Comparative research of algorithms of measuring the geometry of complex profiles of gas turbine engine compressor blades

The paper presents three algorithms for the measurement of gasturbine engine (GTE) compressor blades airfoil (suction side, pressure side, leading and trailing edges) geometry using coordinate measuring machines. The first algorithm is a single scan of the heightwise blade section using a test point. The second algorithm is based on the pre-alignment of the nominal profile with the measured actual profile. An iterative closest-point algorithm is used to carry out the procedure of the best possible alignment of the measured ptofile and the nominal one. In the third algorithm, the coordinates of the measured points of the edges are calculated using the spline defined by the coordinates of the test point (TP) center. The research of errors of measuring the geometry of the elements using the algorithms mentioned above was carried out. To perform the research a model was developed simulating the contact of the TP and the surface of the part being measured. The model makes it possible to calculate the coordinates of the contact point, the center coordinates and the coordinates of the MT of the measured points. The search for the coordinates of the contact was performed using the method of sequential quadratic programming. A procedure was also used that makes it possible to simulate the deviation of the profile and surface position from the nominal. In the course of the simulation dependences for determining the average, lower and upper boundaries of the measurement error distribution for any airfoil point being measured were obtained.