基于粒子系统的火箭尾焰实时模拟

提高虚拟火箭飞行的真实性,火箭尾焰的实时模拟是关键;在对火箭尾焰的静动态特性进行分析的基础上,建立了火箭尾焰的粒子运动模型,实时模拟了火箭尾焰;在建模过程中采用了面片贴图作为粒子体素的方法以简化模型,并通过相应算法,将面片法向量与观察视线的夹角维持在恒定的范围内,保证了观察效果,提高了粒子体素利用率;应用该方法在火箭飞行仿真中模拟火箭尾焰,粒子量少,逼真度高,较好地解决了视景仿真过程中实时性和逼真度的矛盾,证明了方法的可用性。     

基于自组织神经网络的炉膛火焰燃烧诊断系统

针对目前大型锅炉火焰检测手段的落后现状,提出了一种基于数字图像处理与自组织竞争神经网络进行燃烧诊断的方法,设计了一套火焰燃烧诊断系统.利用数字图像处理技术提取火焰特征量,应用神经网络的竞争学习对不同负荷下的全炉膛火焰图像进行识别分类,从而实现燃烧诊断和灭火预警的功能.     

Mechanism analysis on the pulverized coal combustion flame stability and NOx emission in a swirl burner with deep air staging

Low NOx burner and air staged combustion are widely applied to control NOx emission in coal-fired power plants. The gas-solid two-phase flow, pulverized coal combustion and NOx emission characteristics of a single low NOx swirl burner in an existing coal-fired boiler was numerically simulated to analyze the mechanisms of flame stability and in-flame NOx reduction. And the detailed NOx formation and reduction model under fuel rich conditions was employed to optimize NOx emissions for the low NOx burner with air staged combustion of different burner stoichiometric ratios. The results show that the specially-designed swirl burner structures including the pulverized coal concentrator, flame stabilizing ring and baffle plate create an ignition region of high gas temperature, proper oxygen concentration and high pulverized coal concentration near the annular recirculation zone at the burner outlet for flame stability. At the same time, the annular recirculation zone is generated between the primary and secondary air jets to promote the rapid ignition and combustion of pulverized coal particles to consume oxygen, and then a reducing region is formed as fuel-rich environment to contribute to in-flame NO_X reduction. Moreover, the NOx concentration at the outlet of the combustion chamber is greatly reduced when the deep air staged combustion with the burner stoichiometric ratio of 0.75 is adopted, and the CO concentration at the outlet of the combustion chamber can be maintained simultaneously at a low level through the over-fired air injection of high velocity to enhance the mixing of the fresh air with the flue gas, which can provide the optimal solution for lower NOx emission in the existing coal-fired boilers.     

基于循环谱理论的BPSK直扩信号检测

研究了扩频信号的周期平稳性及其循环谱密度函数;在推导出BPSK扩频信号的循环谱密度函数的基础上,提出利用循环谱理论对BPSK直扩信号进行检测,并用MATLAB进行仿真验证。     

直接序列扩频系统中线性调频干扰的抑制

针对直接序列(DS)扩频系统中线性调频干扰的抑制,本文提出了一种基于分数阶傅里叶变换的干扰抑制接收机的结构和相应的干扰抑制算法.根据线性调频信号在不同的分数阶傅里叶域呈现出不同的能量分布这一特性,利用分数阶傅里叶变换实现干扰信号的检测参数和估计,在此基础上,进行干扰分量的重建和抵消,从而实现对干扰的自适应抑制.性能分析和仿真实验表明,该方法不仅可以在较大的动态范围内有效地抑制线性调频干扰,而且计算简单,便于实现.     

衣康酸改性苯丙胶乳及其在阻燃性空气滤纸中的应用

本研究采用衣康酸作为功能性单体对苯丙胶乳进行改性,并将改性苯丙胶乳与阻燃剂复配,以浸渍施胶的方式对阻燃性空气滤纸的性能进行改善。研究表明,经衣康酸改性后的苯丙胶乳颗粒平均粒径为0. 0868μm,比改性前降低34. 7%,机械稳定性、稀释稳定性及固含量均表现良好;当衣康酸用量为2%(占单体总质量)时,浸渍改性苯丙胶乳使纸张透气度降低约2. 27%,挺度及耐破度达最优值,分别为3. 40 mN?m和290 kPa,比浸渍改性前的苯丙胶乳分别提高了27. 8%及18. 4%。将阻燃剂与改性苯丙胶乳按质量比1:1.4进行复配后对空气滤纸原纸浸渍后发现,纸张的挺度、耐破度及极限氧指数达4. 07 mN?m、301 kPa和30. 9%,满足我国有关阻燃性空气滤纸行业标准的性能要求。     

PET共聚阻燃改性研究进展

该文综述了近年来聚对苯二甲酸乙二醇酯(PET)以共聚改性方式制备高性能阻燃PET的最新研究进展,主要从磷系共聚阻燃、高温交联、高温重排、高温离子聚集和高温端基捕获链扩展5个方面对阻燃改性PET的阻燃机理和阻燃性能进行阐述,并总结了不同阻燃共聚改性方法的特点,对未来PET共聚阻燃的研究方向提出展望.     

Calcium carbonate and ammonium polyphosphate flame retardant additives formulated to protect ethylene vinyl acetate copolymer against fire: Hydrated or carbonated calcium?

In this study, the effect of the chemical nature of different calcium (Ca)-based minerals as flame retardant additives in combination with ammonium polyphosphate (APP), in 1:1 proportions, on the flame retardancy behavior and performance of ethylene vinyl acetate copolymer was discussed. Combining APP with partly and completely hydrated calcium oxide led to superior flame-retardant function detected in mass loss calorimeter measurements with respect to the corresponding system containing carbonated calcium. This privileged character was attributed to the higher reactivity of hydrated Ca-based fillers toward APP in comparison with Ca carbonate, which induced the formation of an intumescent residue. The difference between reactivity potential of hydrated and dry Ca was demonstrated by the newly formed thermally stable species, and further evidenced by thermogravimetric analysis performed on APP/fillers blends. Moreover, the presence of more crystalline domains in the Ca/phosphorus-based compounds was evidenced by XRD analysis of the mass loss calorimeter test residues. The results of this work highlight the role of blend additive systems on the performance of flame retardancy of polymer materials.     

催化燃烧炉的节能性分析

传统的火焰燃气炉往往会产生不同数量的氮氧化物(NO和NO2)、一氧化碳等不完全燃烧产物,造成了环境污染和能源浪费.催化燃烧作为一种新的燃烧方式,打破了传统火焰燃烧的可燃界限,实现了贫甲烷/空气混合物在可燃界限以下的燃烧,燃烧效率高,提高了能源利用率.将催化燃烧应用于燃气炉,可以解决燃气炉由于火焰燃烧带来的燃烧效率低等缺点,达到节约能源的目的.以催化燃烧和燃气炉为依据,在催化燃烧炉Ⅰ型的基础上研制出催化燃烧炉Ⅱ型,分析了催化燃烧炉的热损失以及热效率,并与传统火焰燃烧炉做了比较.结果表明,催化燃烧炉Ⅱ型的热损失并不大,热效率较高,且其污染物排放量极低.     

托电2号炉火焰检测系统优化

托电2号机组火检系统自运行以来,存在一些问题,如火检系统经常发出故障报警信号、火检探头的使用寿命较短、火检信号存在"偷看"现象等.针对以上问题,热控专业人员经过认真分析找到了原因所在,提出了行之有效的解决方法,并结合2号机组的检修对火检系统进行了优化改造.