Global Time-Resolved Measurements of Inlet/Isolator Unstart Induced by Mass Injection

Authors

• Andrew N. Bustard, University of Notre DameFollow
• Benjamin L. Bemis, University of Notre Dame
• Aaron Marques, University of Notre Dame
• Matthew J. Zahr, University of Notre Dame
• Thomas J. Juliano, University of Notre Dame

Submitting Campus

Daytona Beach

Department

Aerospace Engineering

Document Type

Article

Abstract/Description

The inner surface pressure of an axisymmetric inlet/isolator model was measured using anodized-aluminum pressure-sensitive paint (PSP) viewing through cast acrylic. Temperaturesensitive paint was utilized to correct for the PSP’s temperature sensitivity. The model was tested under Mach 5.7 flow at 𝑹𝒆 = 7.1 ×106 /m under conventional noise conditions. Transverse jet injection with jet-to-inlet mass-flow ratios up to 0.8 was used to induce unstart in the inlet/isolator. Background-oriented schlieren visualization of the inlet shocks was collected simultaneously with the PSP to determine when the inlet unstarted. Computational fluid dynamics results were used to determine off-wall flow structures and quantify approach conditions in the isolator. The dominant frequency of the quasi-steady shock train was 500 Hz to 600 Hz. Coherence analysis revealed a linear relationship between the unsteady pressures downstream of the shock-train leading edge (STLE). A phase difference of 𝝅 to 3𝝅/2 was seen between the region immediately downstream of the STLE and the region over approximately 1.5 isolator diameters downstream of the STLE. The PSP and conventional transducer measurements of STLE pressure rise agreed well with each other. The unstart process took approximately 10 ms to 45 ms and the peak velocities were 0.142 𝑢∞ to 0.233 𝑢∞, depending on the jet-to-inlet mass flow ratio. The quasi-steady STLE shock front shape was measured with high spatial resolution and matched that of an upstream inlet shock. The pressure profile shape changed quickly due to the presence of inlet shocks and transient changes due to mass-injection, which has implications to unstart detection methods (UDM).

Publication Title

Journal of Propulsion and Power

DOI

https://doi.org/10.2514/1.B40160

Publisher

American Institute of Aeronautics and Astronautics

Grant or Award Name

Air Force Research Laboratory award number FA8650-20-2-2405,

Additional Information

Dr. Bustard was not affiliated with Embry-Riddle Aeronautical University at the time this paper was published.

Scholarly Commons Citation

Bustard, A. N., Bemis, B. L., Marques, A., Zahr, M. J., & Juliano, T. J. (2026). Global Time-Resolved Measurements of Inlet/Isolator Unstart Induced by Mass Injection. Journal of Propulsion and Power, 42(3), 505-524.