A novel coupled algorithm for Studying the performance characteristics of water ramjet in the flight of supercavitating vehicle

Abstract

When a supercavitating vehicle performs a flight, the water ramjet of the vehicle exploits the water in the surrounding environment as an oxidiser and is inevitably affected by the vehicle motions. In this study, the characteristics of the performance change in a water ramjet were investigated when a supercavitating vehicle performs a flight to gain more insights into the design of underwater power systems. Given the principle of independent cross-section expansion of cavities, a longitudinal ventilated supercavity model was built to predict the development of a ventilated cavity and its interaction with the body. A thermal calculation model was developed based on the minimum free energy method to calculate the performance parameters of water ramjets. A novel coupling algorithm was proposed based on the aforementioned model to integrate the motion of a supercavitating vehicle with the operation of a water ramjet. The integration described above was achieved by linking the water intake and body motion and calculating the performance change characteristics of the water ramjet during the flight of the supercavitating vehicle. The operating characteristics of the water ramjet with changes in the designed water-fuel ratios were investigated to provide a basis for exploring the unperturbed flight of the vehicle, depth regulation, and underwater environmental changes. The thrust of the water ramjet is less affected by external factors, and its performance feedback tends to exacerbate external disturbances at a designed water-fuel ratio lower than the optimal water-fuel ratio. A water ramjet with a designed water-fuel ratio higher than the optimal water-fuel ratio has a rapid response time, adaptive thrust, and stable combustion chamber pressure. External disturbances slightly affected the thrust and combustion chamber pressure of the water ramjet when the designed water-fuel ratio was equal to the optimal water-fuel ratio. The results of this study provide technical support for optimising the design of water ramjet.