| In recent years,ship transportation has made important contributions to the world economic development,but it has caused serious air pollution.In the face of the increasingly strict control standards of sulfur content of marine fuel in emission control area,maritime departments urgently need to improve the law enforcement capacity and level of law enforcement of ship exhaust gas supervision and control,and various research departments have also successively carried out relevant ship exhaust gas diffusion and distribution research.Therefore,understanding the distribution characteristics of the sailing ship exhaust in the atmosphere,as well as establishing a feasible and effective calculation method of the tail gas source intensity information by using the monitoring concentration of the ship exhaust gas,is a key technology for the establishment of a remote monitoring platform for ship tail gas and lays a model foundation for the relevant maritime authorities to capture the ships with excessive exhaust emission in the drainage control area of the inland river basin,and investigate the diesel oil use of the ships with excessive sulfur.Therefore,based on the Gaussian model,this paper explores the method of backcalculation of the emission source intensity of inland waterway sailing ships,aiming to provide method guidance for the supervision and control of the emissions of ships in the emission control area.In this paper,the FLUENT software is used to simulate the emission diffusion process of ship exhaust,analyze the temporal and spatial distribution characteristics of ship exhaust diffusion,discuss several specific application forms of the forward diffusion model of ship exhaust under the Gaussian model,and establish the backcalculation model of ship exhaust source intensity.Finally,the inverse calculation problem is solved by pattern search algorithm,genetic algorithm and particle swarm algorithm,and the selection of the stacking step in the inverse calculation model is deeply analyzed.The main research work includes:(1)Use FLUENT software to build a model based on the Nanjing Dashengguan Yangtze River Bridge as a prototype.Through the horizontal and vertical monitoring points of the checkerboard arrangement of the exhaust gas concentration changes,the temporal and spatial distribution law of exhaust emission diffusion of sailing ships is analyzed,and the important influencing factors of exhaust emission diffusion of ships on board are understood.(2)The specific application forms of the Gaussian plume point source model,the Gaussian plume model and the Gaussian line source model were compared and analyzed,and on this basis,the optimized Gaussian model under the condition of ship exhaust gas diffusion in this problem was proposed.An inverse calculation model of ship exhaust source intensity based on optimization theory is established.(3)Use traditional and intelligent multiple optimization algorithms to solve the inverse calculation problem,and analyze the calculation efficiency and accuracy of each inverse calculation method.By adjusting the iteration step length,three algorithms are used to calculate the optimal step length in the inverse calculation model,and the accuracy of the inverse calculation result is improved.The results of the study show that ship exhaust emissions present the following wind direction as the axis to show a normal spatial symmetrical distribution characteristics.Ship exhaust emissions time,wind speed and ship speed are important factors that affect the diffusion of ship exhaust.At the same time,the optimized Gaussian model takes into account the characteristics of ship exhaust diffusion to the greatest extent,and has the best applicability characteristics.The three optimization algorithms used all show good feasibility in the inverse calculation.However,the calculation accuracy and calculation efficiency of the pattern search algorithm are low,while the particle swarm algorithm has shown good calculation accuracy and calculation efficiency,and is more suitable for backcalculation of ships exhaust emission source intensity and ship exhaust positioning.Finally,when the iteration step is 0.1 seconds,the source intensity backcalculation of this problem can achieve the best calculation accuracy.The research results have important guiding significance for the research on the diffusion and distribution of ship tail gas and the development of remote monitoring technology for ship tail gas. |
