Hydrodynamic journal bearings are used to support the planetary gears in the transmission system of a Geared Turbo Fan engine, and they operate under severe working conditions, such as misalignment, high speed, and he...Hydrodynamic journal bearings are used to support the planetary gears in the transmission system of a Geared Turbo Fan engine, and they operate under severe working conditions, such as misalignment, high speed, and heavy load. Surface texture is regarded as an effective approach to improve mechanical properties under severe working conditions. However, the effects of surface texture on misaligned journal bearings under severe conditions have not been well studied. Therefore, a thermoelastohydrodynamic(TEHD) lubricating model with a textured and misaligned journal is presented in this study. Solid deformation, heat transfer between oil and the bearing, and heat convection between air and the bearing are considered in the model. The effects of cavitation and viscosity-temperature are also taken into account. The impacts of surface texture parameters and the misalignment angle on lubricating properties are investigated in the model. Results indicate that the bearing lubricating performance is greatly improved by optimal surface texture considering journal misalignment. The maximum oil film pressure and load-carrying capacity of a journal bearing increase with journal misalignment. Meanwhile, the oil film temperature increases sharply while considering misalignment.展开更多
The complex operating state of aeroengines has an impact on the performance of finger seals. However, little work has been focused on the issue and the dynamic performance of finger seals is also rarely studied. There...The complex operating state of aeroengines has an impact on the performance of finger seals. However, little work has been focused on the issue and the dynamic performance of finger seals is also rarely studied. Therefore, a distributed mass equivalent model considering working conditions is proposed in this paper for solving the existing problems. The effects of the fiber bundle density and the preparation direction of the fiber bundle of a C/C composite on the dynamic performance of a finger seal are investigated in rotor tilt based on the proposed model. The difference between the C/C composite finger seal performances under the rotor precession and nutation tilt cases is also investigated. The results show that the fiber bundle density and the preparation direction of the fiber bundle have an influence on the dynamic performance of the finger seal as rotor tilt is considered, and the dynamic performance of the finger seal is different in the two kinds of tilting modes. In addition, a novel method for design of finger seals is presented based on the contact pressure between finger boots and the rotor. Finger seals with good leakage rates and low wear can be acquired in this method.展开更多
Under-race lubrication applied to the inter-shaft bearing of aeroengine is characterized by spray oil collection and oil delivery to the bearing via flow-path structure. Droplet splashing induced by the collision betw...Under-race lubrication applied to the inter-shaft bearing of aeroengine is characterized by spray oil collection and oil delivery to the bearing via flow-path structure. Droplet splashing induced by the collision between spray oil and the scoop as well as oil flowing characteristics in the flow-path influence bearing lubrication efficiency. In previous investigations, the spray oil collection and oil delivery analysis were separated, and the effect of droplet splashing on bearing lubrication efficiency was not considered. Moreover, time-varying characteristics of oil delivered to the bearing were not accounted for. This is caused by time variations of the circumferential position of rollers and under-race feed holes. To overcome these limitations, a numerical model which integrates the spray oil collection and oil delivery analysis is proposed in this paper. The model is embedded with the function of calculating the flow rate of splashing droplets and analyzing time-varying characteristics of the oil fed to the bearing. Furthermore, the numerical model is validated by experimental investigation. The proposed numerical model facilitates the accurate calculation of bearing lubrication efficiency as well as the design of an efficient lubrication structure.展开更多
For designing efficient lubrication system of an aeroengine bearing chamber,sufficient knowledge on oil/air two-phase flow characteristics is required.When analyzing bearing chamber two-phase flow,the essential prereq...For designing efficient lubrication system of an aeroengine bearing chamber,sufficient knowledge on oil/air two-phase flow characteristics is required.When analyzing bearing chamber two-phase flow,the essential prerequisite is quantifying the oil ligaments,which are detached from bearing rotary elements and shed into the bearing chamber.Related investigations are mainly targeted at liquid shedding on the rotating disk as opposed to the bearing rotary elements.Moreover,the research based on bearing rotary elements is conducted by experiment.Due to the limited operating conditions,experimental studies cannot guide engineering applications.To overcome these limitations,a theoretical model is established in this paper,for revealing the mechanism of oil shedding from bearing rotary elements and quantifying the shedding ligaments.The theoretical model is validated against experimental results from classical studies.In addition,the correlation for shedding ligaments number based on aeroengine bearing structural and operational parameters is obtained via theoretical analysis.The analytical results demonstrate that oil shedding and ligaments formation appear at the edge of bearing inner race outer-periphery.The number of shedding ligaments increases with the rise of shaft rotational speed while decreases with the growth of oil viscosity.展开更多
基金co-supported by the National Natural Science Foundation of China(No.51505384)the Natural Science Foundation of Shaanxi Province of China(No.2017JM5032)
文摘Hydrodynamic journal bearings are used to support the planetary gears in the transmission system of a Geared Turbo Fan engine, and they operate under severe working conditions, such as misalignment, high speed, and heavy load. Surface texture is regarded as an effective approach to improve mechanical properties under severe working conditions. However, the effects of surface texture on misaligned journal bearings under severe conditions have not been well studied. Therefore, a thermoelastohydrodynamic(TEHD) lubricating model with a textured and misaligned journal is presented in this study. Solid deformation, heat transfer between oil and the bearing, and heat convection between air and the bearing are considered in the model. The effects of cavitation and viscosity-temperature are also taken into account. The impacts of surface texture parameters and the misalignment angle on lubricating properties are investigated in the model. Results indicate that the bearing lubricating performance is greatly improved by optimal surface texture considering journal misalignment. The maximum oil film pressure and load-carrying capacity of a journal bearing increase with journal misalignment. Meanwhile, the oil film temperature increases sharply while considering misalignment.
