Nonlinear Dynamics of Shrouded Turbine Blade System with Impact and Friction

Abstract

Dry friction dampers are passive devices used to reduce the resonant vibration amplitudes in turbine bladed systems. In shrouded turbine blade systems, in addition to the stick- slip motion induced by dry friction during the contact state in the tangential direction, the interface also undergoes intermittent separation in the normal direction. The problem can thus be treated as a combination of impact and friction. In this work, the dynamics of dry friction damped oscillators which are representative models of dry friction damped bladed system is investigated. A one dimensional contact model which is capable of modeling the interface under constant and variable normal load is used. The steady state periodic solutions are obtained by multi - harmonic balance method (MHBM). Frequency response plots are generated for different values of normal load using the arc length continuation procedure. The MHBM solutions are validated using numerical integration. A single degree of freedom (dof) model under constant normal load with constant and variable friction coefficients, a dry friction damped two dof system under constant normal load and a two dof system under variable normal load are investigated. In the presence of variable normal load, the system shows multivalued frequency response and jump phenomenon. The optimal value of the normal load which gives minimum resonant response is also obtained.

Extraction of Features due to Breathing Crack from Vibration Response of Rotated Blades considering Tenon Connection and Shroud Contact

“…Each shroud keeps in touch with its adjacent ones. e dry friction model proposed by Santhosh et al [26] is applied, as shown in Figure 6. Contact of adjacent shrouds is regarded as a platform damper with a linear spring, whose stiffness is k s .…”

“…erefore, coupling force exists between tenons. ere is also dry friction force between adjacent shrouds, which is relative to the motion of their contact interfaces [8,19,[24][25][26]. ree sectors are selected to build a lumped parameter model of a bladed disk similar to that in [19], as shown in Figure 3.…”

Numerical and experimental investigation on the vibro-impact responses analysis of shrouded blade

“…Based on lumped mass model, [7][8][9][10][11][12][13][14][15] some scholars have analyzed the nonlinear dynamic characteristics of vibroimpact system. Banerjee et al 7 studied the nonlinear grazing bifurcation characteristics of an impact system by experiment, and their results indicated that the narrow band of chaos could appear under the grazing conditions.…”

“…Banerjee et al 7 studied the nonlinear grazing bifurcation characteristics of an impact system by experiment, and their results indicated that the narrow band of chaos could appear under the grazing conditions. Santhosh et al 8 established a single degree of freedom (DOF) model under constant and variable normal loads to investigate the nonlinear dynamic phenomena of turbine shrouded blade with impact and friction. Jiang and Wiercigroch 9 investigated the grazing bifurcation characteristics of an oscillator with one-sided constraint.…”

“…The impact with clearance is a very common dynamic phenomenon in mechanical system, such as shrouded blades 1,2 and gear systems, 3 which can cause the complicated nonlinear vibration characteristics, and many researchers 1,2,4–6 have discussed the dynamic characteristics of vibro-impact system with clearance theoretically and experimentally. Many mathematical models were proposed to describe the dynamic phenomena of vibro-impact systems, such as lumped mass models, 7–15 beam-stop impact models, 2,4,6,16–22 and beam–beam impact models, 1,5,23,24,28 which enriched the research results of vibro-impact system with clearance.…”