Improvement of reverse-engineered turbine blades using construction geometry

The paper reports the latest outcomes of using design-based reverse engineering on turbine blades. For a long time, the focus of the reverse engineering methods has been the trend toward higher accuracies and faster measurements. Authors introduce a different viewpoint which focuses on design intent of a part. How to reverse engineer a complex shape like a turbine blade is the subject of current research. The attempt toward taking advantage of the construction geometry behind a sample heavy duty turbine blade is thoroughly discussed in three phases. First phase consists of 2D analysis of the reference sections. Then, the stacking axis is introduced as an important non-tangible feature which has the main role to connect the sections in 3D in lean and tilt directions. The third phase uses the concept of blade twist to provide a constraint to define rotational position of the sections with respect to neighbor sections. All the three phases have been applied to different types of original and non-original products which are available in the gas turbine market. The presented comparisons show clearly that the new method of reverse engineering incorporating construction geometry and design intent of the part is quite useful and recognizes many features behind the external geometry which is impossible to follow by the previous conventional methods. The turbine blade 3D model resulted from this new method will have a smooth arc-based surface, straight stacking line passing through turbine axis with maximum section tilt of 0.2 mm and maximum section lean of 0.3 mm to original equipment manufacturer parts and linearly increasing stagger angle from hub to tip which are some of considerable improvements compared to conventional method.

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