Formation of Sink Vortices in a Jet Engine Test Cell

— Vortices can be produced and ingested into the intake of a jet engine during high power operation in the vicinity of solid surfaces causing Foreign Object Damage (FOD) or compressor stall and engine surge problems. This can occur when the engine is mounted on the wing of a plane during takeoff and engine ground runs or when the engine is placed inside a test cell for testing after an engine overhaul and prior to reinstallation onto the aircraft. In order to prevent such vortices from forming, especially in the test cells, it is necessary to be able to predict the onset of the vortex or understand the factors affecting the formation of such vortices. Ho and Jermy [T D 1D T ] investigated vortex formation using a suction tube in a open-end box model simulating an engine in a test cell scenario and found that 3 distinct regimes of flow (regular vortex, deformed vortex and no vortex) exists as the ratio of suction inlet velocity to upstream average velocity (Vi/Vo) varies. The effect of the upstream velocity gradient and suction inlet diameter on the threshold is considered. The results show that the as the size of the suction inlet diameter is increased, the range of conditions over which a vortex forms also increases. This is in line with earlier findings [T D2DT ] in the takeoff and engine run scenarios. The threshold for all three regimes appears to shift to a lower Vi/Vo for a given ratio of height over inlet diameter (H/Di). This indicates that in order to accommodate a larger engine, it is necessary to increase the size of the test cell by more than the ratio of engine diameters if the same margin of safety (with respect to vortex formation) are to be maintained.