2011 年 46 巻 3 号 p. 296-304
This paper discusses the feasibility of high-performance NHV propeller whose blade area is decreased by 20％ compared to a normal NHV propeller without the risk of cavitation erosion and increasing pressure fluctuations, and presents the results of experiments and numerical computations of an NHV propeller with the smallest blade area (SBA-NHV propeller) and an equipped conventional propeller for a 749GT chemical tanker.
In recent studies conducted by the authors, a propeller with a blade area 20% smaller than that of aconventional propeller offered an improvement of about 2% in propeller efficiency with an almost equivalent risk of cavitation erosion and pressure fluctuations in model tests. In order to improve propeller efficiency by decreasing the propeller blade area, four propellers were designed whose blade areas were decreased systematically. An SBA-NHV propeller with a blade area 20% smaller than that of the conventional propeller was designed. Three four-bladed propeller models including the conventional propeller, the above-mentioned SBA-NHV propeller, and the propeller with each blade having a different blade area ratio were manufactured.
Propeller open tests and self propulsion tests were carried out in the towing tank and cavitation observations were made with a high speed video camera, erosion paint tests and fluctuating pressure measurements were carried out in the cavitation tunnel using these three propeller models. The SBA-NHV propeller attained improvements of about 1.3% and about 3% in the propeller efficiency and in the propulsive efficiency, respectively, compared with those of the conventional propeller. The effects of decreasing the blade area ratio on the risk of cavitation erosion and the pressure fluctuations were confirmed and the SBA-NHV propeller demonstrated an almost equivalent performance with that of the conventional propeller. To validate existing numerical tools, propeller efficiencies and cavitation patterns were numerically simulated by a lifting surface theory (LST) and a Reynolds-Averaged Navier-Stokes solver (RANS). The LST and RANS need to be modified to predict the effect of the blade area ratio etc. on the propeller efficiency. Meanwhile, these are found useful as design tools to evaluate the risk of cavitation erosion even though further improvements are still necessary.
