Abstract. Surface-piercing propellers have been widely used in light and high-speed
vessels because of their superior performance. Experimental study of these
propellers is one of the most reliable and accurate ways which can provide
details about the performance and effect of different design parameters on
the performance of the surface-piercing propellers. In this research, a
five-blade surface-piercing propeller was tested in the free surface water
tunnel of Babol Noshirvani University of Technology in order to expand the
available experimental data and database for future engineering designs. The
effects of immersion ratio and shaft inclination angle on the propeller's
efficiency and hydrodynamic coefficients were examined. A free surface water
tunnel and a calibrated dynamometer with the measurability of the thrust
forces and the torque of a propeller were used for this purpose. Comparing
the obtained results with the existing semi-experimental equations shows that
the equations presented in various geometric conditions are not accurate
enough, and developing the existing database is necessary. The details of the
obtained results showed that the hydrodynamic coefficients of the thrust and
torque increased by increasing the immersion ratio, but the coefficient of
hydrodynamic thrust and efficiency reduced. The results also indicated that
the coefficient of torque increased by increasing the shaft inclination
angle. The highest efficiency of the propeller was achieved in the range of
40 %–50 % immersion ratios at all angles of shaft inclination. For
all immersion ratios, the maximum and minimum efficiencies were obtained at 0
and 15 shaft inclination angles, respectively. The best efficiency of the
propeller was at 50 % immersion ratio and zero shaft inclination angle.
Experimental study of immersion ratio and shaft inclination angle in the performance of a surface-piercing propeller
