变工况条件下汽轮机高压缸末级气动及强度性能研究

Research on Aerodynamic and Strength Performance of Last Stage in High-Pressure Cylinder of Steam Turbine Under VariableWorking Conditions

采用单向流固耦合分析方法,对4种抽汽量(0%、8%、15%和20%)工况下的汽轮机高压缸末级气动和强度性能进行了数值研究,获得了末级变工况条件下的气动效率和动叶气动载荷分布。以气动载荷为边界条件,对包含叶顶汽封和叶根结构的末级动叶强度性能进行了分析,揭示了末级动叶的最大应力和变形量随抽汽量的变化规律。结果表明:随着抽汽量增大,高压缸末两级输出功率近似呈线性减小,20%抽汽量工况下末两级输出功率比设计工况(0%抽汽)降低了约44%;末级出口总温逐渐上升,20%抽汽量工况下末级出口总温比设计工况下高约10℃。抽汽量对叶顶和叶根汽封的泄漏特性影响显著,导致变工况时末级总-总等熵效率、反动度和叶栅出口汽流角沿叶高的分布产生变化,尤其是30%叶高以下区域,20%抽汽量时三者较设计工况的最大偏离量分别为3.8%、1.6%和2.4°。在离心力和气动力的作用下,设计工况时末级动叶的最大应力位于T型叶根进汽侧下倒圆处,叶顶最大变形量为0.443 mm,叶片最大应力和最大变形量均随抽汽量的增大近似呈线性减小。

Using the one-way fluid-structure interaction method,the aerodynamic and strength performance of the last stages in high-pressure cylinder of a steam turbine were numerically investigated at four extraction percentages(0%,8%,15%and 20%of the total mass flow rate in stages).The aerodynamic efficiency of last stages,as well as the aerodynamic loads on the blades,was obtained under design and off-design conditions.With the computed aerodynamic loads,the strength performance of the last rotor blade was analyzed,and the maximum stress and deformation in rotor blade at various conditions were derived.The results show that the power output of last two stages is nearly linearly decreased with the increase of extraction percentage.If the extraction percentage equals to 20%,the power output is reduced by 44%as compared with the design case.As the extraction percentage increases,the total temperature at last stage outlet is gradually increased.With 20%extraction rate,the total temperature at last stage outlet is increased by about 10℃compared with the design case.The extraction rate has a significant influence on the leakage performance in the tip and hub labyrinth seals of last stage,resulting in the variations of total-total isentropic efficiency,reaction degree and outlet flow angle distributions along the spanwise direction in the off-design conditions.The influence region in the last stage is mainly existed within 30%blade span near hubs due to varied extractions.Compared with the original design case,the total-total isentropic efficiency,reaction degree and outlet flow angle in the last stage are varied by 3.8%,1.6%and 2.4°at most as the extraction percentage varies from 0 to 20%.With the centrifugal and aerodynamic forces,the maximum stress in the last stage rotor blade is occurred at the upstream side bottom fillet of T-shape root,and the maximum displacement in blade tip is 0.443 mm.As the extraction percentage increases,the maximum stress and maximum displacement in last stage rotor blade are almost linearly decreased.