限界小翼面積プロペラの研究: 第1報 小翼面積プロペラの設計、模型実験と実船実験

摘要

This paper concerns results of model tests and full scale measurements of the propeller designed for inland ship (749 GT chemical tanker) aiming 3% increase of propulsive efficiency comparing with the present conventional propeller. Three concepts, namely①small blade area,②decrease of hub-vortex, and③consideration of ship wake distribution are applied for the propeller design. NHV (Non Hub-Vortex) propeller, of which the blade area was decreased by 20% from the conventional propeller, was designed and towing tank tests (propeller open test and self propulsion test) and cavitation tests (cavitation observation, paint erosion test, and fluctuating pulse measurement) were carried out with the conventional propeller and the SBA-NHV propeller (Small Blade Area NHV propeller). The model test results showed that the propulsive efficiency of SBA-NHV propeller is about 4% higher than that of the conventional propeller and the risk of cavitation erosion and the fluctuating pressure of both propellers are almost equivalent. Finally, sea trial of 749 GT chemical tanker was performed with the SBA-NHV propeller which was newly manufactured. Results of the sea trials and the service performance demonstrated about 4% deduction of engine outputwithout any problem of the ship vibration and cavitation erosion after 15 months operation.%プロペラ効率について重要な要素は「プロペラ荷重度」，「プロペラ回転流」，「翼の粘性抗力」であり，従来，これらを減少させることで効率向上を図ってきた.翼面積を小さくすれば「翼の粘性抗力」を減らしてプロべラ効率を向上できるが，キャビティが増加し，翼のエロージョンや船尾変動圧力（船尾振動）が増大するので小翼面積化をある程度のところで抑えてきた.ところが最近の研究により，翼先端近傍の荷重分布を適当に設計すれば，さらに小翼面積化を進めてもキャビテーションの問題（エロージョンや船尾振動の増大）を回避することが可能と考えられた.いわゆるチップロード化である.従来は翼先端近傍の荷重を減らしてキャビティの発生量を抑えてきたが，小翼面積プロペラのようにキャビティが多く発生する場合，逆に翼先端の荷重を増やしてキャビテーションを減少及び安定化させる（消えにくくする）ことが翼のエロージョンや船尾振動の抑制に有効であることが判明した.