Non-intrusive velocimetry in a supersonic reacting flow using two-point focused laser differential interferometry

Conference item

Two-point focused laser differential interferometry (2pFLDI) is shown to be a viable technique for making non-intrusive measurements of velocity in supersonic reacting flows. Velocity is computed from the cross-correlation of two FLDI signals from two closely-spaced (∼ 168micron in the streamwise direction) measurement volumes. The technique is demonstrated in a 12.7mm-wide dual-mode scramjet combustor with Mach 2 vitiated-air inflow and T_0 = 1300K. Measurements are made at 10 locations along the combustor’s axis for two fuel injection schemes: (1) injection from a single port, and (2) injection from four axially-distributed ports. Measured axial velocity profiles confirm the existence of two distinct operating modes and are qualitatively consistent with velocities deduced by other means (a combination of pressure measurements, chemi-luminescence, and quasi 1-D compressible flow analysis) but are biased low. This bias is partially explained by the large size of the 2pFLDI’s sensitive region which extends beyond the width of the channel (for disturbances with wavenumbers, k_x, less than 12.4mm^−1 ) thereby enabling lower momentum fluid in the boundary layers on the facility’s windows to influence the signal. A cross-spectral analysis of the FLDI signals enables one to calculate velocity as a function of disturbance scale which is important because the instrument’s resolution and sensitivity are functions of disturbance scale. Velocities for k_x > 13mm^−1 are in better agreement with the deduced velocity because the FLDI is sensitive to these disturbances with resolution which is smaller than the width of the channel and closer to the techniques used for the deduced velocity.

Authors: Ceruzzi, A; Kanapathipillai, M; Yu, KH; Cadou, CP

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Institute of Aeronautics and Astronautics
• Host title: AIAA SCITECH 2023 Forum
• Article number: AIAA 2023-0223
• Publication date: 2023-01-19
• Event title: 2023 AIAA Science and Technology Forum and Exposition (AIAA SciTech Forum)
• Event location: National Harbor, MD, USA & Online
• Event website: https://aiaa.org/scitech/utility/past-forums/#2023
• Event start date: 2023-01-23
• Event end date: 2023-01-27
• DOI: 10.2514/6.2023-0223
• EISBN: 9781624106996
• Language: English
• Keywords: supersonic reacting flow; lasers; scramjet; combustors; refractive index; boundary layer transition; fuel injection; compressible flow; velocity profiles; spectral analysis