Optimal location and shape definition of elliptical ventilation openings on aero engine turbine rotors with stress concentration effect

The aero engine turbine rotors are under strong centrifugal load and the highest thermal load.The ventilation openings on the rotors are inevitable,because air flow need to pass through them to cool the temperatures down and keep the air pressure balanced in internal aero engine.The ventilation openings will lead to stress concentration effect.In this paper,the stress concentration factor of elliptical opening on rotating disc is deduced by superposition method.How to define the optimal location and shape of the elliptical opening on rotating disc to decrease the stress concentration effect has been investigated specifically.The reliability and accuracy of the theoretical deviation process is verified by Finite Element Method(FEM).The process of how to obtain the optimal location of the elliptical ventilation opening with particular shape on turbine sealing disc is described as an engineering application case.The investigation provides sufficient theoretical support for optimal location and shape definition of elliptical ventilation opening on aero engine rotors with stress concentration effect by pure mechanics consideration.

Field observations of the thermal stability of permafrost under buildings with an underfloor open ventilation space and pile foundations in warm permafrost at high altitudes

Pile foundations combined with ventilation spaces under floors are the most common method in buildings over permafrost.The safety and stability of buildings are closely related to the temperature of permafrost.However,there are limitations of understanding on this method in the high-altitude,warm(>−1℃)permafrost areas on the Qinghai–Tibet Plateau.In this study,the thermal stability of permafrost foundation soils under buildings with an underfloor open ventilation space and pile foundations in warm permafrost at high altitudes was studied through field observations of ground and air temperatures,wind speed,net radiation from 2017 to 2021.The results indicated that the open ventilation space exerted an effective cooling effect on the underlying permafrost and pile foundations from March to October,while a thermal insulation effect was observed from November to February of the following year,but overall,the cooling effect dominated;the cooling effect of open ventilation spaces differed spatially.The permafrost temperature on the south-facing side was higher than that on the north-facing side,and those on the east and west sides were higher than that directly under the open ventilation space of the building.This study also demonstrated that radiation shielded by the building was a main factor of the cooling effect of open ventilation spaces,and the cooling effect of open ventilation spaces could accelerate the back-freezing of the cast-in-place(CIP)pile foundations.This structure could effectively maintain the frozen state of the underlying warm permafrost at high elevations on the interior Qinghai–Tibet Plateau.