Location of Vortex Formation Threshold at Suction Inlets near Ground Planes – Ascending and Descending Conditions

Authors: Wei Hua Ho

Abstract:

Vortices can develop in intakes of turbojet and turbo fan aero engines during high power operation in the vicinity of solid surfaces. These vortices can cause catastrophic damage to the engine. The factors determining the formation of the vortex include both geometric dimensions as well as flow parameters. It was shown that the threshold at which the vortex forms or disappears is also dependent on the initial flow condition (i.e. whether a vortex forms after stabilised non vortex flow or vice-versa). A computational fluid dynamics study was conducted to determine the difference in thresholds between the two conditions. This is the first reported numerical investigation of the “memory effect". The numerical results reproduce the phenomenon reported in previous experimental studies and additional factors, which had not been previously studied, were investigated. They are the rate at which ambient velocity changes and the initial value of ambient velocity. The former was found to cause a shift in the threshold but not the later. It was also found that the varying condition thresholds are not symmetrical about the neutral threshold. The vortex to no vortex threshold lie slightly further away from the neutral threshold compared to the no vortex to vortex threshold. The results suggests that experimental investigation of vortex formation threshold performed either in vortex to no vortex conditions, or vice versa, solely may introduce mis-predictions greater than 10%.

Keywords: Jet Engine Test Cell, Unsteady flow, Inlet Vortex

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1085752

References:

[1] W.H. Ho, H. Dumbleton and M. Jermy, "Effect of Upstream Velocity Gradient on the Formation of Sink Vortices in a Jet Engine Test Cell", IMECS 2008 Proceedings, pp 1767 - 1772, 2008.
[2] A. Karlsson and L. Fuchs, "Time evolution of the vortex between an air inlet and the ground". AIAA paper 2000-0990, 2000.
[3] A. Secareanu, D. Morioanu, A. Karlsson and L. Fuchs, "Experimental and numerical study of ground vortex interaction in an air-intake, AIAA paper 2005-1206, 2005.
[4] A. Gulia, P. Laskaridis, K.W. Ramsden and P. Pilidis, "A preliminary investigation of thrust measurement correction in an enclosed engine test facility, AIAA paper 2005-1128, 2005.
[5] S. Zantopp, D. Macmanus and J. Murphy, "Computational and experimental study of intake ground vortices", The Aeronautical Journal Vol. 114 No. 1162, 2010.
[6] M. Jermy and W.H. Ho, "Location of the vortex formation threshold at suction inlets near ground planes by computational fluid dynamics simulation", Proceedings of the I Mech E Part G Journal of Aerospace Engineering Vol. 222 No. 3, pp. 393-402, 2008.
[7] W.H. Ho, M. Jermy and H. Dumbleton, "Formation of Sink Vortices in a Jet Engine Test Cell", Engineering Letters 16:3, pp. 406-411, 2008.
[8] W.H. Ho and M. Jermy, "Formation and Ingestion of Vortices into Jet Engines during operation", IAENG TRANSACTIONS ON ENGINEERING TECHNOLOGIES VOL. 1 - Special Editions of the International MultiConference of Engineers and Computer Scientists 2008, pp 132 - 143, 2008.
[9] W.H. Ho and M. Jermy, "Validated CFD simulations of vortex formation in jet engine test cells", 16th Australasian Fluid Mechanics Conference Proceedings, pp. 1102-1107, 2007.
[10] A. Nakayama and J.R. Jones, "Vortex formation in let flow near a wall", AIAA paper 96-0803, 1996.
[11] D.E. Glenny, "Ingestion of debris into intakes by vortex action, Aeronautical Research Council CP No. 1114, 1970.
[12] W. Liu, E.M. Greitzer and C.S. Tan, "Surface static pressure in an inlet vortex flow field", ASME J. Engineering Gas Turbines Power 107, pp. 387-393, 1985.
[13] S.O. Ridder and I. Samuelsson, "An experimental study of strength and existence of domain of ground-to-air inlet vortices by ground board static pressure measurements, Stockholm Royal Institute of Technology, KTH AERO TN 62, 1982.
[14] W.H. Ho and M. Jermy, "Effect of Turbulence Intensity on Vortex Formation Threshold in a Jet Engine Test Cell", 25th European Conference on Modelling and Simulation (ECMS) Proceedings, 2011.
[15] F. De Siervi, H.C. Viguier, E.M. Greitzer and C.S. Tan, "Mechanisms of inlet vortex formation", J. Fluid Mech. 124, pp. 173-207, 1982.
[16] J.P. Murphy and D.G. MacManus, "Intake Ground Vortex Prediction Methods", Journal of Aircraft Vol 48 No. 1, 2011.