TY - JOUR
T1 - Focusing-schlieren visualization in a dual-mode scramjet
AU - Kouchi, Toshinori
AU - Goyne, Christopher P.
AU - Rockwell, Robert D.
AU - McDaniel, James C.
N1 - Funding Information:
The authors appreciate the assistant of Dr. Roland Krauss and Mr. Roger Reynolds in operating the supersonic combustion facility. This work was supported by Young Researcher Oversea Study Program of the Japan Society for the Promotion of Science. This research was also supported by the National Center for Hypersonic Combined Cycle Propulsion Grant FA 9550-09-1-0611. The technical monitors on the Grant were Chiping Li (AFOSR), and Aaron Auslender and Rick Gaffney (NASA).
Publisher Copyright:
© 2015, Springer-Verlag Berlin Heidelberg.
PY - 2015/12/1
Y1 - 2015/12/1
N2 - Schlieren imaging is particularly suited to measuring density gradients in compressible flowfields and can be used to capture shock waves and expansion fans, as well as the turbulent structures of mixing and wake flows. Conventional schlieren imaging, however, has difficulty clearly capturing such structures in long-duration supersonic combustion test facilities. This is because the severe flow temperatures locally change the refractive index of the window glass that is being used to provide optical access. On the other hand, focusing-schlieren imaging presents the potential of reduced sensitivity to thermal distortion of the windows and to clearly capture the flow structures even during a combustion test. This reduced sensitivity is due the technique’s ability to achieve a narrow depth of focus. As part of this study, a focusing-schlieren system was developed with a depth of focus near ±5 mm and was applied to a direct-connect, continuous-flow type, supersonic combustion test facility with a stagnation temperature near 1200 K. The present system was used to successfully visualize the flowfield inside a dual-mode scramjet. The imaging system captured combustion-induced volumetric expansion of the fuel jet and an anchored bifurcated shock wave at the trailing edge of the ramp fuel injector. This is the first time successful focusing-schlieren measurements have been reported for a dual-mode scramjet.
AB - Schlieren imaging is particularly suited to measuring density gradients in compressible flowfields and can be used to capture shock waves and expansion fans, as well as the turbulent structures of mixing and wake flows. Conventional schlieren imaging, however, has difficulty clearly capturing such structures in long-duration supersonic combustion test facilities. This is because the severe flow temperatures locally change the refractive index of the window glass that is being used to provide optical access. On the other hand, focusing-schlieren imaging presents the potential of reduced sensitivity to thermal distortion of the windows and to clearly capture the flow structures even during a combustion test. This reduced sensitivity is due the technique’s ability to achieve a narrow depth of focus. As part of this study, a focusing-schlieren system was developed with a depth of focus near ±5 mm and was applied to a direct-connect, continuous-flow type, supersonic combustion test facility with a stagnation temperature near 1200 K. The present system was used to successfully visualize the flowfield inside a dual-mode scramjet. The imaging system captured combustion-induced volumetric expansion of the fuel jet and an anchored bifurcated shock wave at the trailing edge of the ramp fuel injector. This is the first time successful focusing-schlieren measurements have been reported for a dual-mode scramjet.
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U2 - 10.1007/s00348-015-2081-9
DO - 10.1007/s00348-015-2081-9
M3 - Article
AN - SCOPUS:84947420312
SN - 0723-4864
VL - 56
SP - 1
EP - 14
JO - Experiments in Fluids
JF - Experiments in Fluids
IS - 12
M1 - 211
ER -