Experimental Study Of Ship Sulfur And Carbon Concentration Diffusion Based On Smoke Plume Model

With the development of shipping industry,exhaust gas from ships has become one of the important sources of air pollution.In order to control and slow down the air pollution caused by sulfur oxides,the International Maritime Organization(IMO)and the Ministry of Transport of China have issued relevant conventions and regulations,which have made clear provisions on the sulfur content of ship fuel.Unmanned aerial vehicle(UAV)as the core sulfur detection platform has been gradually applied in the monitoring of sulfur emissions from ship exhaust gas due to its strong flexibility,portability and operability.The sulfur sniffing mobile detection platform can be used to detect the exhaust gas of ships at sea,so as to verify whether the sulfur content information reported by ships is true.At the same time,for ships burning high-sulfur oil but equipped with post-treatment devices,sulfur sniffing mobile detection platform can be used to test the exhaust gas after treatment,so as to verify whether the effect of exhaust gas cleaning is up to the standard.However,in the actual application process,it is found that the sampling process of sulfur sniffing mobile detection platform is not standardized and the influence of environmental factors on sampling accuracy is not taken into account,which leads to large detection errors.Therefore,the study on the diffusion and sampling method of sulfur and carbon concentration of ships is the most critical link affecting the sampling accuracy of sulfur sniffing technology.In view of this problem,the following work is carried out in this thesis: 1.A diffusion model of sulfur carbon concentration in ship exhaust gas is established.2.Taking the real ship chimney structure as the prototype,FLUENT software is used to simulate the diffusion of ship exhaust plume under the conditions of wind force 3-5 at sea.The diffusion shape,plume temperature and sulfur carbon concentration distribution of ship exhaust plume under the conditions of wind speed are obtained,and the model is verified.3.Guided by the simulation results,set the ship exhaust sulfur emissions precision test bench,and in the laboratory environment by scale model to explore the ship fuel sulfur content method.finally,maritime environment wind speed sampling point location and mobile detection platform three factors influence on sulfur sniffer detection precision,eventually give sulfur sniffer mobile detection technology application method.finally the applicable scope of the proposal.Through the research of this thesis,the following achievements have been achieved:(1)The simulation of the diffusion of the ship exhaust plume under the wind of level 3-5at sea is completed.It can be concluded that the diffusion of the ship exhaust plume under the experimental wind speed is in line with the Gaussian plume model,and the distribution of pollutants is spread along the axis of the chimney mouth.At the same time,with the increase of environmental wind speed,the entrainment phenomenon at the end of ship exhaust plume becomes weaker and more inclined to the horizontal direction.In addition,the high temperature area of smoke plume is mainly concentrated within the range of 4m from the ship chimney mouth.With the increase of environmental wind speed,the cooling effect of wind on smoke plume is further strengthened,and the high temperature area is further reduced.When the distance from the axis of the chimney mouth is more than 10 m,the concentration of CO2 and SO2 drops sharply and is diluted rapidly,which is not easy to be captured by the gas sensor.Therefore,when the sulfur sniffing mobile detection platform is used to sample the ship’s exhaust smoke plume under the conditions of level 3 to level 5 wind at sea,the sampling tube should be set against the axis of the plume to collect the exhaust gas,and at the same time,it should be kept 4-10 m away from the ship’s chimney mouth to ensure that the mobile detection platform will not be damaged by high temperature smoke and achieve good detection results.(2)Through the experimental similarity theory to complete the construction of the ship exhaust sulfur emission detection accuracy test platform,in the test by changing the sulfur dioxide concentration in simulated flue gas to simulate the combustion of fuel gas with different sulfur content,verify the effectiveness of sulfur sniffing technology.At the same time,when the measurement environment and detection instrument are the same and the signal-to-noise ratio of the collected data is greater than 8.8,the sulfur content of ship fuel has almost no influence on the detection accuracy.Therefore,sulfur sniffing technology is equally suitable for ships using fuel oil with different sulfur content.(3)According to the experimental results of the influence of environmental wind speed and sampling point location on the sulfur sniffing detection accuracy,the relative error of sulfur content in fuel sampled by sulfur sniffing technology is basically controlled within-10% within the range of 4-10 m sampling points on the mobile detection platform under level3-4 wind.The detection relative error varies greatly within the location range of 4-10 m sampling points under force 5 wind.Therefore,the real ship test should be carried out under force 3-4 wind,and the sampling point position should be controlled within the range of4-10 m to obtain higher detection accuracy.