Research on the air–oil two-phase flow regime in an aeroengine bearing chamber based on Hilbert–Huang transform

The development of aeroengines toward a lighter and compact structure has put forward a stringent requirement on the lubrication systems, especially on the bearing chambers which contain complex air–oil two-phase fluids. Understanding the flow characteristics is of considerable significance to ensure the cooling and lubrication effect and to improve the working reliability of the aeroengine. Hilbert–Huang transform (HHT) was used to analyze the spectral characteristics of the pressure signals in the bearing chamber, in order to establish the correlation between the energy indicator k and the flow regime. The influences of the operating conditions and lubricant physical properties on the flow regime were discussed. The findings indicate that this approach can distinguish two typical flow regimes in the bearing chamber. With the increase of oil inflow and the decrease of draft speed, the flow regime changes from homogeneous flow to stratified flow, and k shifts from high-frequency band to low-frequency band. At the same lubricant mass inflow, k shifts from low-frequency band to high-frequency band with the increase of lubricant density, and the oil film on the wall becomes thinner. As the viscosity increases, the flow resistance grows and more oil accumulates on the wall. The flow regime converts from homogeneous flow to stratified flow, with k shifting from high-frequency band to low-frequency band. In addition, higher surface tension will cause more oil agglomeration, which results in less stable two-phase flow with irregular and uneven distribution of the oil on the wall.