基金co-supported by the National Natural Science Foundation of China (No. 51575445)the Natural Science Foundation of Shaanxi Province of China (No. 2014JM7266)
文摘The complex operating state of aeroengines has an impact on the performance of finger seals. However, little work has been focused on the issue and the dynamic performance of finger seals is also rarely studied. Therefore, a distributed mass equivalent model considering working conditions is proposed in this paper for solving the existing problems. The effects of the fiber bundle density and the preparation direction of the fiber bundle of a C/C composite on the dynamic performance of a finger seal are investigated in rotor tilt based on the proposed model. The difference between the C/C composite finger seal performances under the rotor precession and nutation tilt cases is also investigated. The results show that the fiber bundle density and the preparation direction of the fiber bundle have an influence on the dynamic performance of the finger seal as rotor tilt is considered, and the dynamic performance of the finger seal is different in the two kinds of tilting modes. In addition, a novel method for design of finger seals is presented based on the contact pressure between finger boots and the rotor. Finger seals with good leakage rates and low wear can be acquired in this method.
基金supported by the National Science and Technology Major Project(No.J2019-Ⅲ-0023-0067)the National Natural Science Foundation of China(No.51975475)the Fundamental Research Funds for the Central Universities(No.31020200503002)。
文摘Under-race lubrication applied to the inter-shaft bearing of aeroengine is characterized by spray oil collection and oil delivery to the bearing via flow-path structure. Droplet splashing induced by the collision between spray oil and the scoop as well as oil flowing characteristics in the flow-path influence bearing lubrication efficiency. In previous investigations, the spray oil collection and oil delivery analysis were separated, and the effect of droplet splashing on bearing lubrication efficiency was not considered. Moreover, time-varying characteristics of oil delivered to the bearing were not accounted for. This is caused by time variations of the circumferential position of rollers and under-race feed holes. To overcome these limitations, a numerical model which integrates the spray oil collection and oil delivery analysis is proposed in this paper. The model is embedded with the function of calculating the flow rate of splashing droplets and analyzing time-varying characteristics of the oil fed to the bearing. Furthermore, the numerical model is validated by experimental investigation. The proposed numerical model facilitates the accurate calculation of bearing lubrication efficiency as well as the design of an efficient lubrication structure.
基金supported by the National Science and Technology Major Project(No.J2019-Ⅲ-0023-0067)the National Natural Science Foundation of China(No.51975475)the Fundamental Research funds for the Central Universities(No.31020200503002)。
文摘For designing efficient lubrication system of an aeroengine bearing chamber,sufficient knowledge on oil/air two-phase flow characteristics is required.When analyzing bearing chamber two-phase flow,the essential prerequisite is quantifying the oil ligaments,which are detached from bearing rotary elements and shed into the bearing chamber.Related investigations are mainly targeted at liquid shedding on the rotating disk as opposed to the bearing rotary elements.Moreover,the research based on bearing rotary elements is conducted by experiment.Due to the limited operating conditions,experimental studies cannot guide engineering applications.To overcome these limitations,a theoretical model is established in this paper,for revealing the mechanism of oil shedding from bearing rotary elements and quantifying the shedding ligaments.The theoretical model is validated against experimental results from classical studies.In addition,the correlation for shedding ligaments number based on aeroengine bearing structural and operational parameters is obtained via theoretical analysis.The analytical results demonstrate that oil shedding and ligaments formation appear at the edge of bearing inner race outer-periphery.The number of shedding ligaments increases with the rise of shaft rotational speed while decreases with the growth of oil viscosity.
