Masahiro Takahashi, Kan Kobayashi, Sadatake Tomioka
DOI Number XXX-YYY-ZZZ
Conference Number HiSST-2022-250
A flight-ground test comparison program is undergoing at JAXA to clarify so-called “facility effect” on
hypersonic aerodynamics and combustion phenomena, and to develop a CFD tool, which can predict
actual data in flight from ground test data. The final goal is to conduct a flight experiment to obtain
data of aerodynamic heating and supersonic combustion in a real flight and to validate the CFD tool
using the flight data and corresponding ground test data. The present study is related to design of a
supersonic combustor flow-path suitable to clarify influence of differences in test flow composition
between flight and ground test conditions on combustion. The candidate configurations proposed by
CFD study were evaluated by direct-connect combustion tests with ethylene fuel. The results showed
that a combustor flow was symmetric when fuel equivalence ratio was low, while it became asymmetric
when the equivalence ratio became high and the pressure in the combustor rose. Such the asymmetric
flow is not suitable for the CFD validation so that the total equivalence ratio was limited. The upper
limit of the total equivalence ratio to maintain the symmetric combustor flow was 0.44 in the present
flow condition. The combustor model equipped two-stage fuel injectors and cavity flame holders to
obtain ethylene combustion. A depth of the cavity flame holder had little influence on combustion, but
the number of injection holes for the 2nd injector located downstream of the cavity affected the
combustor pressure. Based on the combustion test results, the combustor flow-path design was
finalized. In addition, an ethylene fuel ignition method using a pilot hydrogen injection, which is
adopted for the flight experiment, was also demonstrated successfully.