Mechanism Research On Flow And Resistance Reduction Of Vortex Reducer In Compressor Bleed Air System

With the continuous improvement of aeroengine performance,the thermal load of hot components is increasing,which puts forward higher requirements on the pressure and temperature of the air used for cooling and sealing of the turbine and other hot components.In this paper,aeroengine compressor bleed air system was set as the research object,aiming at the problem of excessive flow resistance in the process of bleed air,the flow and resistance reduction mechanisms of the drum hole and three kinds of typical vortex reducer in bleed air system were investigated by combined numerical computation and model experiment.The mechanism of resistance reduction and the variation of flow and resistance reduction characteristics with the key structure and aerodynamic parameters of the vortex reducer were revealed.The main research contents and conclusions are as follows:The flow structure,velocity distribution and pressure loss characteristics of a typical condition of the first restricting element of the air bleed system——circular drum hole were presented.On this basis,the influence of the diameter of the circular hole,rotational Reynolds number and dimensionless mass flow rate on the flow and resistance reduction characteristics were carried out,and the corresponding variation law was obtained.A waist-circle hole structure was promoted,the influence of the lengthdiameter ratio and area-ratio on flow and resistance reduction characteristics of air bleed system were analyzed and compared with the circular drum hole.The mechanism of resistance reduction in the waistcircle drum hole and the importance of resistance reduction in the co-rotating cavity were revealed.Based on the analysis of typical condition of the de-swirled nozzle type vortex reducer,the influence of the de-swirl angle,diameter and number of the de-swirl nozzle,rotational Reynolds number and dimensionless mass flow rate on the flow and resistance reduction characteristics of de-swirled nozzle type vortex reducer were investigated.A three-zone model of flow resistance characteristics was established based on the distribution characteristics of swirl ratio and the influence of the structural parameters of the de-swirl nozzle on the flow resistance characteristics,and the resistance reduction mechanism of the de-swirled nozzle type vortex reducer in each zone was analyzed respectively,The prediction formula of temperature drop characteristics in the tube was established with the theoretical analysis.The influence of the structure parameters,rotational Reynolds number,and dimensionless mass flow rate on the flow and resistance reduction characteristics and the temperature drop characteristics of tubed vortex reducer was numerically studied.The internal relations between the flow resistance,temperature drop characteristics and the swirl ratio and flow angle in the tubed vortex reducer were promoted.The resistance reduction mechanism of the fin-type vortex reducer was investigated based on the distribution characteristics of the swirl ratio and the flow characteristics on the surface of the guide vane,and compared with the co-rotating cavity model without vortex reducer.Through numerical calculation,the influences of radial length,axial length,radial position,and relative angle of the guide vane,rotational Reynolds number and dimensionless mass flow rate on resistance reduction characteristics of the fin-type vortex reducer were analyzed,and the mechanism of resistance reduction of fin-type vortex reducer and its correlation with the distribution of swirl ratio were summarized.Finally,a comparative analysis was carried out between three kinds of typical vortex reducer and the co-rotating cavity model without vortex reducer.Compared with the co-rotating cavity model without vortex reducer,although the flow characteristics,swirl ratio and flow angle distribution,and the Coriolis force distribution of the three typical vortex reducer structures were quite different,similar resistance reduction and temperature drop effects were obtained through different vortex reduction measures to inhibit the development of the swirl ratio.These three typical vortex reducers have significant resistance reduction effects,which can improve the coolant quality with lower total temperature and higher inlet pressure.