De-risking of a high-speed intake distortion facility using a small-scale pilot rig

Abstract

This paper presents the development of a sub-scale pilot rig (Mini HI-Sim) designed to de risk the operation of a large-scale, high-speed intake distortion facility (HI-Sim). The Mini HI-Sim replicates key aerodynamic features using a vacuum-driven aspirated configuration able to provide onset Mach numbers up to 1.65. This paper assesses the operating performance of the rig and compares it to estimates of operational runtime based on compressible flow theory and polytropic expansion. The study demonstrates that the runtime and flow uniformity are sensitive to vacuum level and speed of the fast-acting valve. Flow visualization using tuft tracking and image processing confirmed the presence of counter-rotating vortices in the radial exhaust which had been observed in previous computational work of the full-scale rig, offering a preliminary and qualitative validation of the radial exhaust design. Preliminary CFD analysis showed that re-pressurization of the working section was caused by an excessive geometric contraction in the exhaust, which increased the static pressure around the enclosed jet in the working section and prevented the normal shock from being fully displaced downstream. Removing this contraction yielded a uniformly low plenum pressure, improved flow extraction, and enabled the intended Mach-number distribution in the working section. Overall, the Mini HI-Sim offers a cost-effective platform for aerodynamic and instrumentation de-risking, supporting the development of robust supersonic intake systems for future propulsion applications.