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

Andrew N. Bustard; Benjamin L. Bemis; Aaron Marques; Matthew J. Zahr; Thomas J. Juliano

doi:10.2514/1.b40160

journal article Apr 02, 2026

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

Andrew N. Bustard Benjamin L. Bemis Aaron Marques Matthew J. Zahr

Thomas J. Juliano

Journal of Propulsion and Power pp. 1-20 · American Institute of Aeronautics and Astronautics (AIAA)

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Abstract

The inner surface pressure of an axisymmetric inlet/isolator model was measured using anodized-aluminum pressure-sensitive paint (PSP) viewing through cast acrylic. Temperature-sensitive paint was used to correct for the PSP’s temperature sensitivity. The model was tested under Mach 5.7 flow at [Formula: see text] 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 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 [Formula: see text] 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 to 45 ms, and the peak velocities were [Formula: see text], 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.

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Details

Published: Apr 02, 2026
Pages: 1-20
License: View

Authors

A

Andrew N. Bustard

University of Notre Dame

B

Benjamin L. Bemis

University of Notre Dame

A

Aaron Marques

University of Notre Dame

M

Matthew J. Zahr

University of Notre Dame

T

Thomas J. Juliano

University of Notre Dame

Funding

Air Force Research Laboratory Award: FA8650-20-2-2405

Cite This Article

Andrew N. Bustard, Benjamin L. Bemis, Aaron Marques, et al. (2026). Global Time-Resolved Measurements of Inlet/Isolator Unstart Induced by Mass Injection. Journal of Propulsion and Power, 1-20. https://doi.org/10.2514/1.b40160

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

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