A Current Assessment of Combining Distortion Types
This document will address techniques or methods that have been used within the industry to address the problem of engine stability margin accounting when combinations of distortion types exist in an aircraft installation. Its focus is combining temperature, planar wave, and swirl distortion with time-variant spatial total pressure distortion. Example methodologies will be presented along with example cases where co-existing distortions have been evaluated. It will also address the areas where the industries' knowledge base is lacking (experimental data or computational methods) and the future work that is needed for methodology development in these areas. This document is viewed to be updated every five years as more information (data either experimentally or analytically) becomes available.
Rationale: The SAE S-16 Committee has addressed and documented the subject of methodologies for assessing the various types of aircraft inlet distortion. These include time-variant spatial total pressure distortion (ARP1420 & AIR1419), total temperature distortion (AIR5867), planar distortion (AIR5866), and swirl distortion (AIR5686). Although AIR5867 (Temperature Distortion) and AIR5866 (Planar Distortion) have limited discussions addressing co-existing distortion, there is currently no consensus within the industry on combining distortion methodologies. This document will address this subject of how to handle the assessment of loss in compressor stability margin when a gas turbine engine is subjected to different distortion types in combination with time-variant spatial total pressure distortion. It is directed at bringing focus to this area and hopefully lead to industry consensus.