TY - JOUR
T1 - Numerical investigation of upstream cavity enhanced fuel mixing in scramjet combustors
AU - Roos, Tim
AU - Pudsey, Adrian
AU - Bricalli, Mathew
AU - Ogawa, Hideaki
N1 - Funding Information:
The authors would like to gratefully thank the support of the CRC-P50510 Hydrocarbon Fuel Technology for Hypersonic Air Breathing Vehicles and RMIT University , as well as the high performance computing resources and support from the National Computational Infrastructure (NCI) Australia. The CRC Programme support industry-led collaborations between industry, researchers and the community.
Publisher Copyright:
© 2019 IAA
PY - 2020/4
Y1 - 2020/4
N2 - Cavities are commonly used to provide flame-holding in scramjets. While the injector is generally placed inside or upstream of the cavity, placement of the cavity behind the injector limits the influence of the cavity on the jet interaction and limits cavity-induced mixing enhancement. The current study investigates a geometry in which the cavity is placed directly upstream of the injector and examines its effect on scramjet combustor mixing performance. Specifically, enhancement in jet mixing and penetration is considered using chemically frozen hydrogen fuel. The influence of three different thermal boundary conditions (isothermal 300 K, isothermal 1800 K and adiabatic) on the flowfield and mixing was also examined. The upstream cavities are found to improve mixing efficiency and jet penetration relative to a baseline flat plate configuration for most configurations, while they do incur a total pressure loss up to 2% higher than in the baseline. The magnitude of these effects is found to depend on the cavity geometry and wall thermal model. The primary mechanism behind the performance improvement is the shielding of the barrel shock by the cavity recirculation, which introduces extra vorticity into the flowfield and reduces the strength of the bow shock. Increased shielding provided by the cavity is found to enhance mixing by up to 9%. An optimum cavity aspect ratio is observed to exist at a cavity length-to-depth ratio of L/D=15, for which performance is maximum compared to the baseline for all wall treatments. Wall heat flux increases in configurations with cavities, particularly on the aft wall of the cavity, while fuel drawn into the cavity is seen to contribute to wall cooling in case of high wall temperatures. This can reduce wall cooling requirements and simplify combustor design. In general the enhanced mixing and jet penetration induced by the cavity could allow for shorter combustor designs, which in turn allows for more compact flight vehicle design.
AB - Cavities are commonly used to provide flame-holding in scramjets. While the injector is generally placed inside or upstream of the cavity, placement of the cavity behind the injector limits the influence of the cavity on the jet interaction and limits cavity-induced mixing enhancement. The current study investigates a geometry in which the cavity is placed directly upstream of the injector and examines its effect on scramjet combustor mixing performance. Specifically, enhancement in jet mixing and penetration is considered using chemically frozen hydrogen fuel. The influence of three different thermal boundary conditions (isothermal 300 K, isothermal 1800 K and adiabatic) on the flowfield and mixing was also examined. The upstream cavities are found to improve mixing efficiency and jet penetration relative to a baseline flat plate configuration for most configurations, while they do incur a total pressure loss up to 2% higher than in the baseline. The magnitude of these effects is found to depend on the cavity geometry and wall thermal model. The primary mechanism behind the performance improvement is the shielding of the barrel shock by the cavity recirculation, which introduces extra vorticity into the flowfield and reduces the strength of the bow shock. Increased shielding provided by the cavity is found to enhance mixing by up to 9%. An optimum cavity aspect ratio is observed to exist at a cavity length-to-depth ratio of L/D=15, for which performance is maximum compared to the baseline for all wall treatments. Wall heat flux increases in configurations with cavities, particularly on the aft wall of the cavity, while fuel drawn into the cavity is seen to contribute to wall cooling in case of high wall temperatures. This can reduce wall cooling requirements and simplify combustor design. In general the enhanced mixing and jet penetration induced by the cavity could allow for shorter combustor designs, which in turn allows for more compact flight vehicle design.
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U2 - 10.1016/j.actaastro.2019.12.033
DO - 10.1016/j.actaastro.2019.12.033
M3 - Article
AN - SCOPUS:85077644174
SN - 0094-5765
VL - 169
SP - 50
EP - 65
JO - Acta Astronautica
JF - Acta Astronautica
ER -