锅炉低氮燃烧改造对煤灰熔融特性影响

为研究低氮燃烧改造对锅炉主燃区气氛以及对煤灰熔融特性的影响规律,首先对2台完成低氮燃烧改造的燃煤锅炉主燃区烟气成分进行测试,得出烟气成分分布范围;然后搭建一套气氛可调节的煤灰熔点测试系统,依据炉膛烟气成分测试结果,配制相应模拟气氛进行灰熔点测试,研究气氛变化对煤灰熔融特性的影响规律。结果表明:锅炉低氮燃烧改造后,主燃区CO体积分数由2%~3%上升至7%~15%,燃烧气氛由弱还原性气氛转变为强还原性气氛,煤灰熔点明显下降。     

直驱永磁电机绕组匝间短路故障研究

直驱永磁电机包括旋转结构与直线结构,其电磁负荷高,直接与负载相连接,电机的可靠性运行对系统安全非常重要,绕组匝间短路故障是其中一种重要的影响因素。本文以直驱永磁直线电机（PMLM）为研究对象,基于有限元方法分析了初级绕组匝间短路故障对电机性能的影响。首先介绍了直驱PMLM的拓扑结构与气隙磁场,分析了匝间短路对相电流与短路电流的影响,然后计算了短路匝数、短路位置对电机性能的影响,包括三相电流、短路电流、平均推力与推力波动,最后总结了匝间短路故障对PMLM性能的影响,为直驱系统的故障诊断与容错运行提供理论支持。     

Combination of a non-thermal plasma and a catalyst for toluene removal from air: Manganese based oxide catalysts

A series of manganese based catalysts have been tested in a combined plasma-catalyst reactor in the reaction of toluene removal from air. In the standard conditions (toluene = 240 ppm, energy density = 172 J/L, 1 g of catalyst, 315 mL/min), the best catalyst (manganese oxide supported on active carbon) is able to transform 55% of the toluene into carbon oxides. According to the study of the reaction mechanism, it appears that the toluene is oxidized both in-plasma by short-lived species generated by plasma and in post-plasma on the catalyst surface by the ozone formed in the plasma, the reaction on the catalyst being more selective in carbon dioxide formation than the reaction in plasma. We have shown that the toluene conversion increases when the toluene concentration in air decreases. A model able to describe the behavior of the plasma reactor and the plasma-catalyst reactor is proposed.     

Visual measurement and characterisation of quasi-volcanic corrosion at alumina ceramic-oxides melt-air interface

Alumina ceramics undergo quasi-volcanic corrosion at the melt-air interface, which causing severe damage. However, the growth behaviour of quasi-volcanic corrosion requires further investigation. Here, high-temperature visualisation technology was used to characterise and quantify quasi-volcanic corrosion at the melt-air interface at 1600 °C. An evolution model of the corrosion peak area with changes in the melt compositions was also established. The formation and growth of the corrosion peak is closely related to the temperature, soaking time and the dissolution reaction; quasi-volcanic corrosion occurs at ≥ 1600 °C, and is visibly different from normal corrosion at a three-phase interface. The peak height exhibits competitive evolution with the full width at half maximum of the peak. The obtained evolution of the corrosion peak and relationship between the corrosion area and the C/S ratios of the melts can support for prolonging the service life of alumina ceramics.     

Effect of grain size and orientation degree on thermal shock resistance of BN-matrix textured ceramics under cyclic thermal shock

Hexagonal boron nitride (h-BN) has a typical two-dimensional flake structure, so the anisotropy of h-BN grains caused by directional arrangement cannot be ignored when studying the thermal vibration resistance of materials under thermal cycling. In this paper, h-BN-matrix textured ceramics prepared with different holding time were selected, and the effects of thermal vibration temperature difference and thermal cycles on the phase and thermal vibration resistance of h-BN-matrix textured ceramics were studied. The results show that under the condition of high-frequency thermal cycling, the residual strength ratio (RSR) of BN-based textured ceramics is closely related to the holding time and showing obvious anisotropy. At the same time, there is a thermal vibration temperature range in which the internal stress will change from relief to re-accumulation.     

气体渗氮对F92钢在700 ℃空气中氧化行为的影响

利用扫描电镜(SEM)、能谱分析(EDS)、X射线衍射分析(XRD)研究了F92钢供货态和渗氮后在700 ℃静态空气中的高温氧化行为,阐述了气体渗氮对F92钢氧化行为的影响。研究表明,渗氮后F92钢表面形成了氮的过饱和膨胀铁素体相和CrN相。供货态F92钢表面生成了薄且致密的(Cr, Fe, Mn)₂O₃和MnCr₂O₄氧化层,具有良好的保护性。此外,供货态F92钢表面有两种瘤状氧化物生成,一种由连续的Fe₂O₃构成,另一种独立的由外层Fe₂O₃和内层富Cr的(Cr, Fe, Mn)₃O₄组成。渗氮加剧了F92钢的氧化,基体内部观察到了内氧化区。渗氮试样表面氧化膜呈双层结构,其中,外层为Fe₂O₃,内层为富Cr的Fe-Cr氧化物。F92钢渗氮过程中形成的膨胀氮过饱和铁素体相和CrN相以及氧化过程中析出的CrN沉淀相降低了铬的活性,阻碍了有保护性的富铬氧化物的生成,从而导致抗氧化性能的下降。     

超超临界锅炉低温再热器垂直段频繁爆管原因分析

某电厂2台超超临界1 000 MW机组投运2年内低温再热器（低再）垂直段出口频繁发生泄漏失效，通过割取失效管样进行宏观、显微组织及力学检验，测量分析低再管屏壁温、烟温等实际工况数据，对造成低再频繁爆管的原因进行分析。最终确认爆管直接原因为低再垂直段长时过热，壁温测点安装位置不合理且数量偏少及报警温度过高，导致超温不能及时报警；本质原因是烟气上游管屏换热面积偏小、吸热不足导致下游低再管垂直段进口烟温偏高，促使该位置在（超）低负荷时换热严重恶化。为此，提出改造壁温测点位置、增加壁温测点数量、适量安装隔热瓦、降低报警温度等控制手段，采用这些控制手段对该机组改造1年多来未发生超温报警，有效防止了低再管过热爆管。     

Comparative microstructural study of celadon excavated from Housi’ ao kiln site in China (Late Tang and Five Dynasties): Mi-se porcelain and ordinary Yue celadon

Mi-se porcelain provided a step change in the history of Chinese porcelain making and influenced kiln production of later generations as well as the aesthetic orientation of society. This work compares the microstructure of ordinary Yue celadon and Mi-se porcelain. The Mi-se porcelain glaze was found to be simpler and more uniform than ordinary Yue celadon, with only some bubbles existing in the glaze. Compared with ordinary Yue celadon, the residual quartz and pores in the Mi-se porcelain body were smaller. Mi-se porcelain production is more standardized than ordinary Yue celadon. The presence of calcium phosphate in the glaze indicates that grass wood ash was used in the Yue kiln. Our research confirms that Mi-se porcelain was not the best porcelain as selected from the Yue kiln products, but it is a type of celadon that was specially fired using fine raw material processing and certain firing techniques.