Drag Reduction Mechanism And Application Research Of Air Lubrication System On A Bulk Carrier

With the increasingly stringent requirements for energy conservation and emission reduction in the global shipping industry,low-carbon and zero-carbon have become one of the core indicators of ship design.In 2018,in order to reduce carbon emissions in the field of ship transportation,the International Maritime Organization formulated and issued guidelines on the calculation and verification of the existing ship energy efficiency index(EEXI),and forced shipping enterprises and scientific research and design units to research and develop various energy-saving and emission-reduction technologies to meet industry requirements by gradually improving the level of each stage of the energy efficiency design index(EEDI).Air lubrication drag reduction technology sprays air medium to the bottom or side of the ship by arranging a specially designed special jet device in the hull structure to form a thin air layer that separates the hull from the water surface,thereby reducing the wet surface area at the bottom of the hull,reducing the ship’s navigation resistance and reducing fuel consumption.In this paper,Rhino modeling software is used to establish the three-dimensional geometric model of bulk carrier,and STAR CCM+ simulation software is used to explore the drag reduction mechanism of air lubrication system,calculate the sailing resistance of the 64 K bulk carrier model under various speed conditions,and simulate the drag reduction effect of ship model equipped with air lubrication system under different ventilation mass flow rates.Optimize the layout of the drag reducing device,so that the gas distribution at the bottom of the ship is more uniform,reduce the navigation resistance of the ship,and compare and analyze the calculation results of each optimization scheme;The sailing speed and jet flow of the model were changed,the optimal ventilation of bulk carriers at different speeds was explored,and the drag reduction rate under each speed condition was calculated according to the drag reduction rate calculation formula.From the change curve of drag reduction percentage and vent flow rate,the abscissa of the peak point of the graph is found as the optimal optimal ventilation flow rate,so as to plot the change curve between the optimal ventilation flow and the speed,and analyze and summarize the calculation results under different speed conditions.By elaborating the specific structure of the drag reducing device,the working principle of the air lubrication system is analyzed,and the workflow of the device is described in detail based on the drag reduction mechanism.Determine the main technical parameters such as carrying capacity,main engine power,speed,etc.,and refer to the various correction coefficients of the ship type,calculate the energy efficiency coefficient EEXI of the existing ship as an evaluation of whether the 64 K bulk carrier achieves the expected drag reduction effect,and the calculation results show that equipped with air lubrication system has significant energy saving and emission reduction effects,which can help bulk carriers achieve the goal of reaching the third stage level of EEDI.