Effect of Sealing Air on Oil Droplet and Oil Film Motions in Bearing Chamber

Beating chamber is one of important components that support aero-engine rotors and research on oil droplet and oil film motions is an important part of bearing chamber lubrication and heat transfer design. Consid- ering the pressure of sealing air is an important operating condition that affects the oil droplet and oil film mo- tions, the effect of sealing air pressure on airflow in bearing chamber is investigated in this paper firstly ; and then based on the air velocity and air/wall shear force, the oil droplet moving in core air, deposition of oil droplet im- pact on wall as well as velocity and thickness of oil film are analyzed secondly; the effect of sealing air pressure on oil droplet velocity and trajectory, deposition mass and momentum, as well as oil film velocity and thickness is discussed. The work presented in this paper is conducive to expose the oil/air two phase lubrication mechanism and has certain reference value to guide design of secondary air/oil system.

Research into Configuration and Flow of Wall Oil Film in Bearing Chamber Based on Droplet Size Distribution

The lubrication design and heat transfer determination of bearing chambers in aeroengine require a sufficient understanding of the oil droplet-film interaction and physical characteristic in an oil/air two-phase flow state. The analyses of oil droplet movement, mass and momentum transfer during the impingement of droplet/wall, as well as wall oil film thickness and flow velocity are very important for the bearing chamber lubrication and heat transfer calculation. An integrated model in combination with droplet movement, droplet/wall impact and film flow analysis is put forward initially based on the consideration of droplet size distribution. The model makes a contribution to provide more practical and feasible technical approach, which is not only for the study of droplet-film interaction and physical behavior in bearing chambers with oil/air two-phase flow phenomena, but also useful for an insight into the essence of physical course through droplet movement and deposition, film formation and flow. The influences of chamber geometries and operating conditions on droplet deposition mass and momentum transfer, and wall film thickness and velocity distribution are discussed. The feasibility of the method by theoretical analysis is also verified by the ex- isting experimental data. The current work is conducive to expose the physical behavior of wall oil film configuration and flow in bearing chamber, and also significant for bearing chamber lubrication and heat transfer study under oil/air two-phase flow conditions.

A Fast Method to Calculate the Oil Droplet Velocity in Aero Engine Bearing Chambers

The oil droplet velocity in an aero engine bearing chamber can determine the initial film state which is the fundament for lubrication design and heat analysis. This paper studied the droplet motion in a respective aero engine bearing chamber and obtained a fast method to calculate the droplet velocity by an analytical method. Comparing the velocity results calculated by the fast method with those from the literatures by the numerical method under different operating conditions, the method proposed in this paper is confirmed to be fast and reliable. The effects of operating conditions on droplet velocity are obtained at the same time. This study contribute to follow-up research work on droplet deposition properties in aero engine bearing chambers

Analysis of oil shedding and ligaments formation on bearing rotary elements

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.

Measurements of Water-Air Flow Phenomena in a Chamber with a Rotating Shaft

The paper concerns the phenomena of the fluid film that occurs in the bearing chamber of an aircraft engine.The geometry of the system includes two concentric cylinders,between which there is a mixture of oil and air.The fluid circulates in a closed circuit.The rotary movement of the inner cylinder causes creation of the fluid film on the walls of the chamber.The article proposes a measurement method that is allowing observation of this fluid film and,in particular,analysis of the movement of the air bubbles occurring in the film.An own model of the bearing chamber with transparent walls was constructed for the research.For the investigation,water was used instead of oil.Observation of the behaviour of the flow was possible thanks to video recordings made with the use of a fast-capture camera.The results presented in the paper include velocity magnitudes of the air bubbles in the fluid film in dependence on the rotational speed of the shaft and water volume fraction and with a range from 0.37 to 0.91 m/s.The results presented in this article can be used for the bearing chamber numerical models validation.