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1.
The turbulent jet flame in a crossflow with highly preheated diluted air has been numerically investigated. The Favre-averaged Navier–Stokes equations are solved by a finite volume method of SIMPLE type that incorporates the flamelet concept coupled with the standard kε turbulence model. The NO formation is estimated by using the Eulerian particle transport equations in a postprocessing mode. For methane and propane with various conditions of inlet air temperature and oxygen concentration, the three-dimensional characteristics of the flame are successfully captured. The jet-flame trajectory is in remarkably good agreement with the existing cold-flow correlations. When the oxygen concentration is high, the maximum flame temperature becomes high and the two fuels show quite different characteristics in the downstream region. On the other hand, for low oxygen concentrations, the temperature difference between the two fuels is relatively small and remains fairly constant throughout the combustion chamber. The propane gives a higher NO formation compared to the methane especially when the oxygen concentration is high. A higher temperature, longer residence time of the combustion gases may be responsible for the higher thermal NO formation.  相似文献
2.
以工业炉的高温空气燃烧技术应用为背景,对一个新型轴向旋流式单烧嘴燃烧室内天然气的高温空气燃烧特性进行了数值研究。采用数值模拟的方法研究了同心式轴向旋流燃烧器(HCASbumer)中螺旋肋片的旋转角度对燃烧特性的影响,其中湍流采用Reynolds应力模型,气相燃烧模拟采用β函数形式的PDF燃烧模型,采用离散坐标法模拟辐射换热过程,NOx模型为热力型与快速型。计算结果表明,对预热空气采用旋转射流时,能明显降低NOx生成量。对于HCAS型燃烧器,随着空气射流旋转角度的增大,燃烧室内的回流区域增大增强,降低了局部的氧体积分数分布,燃烧室中平均温度和最高温度都有所增加,且燃烬程度大幅度提高,而局部高温区缩小,只在靠近入口处出现。总的NOx排放量随着空气射流旋转角度的增大先减小,后增大。因此,适当调整肋片的旋转角度可以降低NOx生成量。  相似文献
3.
采用商用CFD软件,通过数值模拟和正交实验分析了蜂窝陶瓷的结构参数及各工况条件对换热性能和压力损失的影响,优化了工况参数。数值模拟结果为:进入稳定工作期后,加热期温度效率为94.6%,冷却期温度效率为93.7%,压力损失为457.7Pa。在此基础上,设计了梭式窑高温空气燃烧(HTAC)系统,构建实体模型进行实验,研究余热回收系统的温度效率及烟气在蜂窝陶瓷内压力损失。研究结果表明,加热期与冷却期的温度效率分别为:92.0%,93.2%,测量热烟气和预热空气的压力损失分别为126.3,107.8Pa。  相似文献
4.
采用FLUENT软件和燃烧模型,对烧嘴交错布置的高温空气燃烧器换向后的非稳态过程进行了数值研究,换向后炉内的流场、温度场变化的计算结果表明,在换向后的前3S内燃烧炉的流场和温度场变化很大,但是经过3s的变化后,燃烧逐步稳定,最后重新形成稳定的燃烧,直至下一个换向前保持稳定燃烧。  相似文献
5.
高温空气燃烧技术以其高效节能、低污染物排放等优点受到科学界和工程界的广泛关注.重点探讨了蓄热体破损、炉压偏高及频繁波动、换向阀泄漏等方面的原因及相应解决措施.分析了高温空气燃烧技术在工业化过程中的关键技术及亟待解决的问题,并对高温空气燃烧技术发展进行了展望  相似文献
6.
