【作者】 李智；

【导师】 娄春；

【作者基本信息】 华中科技大学 ， 动力工程及工程热物理， 2021， 硕士

【摘要】 火力发电是重要的发电形式。燃煤锅炉是火力发电厂运行的核心设备,其主要以辐射传热的方式传递能量。利用热力学第二定律分析燃煤锅炉炉内辐射传热过程可以为燃煤锅炉炉内辐射传热提供科学合理的准则,保证辐射传热效率,节约能源。本文参考燃煤锅炉实际情况,通过数值计算以及实验研究的方式,在一维、二维系统内进行了辐射熵产研究,具体工作如下:首先,在一维煤粉燃烧介质中对比了非灰模型与灰体模型对辐射熵产的影响,结果表明灰体模型会对辐射熵产计算造成明显误差。并分析了非灰颗粒介质以及非灰气体介质对辐射熵产的影响,结果表明:对于颗粒介质,燃尽率为100%时对应的辐射熵产明显小于未燃尽时的对应辐射熵产;随着粒径的增大,辐射熵产不断减小。对于气体介质,随着气体浓度、温度、压强的增加,辐射熵产不断增加。然后,在一维燃煤锅炉辐射熵产数值计算中,分别研究介质浓度、过量空气系数、一次风温、二次风温对燃煤锅炉炉膛中辐射熵产的影响,主要结论:当飞灰浓度较小时,随着碳黑体积浓度的增加,辐射熵产减小,辐射熵产数增大;当飞灰浓度较大时,辐射熵产以及熵产数随碳黑体积浓度变化较小。随着过量空气系数的增大,炉内辐射熵产不断减小,辐射熵产数不断增大。一次风温对炉内辐射熵产以及熵产数影响不大。随着二次风温的增大,炉内辐射熵产以及熵产数随之增大。最后,结合辐射反问题的求解结果,利用实验研究以及数值计算的方法对燃煤炉膛三个高度截面的辐射熵产进行了研究。结果表明:三个高度截面的局部辐射熵产呈现中间低,接近壁面处高的分布状态;随着炉膛截面温度不均匀性的增加,温度均方差不断增加,介质辐射熵产以及熵产数随之不断增加;随着炉膛截面辐射热流的不断增大,壁面辐射熵产以及熵产数不断增大。更多还原

【Abstract】 Thermal power generation is an important form of power generation.The coal-fired boiler is the core equipment for the operation of thermal power plants,and it mainly transfers energy by means of radiation heat transfer.Using the second law of thermodynamics to analyze the process of radiative heat transfer in a coal-fired boiler furnace can provide scientific and reasonable guidelines for radiative heat transfer in a coal-fired boiler furnace,ensure the efficiency of radiative heat transfer,and save energy.According to the characteristics of radiative heat transfer in coal-fired furnaces,this paper conducts radiative entropy generation research in one-dimensional and two-dimensional systems through numerical calculation and experimental research.The specific work is as follows:Firstly,the effects of non-gray model and gray body model on radiation entropy generation are compared in a one-dimensional pulverized coal combustion medium.The results show that the gray body model will cause significant errors in the calculation of radiation entropy generation.The effects of non-gray particulate media and non-gray gaseous media on radiation entropy generation are analyzed.The results show that: for particulate media,the corresponding radiation entropy generation when the burn-out rate is 100% is significantly smaller than the corresponding radiation entropy generation;As the particle size increases,the radiation entropy generation continuously decreases.For gaseous media,as the gas concentration,temperature,and pressure increase,the radiation entropy generation continues to increase.And then,in the numerical calculation of radiation entropy generation of one-dimensional coal-fired boilers,the effects of medium concentration,excess air coefficient,primary air temperature,and secondary air temperature on the radiation entropy generation in the furnace of coal-fired boilers are studied respectively.The main conclusion is: When the fly ash concentration is small,as the volume concentration of soot increases,the radiation entropy generation decreases and the radiation entropy generation number increases;when the fly ash concentration is large,the radiation entropy generation and the entropy generation number change less with the volume concentration of soot.As the excess air coefficient increases,the radiation entropy generation decreases and the number of entropy generation in the furnace continues to increase.The primary air temperature has little effect on the radiation entropy generation and the entropy generation number in the furnace.With the increase of the secondary air temperature,the radiation entropy generation and the entropy generation number in the furnace accordingly increase.Finally,combined with the results of solving the inverse radiation problem,the radiation entropy generation of the three height sections of the coal-fired furnace is studied using experimental research and numerical calculation methods.The results show that the local radiative entropy generation of the three height sections is low in the middle and high close to the wall;as the temperature inhomogeneity of the furnace section increases,the temperature mean square error continues to increase,and the medium radiative entropy generation and the number of entropy generation increase with the continuous increase of the radiant heat flow of the furnace section,the wall radiation entropy generation and the number of entropy generation continue to increase.更多还原