Open-Sea Testing of Two-Phase Marine Ramjet Propulsion

Open-sea testing of a two-phase marine ramjet vehicle has been conducted. This experimental phase was accomplished following comprehensive theoretical research. The concept of two-phase marine ramjet propulsion consists of a submerged propulsor acquiring water through an inlet due to the vehicle’s motion. Thrust is generated by injecting and dispersing air (or gas) bubbles within the water flowing through the propulsion unit channel and expelling a jet of the two-phase flow through an exit nozzle. The bubbles injected into the internal flow transmit their expansion work to the outgoing jet, resulting in an increase in the jet velocity, hence generating thrust. The article briefly describes the thrust generation concept, then it presents the overall system and thrust units attached to the test vessel, and finally, it summarizes the open-sea experimental results. Good correspondence between the theoretical prediction and actual test data is shown, revealing the feasibility of the two-phase ramjet concept at the low to intermediate cruise velocity range and a smaller relative thrust margin over the hydrodynamic resistance at the high-speed range.