【作者】 明嵬；

【导师】 李文蛟；

【作者基本信息】 大连理工大学 ， 热能工程， 2007， 硕士

【摘要】 火电站锅炉启动和低负荷稳燃过程中，需要消耗大量的燃料油，我国的油资源贫乏，国际原油价格又呈现不断上涨之势，因此节油急不可待。等离子点火装置可以在完全不需要任何燃油的情况下达到点火及稳燃的目的，是一种有效节约锅炉点火、稳燃和调试用油的手段，对降低发电成本、节约油资源、增强国家能源安全有很大意义。等离子燃烧器是等离子点火系统主要设备之一，其结构特点、点火特性直接关系到该技术的应用和推广，因此，本文对等离子燃烧器的点火特性进行了系统的研究。首先，本文介绍了等离子体点火系统的基本构成、等离子体的基本特性、等离子体对煤粉的促燃效果以及等离子发生器的传热量分析等。在此基础上，运用热力学和物理化学的基本知识，对等离子发生器出口的等离子体射流的温度进行了估算。其次，本文运用磁流体力学模型和k-ε湍流模型，使用ANSYS软件对等离子体发生器内的直流电弧等离子体进行数值模拟，得到温度场和速度场分布，结果显示等离子发生器阳极喷口等离子体的中心温度高，从中心至壁面的温度逐渐降低，呈抛物线分布，阳极喷口的速度类似于温度分布，也呈抛物线分布，将温度和速度分布拟合成方程作为等离子体点火数值模拟的入口边界条件。对不同工况下直流电弧进行数值模拟，得到不同功率、不同进气量、不同冷却水流量对电极温度的影响规律。再次，本文利用商业软件FLUENT，采用合适的数学模型对等离子燃烧器内的点火过程进行数值模拟计算。气相湍流流动采用k-ε模型模拟，气相湍流燃烧采用平衡混合分数／PDF模型模拟，辐射换热采用P1模型模拟，焦炭的燃烧采用动力扩散燃烧模型，对煤粉挥发分的释放采用了双匹配速率模型，煤粉颗粒的跟踪采用了随机轨道方法。模拟得出了一些能反应等离子点火特性的关键参数的分布，如温度场、速度场、CO和CO₂的质量分数以及燃烧筒的壁面温度等，从而对等离子燃烧器的点火特性进行系统研究。最后，对不同工况下的点火过程进行数值模拟，得到了一次风速度、煤粉浓度以及一次风的入口角度对等离子点火的影响规律。这些规律为等离子燃烧器的改进和设计提供参考依据。更多还原

【Abstract】 It needs to consume a lot of oil during the course of pulverized coal boiler commissioning, cold startup and low load combustion stabilization. Oil is very indigent in our country, and oil price is higher and higher in international market, therefore, saving oil is imperative. Plasma ignition system can ignite pulverized coal and stabilize flame without any oil, which is an important means to save oil used for the boiler ignition, flame stabilization and commissioning. It can be used to effectively reduce the cost of power generation, save oil resource and enhance the energy security for China. Plasma ignition combustor is one of the main equipment of the plasma ignition system, whose structure and ignition characteristics play the key role in the application and popularity of plasma ignition technology. Therefore, this paper studies the ignition characteristics of plasma ignition burner in the round.Firstly, this paper introduces constitutes of plasma ignition system, the basic characteristics of plasma, pulverized coal combustion improved by plasma and quantity of heat analysis of plasma electropult. On this condition, applying knowledge of physical chemistry and thermodynamics, this thesis calculates theoretically plasma temperature of plasma generator outlet.Secondly, the temperature and velocity field of DC arc plasma obtained by ANSYS with MHD model. The result shows that the temperature at center of anode spout is highest and temperature fall gradually from center to brim, which presents parabola. Velocity distribution is like as temperature. Distribution of temperature and velocity is described with equations which are used as the boundary condition of plasma ignition numerical simulation. DC Arc is simulated in different condition. The thesis gains the effect of power of plasma generator, flux of compressed air and flux of cooling water on temperature of electrode.Thirdly, the ignition and combustion process of Plasma ignition combustor is simulated with CFD software FLUNT. k-εmodel is employed to simulate gas turbulent flow. Equilibrium Mixture Fraction/PDF Model is employed to simulate gas turbulent combustion. P1 model is used to simulate radiation heat transfer. Two competing rates model is employed to simulate pulverized coal volatilization. Stochastic tracking model is employed to simulate pulverized coal track. Kinetics/diffusion limited model is employed to simulate coke combustion. Key ignition factors distributions such as the temperature field, velocity field CO2distribution, CO distribution are obtained, which studies the ignition characteristics of plasma ignition burner in the round.Finally, ignition and combustion process of plasma ignition combustor is simulated with CFD software FLUNT in different condition. The thesis gains the effect of primary air velocity, pulverized coal concentration, primary air velocity on the ignition characteristics of plasma, which supply gist with ameliorating and designing plasma combustor.更多还原