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Microstructure feature extraction and performance simulations of a Yttria-Stabilized Zirconia (YSZ) abradable coating applied in the high-pressure turbines of aero-engines, with a service temperature over 1000 °C were conducted. The finite element method (FEM) numerical models of the abradability, bonding strength, and thermal shock resistance of the YSZ coating were established. The effects of porosity and pore diameter on the properties of the coating were obtained through simulations and calculations. The results indicated that the abradability, bonding strength, and thermal shock resistance of the coating were jointly determined by porosity and pore diameter. With the porosity increasing from 5% to 50%, the bonding strength of the coating decreased gradually, but the abradability and thermal shock resistance of the coating were significantly improved, especially when the porosity was above 20%. With the pore diameter increased from 0.5 μm to 1.5 μm, the abradability, bonding strength, and thermal shock resistance of the coating increased initially, and then decreased. An evaluation function using the normalized weighting strategy was proposed to characterize the comprehensive properties of the coating. The results of the evaluation showed the optimal abradability, bonding strength, and thermal shock resistance of the coating were obtained under a combination of 25% porosity and 1 μm pore diameter. This study may provide guidance for design optimization, and an improvement in the microstructure and properties of coatings in future research.

Abstract:In order to find a turbulent flow model which can accurately describe the internal mixing process of the nozzle adjustable jet pump, 8 combinations made up by four turbulence models (Standardand RSM) and two wall functions (Standard wall functions and Non-Equilibrium wall functions) were simulated and analyzed. Taking a nozzle adjustable jet pump as an example, the simulation of 8 models were carried out when the opening of the jet pump at 50%, 60%, 70%, 75% and 90%, respectively. And then the field tests were carried out. The comparison between the simulation results and the experimental data of the pressure ratio and efficiency curve was studied. And the turbulent kinetic energy distribution of the jet pump in different models was analyzed. The results show that: the difference of the wall function has little effect on the simulation results, the difference of the curve is mainly caused by differences in turbulence models. The error between the simulated value and the test value of each model decreases with the increase of opening degree and pressure ratio. model can predict the internal flow of the nozzle jet pump well, and it is in good agreement with the experimental data. The Non-Equilibrium wall function is more suitable for the simulation of jet flow, which is closer to the experimental value than the standard wall function. Therefore, the accurate performance prediction and flow field details can be obtained by the combination of Realizable ε − k model and non-equilibrium wall function.

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