Introduction of a Parameter Based Compressor Blade Model for Considering Measured Geometry Uncertainties in Numerical Simulation

Abstract

This paper provides a method to transfer geometric uncertainties of compressor blades into the numerical simulation. Therefore a method to capture geometric variations of measured blades by typical profile parameters is introduced. An optical measurement technique using structured light is applied to scan compressor blades in order to receive a three–dimensional point cloud of the measured blade. The evaluation of these points is done on curves of constant spanwise coordinate between hub and casing. In this way, section outlines are extracted, which then are split into camber lines and chord lines. The derived thickness and camber distributions are used to specify typical profile parameters for each section. To consider the geometric uncertainties in numerical simulation, the design geometry is adapted through a special reconstruction algorithm. Therefore the differences between the measured airfoil and the design geometry are quantified by the profile parameters. Since only the difference is analyzed, few parameters are needed to model the measured geometry. The three-dimensional blade then is reconstructed through assignment of the parameters to the spanwise coordinate. To illustrate the developed method, the whole process chain is applied on a selected compressor blade.

Principal component analysis on 3D scanned compressor blades for probabilistic CFD simulation

“…In addition to the real input parameters, virtual input parameters derived from geometric features were analyzed regarding their influence. Therefore, the parametric blade model of Lange et al 8 is utilized to obtain a vector of representative geometric parameters for each sampled blade. The vector overall contains 16 elements, composed by 14 spanwise averaged profile section parameters and two fillet parameters.…”

“…The section outlines therefore are split into two half-shells with the separating criteria defined by the two intersection points of the camber line with the section outline. The camber line is given by the inverse camber line calculation method of Lange et al 8 that symmetrically splits a unstructured section outline of a compressor blade. The increment of arc length between two adjacent points ∆L = |∆ x| (2) leads to the normalized cumulative arc length distribution of a half-shell (suction side or pressure side)…”

Investigation and analysis of deterioration in high pressure compressors due to operation

“…To gain improved knowledge of the statistical occurrences of airfoil deterioration symptoms on ex-service blades, a geometric examination of two complete HPC blade sets was carried out which follows an approach similar to that of Lange et al [6]. While the present work also relies on a parametric blade model to parameterize 3D digitized airfoil geometries, it concentrates more on a clear separation of manufacture scatter and degradation effects.…”

“…However, since only samples of investigated used blades are analyzed, Krone raised question whether his approach is statistically sufficient to provide a representative round-up of blade wear and overhauled airfoil conditions. A method of geometry acquisition which allows for a robust statistical analysis of airfoil deviations is introduced by Lange et al [6] using a parametric blade model. The described procedure is based on the commonly utilized structured light 3D-scanning backed by a photogrammetry system and originally aimed for an evaluation of manufacturing scatter.…”

Optimal Design and Tolerancing of Compressor Blades Subject to Manufacturing Variability

“…One approach is to construct probability distributions of geometric parameters such as camber, thickness, and chord using measurement data. [3][4][5] Principal component analysis (PCA) has also been used to characterize manufacturing variability. 1,6,7 PCA can be used to construct a probabilistic model of variability from the empirical mean and covariance of surface deviations at different locations on the blade.…”