摘要
在现行的电站锅炉中，尾部烟道内的烟气流动是典型的湍流气固两相流动。由于靠近竖井后墙面的烟气流速很大，飞灰浓度也较大，断面速度分布的最大速度大于最佳设计速度的2-3倍，这样将造成受热面的严重磨损，特别是热管空气预热器前端烟道的几何结构有一定的转角，更增加了磨损的程度。过去，主要用实验和理论分析的办法来确定整个尾部烟道的流场分布是否均匀。然而，在锅炉上的实验肯定要花费很大的人力、物力和时间。因此，本论文提出用数值模拟计算的方法解决这类工程实践中容易出现的问题。
本论文主要运用湍流气固两相流动的基本理论，采用湍流气固两相流动的数值计算模型，先模拟现行运行结构工况下的尾部烟道的流场，与在贵阳电厂9号炉所作的冷态速度分布测量值相比较，验证数值计算模型的可行性和正确性。在此基础上模拟在冬夏两季不同情况下，不同流速对热管空气预热器壁面温度的影响；然后对影响整个流场分布的各种因素：包括分流板长度、厚度、偏离中心流道位置的偏离度、飞灰浓度、飞灰粒径等因素进行数值模拟；最后提出在分流烟道转弯处加装导流板，并模拟加装导流板后的流场分布，得到下级空气预热器出口、热管空气预热器进口处的断面速度场分布、浓度场分布，以论证加装导流板能达到流场均匀化的作用。
本论文尝试用数值模拟的方法解决工程实践中出现的常规问题，节约了大量的人力、物力和时间，对于今后用湍流气固两相流模型解决工程实践的具体问题具有一定的借鉴意义。
Flow type of smoke fluid is turbulent gas-particle two-phase flow in rear smoke channel of power station boiler. There will appear a very uneven flow field, and appear a very big velocity magnitude distribution and ash concentration distribution near back wall. Thus, the velocity magnitude is far bigger than that of optimal design velocity magnitude, which will lead to serious wear and tear in metal face of heater. Especially, because of curve structure in front of heat pipe air preheater, there is more serious wear and tear.
Because there would spend lots of time, money and labor force to experiment in boiler to estimate whether or not flow field is uniformity, using numerical simulation to solve practical problem is very easy and feasible.
In this paper, we mainly use turbulent gas-particle two-phase flow model to simulate flow field of rear smoke channel. Firstly, simulate flow field of rear smoke channel, plot velocity magnitude and ash concentration distribution in section of entry of heat pipe air preheater, compare with data which were measured in Guiyang power station, verify simulation to be reasonable and right. Secondly, simulate all kinds of factors which affect flow field's uniformity such as length, thickness, location of diffluent board, ash concentration, ash diameter, and so on, find the chiefly factors. Thirdly, install guide board in curve channel in rear smoke channel, then simulate its' flow field, plot velocity magnitude and ash concentration distribution.
In the paper, we try to use numerical simulation models to solve normal problem in engineering practice, so that saving labor force money and time. The result of simulation verifies the measure is very valuable.
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