This numerical study systematically investigates the influence of initial injection conditions of reactants on flame characteristics from a parallel multi-jet burner in a laboratory-scale furnace. In particular, varying characteristics from visible flame to invisible Moderate or Intense Low-oxygen Dilution (MILD) combustion is explored. Different parameters examined include the initial separation of fuel and air streams (S), air nozzle diameter (Da), fuel nozzle diameter (Df), and air preheat temperature (Ta). The present simulations agree qualitatively well with previous measurements reported elsewhere for two reference cases investigated by experiment. A number of new and significant findings are then deduced from the simulations. For instance, all S, Da and Df are found to play significant roles in achieving a proper confluence location of air and fuel jets for establishing the MILD combustion. Particularly, varying Da is most effective for controlling the combustion characteristics. It is also found that the stability limits of the non-premixed MILD combustion varies with different combustor systems and inlet reactant properties. Moreover, for the first time, several analytical approximations are obtained that relate the flue-gas recirculation rate and the fuel-jet penetration to Da, Df, S and also reactant properties.  相似文献
7.
以工业炉的高温空气燃烧技术应用为背景,对一个同心式轴向旋流高温空气燃烧器单烧嘴燃烧室内的高温空气燃烧特性进行了数值研究。燃烧室尺寸为600mm×600mm×1 000 mm,燃烧器烧嘴由位于中心的圆形直射流燃气喷口和其外围的同心轴向旋流高温预热空气射流喷口构成。湍流输运方程采用RSM模型,气相燃烧模型采用β函数的PDF燃烧模型,辐射传热过程采用离散坐标法模拟,NO模型为热力型和快速型NO。燃料为天然气。在预热空气温度为1 273K,空气氧摩尔分数为8%,燃烧总过量空气系数为1.1的条件下,进行了数值模拟计算,讨论了燃烧器的螺旋伸展长度对NO排放、局部温度、氧摩尔分数和CO摩尔分数分布等的影响。结果表明,随着螺旋伸展长度的增大燃烧室的燃尽程度将下降,NO排放量先减小到一个最低值,然后随着螺旋伸展长度的增大而增加。当螺旋伸展因子从1.0增加到2.0时,热力型NO的排放摩尔分数从16.8×10-6下降到12.3×10-6。  相似文献
8.
In this paper, from the viewpoints of both the first and the second law of thermodynamics, we conduct a comprehensive study on hydrogen-air counter-flow diffusion combustion in various modes. The effects of air inlet temperature (Toxi) and effective equivalence ratio of fuel (φ) on the reaction zone structure and entropy generation of combustion are revealed over a wide range of Toxi and φ. Through the present work, five interesting features of combustion of this kind, which are quite different from that reported in the literature, are presented. Especially, for the first time we divide various combustion modes in the φ − Toxi map instead of the popular way used in previous studies. Such innovation can help judge the final combustion regime more straightforwardly for any given operative condition.  相似文献
9.
基于GRI-Mech 3.0详细化学反应机理,利用OPPDIF Code研究了CO2稀释比、预热温度及拉伸率对甲烷-高温空气层流对冲扩散火焰温度、热释放率、组分摩尔分数及NO生成特性的影响.研究结果表明,CO2稀释助燃空气能有效降低火焰中H、O及OH等基团摩尔分数,抑制燃烧过程链传播及链引发反应,从而减缓CH4氧化速率.随着助燃空气中CO2稀释比的增加,火焰最高温度逐渐降低,主氧化区及第二氧化区放热峰值变小,燃烧反应高温区变窄,NO生成指数E显著降低.当稀释比大于20%时,热力型NO随助燃空气温度升高规律并不明显.随着CO2稀释比的增加,快速型NO对NO生成量影响逐渐增强,成为高CO2稀释比下甲烷-高温空气扩散燃烧NO生成的主要路径.  相似文献
10.
煤粉炉是我国火力发电的最主要炉型,节约其助燃用油有重要意义。与目前节油技术多基于增强煤粉的点火热源不同。基于提高助燃空气中的氧气浓度强化燃烧的思想,提出了富氧节油的思路,设计了富氧燃烧节油煤粉燃烧器。阐述该燃烧器的原理和结构特点,并对其节油效果进行了验证实验。实验结果表明:与燃烧器结构相结合,局部增强一次风粉气流氧气浓度可以显著增强着火稳燃性能,最后讨论了该新型燃烧器的特点及其应用前景。  相似文献
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