| In order to study the aerodynamic performances of turbomachinery cascades in original profile and modified profile,understand the structure of flow field of two sets cascade,explore the growth mechanism of loss in the different incidences,verify the correctness of the design concept which is based i n blade variants,in this paper,the blowing experiment were implemented on two annular cascade(test cascades)in subsonic wind tunnel with different incidences.There are five different incidences(0o?±5°and ±10o)between flow and test cascades because the exist of guide cascades which has been installed in the test cascade.To measure the aerodynamic parameters distributions along the pitch and blade height of the downstream flow field in the test cascades through the application of five-hole measuring needle.And to measure the static pressure coefficient distributions in the different sections(hub ?middle and tip)using the static pressure holes which have been set in the blade surface.We can find that prototypical cascades adopt the front-load profile which without optimal design through the theoretical analysis of the test results of prototypical cascades.Under the 0° incidences,the longer adverse pressure gradient section result in the higher profile loss on the suction surface exit.The transverse pressure gradient is larger in the front and middle of flow channel.Strong lateral secondary flow causes suction side corner separation,and makes the aerodynamic performances deterioration on the hub and casing area,so the flow efficiency is low of prototypical cascades.According to the problems which are revealed through results of the prototypical cascades experiment,the designers applied commercial software such as CFX to modify the prototypical cascade.The modified cascades adopt the aft-load profile which with optimal design.On the same aerodynamic parameters of wind tunnel test rig,under the same conditions of aerodynamic and boundary with the prototypical cascades,the blowing test has verified the effectiveness of the modified design.Test results of tests show that the lowest pressure point on the suction surface of modified profile has been moved to 90% axial chord length so that the lateral pressure gradient significantly is reduced in the front and middle of flow channel on casing and hub areas,and the length and value of adverse pressure gradient which exists near the suction surface outlet edge is shortened.Therefore,not only the secondary flow loss but also the profile loss are reduced.Compared with the prototypical c ascade,the modified cascades significantly reduce the loss of flow under 0° incidence,and have good adaptability to incidences.The high pressure 12 stage of 1000 MW ultra supercritical units is reaction stage,the stator and rotor blades adopt aft-loaded profile.Under the experimental incidences,the aerodynamic performance is very close of the stator and rotor blades in high pressure 12 stage.At 0o incidence,the profile loss is from 1.314% to 1.712%,owe deflection of airflow is from1.1506o to 1.5214o.The profile loss changes from 1.314% to 2.149% and owe deflection of airflow changes from 1.1506o to1.6614o along with the incidence from +10o to-10o.The incidence do not affect the pressure distribution at the back of the blade in the test range,especially does not affect the axial position of the minimum pressure points at the suction side and the loading type.The test data indicates that 1000 MW ultra supercritical units possess high efficiency and good adaptability to incidences. |
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