超临界压力变压运行水冷壁中间集箱汽-水两相流分配特性的实验研究

超临界变压运行直流锅炉在启动和低负荷运行时,汽-液两相混合物通过水冷壁中间分配集箱后,在垂直水冷壁中要进行流量和相的再分配,存在着流量偏差较大和水冷壁出口汽温偏差较大的可能性,影响锅炉的安全运行.针对这一问题,以600 MW超临界锅炉过渡段水冷壁中间分配集箱及垂直水冷壁为研究对象,在压力10~21 MPa、分配集箱引入管质量流速400~1 200 kg/(m2.s)、干度0.7~1.0范围内,对垂直水冷壁管的分配特性进行了深入的实验研究.结果表明:影响分配集箱并联支管相分配和汽液两相流流量分配的主要因素为引入管质量流速、干度及分配集箱压力.随着分配集箱引入管质量流速的增加,相分配及流量分配的均匀性增强.当分配集箱的工作压力增加时,分配集箱并联支管间干度分配及流量分配的均匀性增加.并联支管间干度分配的不均匀性随着分配集箱入口干度的增加而减小,而入口干度对流量分配的影响规律较复杂,没有明显的变化规律.研究结果不但对保证超临界锅炉安全、高效运行具有重要的工程意义,而且为我国发展具有自主产权的超临界锅炉提供设计依据.

Experimental study on the distribution characteristics of steam-water two-phase flow in the middle header with water wall under super-critical sliding pressure running

When supercritical sliding pressure once-through boiler is running at lower power loads or is starting up,there is possibilely uniformity in flow rate and the steam temperature among the outlets of the distribution header,which will affect the safety of the boiler.The distribution characteristics of the distribution header of a 600 MW supercritical pressure once-through boiler is studied by experiments under the operation pressure of the distribution header of 10～21 MPa,the mass flow rate of 400～1 200 kg/(m2·s) and the steam dryness of 0.7～1.0 in the inlet tubes of distribution header.The experiments show that,the factors of influencing the phase distribution and the flow rate distribution among the parallel tubes after the distribution header are the mass flow rate and the steam dryness in the inlet tubes of the distribution header and the operation pressure of the distribution.The uniformity of the phase distribution and the flow rate distribution among the parallel tubes increases with the increase of the mass flow rate and the operation pressure.The uniformity of the phase distribution decreases with the increase of the steam dryness,while the effect of the steam dryness on the flow rate distribution is complex and there is not obvious law.The research results not only have significant engineering value to ensure the boilers working safely and runing at high efficiency,but also will provide design basis for the supercritical pressure boilers with self-property right in China.