Noise Generated in a Scramjet Combustor

View Video Presentation: https://doi.org/10.2514/6.2023-0314.vid This paper presents measurements of the noise generated inside a two-dimensional scramjet combustor operated under a realistic flight condition for the first time using the Focused Laser Differential Interferometric technique (FLDI). FLDI measurements were taken at 39 mm, 210 mm, and 339 mm from the combustor entry and 12 mm from the bottom wall and at the combustor center plane. Probing at these locations under three conditions, unfuelled, combustion-suppressed, and combustion-on conditions enabled measurement of disturbances radiated from the individual and combined sources of noise in the scramjet combustor. Spectral analysis of the FLDI signal at different flow conditions confirms the capability of this technique for measuring the disturbances in a complex hypersonic flow field. The processed FLDI results show that significant noise is generated inside the scramjet combustor in comparison to the free stream. Among the three conditions, an apparent trend in the increase in the noise level due to combustion is observed across the three probing locations. However, the overall increment in the noise level is modest between the three conditions and across the three probing locations. Therefore, this study concludes that fuel injection and combustion do not introduce a dominant noise source in the scramjet combustor —implying that the base hypersonic flow field inside the scramjet combustor is the main contributor to the noise field.