Numerical Analysis of Propeller Blade Temperature for Pusher Configured Turbo-prop Engine

Abstract

In propeller driven aircrafts, propellers are mounted to turboprop engines in two configurations i.e. pusher and tractor versions. In pusher configuration, propellers are placed in aft end of the nacelle while in tractor configuration propellers are forward of nacelle. Both configurations have its own merits and demerits however particular configuration is selected based on end user’s specifications. In the present work aircraft in pusher configuration is considered. Because of its position, the engine exhaust gas is directly impinging on propeller blades which increase the blade surface temperature. In this work, the surface temperature of aft mounted propeller blade during ground/high speed taxi conditions are analyzed for the given exhaust stub design. Analysis is carried out to understand the exhaust gas impingement and estimate the surface temperatures before conducting the compliance demonstration tests. It is important in pusher applications to ensure that the exposure of the propeller to the hot exhaust gas is minimized and that exhaust gas does not attach itself to the aft nacelle and cause overheating of the spinner/hub area of the propeller. CFD analysis is carried out for studying the flow through and around the nacelle, engine exhaust duct and propeller for given operating conditions. The numerical study was done by using commercially available software ANSYS Fluent. For this problem SST k-ω model for propeller static condition and Realizable K-epsilon model for propeller rotating condition was considered. Special emphasis was laid on developing a good quality mesh for the computational domain with a fine boundary layer mesh along the wall and maintaining a higher density mesh at critical areas. The flow characteristics derived from this CFD analysis remained unaltered during grid dependence studies. CFD results for engine ground static condition with stationary propeller are compared with the analytical work to assess the exhaust temperature at the propeller plane and were found to be in good agreement with each other. CFD results for the propeller rotation and exhaust gas interactions for different aircraft operating conditions which makes the problem more realistic were compared with available experimental results and are in good agreement.