Flow characteristic of tip turbine of additional ducted-fan system

Based on a novel high bypass ratio turbofan propulsion system with additional tip-driving fan, the flow characteristics and working mechanism of the core components tip-turbine were investigated using numerical simulation, which laid a theoretical foundation for the further development of high bypass ratio propulsion. Research results indicated that tip-turbine was essentially the axial flow turbine with low solidity and low aspect ratio characteristic, solidity can be as low as 0.6, aspect ratio as low as 0.4. The reduction of solidity caused the migration of throat position, which led to a substantial decrease in the flow deflection and the acceleration of the expansion; the gap leakage loss caused by the low aspect ratio was 2 times larger than the original one, and the influence of leakage vortex was gradually extended to the vicinity of the root of the blade, which reduced the effective extraction of energy area and the energy extraction rate greatly; for the novel power system, effective extraction of energy region and energy extraction rate were proposed to measure the specific work of tip-turbine qualitatively and quantitatively.