Computation of Transverse Injection into Supersonic Crossflow with Various Injector Orifice Geometries

Mixing Characteristics of Inclined Fuel Injection via Various Geometries for Upstream-Fuel-Injected Scramjets

“…It can be seen that the rectangular (streamwise slot) injectors outperform the other injectors in the mixing efficiency in Fig. 7a, in correspondence with the trends reported in previous studies [21][22][23]. It is particularly noteworthy that the rectangular injector with an aspect ratio of 16∶1 has attained an appreciable mixing efficiency while incurring a minimum total pressure loss in Fig.…”

“…However, the trends observed here commonly appear to disagree with those reported in the preceding studies conducted for fuel injection at a normal angle with various injector shapes. For instance, fuel penetration with the slot injector with an aspect ratio (16∶1) has not been found to be higher than that with the 4∶1 rectangular injector in this study, as opposed to the observations reported by Foster and Engblom [21] and Hirano et al [24] for normal injection into Mach 1.2 and 3 crossflows, respectively, whereas higher mixing efficiency and wider fuel spread have been achieved consistently with the slot injector. A considerable increase in the fuel penetration height with sharp-tipped geometries (e.g., diamond, triangle, stinger) was observed in the preceding study with normal injection [24] or oblique injection at relatively low jet-to-freestream momentum ratios of J 0.08-1.73 [14], but it is not discernible in the present study with 45-deg-inclined injection into a Mach 5 cross stream at J 2.92.…”

“…One can notice that the mixing efficiency grows rapidly until certain streamwise positions and continues constantly at a certain rate in all cases, as can be seen in the slopes with similar inclination, which can be attributed primarily to the effects of diffusion and turbulence and would not occur in the inviscid case [23]. It is also notable that the extent of initial growth after the first peak appears to correspond to the longitudinal length of the injector, which will be associated with the buffering effect [21] later in the flowfield scrutinization.…”

“…8b, which shows a steeper initial rise for injector geometries with a rather blunt fore shape, such as the square and circular orifices, suggesting the influence of the bow shock formation. The rectangular injectors are characterized by milder initial slopes, which extend over the longitudinal length of the injector, suggesting the possible influence of buffering [21]. These slot injectors as well as the diamond injector attain the highest peaks of streamwise circulation, followed by the square, circular, and triangular ones.…”

“…Foster and Engblom [21] computationally investigated the effects of various injector shapes including diamond, circle, square, and rectangular orifices on penetration and mixing caused by subsonic injection into low supersonic crossflow at 1.2, with various aspect ratios AR between 1∕8th (lateral or spanwise) and 8 (longitudinal or streamwise) for the rectangular injector. Longitudinal slot injectors were found to effectively enhance the mixing efficiency as well as fuel penetration and spread owing to buffering effects due to sustained vorticity generation, whereas minor performance differences were observed among the other injector shapes.…”