A computational study of supersonic combustion in strut injector and hypermixer flow fields C. Fureby a,⇑ , K. Nordin-Bates a , K. Petterson a , A. Bresson b , V. Sabelnikov b a Defense Security Systems Technology, The Swedish Defense Research Agency – FOI, SE 147 25 Tumba, Stockholm, Sweden b ONERA – The French Aerospace Lab., F-91761 Palaiseau, France Abstract Achieving sufficiently high combustion efficiency and stability in supersonic combustion is extremely challenging and highly dependent on the fuel-injection and mixing strategies adopted. A viable approach to this is the strut injector, which by inducing flow recirculation, facilitates flame stabilization in the strut- wake. In this investigation we examine in detail the flow, mixing, self-ignition and flame stabilization mech- anisms of conventional and alternating-wedge injection struts. In order to analyze these, we consider NAL’s supersonic combustor, equipped with two conventional two-stage injection struts, and an alternating-wedge injection strut, in conjunction with ONERA’s vitiation air heater. Experimental results, including spontane- ous flame images, wall-pressure and Planar Laser Induced Fluorescence (PLIF) images of hydroxyl (OH) are here combined with computational results based on finite-rate chemistry Large Eddy Simulation (LES) with skeletal hydrogen-air reaction mechanisms. The spontaneous flame images and the predicted flame struc- tures for both injector-strut types agree well qualitatively, demonstrating that combustion LES captures the overall features of the experiments. Detailed comparisons between experimental data and computational results for the wall pressure and for mean and rms OH-PLIF cross-sections show acceptable agreement, indi- cating that the LES results can be used to further study the intrinsic features of the flame structure and the stabilization mechanism. These results indicate significant differences in flow and flame structures between both two-stage injection struts and the alternating-wedge injection strut tested. More specifically, the longi- tudinal vorticity introduced by the alternating-wedge injection strut increases the combustion efficiency but results in an intermittent auto-ignition phenomenon. For the two-stage injection struts combustion consists of auto-ignition pockets surrounded by self-igniting fronts embedded in a background of non-premixed flames or stirred reactors. In contrast, the alternating-wedge injection strut vigorous combustion is observed proceeding through a multi-mode (auto-ignition, non-premixed, premixed) combustion event. Ó 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved. Keywords: Supersonic combustion; Two-stage injection struts; Alternating-wedge injection strut; Large Eddy Simula- tion; Chemical explosive mode analysis http://dx.doi.org/10.1016/j.proci.2014.06.113 1540-7489/Ó 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved. ⇑ Corresponding author. Fax: +46 8 5550 4144. E-mail address: fureby@foi.se (C. Fureby). Available online at www.sciencedirect.com ScienceDirect Proceedings of the Combustion Institute xxx (2014) xxx–xxx www.elsevier.com/locate/proci Proceedings of the Combustion Institute Please cite this article in press as: C. Fureby et al., Proc. Combust. Inst. (2014), http://dx.doi.org/ 10.1016/j.proci.2014.06.113