THE EFFECTS OF WATER INGESTION ON THE TIP CLEARANCE FLOW IN COMPRESSOR ROTORS

As the first core component of commercial aviation engines, compressor is likely to ingest a serious amount of liquid water into its path flow during the situation of heavy rain. Under the influence of centrifugal force, the tip region of compressor rotors may be filled with water. Unfortunately, the instability of tip clearance flow is a major reason for rotating stall. In order to explore the effects of water ingestion on the steady operating boundary of compressor, the change characteristics of tip clearance flow have been investigated in this research by using numerical simulation method. In reality, the compression process after water ingestion can be regarded as a special wet compression. Therefore, on the basis of existing wet compression study, the ingested mass flow and the mean droplet diameters were set as 1% of inlet air flow as well as 100 mu m respectively to investigate how does water ingestion affects the flow field at the tip clearance of rotors. The typical trajectory of water droplet in compressor has been researched firstly to simply understand the situation of water ingestion and to verify the reliability of some special droplet breakup models. Then, the compressor performance in two states of dry and wet have been compared to indicate that the pressure ratio and adiabatic efficiency of compressor will decrease after water ingestion. Among them, the compression efficiency drops by 1 similar to 2% as a whole compared with the dry condition, the operating point moves forward and the surge margin reduces slightly. The simulation results show that the presence of water droplets will change the distribution of airflow parameters along span direction, which leads to the decreases of mass flow rate and flow capacity of blade row, the increase of attack angel at tip region, and the separation of boundary layer in suction surface. Furthermore, the momentum losses caused by droplet impingement and breakup cause a sharp increase in the static entropy at the blade tip region as well. On the other hand, the ingestion of droplet brings an external disturbance to the flow, although it has some dissipated effects on the turbulence kinetic energy, it aggravates the unsteady characteristic of turbulent flow seriously at the tip region of blade.