No abstract

An extensive investigation of influence of rub grooves on dynamics and stability of the rotor, which is subjected to aerodynamic forcing associated with the leakage flow through 44 straight-through seals, was performed by using numerical calculations based on the single control-volume method and the perturbation analysis. Three cases of different groove configurations were chosen for the comparative study, e.g., the seal without rub groove (case1), the seal with upstream shifting of the seal tooth in respect to the rub groove (case2) and the seal with location of the seal tooth in the middle station of the rub groove (case3). The orifice contract coefficient adopted in reduction of rotordynamic coefficients was provided by using Computational Fluid Dynamics (CFD). Influence of rub grooves on the leakage flow was obtained in terms of the close-up view of the flow pattern near the seal tooth, leakage flow rate, distributions of the mean pressure and circumferential velocity in cavities. In comparison to case 1, the leakage flow in case 3 is considerably intensified, while which in case 2 is slightly increased. Dynamics and instability of the rotor in all cases was discussed in terms of the rotordynamic coefficients and the logarithmic decrement, respectively. The results disclosed that the aerodynamic forcing in case 2 intensified the destabilization of the rotor system.

A best-estimate assessment model was established to predict the entire life time of the material due to crack development and propagation in aggressive environment. Stress corrosion cracking (SCC) growth rate was modeled to investigate the influence of corrosion environment on SCC. Uncertainties with respect to material parameters, aggressive medium and mechanical loadings were taken into account. In addition, mean value estimation method (MVM) and monte carlo simulation method (MCS) were used to solve the established theoretical model. The studies demonstrated that the results obtained by using MVM reached agreement to those by using MCS. And the life time of the material due to the crack development and propagation in the aggressive environment was accurately predicted.

A nonlinear mathematical model for the rotordynamics of the rotor under the influence of the leakage air flow through a labyrinth seal was established in the present study. An interlocking seal was chosen for study. The rotor-bearing-seal system with four degrees of freedom was modeled as Jeffcot rotor subject to the aerodynamic force induced by the leakage flow through the interlocking seal and the oil-film force induced by the oil flow in the journal bearing. Particular attention was placed on the spatio-temporal variation of the aerodynamic force on the rotor surface in the coverage of the seal clearance and the cavity volume, which was specifically delineated by using Muzynska model and the perturbation analysis, respectively. The governing equation of the rotordynamics, into which the aerodynamic force integrated over all seal clearances and cavity volumes was incorporated together with the oil-film force, was solved by using the fourth-order Runge-Kutta method to obtain the orbit of the whirling rotor. Stability of the rotating rotor was inspected by using the orbital motions and the phase trajectories. The influence of the leakage air flow through the interlocking seal on the whirling rotor was described in terms of the rotating speed and the seal clearance. The results convincingly demonstrate that the destabilization of the rotor-bearing-seal system was reduced due to the aerodynamic force induced by the leakage air flow through the interlocking seal.

Information revealed from 3D thermal-mechanical simulations of the innercasing over 0.2 million hours by finite element method(FEM) provides detailed local distributions of stress, temperature, and creep damage through the whole configuration. It found that the innercasing of a Ultra-supercritical(USC) turbine is subjected to the complex stress states. Due to this, the multiaxial effect is considered in the creep damage analysis.