy usages that emit greenhouse gas (GHG) into the atmosphere leading to climate change impact. Current knowledge gap among each renewable energy source calculation is rather missing fundamentals of plausible, rational, and logical explanations for the interpretation of results. In the literature, there are rather complicated and mechanically applicable methodologies, which require input and output measurement data match with missing physical explanations. The view taken in this review paper is to concentrate on quite plausible, logical, rational, and effectively applicable innovative energy calculation methodologies with simplistic fundamentals. For this purpose, a set of renewable energy methodological approaches is revisited with their innovative structures concerning solar, wind, hydro, current, and geothermal energy resources. With the increase in the renewable energy utilizations to combat the undesirable impacts of global warming and climate change, there is a need for better models that will include physical environmental conditions and data properties in the probabilistic, statistical, stochastic, logical, and rational senses leading to refined and more reliable estimations with application examples in the text. Finally, new research directions are also recommended for more refined innovative energy system calculations.     

Decomposition of limestone in a solar reactor

The thermal decomposition of limestone has been selected as a model reaction for developing and testing an atmospheric open solar reactor. The reactor consists of a cyclone gas/particle separator which has been modified to let the concentrated solar energy enter through a windowless aperture. The reacting particles are directly exposed to the solar irradiation. Experimentation with a 60 kW reactor prototype was conducted at PSI's 90m² parabolic solar concentrator, in a continuous mode of operation. A counter-current flow heat exchanger was employed to preheat the reactants. Eighty five percent degree of calcination was obtained for cement raw material and 15% of the solar input was converted into chemical energy (enthalpy).The technical feasibility of the solar thermal decomposition of limestone was experimentally demonstrated. The use of solar energy as a source for high-temperature process heat offers the potential of reducing significantly the CO₂ emissions from lime producing plants. Such a solar thermochemical process can find application in sunny rural areas for avoiding deforestation.