Study On The Characteristics Of Induced Airflow During The Pouring Process Of High Temperature Liquid Metal

In the process of metal smelting and casting,amounts of polluted airflow will be induced in the pouring process of liquid metal at high temperature,for example adding molten steel to converter and casting forming.However,the method of maximum exhausted flow is not sufficient energy saving for capturing dynamic pollution.Therefore,the characteristics of the induced airflow during the pouring process of high temperature liquid metal will be studied in this paper,which will be helpful for the reasonable design of the exhaust system.In order to deeply understand the change process of polluted air flow,this manuscript firstly confirms the two flow conditions of liquid metal in the pouring process--chain collision status and discontinuous status.Secondly,the model experiment is used to analyze the change of the emission process of the non-isothermal eddy--diffusion vortex,the main emission source in the chain collision status of the whole pouring process.Besides,the study analyzes the flow process of the airflow induced by the chain collision status and heat transfer characteristics between liquid column and airflow.Finally,the influenced factors of the diffusion angle and propagation velocity of the induced airflow are investigated experimentally in discontinuous status.The main conclusions are as follows:(1)When the rotation speed of jar is 0.013rad/s,the analysis shows that the falling fluid process is a chain collision status.When the speed exceeds 0.03rad/s,liquid discontinuity will occur.Through dimensional analysis,it is found that the number of Archimedes in the boundary layer of the induced airflow in the pouring process is related to the flow rate and height of the pouring fluid as well as the temperature ratio between the liquid and ambient air.The main factors affecting the discontinuous status of pouring are the liquid flow and temperature ratio.(2)The manuscript designs and establishes a model experimental bench for the research,and develops a color schlieren measurement system and a relevant quantitative algorithm method.It was found by color schlieren experiment that a non-isothermal vortex was generated in the chain collision status.It was found that the diameter and distance of the diffusion vortex varied in the whole pouring process according to the form of Fourier series functions.At the two fifths time of the whole pouring period,the falling flow was the largest and the emission was the largest.In addition,the experiment shows that the average distance between the diffusion vortex and the jar outlet is half of the radius of the jar outlet during the whole pouring process.(3)In this study,optical flow PIV technology was developed to analyze the airflow process induced by chain collision status.The dimensionless range and velocity of induced airflow are found under the most pouring flow.In addition,by comparing the induced airflow process at low temperature,it is found that the airflow process is completely opposite at high temperature ratio.The results can identify the hood outlet direction.The relation of decreasing height Z to velocity satisfying 0.5 power is verified in dimensional analysis.The flow vortex is identified by using the Q criterion and airflow vortex is generated at the impact point of the liquid column in the chain collision status,and the flow Q value increases from 0.02 to 0.1 as the pouring height increases.(4)This study developed the infrared imaging auxiliary plane method and analyzed the heat transfer characteristics of induced airflow during the chain collision status.It is found that the temperature field of the induced airflow is decreasing exponentially.Secondly,beyond 1.25 of the liquid air temperature ratio,the horizontal range of the induced air temperature is stable and unchanged,and the distance from the jar port to the furthest point the induced air temperature affects the dimensionless horizontal distance d_h~*=7.By fitting the Nu number of the experimental criterion correlation in the chain collision status,it is found that the chain collision process is mixing convective heat transfer.The results help to estimate the convention heat transfer to the indoor environment.The gas-liquid heat transfer process is visualized by energy flow vector and the heat boundary layer of chain collision status is explained by the field synergy principle.It’s found that schlieren imaging could not measure the airflow velocity,and its essential of movement in imaging is the velocity of movement of mass transfer in the fluid,which is called the propagation velocity.For the control of non-isothermal and different density of gaseous pollutants,not only the velocity but also the propagation velocity of polluted airflow should be considered in the wind speed controlling method.(5)In this study,the airflow induced by discontinuous status was observed through the color schlieren imaging,and it is found that the induced airflow forms a non-isothermal vortex field with a certain diffusion angle and propagation velocity during discontinuous status.The propagation velocity and diffusion range angle of the airflow induced under different temperature ratios and pouring flow rates are studied.It is found that the increase of the pouring flow rate leads to the increase of the diffusion range angle and the propagation speed,while the temperature ratio has no significant effect on the propagation speed and diffusion range angle of the discontinuous status.