Single pulse combustion test of high-frequency instability of rocket engine

Combustion tests were conducted to investigate the high-frequency combustion instability of liquid-propellant rocket engines. An experimental apparatus was designed to examine the rapid and large pressure increase that occurs near the propellant injector, based on the mechanism of the off-design combustion model. The propellants were 2-propanol and gaseous oxygen. The propanol jet created a semi-enclosed base space near the injection port. Pressure in the semi-enclosed space due to combustion was 1.5–3 times higher than the pressure prior to combustion. The duration of the pressure increase ranged from 0.03 to 2 ms. The pressure increase and its duration agreed with the features of the high-frequency combustion instability of liquid-propellant rocket engines. The model temperatures affected the pressure increase and the duration of pressure change. •Propanol-oxygen combustion testing conducted to study rocket engine instability.•Off-design combustion showed quick pressure changes in 0.05 milli seconds.•Amplitude was 1.5–3 times as high as the pressure prior to combustion.•The quick and large pressure change agree with changes of actual rocket engines.•Off-design combustion can be a cause of high-frequency instability of rocket engines.