Mathematical Expressions of Thrust and Torque of Gawn-Burrill Propeller Series for High Speed Crafts Using Artificial Neural Networks

摘要

Gawn-Burrill propeller series are still one of the widely used propeller series for high-speed crafts. The performances of these propellers are well documented by means of model tests in cavitation tunnel for a range of pitch ratios and cavitation numbers as well as blade area ratios. However there is a need for general mathematical expressions of thrust and torque coefficients in terms of pitch ratio, blade area ratio and cavitation number to allow designers to use these series flexibly. This is also a prerequisite for implementation of these series in design and prediction computer tools. The behaviour of thrust and torque in the presence of cavitation is highly non-linear. Therefore usual techniques of curve fitting and polynomial equations are not suited for these series. The paper presents general mathematical equations for thrust and torque of Gawn-Burrill propeller series. The equations take into account effect of cavitation on thrust and torque in addition to influence of pitch ratio, blade area ratio and advance coefficient. Artificial Neural Networks method is used to develop the equations based on published model test results. The developed equations capture very well the non-linear behaviour of thrust and torque in cavitating conditions. These equations allow the designer to flexibly choose pitch ratio, blade area ratio, cavitation number and advance coefficient. Therefore they are not restricted to the tested configurations and conditions. The method used is described and the constants required for the thrust and torque equations are tabulated. Verification diagrams and interpolation examples are presented.