The unsteady flow in an afterburning oil pump on a certain type of aero-engine was simulated for the uncommon cavitation damage problem near its casing tongue

with arbitrary sliding mesh technology.The discharge chamber internal flow characteristics at off-design conditions were investigated to find out possible conditions causing the casing tongue cavitation.The results showed that:under large flow-rate condition

there are two separated vortices of different sizes located in the cone-shaped tube passage

while the fuel flowed past the casing wall without obvious separation in the annular chamber

which hardly trigger cavitation;under small flow-rate condition

the two separated vortices extend to take up most part of the cone-shaped passage

incoming flow of the diffuser is choke up with a part of the fuel blocked at right side flowing back to the annular chamber around the tongue.As a result

serious flow separation is raised with a high pressure decrease

which is expected to generate cavitation and following damage on the casing tongue.