【作者】 谭灿燊；

【导师】 张新铭；

【作者基本信息】 重庆大学 ， 热能工程， 2006， 硕士

【摘要】 我国是以煤炭为主要能源的大国,煤炭占能源生产总量的比重为70.7%(2002年),我国大部分煤炭都是直接用于燃烧的,其燃烧产生的污染物是破坏生态环境的主要污染源之一。锅炉的设计制造、调峰机组低负荷稳燃、炉内结渣、污染物控制等,都需要了解炉内的燃烧、流动、温度等状况。而通过传统试验测量的方法只能够得到有限的数据,而今随着计算机和煤粉燃烧理论模型的发展,数值试验成为了炉内过程研究的另一个重要手段,而且通过数值试验的方法还可以弥补传统试验的不足。切圆燃烧煤粉炉,在世界范围内都占有很大市场,从我国的电厂现状来看,直流燃烧器四角切圆燃烧方式约占80%。本文用数值模拟的方法,对三菱公司生产的MB-FRR型锅炉(最大连续蒸发量为2290t/h)的燃烧过程进行了多个工况的计算分析,以期对锅炉的优化设计和运行提供有益的指导。锅炉内的燃烧过程是非常复杂的湍流流动和反应过程,它涉及到三维湍流、多相、多组分流动;而热量的传递又包括对流换热、辐射换热、热传导;涉及到相关的化学反应又包括气相燃烧、颗粒相燃烧等。本文采用非预混燃烧模型,挥发分的气相湍流燃烧用混合分数法来模拟,用标准k-ε紊流模型模拟气相湍流输运,用P-1辐射模型计算辐射传热,对气相流场采用非交错网格的SIMPLE差分方法求解,对固体颗粒湍流扩散的求解则采用随机颗粒轨道模型。颗粒的挥发分析出及焦炭的氧化过程是颗粒反应的模拟重点,颗粒挥发分析出过程的模拟采用Kobayashi模型;焦炭燃烧过程模拟则采用动力学/扩散控制反应速率模型。本文的特点有:(1)结合图像处理技术,进行了冷态模拟的伪扩散研究,提出了对计算网格体系进行评价的方法,该方法能选出有效减少伪扩散影响的网格体系。(2)对大型锅炉降负荷运行的炉内过程进行了研究分析,并提出了改进配风,降低NOx生成,稳定燃烧的措施。(3)对锅炉改烧混煤进行了多个工况的计算分析,并比较了煤种、配风和空气过量系数对炉内燃烧过程的影响。本文的计算结果和锅炉热态试验数据吻合较好,计算精度能够满足工程应用要求。更多还原

【Abstract】 Coal is the main fuel in china and takes a probability of 70.7% in all energy sources output in 2002. It is always burnt directly, and the contamination concerned with this process is one of the main contaminative sources destroying the environment.There are many aspects such as the design and manufacture of the boiler, the steady combustion of the accommodate sets, the scorification in the boiler, the control of contamination and so on that need to know the combustion, flow and temperature in the boiler. But only finite data can be got through the measurement of traditional experiment. These days, along with the fast development of computer and the theory of pulverized coal’s combustion, numerical experiment, which can complement the shortcoming of the traditional means, becomes another crucial method to study the above casesThe tangentially fired boiler possesses a large part of the market all over the world. In China, about 80% of the direct current burners take tangentially fired combustion as their burning way. This paper focuses on the burning process of the MB-FRR boiler produced by Mitsubishi, and several conditions are simulated to provide instructive guidance for the optimum design and operation of the boiler.The combustion process in the boiler, about turbulent flow and chemical reaction, is very complex, which is concerned with three-dimensional turbulent flow, multiphase and multicomponent flows. Heat transfer includes convection, radiation and conduction, while chemical reaction includes gas combustion, char combustion and so on. The paper adopted non-premixed combustion model. The equations for the mixture fraction are used to simulate volatile’s turbulent combustion, and the simulation of gas turbulent transport employs theκ-εturbulent model, then for the radiation P-1 model is used. Besides, it selects the SIMPLE difference methods of non-interleaving gridding for the gas flow field, and accordingly the resolution of the turbulent diffusion about solid particle chooses the stochastic tracking model. The simulation emphases of the particle reaction are the separateness of the volatile and the oxidation of the char, while the first one’s simulation uses Kobayashi model, and the other one takes the kinetic/diffusion surface reaction rate model.The paper’s stressing points are as follows: (1) It studies the pseudo diffusion of cold simulation through image processing, and a method for gridding evaluation is put更多还原