With the development of science and technology, the performance of an aero-engine has been given more rigorous requirements. Seal device is an important component part of an aero-engine, and the improvement in its performance may be an efficient way to further improve the performance of an aero-engine. Finger seal is a flexible seal and has higher performance price ratio, therefore it gets more attention and research recently. The phenomenon of noncontact state converting to contact state will occur in every working cycle of finger seal that inevitably lead to the finger seal bearing the impact effect of rotor. But so far, the influence of impact on the finger seal performance has not been discussed and researched. To overcome this shortcoming, the stress–strain curves of C/C composite under different impact velocities are obtained by the Gleeble3500 thermo-simulator system in the paper, and then the elastic modulus of C/C composite in three directions is calculated by experimental data. The effects of impact velocity and impact damping on the impact force are analyzed by means of the impact theory. The new structural stiffness of finger seal and the impact displacement excitation of the rotor are built through impact effect analysis. On this basis, the equivalent dynamic model of C/C composite finger seal with distributed mass is established to evaluate the impact effect. By the model, the difference of calculated results is analyzed under whether considering the impact effect or not. And the effect of impact velocity and coefficient of restitution on the dynamic performance of the finger seal is also analyzed under considering the impact effect, respectively. The above results show that the impact effect has significant influence on the leakage and wear of finger seal, therefore when the performance of the finger seal was analyzed, it is necessary to consider the impact effect.
Properties of the geodesic acoustic mode (GAM) density fluctuations are studied using two toroidally separated Langmuir triple-probe arrays on the top of HT-7 tokamak. The GAM scenario is identified in the potential fluctuations with the toroidally symmetric structure (n = 0) and satisfying the temperature scaling of GAM mode frequency. Some theoretical predictions about the mode features of GAM density fluctuations are verified in our experiments: the toroidal mode number of GAM density fluctuations is n = 0; its amplitude is consistent with the theoretical prediction in a factor of 2; the density and potential fluctuations of GAM is in anti-phase at the top of plasma cross-section. Strong nonlinear interactions are found between GAM density fluctuations and ambient turbulence (AT). The results support the conclusions that the envelope modulation of potential fluctuations is dominantly caused by the direct regulation of GAM in the generation processing, and the envelope modulation of density fluctuation is due to the GAM shear effect.
With the development of aero-engine industry technology, the operating conditions for finger seal become more horrible, including that high temperature, assembly type of finger seal, rotor tilt, and impact of rotor coexist. Unfortunately, the coupled effect on the dynamic performance of finger seal is not studied in previous works for the dynamic of finger seal. In this paper, the parameters of equivalent dynamic model for finger seal, including the equivalent structure stiffness of finger stick, the contact stiffness between finger stick and rotor, the friction heat between finger boot and rotor and the rotor displacement excitation, are corrected when the coupled effect of rotor tilt, assembly condition, temperature, and impact are considered. In addition, the distributed mass equivalent dynamic model is developed for considering the complex working conditions (including rotor tilt, assembly condition, temperature effect, and impact effect). Based on this model, the dynamic performance of finger seal in the complex working state is analyzed, and the influence of the complex working state on the dynamic performance is also studied. The results indicate that effect of the complex working state on the leakage performance and wear performance of finger seal is complex. The work in this paper demonstrates the necessity of considering the complex working conditions in the analysis of the dynamic performance of finger seal.
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