Novel Sectional Profile Matching Algorithm for Gas Turbine Blades Based on Curve Chord-Length Invariant Feature

Aiming at the non-datum coordinate matching for large-scale gas turbine blade profile in high-precision detection and evaluation,an accurate coordinate matching algorithm is proposed based on the chord-length invariant feature of sectional profile.After acquiring the point data of corresponding sectional profile,the objective function is established according to the corresponding chord-length invariant feature of blade sectional profile curve.The points corresponding to the measured ones in the theoretical profile curve are calculated with the proposed algorithm.Moreover,the indeterminate equations for coordinate transformation can also be constructed.The least-square optimal solution of coordinate transformation of sectional profile can be calculated by Householder matrix transformation.As the coordinate transformations of multiple sectional profiles are calculated,the optimal coordinate transformation matrix can be obtained by linearly averaging the transformation relationships.Then,the coordinate system can be unified.The coordinate transformation matrix between simulatively measured data and theoretical data of a blade sectional profile curve is calculated with the proposed algorithm to obtain the evaluation result of sectional profile.The deviation of evaluation result gets within the acceptable range(less than 1.5 μm).