根部負載下降對於斜軸狀況下高速螺槳之性能改善

Performance Improvement of High-Speed Propellers at Inclined Shaft Conditions by Root Unloading

本文將探討根部負載下降對螺槳於斜軸狀況下之效率以及空化現象之影響，為此本文設計四組螺槳，其中兩組為四葉螺槳，無歪斜，其中一個螺槳無根部負載下降，另外一個具負載下降。另兩組為五葉螺槳，具歪斜以及不同程度之根部負載下降，以上四組螺槳面積比均為1.0，螺距比為1.4。此四組螺槳將於斜軸狀況下測試比較於不同空化係數時之效率以及螺槳葉面上空化之程度。由實驗結果發現根部負載下降於低空化係數時確實可以明顯提高螺槳於斜軸狀況下之效率，同時降低根部之空化狀況，然而過度之負載下載，亦會使螺槳於斜軸狀況下葉片轉至90度時，空化現象由根部往0.5~0.6R移，且葉尖渦強度增加。 The influences of root unloading on the propeller efficiency and cavitation at inclined shaft conditions are investigated in this paper. Four propellers are tested at inclined shaft conditions and at different cavitation numbers to compare the propeller efficiency and cavitation pattern. Two of these propellers are four-bladed propellers without skew, and one is root unloaded, and the other one is not. Two of these propellers are five-bladed propellers with skew, and have different root unloadings. All of these propellers have expanded area ratio 1.0 and pitch ratio 1.4. From the test results, it is evident that root unloading can significantly increase the propeller efficiency for low cavitation number at inclined shaft conditions. However, the cavitations will be moved to 0.5~0.6 propeller radius, and the strength of the tip vortex cavitation will be increased if a strong root unloading is applied.