Mixing enhancement in supersonic jet flow via air tabs.
Ong, Lawrance Yin Keat.
Date of Issue2009
School of Mechanical and Aerospace Engineering
Research in supersonic jet mixing enhancement has seen a revival with the increased awareness of environmental impacts aircrafts have as well as with the advent of the scramjet. Passive and active means or mixing enhancement haven been researched into, and while delta/solid tabs have proved to be the best in terms of entrainment, air tabs have shown to be able to reproduce the results obtained by the delta/solid tab in subsonic regimes. In this paper, air tabs would be compared to a delta/solid tab in a supersonic regime. The primary jet would be at M=1.3 while the secondary jet would be at M=1.0. Modifications were done to the air tabs in an effort to enhance mixing. The secondary injectors would be tilted at an angle (15 and 30 degrees) to introduce a swirl to the primary jet, which in theory would improve mixing. By tilting the secondary injectors, the secondary jets would have a moment arm with respect to the primary jet as it enters the primary jet. This would disrupt the primary jet flow, causing it to have a radial velocity component, which would result in swirling of the primary jet. Measurements for centreline velocity, cross sectional velocity profile are taken using pitot tubes connected to transducers and the mass flux at selected distanced are obtained. The results show that in the supersonic regime, the delta/solid tab reigns supreme. Although bifurcation of the primary jet can be observed for all tabs at nearfield, they did not persist downstream for the modified air tabs. This is attributed to the angled entry of the secondary jet into the primary jet. As such, the entrainment rate was not enhanced with the use of the modified air tabs.
Final Year Project (FYP)
Nanyang Technological University