Unsteady flow field inside an after-burning fuel pump was investigated by large eddy simulation method with the dynamic subgrid-scale stress model.The cavitation erosion mechanism of the original casing tongue was discussed

and then

the characteristics of transient flow around the casing tongue and pump performance were investigated under different filleting radius conditions.The results show that the flow separation at the original tongue under small flow-rate condition brings strong shearing vortex which induces cavitation.The separation attachment location formed by the vortex shedding agrees well with the real cavitation damage core region.Under small flow-rate condition

tongue filleting results in diversion vortex in the diffuser tube

which suppresses the flow separation around the tongue face as well as the attached shearing vortex

while the 4mm filleting radius case can avoid tongue cavitation.Within the design flow-rate

tongue filleting raises the pump head

and the smaller the flow-rate

the larger the head increase amplitude

which reaches 3% under small flow-rate condition.