蒸汽轮机长叶片颤振预估方法研究

本文根据叶栅实验和流场计算结果对蒸汽轮机末级流动特征进行了分析。在小容积流量工况 ,末级流场可分为根部脱流区、脱流区之上的主流区叶栅槽道存在附体流区和分离区。三区大小随容积流量变化。由于末级流动复杂 ,发展工程上实用的算法很有吸引力。实验结果和理论分析表明 ,在小容积流量工况容易诱发叶片自激振动。为了能预估叶片颤振 ,本文发展了系列变形激盘法(机时少 ,适于工程应用 )、数值方法 (能给出叶片表面压力分布和激波振荡 ,有助于了解叶片颤振发作机理 )。经实验证明 ,可以用于叶片设计阶段颤振预估。

PREDICTION OF LONG BLADE FLUTTER IN A STEAM TURBINE

The flow characteristics of the last stage of the steam turbine are analysed on the basis of the results obtained from the cascade experiments and flow field calculation.In the case of low volumetric flow rate,the large scale separation occurs in the last stage rotor hub,and the height of separated flow region increases as the volumetric flow rate decreases.Flow separation appears at the blade pressure surface as the bulk flow enters the rotor with large negative incidence.The flow in the rotor can be divided into three regionsa separated hub flow region,an attached-flow region and a separated-flow region.The dimensions of the three regions vary with the flow rate.The flow pattern in the last stage is very complicated.Aseries of deforming actuator disk methods and a numerical method have been developed to predict the blade flutter.The deforming actuator disk method system is applicable to calcalating 2-D and 3-D unsteady flow fields and also to calculating the bending mode and the torsional mode blade flutters.The analytical and numerical deforming actuator disk methods for predicting the blade flutter in a compressor or a steam turbine have been developed in consideration of variability of or invariabiity of the interblade phase angle.The small-disterbance potential amplitude equation is adopted in the numeried method for unsteady flow in the cascade,while the airfoil thickness and bending degree are arbitrary and the rotating finite difference scheme is employed in the calculaton of transonic flow field.The comparison between the computational and the experimental results shows that the presented methods are feasible in prediction of the flutter in blade design.