Abstract
The AUV (Autonomous Under-water Vehicle), which is used for the present seabed investigations, has obtained the thrust with the screw driven by the battery. However, it has a disadvantage because of its size and cost. Therefore, this research is carried out to propose the Bubble Jet Engine (BJE) as a new propulsion device. It can directly transform combustion energy into speed energy, so it is expected that BJE rises propulsion efficiency too. This research aims at measuring exhale flow and thrust to design ejectors, which become the core of BJE, and exploring practical use possibility of BJE. Ejector is the element in which gas is mixed with water, and the improvements in the propulsion efficiency are realized by taking in ejector as much water as possible. Vertical type gas-water ejector experimental apparatus for measuring water entrainment was employed in order to understand the characteristics of operation conditions, such as inlet distance, nozzle pressure, diameter of nozzle, and so on. In addition, experiments for measuring the thrust in the condition of ejector were actually executed with horizontal type apparatus in water. At present, however, the influence of the ejector to improve thrust can't have been recognized yet.
