Global kinetic models for the oxidation of NO on platinum under lean conditions

Different global kinetics for the oxidation of NO on platinum are compared in this work. The general form of the equation for the reaction rate is NO}^\alpha \cdot c_{O_2 }^\beta \cdot c_{NO_2 }^\gamma \cdot TD^\delta$" align="middle" border="0"> with NO_2 } \cdot c_{NO}^{ - 1} \cdot c_{O_2 }^{ - 0.50} \cdot K^{ - 1} } \right)$" align="middle" border="0"> . Furthermore steady-state and temperature-programmed experiments were performed. The best results of simulation coupled with parameter estimation were obtained using α = 0.28, β = 0.49, γ = 0 and δ = 1, along with an activation energy of 47.5 kJ mol⁻¹.     

Electrochemical promotion in a monolith electrochemical plate reactor applied to simulated and real automotive pollution control

The novel monolithic-type electrochemical promoted reactor (MEPR), filled with thick Rh and Pt coated films on thin yttria-stabilized zirconia (YSZ) plates, has been tested in simulated and real automotive exhaust gas. Ethylene oxidation and NO reduction by C₂H₄ in presence of oxygen were investigated in laboratory scale while the automotive bench testing was performed in the exhaust of a diesel engine. In all cases electropromotion was achieved, an advance which in addition to their compact and simple design, makes electropromoted units quite promising for automotive exhaust pollution control.     

硝酸钡特性对平面波发生器波形精度的影响

针对常用平面波发生器爆轰波形难以达到高平面度的问题,利用Ф100 mm×37°平面波发生器模具与炸药装药基础配方,就硝酸钡特性对平面波发生器波形精度的影响进行研究。结果表明:外形结构圆滑均匀的硝酸钡有利于在浇注产品中的堆积、沉降以及成分均匀性的提高;硝酸钡粒度分布及级配影响其在低速层结构中的含量和内部质量,合理调整粗、细品比例可制得波形差不超过0.08μs的平面波发生器。     

用WO3纳米材料制备矿业安全用NO2气体传感器

以钨酸钠为钨源、草酸和硫酸钾混合物为辅助剂,采用水热合成法在不同pH值条件下制备WO₃纳米材料,对反应产物的相组成和微观结构进行表征并考察其气敏性能。结果表明：产物形貌由pH=0.8时的无规则过渡到pH=1.0时的微米球,直至pH=1.6时的板状结构;在pH=1.0条件下获得具有最大比表面积的WO₃微米球,且形貌均匀一致;pH为1.0时合成的WO₃纳米材料对NO₂具有优良的气敏性能,在工作温度100 ℃时可获得最大气体灵敏度。对pH值为1.0时制备的WO₃纳米材料在工作温度100 ℃时进行不同浓度NO₂的响应-恢复特性曲线分析表明,气体灵敏度随着WO₃纳米材料比表面积和NO₂浓度的升高而增加。从材料微观结构设计角度出发来研制新型矿业安全用气体传感器是一种有效的方法。     

A novel method for locating the source of sustained oscillation in power system using synchrophasors data

Large interconnected power systems are usually subjected to natural oscillation (NO) and forced oscillation (FO). NO occurs due to system transient response and is characterized by several oscillation modes, while FO occurs due to external perturbations driving generation sources. Compared to NO, FO is considered a more severe threat to the safe and reliable operation of power systems. Therefore, it is important to locate the source of FO so corrective actions can be taken to ensure stable power system operation. In this paper, a novel approach based on two-step signal processing is proposed to characterize FO in terms of its frequency components, duration, nature, and the location of the source. Data recorded by the Phasor Measurement Units (PMUs) in a Wide Area Monitoring System (WAMS) is utilized for analysis. As PMU data usually contains white noise and appears as multi-frequency oscillatory signal, the first step is to de-noise the raw PMU data by decomposing it into a series of intrinsic mode functions (IMF) using Improved Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (ICEEMDAN) technique. The most appropriate IMF containing the vital information is selected using the correlation technique. The second step involves various signal processing and statistical analysis tools such as segmented Power Spectrum Density (PSD), excess kurtosis, cross PSD etc. to achieve the desired objectives. The analysis performed on the simulated two-area four-machine system, reduced WECC-179 bus 29 machine system, and the real-time power system PMU data set from ISO New England, demonstrates the accuracy of the proposed method. The proposed approach is independent of complex network topologies and their characteristics, and is also robust against measurement noise usually contained in PMU data.     

