Design, Cavitation Performance, and Open-Water Performance of a Series of Research Skewed Propellers

Abstract : Cavitation tunnel and open-water results are presented for a series of skewed propellers that were designed by lifting-surface methods. The four model propellers had maximum projected skew at the blade tip equal to 0, 36, 72, and 108 deg. The results showed that the cavitation-free bucket becomes substantially wider with increasing skew; however, there was some crossover in the inception of back cavitation and tip vortex cavitation among the three skewed designs near design advance coefficient. Near the self-propulsion condition, the propeller with 36 deg of skew had the highest cavitation inception speed. Forward open-water propulsion performance including lift effectiveness and performance breakdown due to cavitation were substantially the same for four propellers. All four propellers developed the design thrust loading coefficient within 1 percent of design rpm in open water. At constant power and thrust loading coefficients, the backing speed decreased slightly with increasing skew (respective reductions of 1.5, 8.0, and 12.5 percent for 36, 72, and 108 deg of skew).