二重反転プロペラの設計について : 高速コンテナ船への適用

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In this paper, an improved design procedure for contrarotating propellers is presented which is essentially based on Morgan's method. Two kinds of contrarotating propellers for a 23.9 knots container ship are designed. Extensive and systematic experiments are performed; propeller open test, self-propulsion test, cavitation observation, pressure fluctuation measurement and velocity field measurement by using laser doppler velocimeter. After a brief description of the difference between Morgan's method and the present method, a new design method for propeller blade sections is proposed in order to avoid or to reduce face cavitation causing cavitation erosion. A set of contrarotating propellers CRP-1 is designed assuming that the wake distribution is uniform. Another set of contrarotating propeller CRP-2 is designed according to Lerbs' wake-adapted optimization hypothesis and an improved determination of the blade camber-line. From the results of propeller open test, the gain in propeller efficiency over the single propeller is 6 or 7 per cent for the designed contrarotating propellers. The results of the self-propulsion test indicate that the reduction of the required power to two sets of the contrarotating propellers is 7 per cent in DHP at the basic ship speed, as compared with the conventional single propeller and unfavorable influence of the rudder on propulsive efficiency is remarkable. It is found that Lerbs' wake-adapted optimum propeller CRP-2 does not give us better efficiency, not even in the behind condition. The back cavitation extent on the forward and aft propeller of CRP-1 is rather small, while a large amount of face cavitation is observed for CRP-1. On the other hand, a little face cavitation on CRP-2 is found, owing to the present determination of the pitch distribution. The pressure fluctuations induced by unsteady cavitation are measured. From the comparison of the first blade frequency amplitude for each propeller, CRP-1 presents a lower amplitude than the single propeller in the cavitating condition. Velocity field measurement around CRP-1 shows that the induced velocities given by the present design procedure correspond reasonably with the measured ones. Through the above-mentioned systematic experiments, it is recognized that the present design method for contrarotating propellers is useful. This paper also indicates that in the present design procedure further refinement is necessary of the theoretical treatment of mutual interference velocities induced by the forward and aft propellers.
社団法人日本船舶海洋工学会の論文
1988-03-22

二重反転プロペラの設計について : 高速コンテナ船への適用

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