Experiments on Jet Noise Reduction with a Liquid Column

A liquid column is designed and placed into the tail tube to effectively reduce the gas jet noise of a single rocket. The diffusion and mixing process of high-temperature high-pressure gas flow in the liquid water column in the air is studied by means of a high speed photographic system. The gas-liquid mixture jet noise has also been measured. The experimental results indicate that, when the liquid water column is put into the tail tube, the jet flow structure is changed and the jet flow parameters (velocity, temperature, etc.) are decreased due to the interaction of the gas jet with the liquid column. In addition, the jet noise is significantly reduced in the presence of the liquid column, compared with the condition without the liquid column. When the mass of the liquid column increases to 1.485 kg, the jet noise is reduced to a minimum in the shooter location. The peak sound pressure level also decreases with increasing polar angle. Most importantly, the thrust performance of the rocket engine is maintained when the liquid column is introduced.