电厂燃煤锅炉局部烟道导流装置设计优化

Design and optimization of local flue guide plate of coal-fired boiler in power plant

电厂燃煤锅炉尾部烟道流场对其设备使用寿命影响很大。为了改善锅炉尾部烟道的流场,解决低温省煤器的管束由于流场不均匀而产生的磨损泄漏问题,研究不同设计结构的导流装置对该系统内流场的影响,基于ANSYS18.0-FLUENT流场模拟软件,对原系统烟道的流场进行了模拟分析,结果表明,因烟道截面变化及方向偏转导致低温省煤器前烟道流速不均匀,无导流板的情况下,在Y=1700 mm处的换热器截面的标准偏差值C_(v)达到70.7%,导致换热器流场不均匀从而使得局部流速过高而加剧管束磨损。根据烟道特点,在每个影响流场的关键位置设置了若干个不同结构参数的导流板,经过对一系列设计方案的详细分析和比较发现,在烟道方向偏转或截面突变位置设置的导流装置的板件长度、间距和安装角度对流场有显著影响。根据影响烟道流场位置的不同特点,对导流装置所有结构参数进行优化分析后,获得最佳优化导流装置的结构参数,设计出性能优异的导流装置。在对应位置增加对应导流装置后,方案1的换热器区域速度标准偏差为65.1%,方案2的换热器区域为55.4%,而方案3使得换热器区域的流场大幅改善,换热器区域的速度标准偏差可降至9.6%,且系统阻力只增加了109.8 Pa,达到设计要求。该方案可实施性高,效果明显,为实际工程设计提供借鉴。

The flow field in the tail flue of coal-fired boiler has a great influence on the service life of its equipment. In order to improve the flow field of the flue at end of the boiler and solve the wear and leakage problem of low-temperature economizer tube bundle due to uneven flow field, and study the influence of guide plates with different design structures on the flow field in the system, the flow field in the original system flue was simulated and analyzed based on ANSYS18.0-FLUENT field simulation software. The results show that the velocity of the flue in front of the low-temperature economizer is uneven due to the change of cross section and the deflection of the direction of the flue. Without the guide plate, the standard deviation(C_(v))of the cross section of the heat exchanger at Y=1 700 mm reaches to 70.7%,resulting in the uneven flow field of the heat exchanger, which makes the local flow velocity too high to aggravate the wear of the tube bundle. According to the characteristics of the flue, several guide plates with different structural parameters are set at each key position affecting the flow field. Through a series of detailed analysis and comparison of design schemes, it is found that the plate length, spacing and installation angle of the guide plates set at the position of flue direction deflection or section mutation have a significant impact on the flow field. According to the different characteristics of the positions that affect the flow field of the flue, all the structural parameters of the guide plates were optimized and analyzed. The optimal structural parameters of the guide plates were obtained, and the guide plates with excellent performance was designed. After the corresponding guide plates are added at the corresponding positions, the standard deviation of velocity in the heat exchanger area of scheme 1 is 65.1%,and that in the heat exchanger area of scheme 2 is 55.4%,while scheme 3 greatly improves the flow field in the heat exchanger area, and reduces the standard deviation of velocity in the heat exchanger area to 9.6%.The system resistance only increases by 109.8 Pa, meeting the design requirements. The scheme has high practicability and obvious effect, which provides a good theoretical guidance for practical engineering design.