针对某电厂350 MW超临界机组汽轮机低压缸结构，建立了由末5级叶栅通道组成的低压缸通流区域单通道三维模型。选取从热耗率验收工况（THA）降低至1.5%THA的7种运行工况，构建了低压缸蒸汽流量变化全域图谱。利用计算流体动力学方法，在不同蒸汽流量下对末级汽轮机低压缸低压流场以及温度场进行计算。计算结果表明：在THA工况下，蒸汽能够顺畅地流过低压缸通道；随着蒸汽流量降低，回流涡出现在末级动叶叶根以及中弦后方区域，叶栅通道蒸汽流动混乱度逐渐增强；当蒸汽流量降低到14%THA时，末级动叶进入到鼓风加热状态，蒸汽对末级动叶做负功，末级动叶内功率为负值；当蒸汽流量降低到5.8%THA时，末级动叶吸力面顶部出现小范围200 ℃高温区域；当蒸汽流量降低到3.0%THA时，鼓风加热现象加剧，末级动叶顶部和静叶吸力面的叶尖区均出现了200 ℃高温区域,必须采取必要的措施予以低压缸降温。
Aiming at the steam turbine low pressure cylinder structure of the 350 MW supercritical unit in a power plant, a singlechannel threedimensional model of the low pressure cylinder flow area composed of the last five cascade channels was established. Seven operating conditions reduced from turbine heat acceptance (THA) operating condition to 1.5% THA operating condition were selected, thereby constructing a global map of the lowpressure cylinder steam flow change. The computational fluid dynamics method was used to calculate the low pressure flow field and temperature field of the last stage steam turbine low pressure cylinder at different steam flow rates. The research results show that steam can flow smoothly through the low pressure cylinder passage under THA working condition. With the decrease of steam flow, the recirculation vortex appears at the area behind the middle chord area and the last stage moving blade root, and the steam flow chaos in the cascade channel gradually increases. When the steam flow is reduced to 14% THA, the last stage moving blade enters into the blast heating state, the steam does negative work on the last stage moving blade, and the power inside the last stage moving blade is negative. When the steam flow is reduced to 5.8% THA, a small area of 200 ℃ high temperature appears on the top of the last stage moving blade suction surface. When the steam flow is reduced to 3.0% THA, the blast heating phenomenon is intensified, and the high temperature areas of 200 ℃ both appear on the top of last stage moving blade and the tip area of stationary blade suction surface. At this time, necessary measures must be taken to cool the lowpressure cylinder.