Enhancement of Hydraulic Machinery by Use of Shape Memory Alloys

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A shape-controlled airfoil was developed by the use of shape memory alloys (SMA). The developed airfoil consisted of the leading and trailing parts, between which the SMA rods were inserted. While the trailing part was fixed on the wall of the test section in the wind tunnel, the leading part could be turned about 9 the SMA. The two way change in the blade shape was realized by the use of a differential two way element in which the two different shapes were memorized. The developed airfoil was tested in the wind tunnel in order to check the effect of the shape change on the characteristics of the airfoil. The flow visualization experiments in the smoke tunnel showed that th e shape change by an electrically heated SMA produced a marked change in flow around the airfoil near the stall angle of the original shape. Moreover, the traverse of the wake behind the airfoil also exhibited the effect of the shape change in the airfoil. As a result of this study, it was found that the developed SMA actuator was effective for the control of flow separation from the blade surface. And it is suggested that the SMA actuator can be applied to the turbomachinery as an active control for the airfoil.