Effects of water ingestion on the tip clearance flow in compressor rotors

The tip region of compressor rotors may be filled with water when aircraft is flying in heavy rain environment. In order to explore the effects of water ingestion on the compressor performance and the characteristics of tip clearance flow, the Euler-Lagrange method has been utilized to simulate the two-phase flow inside a transonic rotor (NASA rotor 35). The typical trajectory of water droplet in compressor has been introduced firstly to simply understand the situation of water ingestion and to verify the reliability of some special droplet breakup models. The simulation results show that water droplets will change the distribution of airflow parameters along the span direction, which leads to the decrease of mass flow rate and the increase of attack angle at the tip region, as well as the separation of boundary layer on the suction surface. Furthermore, the momentum losses caused by droplet impingement and breakup directly causes a sharp increase in the static entropy at the blade tip region. On the other hand, the ingestion of droplet brings an external disturbance to airflow, and although it has some dissipated effects on the turbulence kinetic energy, it aggravates the unsteady characteristics of turbulent flow seriously at the tip region. Finally, by comparing the compressor performance under wet and dry states, it can be concluded that the pressure ratio and adiabatic efficiency of compressor decrease after water ingestion, and the compression efficiency drops by 1-2% on the whole while the operating point moves forward and the stable working boundary becomes narrow.