锯齿形尾部叶片在不同攻角下的水力特性数值计算

Hydraulic Characteristics Numeric Calculation of Trailing Edge Serrations Structure Blade in Multiple Attack Angles

建立了尾部带锯齿与不带锯齿的NACA0012型叶片攻角分别为0°、5°、10°、15°、20°的数学模型,并使用大涡模拟对其进行了数值计算,得到上述工况的速度场、压力场、流场中压力脉动数据。计算结果表明,锯齿形结构能够减小叶片背水侧的脱流及尾迹中的漩涡,且减小效果在攻角10°时最为明显。攻角为0°及5°时,锯齿形结构会增大流场中的压力脉动,攻角10°、15°、20°时,锯齿形结构减小流场中的压力脉动;由于攻角0°及5°不带锯齿时压力脉动值很小,带锯齿的工况增加的压力脉动值也很小,说明尾部锯齿结构能够有效减少水力机械叶片在一般运行攻角范围内的压力脉动值,改善叶片运行的水力特性。

The geometric models of NACA0012 symmetrical airfoil blade with and without trailing edge serrations are established respectively, in which, the attack angles of the blade is set in 0°, 5°, 10°, 15° and 20°. By using large eddy simulation for numerical calculation, ten group of velocity field, pressure field and pressure pulsation data are obtained. The calculation results show that, （a） the structure of trailing edge serrations can reduce flow separation in back side and vortex in wake, and the reduction is more significance when the attack angle is 10°; （b） the structure of trailing edge serrations will aggravate pressure fluctuation in flow field when the attack angle is 0°or 5° and can reduce pressure fluctuation in flow field when the attack angle is 10°, 15° or 20°; and （c） because the pressure fluctuation is low in the case of blade with no structure of trailing edge serrations and the attack angle of 0 ° or 5 °, the increment of pressure pulse value is few in the case of blade with structure of trailing edge serrations. The structure of trailing edge serrations can reduce hydraulic vibration of hydraulic machinery blade and improve its hydraulic performance in blade＇s common variation range of attack angle.