| Research group proposed a novel additional ducted fan structure can solve SSMI(Spool-Speed Mismatching Issue)well,and the core components tip-turbine of the novel power system has the double characteristics of low solidity and low aspect ratio,solidity can be as low as 0.6,aspect ratio as low as 0.4.The flow mechanism and the design technology of the tip-turbine did not form relatively perfect theory system.The novel additional ducted fan structure principle prototype based on the numerical simulation method was adopted to carry out the research of low solidity tip-turbine flow characteristic and its design technology,and laid the theoretical foundation for the subsequent development of new high bypass ratio propulsion vehicle.The main work is as follows:1?Aiming at the structure of a novel additional tip-driving fan system which can greatly improve the bypass ratio,using numerical simulation analyzes the loss structure and flow characteristics of the tip-turbine which is its core components.Besides,the design rules of the camber line are preliminarily studied,which laid the theoretical foundation for the further development of high bypass ratio propulsion.It is found that the main loss of this tip-turbine under low solidity is profile loss,accounting for 70% of the total loss,and its loss is 5 times of the profile loss under the normal solidity.The large area separation vortex generated on the suction surface is the main source of the profile loss,the load advancement,and the position of the throat gradually introduced into the leading edge with the decrease of the solidity are the main flow characteristics;The mechanism of large-scale separation vortex comes from two aspects: on the one hand,the throat moves to the leading edge and the separation occurs prematurely on the leading edge,on the other hand,the influence range of the velocity potential at the leaf basin becomes smaller.Based on this feature,advancing the maximum deflection position of the camber line can effectively improve the tip turbine Efficiency and energy extraction rate.2?Combining with the flow characteristics of low-solidity tip turbine,the design method based on the reaction is proposed to improve the pressure ratio and efficiency of the impeller at a low solidity,and the research on the design method and the specific influence of the reaction is carried out: High reaction design can effectively inhibit the flow separation in the runner.Under the very low solidity(below 0.9),it is absolutely superior in work efficiency and efficiency.It can be considered that the high reaction design is the effective measures to improve the Efficiency and work efficiency of the very low-solidity turbine rotor.While the low reaction design is not suitable for very low solidity;under the conventional low solidity(0.9-1.3),high reaction design and low raction design are generally superior to the conventional reaction design,high reaction efficiency has efficiency advantage,low reaction has pressure ratio advantage.The choice of both the solidity is close to 0.9 high reaction,close to 1.3 low reaction.3?Based on a novel turbofan propulsion system with additional tip-driving fan which can high improve the bypass ratio,we carried out an experimental study,set up a set of test bed that can achieve the principle of the structure?The results show that: The working condition of the test bed is stable.Besides,the smooth operation of the additional tip-driving fan rotor can be maintained at high rotational speed.The measurement system is reasonable and the measurement result is reliable.The test results confirm the principle of increasing the principle of the prototype.However it still has a lot of room for improvement;If the efficiency can be a certain,the bypass magnification ratio be determined,the higher the unit power of the turbine,the fan thrust and power ratio is lower. |
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