The dynamical characteristics of liquid rocket engine propellant feed system after pump have important effect on the stability of thrust chamber. In order to investigate the dynamical characteristics of the propellant feed system after pump in an engine

the hydraulic vibration experiments within the medium and high frequency ranges of the full scale engine feed system after oxidizer pump were conducted. Test data indicate that resonance characteristics of the engine feed system were excited. Under the test condition

the first four resonant frequencies and the vibration modes can be clearly revealed. The first resonant frequency had highest response amplitude

while the second resonant response amplitude was lower than the first one

and similar to the third one. The fourth resonant response amplitude was further lower than the third one. Under the external pressure fluctuation

this engine feed system after pump can easily achieve the resonant condition. When the fluctuation frequency was close to the resonant frequencies of the feed system

the pressure oscillations along the feed system presented obvious resonant wave shapes. The position of the injector manifold is always the wave node of pressure oscillation

namely the wave anti-node of flow oscillation

under different resonant frequencies.