室内沙发燃烧的全尺寸实验和数值模拟

在ISO9705标准的全尺寸燃烧间(3.6m×2.4m×2.4m)内对单人沙发进行全尺寸火灾实验模拟,测量了沙发燃烧的热释放速率、室内烟气温度分布等火灾参数,分析比较了它们之间的关系,同时也用数值模拟的方法对聚氨酯(PUF)材料燃烧占支配地位的沙发燃烧过程进行了模拟,计算得到了沙发燃烧的热释放速率、室内温度场分布和烟气中性面高度.结果表明,计算得到的热释放速率、温度分布和烟气中性面高度与实验测得的结果比较吻合.     

轮胎的全尺寸火灾实验研究

介绍ISO ROOM火灾实验方法及其对轮胎火灾的热释放速率的测试与研究,研究了热释放速率与其他动力学相关参数的关系,通过在全尺寸多功能热释放速率实验台对不同数目轮胎的燃烧特性进行研究类比,得出轮胎燃烧的特性。结果表明,轮胎不易着火,但一旦被引燃,其火灾规模十分巨大;且火灾极容易因为轮胎液体熔融物的流淌而蔓延;同时,轮胎火灾产生的有毒烟气也相当浓密;控制轮胎火灾的最佳时机是在其火灾的早期。因此轮胎火灾的探测工作是十分重要的。     

热塑性材料与底板间距对其燃烧行为的影响

为研究热塑性材料下端与底板间距对其熔融燃烧行为的影响,选择 6 mm厚和 4 mm厚 PP 板材作为研究对象,在 ISO 9705 燃烧室内进行了12组大尺寸燃烧实验,分别考虑了0cm、5 cm、10cm、15 cm、25 cm和35 cm不同间距的工况.实验过程中测量了热释放速率、消光系数、CO 体积分数以及温度场等火灾动力学参数.实验结果表明,热塑性材料的下边缘与底板的间距对火灾增长速率影响很大,但是对热释放速率峰值的影响不明显;随着间距的增加,壁面火和油池火之间的相互影响作用逐渐减弱,且当间距增加至 15 cm 以上时,各组实验的燃烧过程没有明显的区别.     

细水雾对油池火热释放速率影响的初步研究

热释放速率是反映火场规模与发展的最重要的基础参数，利用ISO9705实验台进行细水雾灭火有效性的影响因素及相关机理研究，不仅能营造出一个真实的室内火灾环境，而且能够得到火场的热释放速率。对汽油池火的初步实验表明：热释放速率曲线能直接反映出细水雾对火源的作用；细水雾作用下燃烧总的热释放量减少很大；开启水雾的时间不同，细水雾对热释放速率峰值的削减程度不同。     

胶合板室内火灾行为全尺寸实验研究与模拟分析

选择4种典型的胶合板作为研究对象,即三厘板、五厘板、九厘板和十二厘板,在ISO 9705标准的全尺寸燃烧间(3．6m×2．4m×2．4m)内对其进行全尺寸火灾实验模拟,从热释放速率方面研究了胶合板的火灾行为并获得了室内轰燃发生的时间,分析比较了材料厚度对于胶合板室内火灾过程的影响．同时将顺流(Wind-Aided)火蔓延的理论引入到室内墙角火蔓延中,对胶合板的表面火蔓延进行模拟,得到了胶合板室内火灾的热释放速率和轰燃发生时间．通过比较发现,五厘板、九厘板和十二厘板的计算结果与实验测量结果吻合得比较好,三厘板的计算结果与实验测量结果吻合得比较差些．     

10 mm钢化玻璃全尺寸火灾实验

在ISO 9705标准燃烧室内,位于室中央,采用不同规模的油池火,对常用的厚10mm钢化玻璃窗的火灾特性进行了全尺寸火灾实验研究,完成了8组实验.给出了包括热释放速率、热辐射通量、室内和玻璃附近气体温度分布、玻璃暴露表面温度、玻璃遮蔽表面温度、玻璃首次破裂时间和破裂模式等实验数据.分析了玻璃破裂与其表面温度分布等参数的关系,研究结果可为性能化防火设计中评估钢化玻璃发生破裂和失效提供参考.     

本色和炭化竹地板燃烧特性的对比分析

为了研究竹地板的燃烧特性,以锥形量热仪为研究手段,对本色和炭化胶合竹地板、本色和炭化重竹地板这4种竹地板的燃烧特性进行了对比研究.结果表明,与本色胶合竹地板相比,炭化胶合竹地板的点燃时间提前了3,s;热释放速率、有效燃烧热、总热释放量和质量损失速率的峰值到达时间均提前了2,min,热释放速率、有效燃烧热和质量损失速率的峰值均上升,总热释放量的峰值下降;最终成炭率有所提高.与本色重竹地板相比,炭化重竹地板的点燃时间没有变化;热释放速率、有效燃烧热、总热释放量和质量损失速率的峰值到达时间没有变化,但是峰值均有所下降;最终成炭率有所提高.炭化胶合竹地板的阻燃性能弱于本色胶合竹地板,炭化重竹地板的阻燃性能优于本色重竹地板;总体上,重竹地板的阻燃效果优于胶合竹地板.     

