Hub Effects in Propeller Design and Analysis
MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF OCEAN ENGINEERING
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A numerical model is established for the design of propeller blade shape for a prescribed circulation and a given hub geometry. The vortex lattice approach is adapted for blades and their wakes. The hub is represented by a distribution of dipoles which ends at the hub apex. It is shown that consideration of the hub results in a lower pitch and lower camber at the inner radii. An iterative method is developed for analyzing the interference between the blades and the hub. It is shown that the circulation at the root of a propeller with a hub. It is shown that the circulation at the root of a propeller with a hub is larger than the circulation at the root of a propeller without a hub. Two examples show that the increase in thrust due to hub effects has the same order of magnitude as the drag force effects on the hub for propellers which are moderately loaded at the hub. Experiments are carried out for comparison with the numerical results. Excellent agreement is obtained in the circulation distribution for a conventional propeller, and fair agreement for a controllable pitch propeller. Experimental results show what the circulation is, roughly speaking, conserved. A method for estimating the drag force of the hub due to the hub vortex is established by assuming that the circulation is conserved.
- Marine Engineering
- Fluid Mechanics