以大範圍變負荷試驗探討推進因子間之交互作用

Abstract

效率始終是船舶與螺槳設計中不可忽視的一環。透過模型尺度的試驗將螺槳與船體的流體動力現象拆解成數個環節，並透過對各式參數的修正，求得實尺寸船隻與螺槳搭配的綜合性能。依照國際船模拖曳水槽會議(International Towing Tank Conference, ITTC)的建議程序，實驗時的螺槳前進係數不同於實船，且推估過程中假設推減係數沒有尺度效應。然而前進係數不同導致的交互作用速度差異，可能使跡流係數被低估，且模船與實船之間前進係數與跡流係數皆存在差異，此差異可能對推減係數產生影響。本研究對一艘球艏油輪進行大範圍的變負荷試驗，涵蓋四組不同船速，探討三個推進因子之間的交互作用。實驗數據顯示螺槳推力與螺槳對船殼吸力之間的線性關係，且隨著前進係數的增加，跡流係數和推減係數均增加。扣除前進係數的貢獻後，跡流係數對推減係數的影響尚不明確，需要進一步研究。針對ITTC程序可能導致的推減係數和跡流係數低估，本研究提出將跡流係數與推減係數視為前進係數函數的推估方法，然而兩方法計算出的實船轉速與效率差異並不顯著。

Efficiency has always been an integral part of ship and propeller design. Through model-scale experiments, researchers break down the fluid dynamic phenomena of propellers and hulls into various components, and through adjustments to various parameters, they determine the comprehensive performance of full-scale ships and propellers. Following the recommended procedures of the International Towing Tank Conference (ITTC), the advance coefficient of the propeller during experiments differs from that of the full-scale ship, and it is assumed during estimation that the thrust deduction coefficient has no scale effect. However, the difference in interaction velocity resulting from advance coefficients different may lead to an underestimation of the wake coefficient, and there are differences in advance coefficients and wake coefficients between model ships and full-scale ships, which may affect the thrust deduction coefficient. This study conducted large-scale load variation tests on a bulbous bow oil tanker, covering four different ship speeds, and explored the influence of three propulsive factors. The experimental data showed a linear relationship between propeller thrust and propeller-induced hull suction. As the propeller advance coefficient increases, both wake fraction and thrust deduction factor increase. After subtracting the contribution of the advance coefficient, the impact of wake fraction on the thrust deduction factor remains unclear and requires further study. This study proposes an estimation method that considers the wake fraction and thrust deduction factor as functions of the advance coefficient to address the potential underestimation of these factors in the ITTC procedures. However, the differences in the rotation rate and efficiency between the two methods are not significant.