Coupling Computational Approach Of Secondary Airsystem And Heat Transfer In Aero-engine

The secondary air system of aero-engines, is designed to fulfil multipletasks, such as providing sufficient cooling of the engine hot components,sealing the bearings, controlling the axial bearing loads and anti-icing. Thethermal analysis of hot components, aims at obtaining the temperaturedistribution for providing the analysis data for structural calculations. Duringthe air system calculation and thermal analysis porcess, the heat transferbetween the structure and secondary airflow should be taken into account.The secondary air porperties not only is characterised by complex flowpassages, but also is impacted by the material temperatures of hotcomponents. The material tmeperatures of hot components, not only dependson the structure and conduction conditions, but also is influenced by gastemperature, pressure and mass flow rate.The coupling effect, estimated tobe strong, should be taken into consideration. However, during theengineering design process, the fluid temperature rise is artificially estimatedaccording to the experience, and the secondary air system calculation andthermal analysis are carried out separately with a manual iterativecalculation.In this paper, for air system calculation, the fluid network method isused to get the fluid properties; for thermal analysis of hot components, atwo dimensional finite element method is used to get the temperaturedistribution with ANSYS secondary development technology. With the calculation process’s establishment of thermal analysis boundary conditionsand air temperature rise, the data are transferred between air system and hotcomponents calculations. Based on the calculations process, the couplingcomputational approach is develop between secondary air system andthermal analysis to get more accurate air system and thermal analysis results,providing reference for the engine design. With the Visual Basic6.0beingdevelopment tool, the coupling computational platform of secondary airsystem and thermal analysis is set up.In the paper, the typical aircraft engine structures, the high pressureturbine casing and turbine disc with former cavity, are taken out as examples.For static component-high pressure turbine casing, the coupling calculationresults show that the fluid temperature and component temperaturedistribution change a lot, specially the strong convective heat transferationarea; the fluid pressure and flow rate don’t change much. For rotationalcomponent-turbine disk with former cavity, the coupling calculation resultsshow that fluid temperature, pressure and flow rate all have a big change;and the component temperature distribution also change a lot.With the coupling calculation approach of secondary air system andthermal analysis, the calculation platform can be applied to the currentengineering practice and play a large role.