Description Table. 1 Parameters used for wind turbine vibration analysis and control. Blades and Hub Parameters Number of blades Tip speed ratio () 3 6 Blade Young's modulus axial (E) 20GPa Blade Shear modulus axial (G) Blade Density (pb) Blade length (L) Nominal (min & max) wind speed (Ux) Blades and hub total mass (Mb) Radius of gyration of blades and hub (krg_b) Transmission Parameters Blade shaft Young's modulus (E) Blade shaft Poisson's ratio (v) Blade shaft length and radius: (Lbs, lbs) Generator shaft length and radius: (Lggs) Generator parameters Generator total rotating mass (Mg), total mass (Mgfig) Radius of gyration of generator rotating inertia (krg_g) Radii of gyration of generator in xyz planes (px), Pz. px) Generator mount parameters Vertical distance between centre of mass and mounts (ax-ay) Horizontal distance between centre of mass and mounts (bxy, by) Old mount vertical stiffness (ky) Old and new mount damping ratio (5) Notes *SN is the last 2 digits of the first group member, alphabetically. 7.143GPa 1820kg/m 65(1+SN*/100)m 5 & 28 m/s (1.5L/m) tonne 0.4L 210GPa 0.3 4m, 0.3m 4m, 0.2m 30 tonne, 30x1.2 tonne 0.8 m 0.26m, 0.275m, 0.26m 0.2m 0.48m, 0.225m 4.315 MN/m 0.15 MECH3200 Group Consulting Assignments Assignment A2 (due start of wk 7: 10%) A2.1 Calculate the natural frequencies of the mounted generator for rigid body vibration in all the planes using the existing mounts. Assume the lateral stiffness is 1/7 of the vertical stiffness. Predict the dominant mode/s associated with excessive transmitted forces from generator excitation. (12 marks) A2.2 Assuming the damping ratio of the mounts is less than 0.15. Calculate maximum transmissibility for each of the natural frequencies identified in A2.1. Explain the magnitude of the dominant contributions and discuss why the existing mounts are not providing adequate isolation. (8 marks) A2.3 Design the minimum (amplitude) % stiffness change of the new mounts (compared to the old) that achieves at least a 5 times reduction in the worst case transmissibility calculated in A2.2. Assume the lateral stiffness is 1/7 of the vertical stiffness and the damping ratio of the mounts is less than 0.15. (8 marks) A2.4 Identify any limitations that may constrain your design in A2.3. Identify the advantages of mount damping during generator runup or rundown from its operating speed. (6 marks) A2.5 Research and discuss the use of one alternative vibration control technique for the generator such as dynamic vibration absorbers, adding mass or stiffness. Identify the advantages and limitations of the technique for this application. (6 marks)