Turbulent flame structure characteristics of hydrogen enriched natural gas with CO2 dilution

This paper investigated the hydrogen enriched methane/air flames diluted with CO₂. The turbulent premixed flame was stabilized on a Bunsen type burner and the two dimensional instantaneous OH profile was measured by Planar Laser Induced Fluorescence (PLIF). The flame front structure characteristics were obtained by extracting the flame front from OH-PLIF images. And the turbulence-flame interaction was analyzed through the statistic parameters. The role of hydrogen addition as well as CO₂ dilution on the features of turbulent flame were revealed by those parameters. In this work, hydrogen fractions of 0, 0.2 and CO₂ dilution ratios of 0, 0.05 and 0.1 were studied. Results showed that hydrogen addition can enhance turbulent burning velocity ST/S_L through decreasing the scale of the finer structure of the wrinkled flame front, caused by the smaller flame instability scale. In contrast, CO₂ dilution decreased turbulent burning velocity S_T/S_L due to its inactive response to turbulence perturbation and larger flame wrinkles. For all flames, the probability density function (PDF) profile of the local curvature radius R shows a bias to positive value, resulted from the flame intrinsic instability. The PDF profile of R decreases with CO₂ dilution, while the value of local curvature radius corresponding to the peak PDF is larger. This indicates that larger wrinkles structure was generated due to CO₂ dilution, which leads to the decrease in S_T/S_L as a consequence. Hydrogen addition increases the flame volume and results in more intense combustion. CO₂ dilution has a decrease effect on flame volume for both X_H2 = 0 and X_H2 = 0.2 while the decrease is obvious at X_H2 = 0.2, Z_CO2 = 0.1. In all, hydrogen enrichment improves the combustion while CO₂ can moderate combustion. Therefore, adding hydrogen and CO₂ in natural gas can be a potential method for adjusting the combustion intensity in combustion chamber during the combustor design.     

600 MW前后墙布置燃烧器锅炉的NOx排放特性及其影响因素的分析

以2台600 MW超临界机组前后墙布置燃烧器的锅炉为研究对象,采用现场燃烧调整试验方法,进行了氧量、燃烧结构参数(包括一次风速、中心风量、二、三次风风量和二次风旋流强度等)、磨煤机运行组合方式、燃尽风量、煤质变化等运行条件对锅炉NOx排放特性影响的试验研究;采用统计分析方法对各种影响因素进行了定量分析和比较.结果表明:锅炉的运行氧量、磨煤机组合投运方式变化、燃尽风量是影响锅炉NOx排放浓度的主要因素,煤质的变化也不可忽视,经比较,燃烧器结构参数变化的影响较小;通过对主要因素的控制,可以显著降低锅炉NOx排放浓度,同时实现高锅炉效率.     

焦炉前反馈热工控制系统运行实践

焦炉生产是典型的大惯性、非线性、时变快的复杂系统,以“火落温度”为基础的焦炉前反馈热工控制系统,通过立火道温度自动测量与人工测温相关性分析、粗煤气温度测量与火落判断、标准温度的优化等运行实践,达到了自动火落时间判断、标准温度指导、加热和燃烧优化、高低温炉号判别等目的,对于稳定炉温、降低回炉煤气消耗、提高焦炭质量以及推进焦化企业技术进步具有重要意义。     

Flame Front Deformation Instabilities of Filtration Combustion for Initial Thermal Perturbation

The flame front deformation instability of low-velocity filtration combustion within an inert packed bed is studied based on the initial preheating non-uniformity. Based on the experimental phenomena, an initial thermal perturbation model is numerically proposed so as to predict the deformation behaviors of the flame front instabilities. The numerical prediction indicates that the assumption of an initial thermal perturbation is a feasible explanation as the cause of the flame front inclination instability. As the initial thermal perturbation increases, the phenomena of the flame front break and shrinking instabilities could easily occur at high filtration velocity or low equivalence ratio. Moreover, the evolutions of the flame front break rate and the shrinking rate are quantitatively analyzed.     

美国食品Facts up Front标签的主要经验与启发

采集美国Facts up Front标签官方网站发布的资料与信息,从Facts up Front标签的特点、类型,与相近包装正面(FOP)标签的基本情况对比,与其他包装正面(FOP)标签的实施效果比较等方面凝练实践经验,并为中国启动与发展包装正面(FOP)标签提出建议.     

导爆管雷管起爆网路逐孔起爆设计

提出了逐孔起爆网路各炮孔孔内雷管起爆时间计算公式,并通过计算机编程设计,快捷方便地计算出了在既定延时导爆管雷管组合下各孔的起爆时间,并清楚地显示出点燃阵面;计算出了不同段别导爆管雷管在不同组合情况下的各炮孔孔底起爆时间。据此,可根据实际情况选择合适的延时时间,从而选择合理的雷管组合和联网方式,实现使用导爆管雷管实现不同延时时间的逐孔起爆,为导爆管雷管起爆网路逐孔起爆设计提供参考。     

前轮操舵驱动移动机器人前后轮横滑刚度测量

通过对移动机器人进行平面运动动力学及运动学分析，建立平面运动移动机器人稳态圆运动动力学方程组；结合前轮驱动电机编码器、舵电机编码器以及机架陀螺仪分别采集到的前轮移动速度、舵角和机器人本体偏摆角速度，利用牛顿-拉夫森方法对动力学方程组进行求解，得到机器人前后轮的横滑刚度。研究结果为轮式移动机器人横滑特性及动力学研究提供了一种简单有效的手段，对路径跟踪研究也具有一定的参考价值。     

A numerical analysis of the elastohydrodynamic line contact film formation at motion start-up

A mathematical model is proposed of the process of formation of the elastohydrodynamic (EHD) lubricant layer between resilient cylinders that begin to rotate in the lubricating material medium from the resting state. The model assumes division of the whole contact region into three zones: the zone within which dry motion is described by the equations of the elastohydrodynamic theory of lubrication, the transient zone, and the dry contact zone. The method of the numerical solution of this system of equations is presented. The calculations are performed for the lubricating material that was used in the published experimental study of the process of formation of the EHD lubricating layer between the resilient ball and the flat resilient base. It is shown that the calculation results well agree with the experimental data both qualitatively and quantitatively providing that the transient region dimensions are adequately selected. The function of the pressure distribution, the lubricating layer thickness, the lubricating material flow, the rate of approach of the surfaces over the contact region at different moments of time, the time dependencies of the lubricating layer thickness at different points of the contact region, and the coordinates of the boundary points of the dry contact region is also presented.     

基于强度与模态灵敏度分析的轿车前副车架轻量化设计

根据轿车前副车架的结构特点,建立了前副车架有限元模型。在转弯、制动、垂向冲击和倒车4种工况下对前副车架进行强度分析,然后分析与前副车架有关的各种扰动激励频率对前副车架振动特性的影响。根据长期研究,提出了前副车架结构模态评价原则,依据此原则,得到前6阶的模态频率和模态振型,最后确定出轻量化方案。