tailieunhanh - UNSTEADY AERODYNAMICS, AEROACOUSTICS AND AEROELASTICITY OF TURBOMACHINES Episode 12

Tham khảo tài liệu 'unsteady aerodynamics, aeroacoustics and aeroelasticity of turbomachines episode 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 572 with the use of the instantaneous pressure field calculated form the fbw code Gnesin and Rzadkowski 2000 . 4. Numerical Results The numerical calculations presented below were carried out for the stage of the turbine with rotor blades length of m. The number of stator blades is equal to 56 the number of rotor blades is equal to 96. The stator to rotor blade number ratio of 56 96 7 12 . All geometrical parameters of the blade are presented in Rzadkowski 1998. It was assumed that the pressure behind the rotor blades is changing in the circumferential direction measured by the angle around the axis of rotation of the turbine . For circumferential angle a G 0 90 p2 6000 Pa a G 90 180 P2 7500 Pa a G 180 270 P2 9000 Pa a G 270 360 P2 7500 Pa see Figures 2 pressure p2 pka2 Pk 2 9467 Pa . The unsteady forces acting on the ith rotor blades in axial tangential and radial directions were found. Figure 2. The pressure distribution behind the rotor wheel The numerical and experimental verification of the numerical code is presented in Rzadkowski and Gnesin 2000. The numerical calculations have been made using the computational H-grid of 11 24 60 grid points for each stator passage and 11 14 60 grid points for each rotor passage. One of the important aspects of stator-rotor interaction is the effect of the blade response with taking into account the excitation caused by the ft w uniformity and excitation due to blades oscillations. Stator-Rotor Aeroelastic Interactionfor a Turbine Last Stage in Transonic Flow 573 The blade vibrations are defined with taking into account the first ten natural modes shapes of rotating blade. The values of natural frequencies and the mechanical damping coefficients hi 2wi i are given in Table 1. The modal damping coefficients were assumed Rzadkowski 1998 1 2 3 3 4 10. Table 1. Natural frequencies and mechanical damping coefficients of the rotating rotor blade L m Mode Number 1 2 3 4 5 6 7 8 Ui Hz 99 160 268 .