Dynamic Research On Oblique Impact Of Steam Turbine Blades

The impeller blade crown is one of the core vibration damping devices of impeller machinery,it realizes energy dissipation through the vibration and collision between adjacent blade crowns,the nonlinear collision of the gap will cause the system to have a complex harmonic responsedan and wave response will affect the damping effect.This paper aims to research the vibration response and dynamic behavior characteristics between adjacent leaf crowns.First,establish a kind of dynamic model of the rigid oblique collision of two masses of the leaf crown,and establish the ordinary differential equations of motion of the model,at the same time,using the method of multi-parameter collaborative solution,the collision section and the time section are respectively selected as the Poincaré mapping section to derive the conditions for the existence of periodicity.The Jacobi matrix of the Poincaré map is obtained by the semi-analytical method,The instantaneous collision of the rigid inclined plane is used as the reference interface,and the momentum is conserved during the collision and collision.Using the impulse-momentum theorem and Poission hypothesis,the conditions of the oblique collision of two masses and the relationship between the speed states before and after the collision are analyzed,and the state equation after the collision is determined,which to analyze the influence of the external excitation frequency parameter ? on the dynamic performance of the system when the two masses collide in an oblique collision.Through studying the mechanism of the oblique collision vibration of two masses,it is found that the steady-state response of the oblique collision system has undergone period-doubling bifurcation,Hopf bifurcation and period-doubling bifurcation,which makes the steady-state periodic collision of the system produce the conversion of different periodic motions,Hopf Bifurcation and boundary sudden changes make the motion system enter the chaos.Secondly,the three-mass oblique impact vibration system is simplified from the full circle of crown blades of the steam turbine as the dynamic model of the theoretical study.Because the oblique impact vibration research of the multi-degree-of-freedom system involves system modeling and the various degrees of freedom before and after the collision.Speed jump relationship.Therefore,the three-mass collision dynamics model studies the jump relationship between the speed and displacement of each mass before and after,and then uses the fourth-order Runge-Kutta integration method for numerical integration.By controlling the change of the state parameter ? of the external excitation,the Poincaré map cross-section diagram,phase diagram and time history diagram are selected to analyze the dynamics of three-mass oblique impact vibration system in detail.Researches have shown that in the low-power external excitation frequency band of the system,the steady-state response of the three-mass oblique collision system is extremely unstable,and there are many types of periodic motion conversions and a large number of small chaotic motions.In the mid-octave band,the steady-state response of the system has multiple periods of periodic motion.The system is relatively stable.In the high-order frequency band,the system has multiple periodic collisions and chaotic motion transformations.Finally,the amplitude-frequency characteristic diagram of the oblique impact vibration motion composed of three masses and the analysis of the mechanical energy loss of each mass body of the system,summarize the damping characteristics of the three mass oblique impact vibration system.The research results show that the oblique collision of the symmetrical body will dissipate the mechanical energy of the mass body itself.By selecting the system parameters reasonably,the energy of the forced vibration of the main component of the system can be absorbed by the auxiliary system composed of the secondary components of the system during the collision.Absorption,so that the main component of the oblique collision system constructed by the three-mass body achieves the effect of damping vibration.Therefore,it is concluded that the mechanical energy dissipation of double-side collision is more obvious than that of single-side collision,and the vibration damping effect is better.At the same time,it is also in line with the application of full circle blade collision damping in actual industry.