4 mm单层浮法玻璃全尺寸火灾实验研究

在ISO9705标准燃烧室内,对普通4 mm厚浮法玻璃的火灾特性进行了实验研究.完成了4组单层玻璃窗暴露于室中央不同规模油池火的全尺寸火灾实验,给出了包括热释放速率、热辐射通量、室内和玻璃附近气体温度分布、玻璃暴露表面温度、玻璃遮蔽表面温度、玻璃首次破裂时间和破裂模式等实验数据,为性能化防火设计中,评估单层玻璃发生破裂和失效提供参考.     

全尺寸墙角火实验中木工板表面火蔓延研究

对木工板表面火蔓延进行了全尺寸墙角火实验研究，实验是在符合ISO9705标准的ISO ROOM全尺寸实验装置内进行．通过测量材料表面的温度来研究火蔓延的情况，同时还将火蔓延与火灾过程中的重要参数如热释放速率、热流密度和室内温度等进行了比较，分析了相互之间的关系．研究结果为火灾安全设计和计算机数值模拟提供了实验依据．     

细水雾作用下火灾烟气典型特性参数的变化规律

利用ISO 9705全尺寸多功能热释放速率测试仪研究细水雾作用下火灾烟气的消光系数、质量密度及辐射热通量等特性参数的变化规律,通过改变细水雾工作压力、喷头种类和喷头数量等参数研究雾滴粒径、喷雾强度等对烟气特性参数的影响规律.确定了受限空间通风助燃和熄灭火焰的临界速率.实验发现,火源热释放速率是影响烟气特性参数变化规律的主要内在因素.研究结果为细水雾技术用于火灾烟气抑制提供了科学的参考依据.     

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.     

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.     

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.     

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.     

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。     

Biohydrogen production by Anabaena sp. PCC 7120 wild-type and mutants under different conditions: Light, nickel, propane, carbon dioxide and nitrogen

Increasing awareness of environmental problems caused by the current use of fossil fuel-based energy, has led to the search for alternatives. Hydrogen is a good alternative and the cyanobacterium Anabaena sp. PCC 7120 is naturally able to produce molecular hydrogen, photosynthetically from water and light. However, this H₂ is rapidly consumed by the uptake hydrogenase.This study evaluated the hydrogen production of Anabaena sp. PCC 7120 wild-type and mutants: hupL⁻ (deficient in the uptake hydrogenase), hoxH⁻ (deficient in the bidirectional hydrogenase) and hupL⁻/hoxH⁻ (deficient in both hydrogenases) on several experimental conditions, such as gas atmosphere (argon and propane with or without N₂ and/or CO₂ addition), light intensity (54 and 152 ??Em⁻²s⁻¹), light regime (continuous and light/dark cycles 16 h/8 h) and nickel concentrations in the culture medium.In every assay, the hupL⁻ and hupL⁻/hoxH⁻ mutants stood out over wild-type cells and the hoxH⁻ mutant. Nevertheless, the hupL⁻ mutant showed the best hydrogen production except in an argon atmosphere under 16 h light/8 h dark cycles at 54 ??Em⁻²s⁻¹ in the light period, with 1 ??M of NiCl₂ supplementation in the culture medium, and under a propane atmosphere.In all strains, higher light intensity leads to higher hydrogen production and if there is a daily 1% of CO₂ addition in the gas atmosphere, hydrogen production could increase 5.8 times, related to the great increase in heterocysts differentiation (5 times more, approximately), whereas nickel supplementation in the culture medium was not shown to increase hydrogen production. The daily incorporation of 1% of CO₂ plus 1% of N₂ did not affect positively hydrogen production rate.     

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.     

Investigation of the thermodynamic and kinetic properties of La–Fe–B system hydrogen-storage alloys

La–Fe–B hydrogen-storage alloys were prepared using a vacuum induction-quenching furnace with a rotating copper wheel. The thermodynamic and kinetic properties of the La–Fe–B hydrogen-storage alloys were investigated in this work. The P–C–I curves of the La–Fe–B alloys were measured over a H₂ pressure range of 10⁻³ MPa to 2.0 MPa at temperatures of 313, 328, 343 and 353 K. The P–C–I curves revealed that the maximum hydrogen-storage capacity of the alloys exceeded 1.23 wt% at a pressure of approximately 1.0 MPa and temperature of 313 K. The standard enthalpy of formation ΔH and standard entropy of formation ΔS for the alloys' hydrides, obtained according to the van't Hoff equation, were consistent with their application as anode materials in alkaline media. The alloys also exhibited good absorption/desorption kinetics at room temperature.     

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.