A consolidated study regarding the formation of the aero-inlet vortex

Abstract

Under certain flow conditions, when an air inlet is aspirated in close proximity to a solid surface, an inlet vortex will form between the inlet and the surface under certain flow conditions. This phenomenon can manifest itself during the operation of aircraft engines either when the aircraft is on the runway prior to take-off or during engine ground run, or when the engine is in a test cell during post maintenance tests. The vortex can pitch debris into the intake causing foreign object damage (F.O.D.) to the engine blades or result in compressor stall. The take-off problem can be partially solved by keeping the runway clear of debris and scheduling the throttle appropriately whenever possible. However throttle scheduling will not be appropriate during engine tests both on the ground and in a test cell. The characteristics of the vortex depends on a number of geometric and flow conditions such as the position of the engine relative to the surface, intake flow capture ratio and upstream flow. To eliminate these vortices at the design stage of aircraft configuration or new test cell, it is essential to be able to predict the onset of the vortex or at least understand the factors affecting their formation. In addition, it is also very important to understand the characteristics of such a vortex to be able to determine the potential damage if complete prevention is not possible. This paper seeks to provide an understanding of this flow phenomenon by collating and analysing previous investigations and implemented solutions in both aircraft ground operations as well as during engine tests in a jet engine test cell. It will contain information from computational as well as experimental studies with emphasis on computational methods. The paper will present computational and experimental results from various sources with regards to the threshold conditions at which such vortices are formed in addition to their characteristics. To permit interested readers sufficient information to perform similar calculations, it will also contain details of the computational methods and parameters, such as the required computational domain as well as the solution schemes. The computational simulations were performed on commercial computational fluid dynamics (CFD) package Fluent 13.0 which utilises the finite volume method to solve the governing Navier-Stokes equations. © 2012 Springer Berlin Heidelberg.