High-precision reconstruction of blade leading edge

The shape of leading/trailing edge is very important to the performance of the turbine blade. Precise description is the premise for turbine blade machining. Generally, the leading/trailing edge is a circular arc or elliptic arc. In order to reconstruct them accurately, a method for fitting the ellipse based on the principle of conditional least square was applied at first, and then its fitting result was used as an initial value to find a more precise result according to the polar line geometrical properties of the ellipse. Some examples were given to prove the good robustness and high accuracy of this fitting method, especially for a part of ellipse. During the reconstruction of the blade, some outliers which are difficult to exclude beforehand may influence the accuracy of fitting result greatly. Because of our method's good robustness, this fitting method was applied to the progressively increasing number of data centered at leading edge for several times to exclude outliers. Numerical experiments show the effectiveness of this scheme. In conclusion, the method presented is suitable for the reconstruction of blade in the reverse engineering.