Numerical investigation of critical lip thickness of subsonic co-flowing jet
Aircraft Engineering and Aerospace Technology
Article publication date: 29 August 2021
Issue publication date: 6 September 2021
The effect of increasing lip thickness (LT) and Mach number on subsonic co-flowing Jet (CFJ) decay at subsonic and correctly expanded sonic Mach numbers has been analysed experimentally and numerically in this study. This study aims to a critical LT below which mixing enhances and above which mixing inhibits.
LT is the distance, separating the primary nozzle and the secondary duct, present in the co-flowing nozzle. The CFJ with LT ranging from 2 mm to 150 mm at jet exit Mach numbers of 0.6, 0.8 and 1.0 were studied in detail. The CFJ with 2 mm LT is used for comparison. Centreline total pressure decay, centreline static pressure decay and near field flow behaviour were analysed.
The result shows that the mixing enhances until a critical limit and a further increase in the LT does not show any variation in the jet mixing. Beyond this critical limit, the secondary jet has a detrimental effect on the primary jet, which deteriorates the process of mixing. The CFJ within the critical limit experiences a significantly higher mixing. The effect of the increase in the Mach number has marginal variation in the total pressure and significant variation in static pressure along the jet axis.
In this study, the velocity ratio (VR) is maintained constant and the bypass ratio (BR) was varied from low value to very high values for subsonic and correctly expanded sonic. Presently, commercial aircraft engine operates under these Mach numbers and low to ultra-high BR. Hence, the present study becomes essential.
This is the first effort to find the critical value of LT for a constant VR for a Mach number range of 0.6 to 1.0, compressible CFJ. The CFJs with constant VR of unity and varying LT, in these Mach number range, have not been studied in the past.
The authors wish to thank Dr. R. Jaganraj, Dr. N. Lenin, Dr. A.T. Ravichandran, and Dr. S. Sivaperumal from Vel Tech Rangarajan Dr Sagunthala R&D Institute of Science and Techology, for supporting us during the numerical investigation. The authors wish to thank the supporting staffs in the High Speed Jet Lab of KCG College of Technology during the eperimental work.
R., N.S., V.G., G., N., D.R., K., S.K. and K., V. (2021), "Numerical investigation of critical lip thickness of subsonic co-flowing jet", Aircraft Engineering and Aerospace Technology, Vol. 93 No. 7, pp. 1193-1203. https://doi.org/10.1108/AEAT-10-2020-0225
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