The Impact of Air Lubrication on a Boat's Propeller
Authors:Richard Copca, Paul Lou, Jit Malay, Christopher Morales
- Marko Princevac, Associate Professor of Mechanical Engineering, University of California, Riverside
- Campbell Dinsmore, Graduate Student, University of California, Riverside
The impact of micro-bubbles, used for the air lubrication of a boat’s hull, on a boat’s propeller was examined using a digital thrust measuring apparatus in a water tank. This impact was measured by comparing the thrust of a model boat when the micro-bubbles were interacting with the propeller and when the boat was running without artificially introduced bubbles. The thrust produced by the model boat was transferred to the apparatus through a harness specifically constructed according to the boat's dimensions. Air lubrication conditions were simulated by attaching an array of bubble producing blocks onto the hull of the boat to ensure the propeller would be immersed in the resulting bubble field. These bubbles were generated by connecting an air pump to the block array. Twenty-four trials were conducted. Twelve of these trials were run with bubbles and the other twelve were run without. The data show a noticeable 4.5% decrease in thrust when the micro-bubbles were introduced. From this, we can conclude that micro-bubbles ingested by a propeller will reduce the thrust. It remains to be seen, however, whether these results are scalable and whether this decrease in thrust translates to an overall reduction in propeller efficiency. If these results are scalable and the propeller efficiency is negatively impacted, this could have substantial ramifications on the design of ships using air lubrication or it may even call into question the feasibility of using air lubrication in the first place.