A Parametric Study on the Effects of Inlet Swirl on Compression System Performance and Operability Using Numerical Simulations

Abstract

The integration of the airframe and propulsion system is a key design issue in the development and deployment of military aircraft. Many disciplines comprise this issue, one being the aerodynamic interaction between the inlet system and the engine. The external airframe and inlet system must capture flow from the free stream and deliver it to the installed engine in a manner that maintains engine stability. Using the existing SAE S-16 developed methodologies, inlet distortion has traditionally been characterized by consideration of total-pressure distortion, total-temperature distortion, or planar waves, either singularly or in combination. However, many gas turbine installations can generate significant flow angularity as well as total pressure distortion at the Aerodynamic Interface Plane (AIP). The flow angularities may have both radial- and circumferential-velocity components. Swirl is generally considered as being that portion of the flow vector which is directed circumferentially, since it is this velocity component which directly affects the work of a downstream fan or compressor. The objective of this paper is to demonstrate that simple but effective numerical simulations can provide qualitative insights into the effect of swirl on compression system performance and operability. The analysis presented in this paper uses both a single rotor and an advanced 2-stage fan exhibiting many modern military turbofan design features.