Isolation of back pressure waves in a valveless pulse detonation combustor with inlet air of high total temperature

Abstract

In order to achieve the effectively isolation of back pressure waves in a valveless pulse detonation combustor (PDC) within a short axial distance, a combined aero-valve was designed and tested with a single tube PDC at firing frequencies from 10 Hz to 25 Hz. Nozzles of different size were designed to adjust the bleeding air of the combined aero-valve. The nozzles’ effect on the isolation of the back pressure waves were discussed. Numerical simulations were carried out to reveal interactions between the back pressure waves and the combined aero-valve. The experimental results proved that the combined aero-value was effective in isolating the back pressure waves at firing frequencies from 10 Hz to 25 Hz for the baseline case. When a smaller nozzle was installed, the combined aero-valve would lose the ability to isolate the back pressure waves at low firing frequencies. Numerical simulations showed that the supersonic flow in the shock isolator channel was the key factor to realize completely isolation of the back pressure waves. For the cases with pressure oscillations appeared at the inlet of the isolation section, the back pressure waves would push the shock wave out of the channel and destroy the supersonic flow in the shock isolator channel, while the supersonic flow did not disappear for the cases when the back pressure waves were completely isolated, the shock wave in the shock isolator channel was just pushed forward a certain distance and would recover to the initial position as the filling process of the PDC started.