Research On The Internal Coating Technology Of Shipsconsidering The Influence Of Airflow Organization

With the increasing development of the global maritime economy,ships have become an increasingly important transport carrier and ship construction technology is developing rapidly towards modernisation under the impetus of technology.As a key process in the integrated concept of "hull,outfitting and coating",painting plays a very important role in the shipbuilding process.Especially nowadays,with the prevalence of environmentalism,internal painting technology is also receiving a lot of attention from engineers.Nowadays,internal painting is mainly carried out using high-pressure gas spraying technology,and the work must be carried out in a closed space with a special air supply and exhaust system.The professional environment of the interior painting workshop not only provides a comfortable working environment for the workers,but reasonable airflow organisation control also has a certain improvement on the quality of the painting.In addition,a large number of pollutant gases are generated during the spraying operation and the spraying workshop has to take into account the transport and purification of pollutants.For internal coating technology,countries are more concerned with the development of coating equipment,spray atomisation mechanism and process parameters for the impact of spraying quality research is less.In order to study the impact of different ventilation methods and air changes on the airflow organisation in the workshop,as well as the impact of different process parameters on the spraying quality,the following aspects of work were carried out in this thesis based on numerical simulations.(1)The solidworks software is used to build the workshop model and imported into the fluent module of the ansys software for analysis.By comparing the velocities of the test points under different grid sizes and time steps,a suitable grid size and time step were selected to complete the validation of the numerical simulation method.(2)Numerical simulation analysis of the velocity field and pollutant concentration field of the workshop under different ventilation conditions.By analysing the velocity field under natural ventilation conditions,it was found that the airflow organisation in the workshop under natural ventilation conditions is very uneven,which is not conducive to the diffusion of pollutants and workers’ work.In addition,the velocity and pollutant concentration fields of the workshop under three different ventilation methods,namely side feed and side return,top feed and bottom return and top feed and side return,are compared.The study found that under mechanical supply and exhaust air,the airflow in the workshop is well organised,which is beneficial to the transport of pollutants in the workshop.(3)Various evaluation indexes are proposed for the airflow organisation of the workshop under different ventilation quantities,and the airflow organisation of the workshop under different conditions is analysed through the concentration of pollutants at the exhaust air outlet and the concentration of measurement points in the workshop.The study found that increasing the ventilation volume can help to trap pollutants,but it will cause economic pressure.In addition,it was found that the top and bottom return ventilation method provides better control of pollutants.(4)To address the need for heating the workshop in winter,the temperature field of the workshop under three different ventilation methods were compared under the same heated fresh air conditions.The results of the study found that the temperature uniformity of the workshop was better under the side-feed and side-return ventilation methods,but the high temperature airflow could not play a good heating effect on the working area.The temperature of the working area of the workshop is high under the top air supply condition,but the temperature uniformity is poor.This thesis uses the idea of layered air conditioning to analyse and compare the temperature field of the workshop under different air supply heights with side air supply,which is good for improving the temperature of the working area while maintaining the uniformity of the workshop temperature.(5)For high pressure airless spraying quality defects,analyse the atomisation mechanism of high pressure airless spraying,select the built-in rotating cup atomisation model of Fluent software,establish the flow field and set the boundary conditions to study the spraying effect under different process parameters.The results found that the higher the spraying pressure,the smaller the diameter of the atomised droplets,the greater the droplet movement speed and the greater the thickness of the resulting paint film.Changes in spray spacing have little effect on droplet velocity,but result in larger spray areas and thinner films.The wind speed of the external environment has a certain influence on the quality of spraying,at a wind speed of1.0m/s,the painted film is less affected,but when the wind speed is raised above 2.0m/s,the deformation of the air phase velocity field is obvious and the uniformity of the paint film is poor.Therefore,the spraying operation should pay attention to the control of the ambient wind speed.In this thesis,the distribution of the airflow group in the workshop under different ventilation methods and different ventilation volumes is studied based on numerical simulations.The effect of different spraying parameters and external wind speed on the coating effect is also studied.The results of the study can provide some reference for the ventilation design of the painting workshop and the selection of painting parameters.