Reduced-order-modeling of the transient starting in supersonic passages

Characterizing the time scales of starting in supersonic passages is essential for future aerospace propulsion systems, such as supersonic intakes, Rotating Detonation Engines, and power generation systems based on Organic Rankine Cycles. This paper first compares 2D URANS results with 1D Euler results to identify the equations that govern the acceleration and deceleration of the strong shock during the starting process's time evolution. Secondly, we characterized the effect of the frequency of pulsating flows on the starting process; intermediate frequencies around 1 kHz show best startability while higher and much lower frequencies can cause unstarting. Finally, using the governing terms for the shock acceleration and deceleration in the momentum transport equation, a reduced-order model was developed and coupled with an optimization algorithm to enable rapid designs with improved flow starting capability. An optimized design demonstrated dominant startability using URANS simulations in comparison to two other geometries. The developed method represents an essential tool for reduced time-to-market solutions for aerospace propulsion components, such as inlets, supersonic turbomachinery, and nozzles.