Shear-Coaxial Jets from a Rocket-Like Injector in a Transverse Acoustic Field at High Pressures

Abstract

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A Unified Approach on Combustion Instability in Cryogenic Liquid Rockets (Preprint)

“…It is noted here that measured mean (intact) dark-core length for SSME-like momentum flux ratios by Woodward et al [9] in a LOX/GH 2 fired single-element rocket engine agrees with those of Davis and Chehroudi's [6] nonreacting case. And, in addition, existence of the dark-core length fluctuations has also been reported by Woodward et al [9].…”

“…The effect of temperature ramping was linked to its impact on the outer-to-inner velocity ratio and hence was also explained. More details can be found in Davis and Chehroudi [6], Davis [7], and Leyva et al [8]. In other words, the dynamic behavior of the dark-core, specifically its length, is considered to be the primary culprit.…”

“…In Davis and Chehroudi's [6] non-reacting coaxial jet work at high pressures, where an externally-imposed acoustic field is used to simulate certain key aspects of their interaction in real engines, it is shown that at subcritical conditions the dark-core length root mean square (RMS) fluctuation values were much higher than those at near-critical and supercritical conditions by a factor of 4 to 6 at all velocity ratios. Also, as the outer-to-inner jet velocity ratio declines, the RMS value increases from 1-2 to values of about 7-8 inner jet hole diameters at subcritical pressures.…”

“…In Davis and Chehroudi's [6] experimental work, we have offered a plausible explanation of why temperature ramping (progressive reduction of the propellant temperature for engine combustion stability rating purposes) and decreases in outer-to-inner jet velocity ratio (for shear coaxial injector) push a LOX/H 2 cryogenic liquid rocket engine (LRE) into an unstable zone. In Davis and Chehroudi's [6] non-reacting coaxial jet work at high pressures, where an externally-imposed acoustic field is used to simulate certain key aspects of their interaction in real engines, it is shown that at subcritical conditions the dark-core length root mean square (RMS) fluctuation values were much higher than those at near-critical and supercritical conditions by a factor of 4 to 6 at all velocity ratios.…”

“…More relevant to the work reported here, are a few reports and articles on gaseous and (in particular) liquid jets under the influence of external (transverse and longitudinal) acoustic fields. These have been reviewed in Chehroudi and Talley [5] and Davis and Chehroudi [6]. 1 Principal Scientist, ERC Inc., AFRL, Edwards AFB, CA 93524, AIAA Associate Fellow.…”