Experimental and Numerical Investigation of the Flow Characteristics of a Strut Injector for Scramjets

Abstract

A peculiar dynamical interaction of two supersonic counter-rotating vortex pairs (CVPs) has been generated by a pair of overlapping expansion ramps mounted on a strut injector in a Mach 2.5 flow. Similar CVP configurations generated by overlapping ramps on the same modular strut injector have previously been studied by the authors and experimentally corroborated the predictions based on the in-house developed reduced order model, VorTx. Two co-rotating vortices at the center of the generated structure have either merged or begun to orbit each other. However, for the case discussed in this work, experiments have revealed an additional structure; in fact, instead of the expected four streamwise vortices in the flowfield consisting of two inner co-rotating vortices and two oppositely rotating external vortices, the formation of a fifth structure, a central vorticity patch, was detected. The manuscript presents a detailed experimental characterization of the flow of interest via the use of stereoscopic particle image velocimetry and a parallel computational effort based on the solution of the Reynolds Averaged Navier-Stokes equations with the ANSYS Fluent CFD Package. The results of the CFD simulations highlight the near injector flowfield, which is unable to be characterized experimentally, in order to focus upon the mechanism that result in the formation and the effects of the central vorticity patch. Nomenclatureh = Ramp height, mm M = Mach number ω = Vorticity, s -1 Subscripts ∞ = Free-stream

RANS Analysis of Merging Supersonic Streamwise Vortices for Enhanced Mixing in Scramjet Combustors

“…While the researchers at UTA have established this capability across several experiments, the merging interaction of supersonic streamwise vortices remains relatively unexplored numerically. Previous numerical work related to this experimental campaign investigated the behaviour of adjacent co-rotating vortices which do not merge, using a RANS approach [11]. In this case the authors were able to identify what prevented the vortices from merging (a small induced patch of vorticity) and reproduced the phenomenology of the flowfield well, however the magnitude and shape of the vortices was slightly different due to numerical dissipation.…”

Effect of added struts and intake velocity on flame stabilization in supersonic combustors

“…The oblique shock augmented the recirculation zone length and increased the mixing of hydrogen fuel and air significantly. Flame anchoring and flame stabilization in a supersonic combustor have been accomplished using enhancement methods like struts (Rust, Gerlinger, and Aigner, 2010;Kumar, Das, and Sheelam, 2014;Ground et al, 2014;Bao et al, 2013), backward-facing step (Kumaran and Babu, 2009a), Diamond strut (Deepu, Gokhale, and Jayaraj, 2007), ramp (Hönig et al, 1996), pylon (Vergine et al, 2012), cavity (Ben-Yakar andHanson, 1998;Lee et al, 2013;Choi, Ma, and Yang, 2005;Baurle and Gruber, 1998;Grady et al, 2012), and combinations of these (Kumaran and Babu, 2009a;Grady et al, 2012). From the abovementioned practices, the strut-based parallel fuel injectors are preferred in most of the supersonic combustors, as the overall pressure loss associated with them is the least when compared to the normal injection.…”