【作者】 张佳男；

【导师】 王岳；

【作者基本信息】 中国科学院研究生院（工程热物理研究所） ， 工程热物理， 2011， 硕士

【摘要】 柔和燃烧具有温度场均匀、燃烧噪音低以及低污染排放的优势,这使得其在燃气轮机中有很好的应用前景。针对燃机应用的柔和燃烧主要通过新鲜燃料空气和烟气掺混实现,所以理解新鲜燃气和烟气之间的相互作用对促进柔和燃烧的应用很有意义。另外在柔和燃烧的实现形式中,分级燃烧方式可以方便地提供高温烟气而不需要依靠复杂的结构来回流大量烟气,故以分级方式实现柔和燃烧也有较好的发展前景。而本文设计的串行分级式柔和燃烧器可以同时兼顾这两方面的研究,即一方面研究新鲜预混气和烟气的相互作用对柔和燃烧的影响,另外一方面对柔和燃烧和分级燃烧技术相结合进行初步探索。本燃烧器利用首段产生轴流高温烟气,并在掺混段采用交叉射流的方式进行新鲜预混气和高温烟气的掺混,然后混合物在柔和燃烧段实现燃烧。根据实验目的不同,实验采用了两种结构形式的燃烧器。其中渐扩型燃烧器主要用于研究不同工况下柔和燃烧的火焰形态以及不同条件下的着火延迟现象。而直筒型燃烧器主要用其研究分段式燃烧器的污染排放性能。实验研究中主要考察四个变量对柔和燃烧的影响,其分别是第一段的质量流量、第一段当量比、第二段质量流量和第二段当量比。对于渐扩实验器,实验测得了其OH-PLIF图像并结合CFD模拟分析了内部流场、组分场以及温度场,从而研究各个量对火焰特性以及着火延迟的影响。结果显示掺混段掺混性能和燃烧初温对火焰形态和着火延迟影响较大。在其他条件不变的情况下,较好的掺混以及较高的初温都会减小着火延迟距离,并使燃烧区域减小。实验测得了直筒式燃烧器的CO和NO排放,并结合化学反应网络模型对结果进行分析,其中柔和燃烧段采用柱塞流模型进行简化处理。结果显示NO排放主要受燃烧温度以及在燃烧器内的停留时间影响,在燃烧温度越高、停留时间越长的情况下NO排放越高。由于不考虑散热影响,模拟燃烧温度要高于实际值,而高温下CO2分解造成CO排放值在模拟结果中比实验结果较高。通过本文研究,对串行分级燃烧器中的柔和燃烧状态、着火延迟距离以及污染排放性能有了较为全面的认识。更多还原

【Abstract】 Mild combustion is characterized by homogenous temperature field, low combustion noise and low pollution emission. All of these features make mild combustion is promising in being utilized in gas turbine combustor. In present study, mild combustion focusing on gas turbine combustor is mainly achieved by mixing fresh fuel/air with flue gas. Therefore, a better understand of the interaction between fresh fuel/air and flue gas is meaning for promoting the application of mild combustion. Besides of this, among all of the combustor structure used to achieve mild combustion, staged combustion, which can supply flue gas in a convenient way and does not depend on complicated structure to achieve flue gas recirculation, is a promising method. While with the present serial staged combustor both topics mentioned above can be investigated.First stage of this combustor is used to produce axial flow high temperature flue gas, which is used to assist to achieve mild combustion. In the mixing part, fresh CH4 and air mixture mix with flue gas in the way of crossflow injecting. In the result, mild combustion happens in the second stage. In the experiment, two types second stage, one with divergent part and the other’s shape is cylinder, are utilized based on different research purposes. For the one with divergent part, flame structure and phenomena of ignition delay are studied. While cylinder shape second stage is mainly used for investigating the properties of pollution emissions. In the research, four variables, which include first stage equivalence ratio, first stage mass flow rate, second stage equivalence ratio and second stage mass flow rate, are considered.For combustor with divergent part, OH-PLIF images and CFD simulation are used to analysis the flow field, composition profile and temperature field of second stage. Based on the results, flame characteristics and ignition delay features are investigated. Results show that mixing characteristics and initial temperature are the most important factors. When keeping other parameters unchanged, better mixing and higher initial temperature will make shorter ignition delay time and more intense combustion region.Pollution emissions, which include NO and CO, of cylinder shape combustor are measured. Together with chemical reaction network simulation, emission properties of the combustor are investigated. In the simulation, the mild stage is simplified to Plug Flow reactor. Results indicate that NO formation mainly influenced by combustion temperature and residence time. Higher combustion temperature and longer residence time will result in more NO formation. While for CO emission, the simulation results are much higher than measurement results. This is because simulation employs adiabatic model and theoretical temperature is much higher than real one. In this condition some CO2 will dissociate to CO, as a result, CO concentration become much higher.Based on the present study, the flame feature, ignition delay and properties of pollution emission of mild combustion are better understood.更多还原