Impact vibration characteristics of a shrouded blade with asymmetric gaps under wake flow excitations
- PDF / 1,193,581 Bytes
- 16 Pages / 547.087 x 737.008 pts Page_size
- 34 Downloads / 197 Views
O R I G I N A L PA P E R
Impact vibration characteristics of a shrouded blade with asymmetric gaps under wake flow excitations Shiming Chu · Dengqing Cao · Shupeng Sun · Jianzhi Pan · Ligang Wang
Received: 11 July 2012 / Accepted: 20 December 2012 / Published online: 17 January 2013 © Springer Science+Business Media Dordrecht 2013
Abstract The vibro-impact mechanism of a rotating shrouded blade with asymmetric gaps is investigated. The Frobenius method is employed to determine the dynamic frequencies and corresponding mode functions of the shrouded blade under the action of dynamic stiffness. The mode functions are used to truncate the governing partial differential equation of the shrouded blade to ordinary differential equations by using the Galerkin method. Taking into account the influence of the rotating speed, the contact stiffness of adjacent blades is assumed to be an equivalent contact spring stiffness which is determined by the bending dynamic stiffness of the blade. Then the average method is employed to obtain the dynamic responses of the primary, the sub-harmonic and the super-harmonic resonances of the shrouded blade with wake flow excitation, respectively. Finally, the dynamical responses of a shrouded blade with a set of typical material constants and geometrical parameters are given to illustrate the influence of the blade shroud gaps on the vibration amplitude.
S. Chu · D. Cao () · S. Sun · J. Pan School of Astronautics, Harbin Institute of Technology, PO Box 137, Harbin 150001, China e-mail: [email protected] L. Wang School of Science, Harbin Engineering University, Harbin 150001, China
Keywords Vibration · Flexible shrouded blade · Impact · Contact stiffness
1 Introduction In order to prevent high cyclic fatigue failures of turbomachinery blades, a blade shroud device used to be installed on the turbine blade in practical engineering. There is an initial gap between the assembled adjacent static blade shrouds. Interface of adjacent blade shrouds will be close mutually, when the blade torsion is recovered for blades rotation. When a vibration is generated, relative displacement occurs between the adjacent shrouds, and the vibration energy is absorbed through the impact and friction between the adjacent shrouded blades [1]. In this case, the vibration amplitude can be reduced due to the increase of the blade damping. Contact kinematics of shrouded blade is very complex, which includes slip, stuck and separations, and possesses typical nonlinear characteristics. This leads to the difficult task to predict its dynamic response accurately. Many investigations have been focused on nonlinear behavior of dynamical systems of integral shrouded blade. Because of the strong nonlinear nature, approximation methods and numerical integration methods were adopted to deal with the system. Some investigations are based on the widely used “macro-slip” model [2–5], in which the interfaces are
540
modeled as a rigid body, and either slip state or stick state is included. Assume that the normal load of all po
Data Loading...
