燃煤电厂亚临界压力垂直并联管组变质量流速流量分配特性研究

STUDY ON FLOW DISTRIBUTION CHARACTERISTICS OF SUB CRITICAL PRESSURE VERTICAL PARALLEL TUBE GROUP WITH VARIABLE MASS VELOCITY IN COAL-FIRED POWER PLANT

为研究亚临界压力下变质量流速垂直并联管组水动力特性,建立了亚临界压力垂直上升水冷壁管工质流动计算数学模型,对比分析亚临界压力下垂直光管和垂直内螺纹管并联管组在定管长变质量流速下管组内工质质量流量分布等特性。结果表明:在水冷壁结构、初始工质参数及热负荷一定的条件下,并联管组中各水冷壁管相变点所在位置高度随平均质量流速的增加而增加;相同条件下,垂直光管并联管组内工质的正流量补偿特性优于垂直内螺纹管;对于垂直内螺纹管,当管组平均质量流速低于临界质量流速时具有良好的正流量补偿特性。反之,垂直内螺纹管并联管组内工质的正流量补偿特性随平均质量质量流速的增大逐渐减弱直至消失并最终转化为负流量补偿特性。相关计算结果的确定,为锅炉水冷壁的设计布置及安全运行提供参考。

In order to study the hydrodynamic characteristics of vertical parallel tube groups with variable mass velocity under subcritical pressure,a mathematical model for the calculation of working fluid flow in vertical upward water-cooled wall tubes under subcritical pressure was established,and the characteristics such as the mass flow distribution of working fluid in the tube groups with vertical smooth tubes and vertical internally ribbed tubes under subcritical pressure were compared and analyzed under the condition of fixed tube length and variable mass velocity.The results show that the height of the phase change point of each water wall tube in the parallel tube group increases with the increase of the average mass flow rate under the condition of a certain water wall structure,initial working fluid parameters and heat load;Under the same conditions,the positive flow compensation characteristics of the working fluid in the parallel tube group of vertical light tubes are better than those of the vertical internally threaded tubes;For vertical internally ribbed tubes,when the average mass flow rate of the tube group is lower than the critical mass flow rate,it has good positive flow compensation characteristics.On the contrary,the positive flow compensation characteristic of the working fluid in the parallel tube group of vertical internally threaded tubes gradually weakens and disappears with the increase of the average mass flow rate,and finally turns into a negative flow compensation characteristic.The determination of relevant calculation results provides theoretical basis and technical support for the design,layout and safe operation of boiler water wall.