不同预报方法对前置预旋类型装置节能效果的影响

Influence of Different Prediction Methods on Energy Saving of Pre-swirl Devices

对于预旋类型的桨前节能装置,在对各水池试验数据分析时会采用不同的换算方法。以实际建造项目38000 t散货船为研究样本,讨论二因次法、三因次法、各种伴流修正方法以及节能装置自身引起的阻力变化对节能效果评估的影响。二因次和三因次阻力分析方法对节能效果有少许影响,但三因次法预报的节能效果较好。在伴流修正方法中,ITTC1999方法和E_(i)法预报的效果接近,都比ITTC1978方法预报的节能效果好。在基于ITTC1999或E_(i)法修正伴流时,无论是使用二因次法还是三因次法,因节能装置自身导致的阻力增量对节能效果的影响微弱。但在用ITTC1978方法修正伴流时,若计及节能装置导致的阻力增量,预报的航速会降低,从而节能效果变差。

Energy saving devices discussed in this paper are those with pre-swirl function and installed in front of the propeller.There are different conversion methods used in different water tanks for analyzing energy-saving of the device.A real 38,000-ton bulk carrier is selected to study the influence of two/three-dimensional method,wake correction methods and resistance change on the effect of energy-saving.The results show that resistance analysis methods have a little effect on energy-saving,and forecast of energy-saving with the three-dimensional method is higher than the two-dimensional one.In wake correction methods,ITTC1999 method and E_(i)method have similar forecast of energy-saving which is higher than ITTC1978 method.When the wake is corrected based on ITTC1999 or E_(i)method,resistance change induced by the device has no influence on energy-saving no matter using the two-dimensional method or the three-dimensional method.When ITTC1978 method is used for wake correction,the predicted ship speed will be reduced and the energy-saving will be worse due to resistance increase induced by the device.