Study On Structural Characteristics Of Inlet And Outlet In Cooling Air Pre-Swirl System

The aero-engine pre-swirl system is an important part of air system,and its purpose is to provide higher quality cooling air for turbine blades.Numerical simulation method was used to design and study the inlet and outlet structures of pre-swirl nozzles,receiver holes,cover plates and guide vanes in the pre-swirl flowing path.And the influence mechanism of flow structures on cooling air quality and structural temperature-stress change was researched in the pre-swirl system.The main research details and conclusions are as follows:1.The structure of pre-swirl nozzles and receiver holes with orientation angle is put forward.The influence of nozzle radial angle(belong to orientation angle),receiver hole orientation angle and receiver hole radial angle on airflow,temperature drop and total pressure loss was studied.The research results show that: in the range of calculation conditions,when the pre-swirl nozzles radial angle increases,the air flows better,leading the mass flow rate of system increasing,and the dimensionless temperature drop increases first and then decreases.The dimensionless temperature drop increases and the total pressure loss coefficient decreases with the increase of receiver holes radial angle.The dissipation loss of pre-swirl system will reduce when increase the receiver hole orientation angle.Thereby it can reduce the difference between the system outlet airflow circumferential velocity and the exit line speed of the rotational disk,consequently improving the temperature drop effect of the pre-swirl system.2.The fluid-structure coupling heat transfer of the cover plate structure at the downstream of the nozzles was researched,and compared with the adiabatic condition.The influence mechanism of the pre-swirl nozzles exit swirl ratio and the cover plate energy transfer coefficient on air flow and structural temperature-stress change was researched in the pre-swirl system.The research results show that: The difference of temperature gradient and structural equivalent stress of cover plate are large under coupling heat transfer and adiabatic conditions.When the nozzle exit swirl ratio of the air flow increases,the maximum equivalent stress value of the cover plate decreases first and then increases.And there is a certain swirl ratio that minimizes the equivalent stress of the cover plate.Increasing the cover plate energy transfer coefficient can effectively reduce the maximum temperature gradient and the maximum thermal stress of turbine disk,and the maximum thermal stress of the cover plate is almost unchanged.3.Circular arc guide vanes were set up on the wall of rotating cavity before the exit of the pre-swirl system.The influence mechanism of low radius arc angle variation on airflow characteristic,temperature drop and total pressure loss was studied in the pre-swirl system.And the mechanism reason of temperature drop and flow resistance well at the 90 degree low radius arc angle was explored.The research results show that: increasing the low radius arc angle of the guide vane can reduce the static pressure of the inlet cavity and the pre-swirl cavity in pre-swirl system.Furthermore,it can increase the dimensionless temperature drop coefficient and reduce the total pressure loss coefficient of the flow path.The streamline distribution is great different under different mass flow rates at the 90 degree low radius arc angle guide vanes.The change of the angle between air flow direction and the guide vane inlet direction is the main factor affecting the temperature drop and flow resistance.