1 Turbopower Program Conference April 14-15, 2010, Linköping Compressor Technology Structural Damping (WP3) Jia Sun, MWL, KTH

2 TurboVib Synthesis Aeromechanical Analyses AROMA

3 [WP3 – Structural Damping] What this is about… Structural damping depends on the properties of material and geometry of the structure. Its mechanism is to convert vibration energy into heat, finally to suppress the vibration amplitude. Normally, the structural damping of pure metal material is small. Additional damping layer can improve damping effect, increase one, even two magnitude order. Loss factor

4 State-of-the-Art Today analytical damping models for unconstrained and constrained structures for specimens have been developed (Edward Jr., 1959, Ross, D., Ungar, EE, 1959, Cremer, Heckl and Petersson, 2004) Most of researches work on the evaluation of damping by FE model (Sophoclis Patsias and Robin J. Williams, 2003, HCF conference) and experiments (J. B. Kosmatka Oral Mehmed, 2003, HCF conference) Structural damping is much smaller than other damping factors, such as aero damping at some nodal diameter where the aero damping is low or even negative the structural damping is critical. At present, in engineering application structural damping is assumed a constant and hence less accurate.

5 Beyond State-of-the-Art What is new? Go into details about structural damping, i.e., give a frequency dependent damping ratio model. More accurate damping ratio can give more accurate the overall HCF life prediction. What are the challenges? The initial data comes from measurement and scattering results have around 20% difference. How to minimize this difference and improve its accuracy. Application on real blades, more factors are needed to be considered, such as stress distribution on the blade surface…

6 Methodology

7 Test Results 3 types of specimens: Titanium with 250 µm magnesium aluminum spinel (Al), Stainless steel with 250 µm Al and titanium with 800 µm epoxy Research Results up to Now

8 Calculation of loss factor of aluminum spinel treatment Curve fitting by using measured data from two types of specimens (aluminum on Ti and SS) Curve fitting: Smoothing spline Polynomial fit Ti with Al SS with Al 20% Difference Validation

9 Research Results up to Now Calculation of loss factor of epoxy treatment

10 Research Results up to Now Case one: Titanium with aluminum Refer to: Pure Ti Specimens

11 Research Results up to Now Case two: Titanium constrained-layer with epoxy Refer to: Pure Ti Specimens

12 Physically and Industrially Possible Variation Parameter: Coating thickness, 0 – 0.45mm Increase of 2500% in material damping (drs) Decrease of 69% in HCF risk Numerical Prediction Accuracy Increase of 1% in material damping Decrease of 0.19% in HCF risk Decrease of 6.32% in material damping Increase of 0.57% in HCF risk Relation to TurboVib Synthesis

13 Dissemination Activities Name (Main author)TitleType Jia SunDevelopment of a Dynamic Rotating Turbine Blade Model ICSV16 Paper (2009) Jia SunMethods to Increase Material Damping of Compressor Blades – Measurements and Modeling ASME Paper (2010) Meng TianDamping Measurements of Turbine BladesMSc thesis (2009) Journal Paper Thesis

14 Research Efforts Planned Deep experimental investigation on real blades treated with damping materials, a laser sensor is planned to scan the whole surface of the blade to obtain its vibration behaviors Verify the numerical model for damping prediction with comparison of experimental results Import the frequency dependent damping data into FEM model through ANSYS A simple beam FEM model will be calculated by ANSYS to compare with experimental results