Experimental exploration on NO x diminution by the combined effect of antioxidant additives with SCR in a diesel engine powered by neem biodiesel

ABSTRACT

The use of biodiesel in diesel engines leads to the reduction of tail pipe emissions; But, several researchers portray that the use of biodiesel produces more NO_x pollution than diesel-fuelled engines, which is an hindrance for the scope of biodiesel usage. In this work, an experimental investigation of the combined effect of antioxidant additive added in the fuel as a fuel modification technique and SCR (selective catalytic reduction) as after a treatment technique on NO _x reduction in a neem biodiesel-powered compression ignition engine has been conducted. Results show that the antioxidant additive combined with the SCR technique reduces the NO _x emission significantly by 82% and there was a slight increase in UBHC and CO emission due to the addition of oxidation-suppressing additives with neem biodiesel and aqueous urea solution injection at the exhaust without a major drop in BTE and fuel consumption.     

SO_2促进的碳纳米管负载V_2O_5催化剂用于NH_3选择性还原NO

采用透射电镜(TEM)、X射线光电子能谱(XPS)、红外光谱(FT-IR)、SCR反应和程序升温脱附(TPD)等手段研究了碳纳米管(CNTs)担载的五氧化二钒(V2O5/CNTs)催化剂的形貌、表面形态以及SO2对选择催化NO还原活性的影响.结果表明,SO2对V2O5/CNTs催化剂的催化活性具有明显的促进作用,其促进作用源于SO2在催化剂表面的吸附.吸附的SO2主要位于碳表面而非钒表面,而且这种促进作用与V2O5和碳表面之间协同作用有关.     

On the promotional effect of Sn in Co–Sn/Al2O3 catalyst for NO selective reduction

NO reduction with propylene over Co/Al₂O₃ and Co–Sn/Al₂O₃ catalysts has been investigated. For the Co/Al₂O₃ catalyst, a calcination temperature exceeding 800°C led to a decrease of NO conversion. Calcination of the Co/Al₂O₃ catalyst at 1000°C resulted in the formation of -Al₂O₃ and Co₃O₄. The presence of 20% water vapor showed a significant shift for the maximum NO reduction temperature from 450 to 600°C over Co/Al₂O₃. It has been found that modification of 6 wt% Co/Al₂O₃ with 2 wt% Sn significantly enhanced the catalyst thermal stability and improved the inhibitory effect of water on NO conversion and reaction temperature. The promotional effect of Sn on the catalyst thermal stability was attributed to the suppression of the phase transformation from highly dispersed Co²⁺ species on -Al₂O₃ to -Al₂O₃ and Co₃O₄. The smaller influence of water vapor on NO reduction conversion and temperature over Co–Sn/Al₂O₃, compared to Co/Al₂O₃, was attributed to the dispersion effect of Sn species on Co²⁺ species as well as the involvement of Sn species in NO reduction at a relatively lower temperature. The synergetic effect between the octahedral Co²⁺ species and -alumina plays a significant role in the catalysis of NO selective reduction by C₃H₆.     

燃料型NO在对冲扩散火焰中的生成和还原特性

在CH4/空气对冲扩散火焰的燃料侧人为地掺混一定体积分数的NH3或HCN,数值模拟燃料型NO的生成和还原.模拟使用CHEMKIN和GRI3.0反应机理.结果表明,NO的生成和还原集中在火焰锋面,在火焰中心附近体积分数值最大.在燃料侧,NO的体积分数分布与燃料N的含量及NO初始体积分数值相关,而在空气侧主要受燃料N的影响.不加燃料N时,火焰中NO主要为热力型NO,受拉伸的影响大于燃料的影响;加入燃料N时,火焰中的NO主要为燃料型NO,受燃料体积分数的影响大于拉伸的影响,含量相同时NH3比HCN有更明显的促进NO生成的作用.     

含氨燃料预混火焰的层流火焰速度及NO排放特性

将甲烷或氢气与氨气共燃可以克服NH₃火焰的点火能量高、燃烧速度慢的缺点。为了解NH₃作为燃料的燃烧特性,对含NH₃燃料进行一维层流预混火焰数值模拟,研究其层流火焰速度及NO排放特性。采用文献中5个简化反应机理进行数值计算,发现Okafor机理模拟NH₃/CH₄/air火焰精度更高;Xiao机理模拟NH₃/H₂/air、NH₃/air精度适中,计算时间较短。此外,开展了当量比、燃料混合物组分比例、压力等参数对含NH₃燃料燃烧时烟气中NO浓度影响的研究。研究发现：含NH₃燃料燃烧时NO主要通过OH、H、O自由基和O₂分子的消耗而生成,主要通过与NH_i（i=0, 1, 2）自由基反应消耗;含NH₃燃料在富燃状态下燃烧可有效减少NO排放,但富燃燃烧效率低,可采用富燃-贫燃分级燃烧技术来提高燃烧效率,同时保持NO的低排放;掺有较多NH₃的含NH₃燃料在中高压下燃烧时可有效减少NO排放。