| In the 21 st century,the global industry has developed rapidly.Regard to the advanced power devices,gas turbines are the most strategic defense industrial products,which affect the national defense security and the industrial development level directly.As the core components of a gas turbine,the performance and stability of the compressor directly challenge the efficiency and safety of the gas turbine.It is crucial to research the flow control method to reduce the compressor flow loss and improve the flow stability,which is crucial to improve the performance and stability of the compressor,especially in non-design conditions.The development of flow control technology has great significance in breaking through the technical bottleneck with high load and margin in the compressor,and promoting the development of gas turbine technology.In this thesis,a numerical simulation method was used to study the control mechanism of the bionic chamber,tip groove,and tip winglet on the clearance leakage and corner separation of the compressor cascade from bionic perspectives.The effects of design parameters of various bionic structures on flow loss were summarized and applied to the compressor stage.The improvement mechanism of the bionic structures on the compressor flow field was analyzed,and the improvement scheme of compressor performance and stability was finally obtained.Firstly,the numerical calculation method in this thesis was verified by the existing experimental results,which verifies the accuracy of the numerical analysis.At the same time,the idea of the bionic structures based on the wing characteristics of dragonflies and birds has been introduced and designed in this thesis.Secondly,the geometric size and arrangement position of the tip bionic chamber,casing bionic chamber,and tip winglet structures on the clearance flow and aerodynamic performance were studied in the linear cascade by the numerical calculation method.The results illustrate that the clearance leakage flow and the separation range of the leakage vortex can be suppressed by each bionic structure,but there are some differences in the mechanism and effect.The flow resistance in the tip clearance is increased with the trapped vortex induced by the bionic chamber,which controls the separation range of the leakage vortex along the pitchwise and reduces the clearance leakage flow.However,the intensity of the concentrated shedding vortex is enhanced,and the range of the high loss area is expanded along the spanwise,increasing the total flow loss.The tip bionic chamber performs a bit effect on the flow field structure near the clearance,which can slightly reduce the leakage flow rate and flow loss.The casing bionic chamber has a significant suppression effect on the leakage vortex and leakage flow.The casing bionic chamber should be arranged near the initial position of the leakage vortex.The suppression effect on clearance leakage is enhanced and weakened afterwards with the bionic chamber height increasement,and enhanced with the expansion of the arrangement range.When the chamber is arranged from the leading edge to the trailing edge,and the chamber height is equal to 0.6% H,the leakage flow ratio is decreased by 1.82%.The tip winglet can suppress the intensity and separation range of the leakage vortex by controlling the spanwise flow of the pressure and expanding the range of the tip separation vortex.The cascade with the tip winglet exhibits good incidence characteristics.When the fusion length range of the tip winglet can include the initial position of the leakage vortex,the suppression effect on the leakage vortex is more significant.What’s more,the suppression effect is enhanced with the narrower fusion height and the longer fusion length.When the fusion height is equal to 1% H and the fusion length is the full chord,the tip winglet exhibits the most significant effect,which can reduce the total pressure loss by0.64% and the leakage flow ratio by 16.8%.Then,research on the corner separation of compressor cascade,and the flow control effects of bionic structures such as the endwall bionic chamber,leading-edge vortex generator of suction,and tip groove were compared and analyzed separately.The control mechanism of bionic structures on corner separation was presented.The selection rules and principles of bionic structures parameters were obtained based on the corner separation flow.The results indicate that the tip groove performs the strongest suppression effect on the corner separation.The high-pressure flow of the pressure is injected into the corner region,which induces the initial position of the corner separation to move backward and controls the corner separation along the pitchwise and spanwise.The cascade with the tip groove exhibits a good positive incidence characteristic.However,when the incidence angle is less than the minimum loss incidence angle,the tip groove leads to an increase in the flow loss of the cascade.The tip groove should be installed near the initial position of the corner separation.The suppression effect on corner separation is enhanced and weakened afterwards with the higher groove height.When the groove height is equal to 4% H,the flow loss of the cascade is reduced by14.4%.What’s more,the corner separation along the pitchwise can be suppressed by the trapped vortex induced by the endwall bionic chamber,reducing the flow loss.The cascade with the endwall bionic chamber exhibits good incidence characteristics.The endwall bionic chamber should be set before the initial position of corner separation.The suppression effect on corner separation is enhanced with the increase of the number of chambers arranged from the leading edge,and enhanced and weakened afterwards with the deeper chamber depth.When the chambers are arranged from the leading edge to the trailing edge,and the chamber depth is equal to 0.2% H,the flow loss can be decreased by 11.2%.The induced vortex generated by the leading-edge vortex generator of suction is near the end wall of the passage inlet,which causes the initial position of the corner separation to move backward,narrows the range of corner separation along the pitchwise,and reduces the flow loss.The cascade with the leading-edge vortex generator of suction exhibits good positive incidence characteristics.However,when the incidence angle is less than the minimum loss incidence angle,the vortex generator leads to an increase in the cascade flow loss.The vortex generator should be arranged near the initial position of corner separation.The suppression effect on corner separation is enhanced and weakened afterwards with the higher height of the vortex generator and an increase in the distance between the arrangement position and the suction.When the vortex generator is arranged at the boundary between the endwall reverse flow and the mainstream region,and the vortex generator height equals 4% H,the flow loss can be reduced by 10.3%.Finally,based on the action mechanism of the bionic structures formed on the cascade end-zone flow and the selection principle of the design parameters of the bionic structures,the bionic structures were applied in the compressor rotor and stator respectively.The effects of the bionic structures on the compressor performance and flow field structure were explored separately.The results illustrate that the stability margin and the total pressure ratio of can be expanded by the casing bionic chamber and tip winglet of the rotor in the near stall condition.The stability margin can be enlarged by 16.1% and 11.9% respectively by the casing bionic chamber and the tip winglet.Although the compressor stability margin is reduced by using the three kinds of stator bionic structures,the leading-edge vortex generator of stator suction and the tip groove can increase the efficiency and total pressure ratio from the 98.7% choke flow point to the near stall condition.The improvement effect of the tip groove is most significant.The tip winglet and the tip groove are applied to the compressor at the same time based on the previous analysis.It can be identified that the combined bionic scheme can improve the compressor stability margin by 4.1% by weakening the intensity of the tip leakage vortex of the rotor,pushing the position of the shock wave in the passage,and suppressing the corner separation of the stator.Except for the slightly lower peak efficiency,the performance of the combined bionic scheme is superior to the prototype in other conditions.In conclusion,the combined bionic scheme proposed in this thesis can enhance the stability and the off-design performance of the compressor. |
PDF Full Text Request