Basic Study on the Wind- assisted Propulsion Support System

以大型船舶节能为目的，对风助推进支撑系统进行了基础性研究，得出了以下结论：1)利用现有的避雷器支撑结构和空气吸力，构思了一种柱式圆柱体推进助推系统。柱体周围的流场通过位于气缸后部的进气口被吸入机舱。控制近场边界层，产生分离自由流场，施加水动力升力。大型风洞模型试验表明，进气系统的最大升力系数约为7.5，升阻比约为1.3，为舰船获得有用的推进推力提供了可能。2)研究了两种进气系统，即冲压金属进气系统和缝隙进气系统。从最大升力和风向一致性的角度来看，‘狭缝式’比‘冲压金属式’更适合于实际船舶应用。3)在一些实际的现有船舶上测量了主机等所用的风量，分析得出了风帆可能的升力与所需风量的关系。用流动显示方法和热线法对圆柱形风帆的绕流进行了研究。空气吸力的作用明显减小了流动分离区，并在气缸周围产生了循环。研究还发现，控制缝隙尺寸有助于优化风帆在不同风速和风向下的性能。5)对于圆柱形风帆的实际应用，需要进一步提高风帆性能。为了满足这一要求，动态控制缝隙尺寸可以作为引入百叶窗控制系统的一种可能措施。

For the purpose of energy saving of large vessels, basic study on the wind- assisted propulsion support system was conducted, and following conclusions were obtained.1) The concept is a column-type circular cylinder propulsion assistance system which utilize the existing dodger-support structure and air suction power. Flow field around the column is sucked into the engine room through the intake located in the after part of the cylinder. Boundary layer in the near field is controlled and separation free flow field is generated to exert hydrodynamic lift. Model test in a large wind tunnel test indicated that the maximum lift coefficient is about 7.5, lift drag ratio about 1.3, implying a possibility for obtaining useful propulsion thrust for ships.2) Two types of air intake system were investigated, namely, 'punched metal type' and 'slits type'. In terms of the maximum lift and consistency for wind direction, 'slits type' was concluded to be superior to 'punched metal type' for actual ship applications.3) Air volume used for main engine etc. was surveyed on some actual existing ships, and the analysis showed a relation between the possible lift by the sail and required air volume. This implies a possibility of development of circular cylinder sail.4) The flow around the circular cylinder sail was investigated by flow visualization method and hot wire methods. The effect of air suction was clearly indicated to diminish the flow separation region and generate circulation around the cylinder. It is also found that controlling the slit size may contribute to optimize the sail performance at various wind velocity and direction.5) For practical application of the circular cylinder sail, further improvements of sail performance are necessary. To meet this requirement, dynamic control of slit size can be a possible measure introducing louver control system.