一、前言现代汽轮机单机功率越大,末级叶片就越长。末级的功率占整台机组功率7～9％左右。因此,保证汽轮机低压末级长叶片在设计工况特别是在变工况下的安全经济运行,是发展大功率供热、调峰、空冷机组的关键技术问题在深度变工况下,末级喷嘴与动叶之间的轴向间隙顶部产生旋涡,动叶出口根部产生脱流和倒流,排汽部分过热,使末级效率显著降低,动应力水平增高,发生失速颤振和动叶根部出汽边水蚀,造成叶片断裂事故。为了保障末级叶片的工作可靠性,应从 I. INTRODUCTION The greater the power of modern steam turbines, the longer the last blade will be. Last stage of the power of the entire unit power of about 7 to 9%. Therefore, it is a key technical issue to develop high-power heat supply, peak-shaving and air-cooled units under the condition of variable depth in the design conditions, especially under varying conditions, so as to ensure the safety of low-pressure long- The vortex is generated at the top of the axial gap between the nozzle and the moving blade. The root at the outlet of the moving blade is caused to flow off and back, the exhaust part is overheated, the efficiency of the final stage is significantly reduced, the dynamic stress level is increased, Steam edge water erosion, resulting in blade fracture accident. In order to ensure the reliability of the work of the last blade, should be from