Acoustic Excitation as Triggering Mechanism of the “DC Shift” in Hybrid Rockets

What is it about?

A positive “DC shift” is the sudden rise of mean chamber pressure, which is often observed in hybrid rockets during unstable motor instances. We show that, by stimulating the thermal lag system with mass fluxes oscillating at acoustic frequencies, due to the boundary-layer delay time, the system is unstable, yielding fluctuations with the hybrid fundamental low frequency and a significant shift of the baseline steady-state value, whose magnitude depends on the time delay.

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