Accession Number : ADA195699


Title :   Empirical Flutter Prediction Method.


Descriptive Note : Final rept. Sep 84-Sep 87,


Corporate Author : GE AIRCRAFT ENGINES CINCINNATI OH ADVANCED TECHNOLOGY OPERATION


Personal Author(s) : Casey, J K


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a195699.pdf


Report Date : 05 Mar 1988


Pagination or Media Count : 358


Abstract : Design of advanced technology engines is often limited by compressor blade instability or flutter. Test points from the annular cascade data base were analyzed, to predict from aeromechanical data which of 14 types of stability or instability would result. The basic approach was to identify for each pair of stability regions, linear combinations (hyperplanes) of the aeromechanical variables, whose numerical value would be above a critical level for all test points in one stability region and would be below the critical level for test points in the other stability region. It was found that 76% of the pairs of stability regions allowed a hyperplane to discriminate between the two regions, but for 24% a curved surface or nonlinear combination variables would be needed. Review of 85% of the 891 test points used to construct the hyperplanes revealed that the hyperplanes correctly identify the stability condition of 59% of the points in a literal sense, but are correct in a broader practical sense for 79% of the points. When the hyperplanes were applied to 51 validation test points taken from several actual engine/rig test data, they gave virtually no correct results. This result is not immediately explainable. Keywords: Stall; Choke; Discriminant; Cluster. (edc)


Descriptors :   *FLUTTER , AERODYNAMIC LOADING , COMPRESSOR BLADES , CURVATURE , DATA BASES , ENGINES , EXPERIMENTAL DATA , MECHANICS , NONLINEAR SYSTEMS , NUMBERS , PREDICTIONS , REGIONS , STABILITY , SURFACES , VARIABLES


Subject Categories : Fluid Mechanics
      Jet and Gas Turbine Engines


Distribution Statement : APPROVED FOR PUBLIC RELEASE