Ship Floating Attitude/Speed Optimization And Fuel Consumption Performance Forecast

As an important means of transportation,ships play an important role in international trade as the statistical datas showed that its transportation accounts for about 80%all over the world.However,ship transportation also has some disadvantages,like lower energy utilization rate,which is likely to cause emission pollution.Recently,in response to the increasingly stringent carbon and sulfur emission restrictions of the International Maritime Organization(IMO),Green and energy-saving has become an important topic of the shipping industry.Meanwhile,with the improvement of the level of information technology,the trend of Smart ship has become more and more obvious,and intelligent energy efficiency management has received increasing attention.This paper mainly focuses on the issues of trim optimization,speed optimization and power/fuel consumption prediction research for a full scale VLCC ship in order to improve the ship's energy efficiency so that help ship operator save energy and reduce emission.For the trim optimization problem of VLCC ship,the relationship between the center of mass position and the trim angle was analyzed.Both the experiment and CFD numerical methods were used to study the variations of resistance,sinkage and trim angle under different initial trim conditions.The total resistance was divided into shear force which in the tangential direction and pressure force in the normal direction.The change of resistance components,wetted surface area,length of waterline,pressure distribution along the hull surface,free surface at different trim conditions were analyzed.The components of the ship's trimming moment were studied.The results show that the change of total resistance was mainly caused by the change of pressure resistance,and the trimming moment is mainly induced by pressure moment The friction resistance did not change obviously.At the same time,the numerical simulation results were compared with the model test,and it is found that the numerical results are in good agreement with the experiment datas as a whole,but there were some errors in some conditions,especially at low speed conditions,as the change of resistance and floating attitude changes were small.The impact from various aspects of error need to be pay attention toIn terms of speed and engine power prediction,the three-dimensional method is used to convert the resistance to full scale ship,the CFD method is used to analyze the open water characteristic of the propeller,and the convergence of grid and time step were studies.The steady and unsteady simulation methods are compared.The open water results are converted to full scale propeller.The self-propulsion experiment was carried out in the towing tank.The self-propulsion factors and propulsion efficiency components were analyzed.The performance of full scale VLCC ship is estimated using the ITTC1978 method.The relationship between ship speed and power was analyzed and it laied the foundation of fuel consumption.According to the formula recommended by IMO,the additional resistance of wind and waves were estimated.The model of fuel consumption of the main engine is established in combination with the fuel characteristic curve of the main engine.The influence of wind and waves on fuel consumption of the main engine was analyzed.The genetic algorithm of MATLAB softwere was used to investigate the problem of speed optimization to minimum fuel consumption under the fixed route.The optimization model was compared with a existing method to verify its reliability indirectly.The results of speed optimization under different sailing period in 4 seasons were analyzed.Compared with punctual constant speed,optimized speed and service speed,the results shows that the optimized speed fluctuates near the punctual constant speed.As a whole,the single fuel saving rate is lower compared with the punctual and constant speed(less than 0.5%,This has a certain relationship with the sailing time and the weather conditions of the flight segment).While compared with the service speed(take 15kn),the saving rate can reach about 20%.At the same time,it can be found that the fuel consumption varies in different seasons,and the fuel consumption can change up to about 3%.The analysis results can be a reference for speed decision in actual operation of VLCC ships.