Journal of The School of Marine Science and Technology,Vol.6 No.1
Basic Study of the Performance of A Cylindrical Sail for Large Ships
Hikaru YAGI, Akihiko FUJII and Naoya MATSUBARA
Abstract
Recent soaring bunker price forces ship operators to improve ships’economy. The most direct measure is to improve propulsive performance.In addition,various energy saving devices become feasible in terms of the possible amount of saving money proportional to the percentage of saving and to the oil price even if there exists technological difficulty or density of saving energy.Natural energy, such as wind,wave or solar is very popular for land use energy to cope with global thermal gases.The utilization of wind energy by sails is the most traditional method for ship operation.However,very limited application has been made for modern motor ships.Novel sail concepts,such as rotating cylinder using Magnus Effect,or Turbo Sail utilizing fans had been introduced,but did not reach to the practical or commercial use. It is mainly due to the technological difficulties in large structural mechanism or additional energy to operate the system.
The authors have reached a new concept utilizing the endowed structure and power to minimize the difficulty, focusing in very large ships(VLCC,VLBC).It is a cylindrical sail with air suction,utilizing dodger support structures and power of air intake for main engine and ventilation of ship.As a feasibility study,model tests were conducted in wind tunnel to grasp the order of possible saving as well as the mechanism of flow around the sail.
The results have shown that the maximum lift coefficient reaches to the order greater than 7,and reasonable amount of saving can be expected when a total system is realized.
In this paper,lift-drag performance of the cylindrical sail with a fin is presented,including the newly developed
test method and the evaluation of air-intake type.