1 Turbopower Program Conference April 14-15, 2010, Linköping Compressor Technology WP1 Aero Forcing Florian Fruth, KTH

2 TurboVib Synthesis Aeromechanical Analyses AROMA

3 Vibration modes Campbell diagram Structures are elastic and withstand certain amount of static and dynamic stress Turbomachinery vibrations due to aerodynamic forces Aerodynamic Disturbance Forces (Forced Response) Aerodynamic Damping Forces (Flutter) Disturbance Forces due to Wake Interaction Vortex Shedding Potential Interaction WP1 – Aero Forcing

4 State-of-the-Art Main geometrical approaches to reduce aerodynamic forcing in turbomachines Axial Gap Clocking Blade Count Ratio Influence of Blade Count Ratio not discussed deeply and understood for transonic turbomachines Numerical Simulations in Industry Navier-Stokes using parallel computing Multistage turbomachines Techniques for reduction of calculation Optimizations require faster means Better understanding of phenomenon

5 Beyond State-of-the-Art Studies on the Influence of Blade Count Ratio on Aerodynamic Forcing in Transonic Turbomachines GT ASME 2010 in Glasgow Contribution to HCF Problem: Optimizing the BCR amongst others can reduce HCF due to Change in unsteady flow Change in mode shapes and frequencies Challenge due to non-linear interaction of perturbations Phase shift (timing) Movement (location) Reduction/increase

6 Beyond State-of-the-Art Influence of BCR on Unsteady Flow BCR=0.75 Stator, 90% SpanBCR=3.0 Generalized Forces (GF) as means to describe excitation of structure Unsteady Norm. Pressure SSPS

7 Stator Original BCR=2.22 Study BCR: Trend of Generalized Forces with BCR Low change in BCR can lead to high change in GF Explained behaviour BestWorst Rotor72.5%-405% Stator95.6%-106.4% Summary of Reductions for Single Modes 1st Harmonics BCR Influence - Transonic Compressor Change in Excitation BCR=0.75 BCR=3.0

8 BCR Influence - Transonic Compressor Source of Change in Excitation Stator Minimal difference in GF Only a few modes and BCRs influenced and show different trend Main contribution to change in GF due to change in unsteadiness Unst. + Mode Unst.

9 BCR 2.25 closest to real BCR Rotor Blade, Mode 28: GF reduced by 52% for BCR rpm  17880rpm BCR Influence - Transonic Compressor Use of Change in Excitation Stator Blade, Mode 4: GF increased by 32% for BCR 2.5 BCR 2.17/2.00 better choice Optimization Problem Other modes to be considered

10 Relation to TurboVib Synthesis Direct influence of Blade Count Ratio on High Cycle Fatigue -12.7%<BCR<9.8%  -30%< Generalized Forces<+30% Example: Rotor blade, Mode 2  Haigh Diagram OriginalBest CaseWorst Case % (GF)-60.1% (GF) % (SF) -60.2% (SF) SF= Stress Factor

11 Dissemination Activities Name (Main author)TitleType Maria MayorcaEffect of Scaling of Blade Row Sectors on the Prediction of Aerodynamic Forcing in a Highly- Loaded Transonic Compressor Stage ASME J. of Turbomachinery (2010) Maria MayorcaEffect of Scaling of Blade Row Sectors on the Prediction of Aerodynamic Forcing in a Highly- Loaded Transonic Compressor Stage ASME Paper (2009) Florian FruthInfluence of the Blade Count Ratio on Aerodynamic Forcing – Part I: Compressor ASME Paper (2010) Jesus de AndradeEffect of the scaling technique of blade row sectors on the prediction of aerodynamic forcing MSc thesis (2008) Seyed Mohammad Hosseini Aeromechanic Analysis of an Industrial HPT Rotor MSc thesis (2010) Adrián García DomingoValidation of a Harmonic Balance Method for Prediction of Aerodynamic Forcing MSc thesis (2010) Antonio SanzParametric Study … Part IIA: Forced Response Behavior of a Turbine MSc thesis (2010) Alessio ContranParametric Study of … Part IIB: Forced Response Behavior of a Compressor MSc thesis (2010) Journal Paper Thesis

12 Research Efforts Planned Influence of BCR on Transonic Turbine (3D) Compressor & Turbine Phenomenological changes due to BCR (2D) Generic case Application to Compressor Aspect ratio constant Physical understanding

13 THANK YOU FOR YOUR ATTENTION