Numerical study on inlet angle of guide vane in recess vaned casing treatment

This paper studies the effect of inlet angle of guide vane in the recess vaned casing treatment (RVCT). The smooth casing fan and the casing treated fans with different vane angles have been numerically simulated respectively. The result shows that the application of RVCT brings about noticeable improvements in the fan's stall margin and the modification of guide vane inlet angle leads to various effects. RVCT functions as a bridge that contributes to the extra flow circulation at the blade tip region and mitigates the flow blockage. The inlet angle of guide vane determines the amount as well as the potential in terms of accommodating fluid passing through the RVCT. Based on the evolution of flow topology, it is hypothesized that the separation on the guide vane surface is a prerequisite to the stall of the fan. The scenario that the attachment line totally blocks the vane inlet passage is a criterion of the stall. The deflection of inlet angle from positive to negative enables to enhance the stall margin by delaying the formation of the prerequisite and the criterion of the stall.