The Flow Field Characteristics Of Discontinuous Buoyant Jet Under The Influence Of Plume And Local Exhaust Hood

In the processes of ferrous metal production and chemical engineering,such as metal smelting,coking.Especially in the process of dumping high temperature liquid,there are two forms of high-temperature airflow in the industrial plant,the one is the intermittent polluted airflow caused by the instantaneous dumping of high temperature metal liquid.The other is high temperature plume after dumping.The dumping of hot metal liquid will produce a large amount of polluted air.The concentration of polluted source will increase rapidly,which will intensify the instantaneous exhaust pressure of the local exhaust system.As a result,the exhaust hood will cannot capture the polluted airflow and cause a large amount of contaminated airflow to escape to the factory,then will endanger the health of workers and lead to many occupational diseases such as pneumoconiosis.In a word,the environmental problem caused by paroxysmal buoyant jets under the influence of buoyant plume and side suction flow in the smelting workshop needed to be solved urgently.Combined with engineering practice the article study on the flow field characteristics of discontinue buoyant jet under the influence of local exhaust hood and plume.Using theory analysis,experiment and simulate,the following contents are studied:First,through theoretical analysis,the article obtain a number of factors that affect the flow field characteristics of discontinue buoyant jet,and carry out the orthogonal experiments.The analysis of variance has qualitatively obtained the significant ranking,the trend of each factor,and the optimal experimental condition.Second,the research set up an equal-scale experimental platform and carry out large of experiments.The result gave the distribution of discontinue buoyant jet,the effect of the local exhaust hood and the location of two heat sources.Finally,using numerical simulation method to complete more research.Based on the independency analysis of the number of grid and the time step.After validity verification of simulation and experiment,the article got the influence of the height between the exhaust hood and the heat source,the spatial distribution.At the meantime,the research showed the dynamic capture efficiency of the local exhaust hood,and used the MATLAB software to fit the multi-factor discontinue buoyant jet.The main conclusions are as follows:(1)The article obtained many variables that will affect the flow of the buoyant jet by analyzing the equation of motion of the jet.Through orthogonal analysis,it conducted that both the U_e(exhaust volume of local exhaust hood)and U_d(speed of buoyant jet)are highly significant.The T_d(temperature of discontinue buoyant jet),?d(horizontal distance of the two heat sources),h(vertical distance between the bottom of the local exhaust hood and the surface of discontinue buoyant jet),and T_p(temperature of discontinue buoyant jet)are significant factors.(2)When the source is discontinue buoyant jet,there is a paroxysmal response area in the space.That is range of the 3.33 times hydraulic diameter of the heat source on the vertical direction.On the horizontal direction that perpendicular to local exhaust hood,the range is 1.82 times hydraulic diameter of the heat source half-width.On the horizontal direction that parallel to the local exhaust hood is within a range of 0.8 times hydraulic diameter of the heat source half-length.(3)The flow rate is defined by the ratio of U_d(speed of discontinue buoyant jet)to U_e(velocity of local exhaust hood).When the R(flow rate)is same but U_e increases,the temperature distribution on the Y-axis direction changes from the double peak curve to the single peak curve,the peak between local exhaust hood and discontinue buoyant jet disappears,and the temperature of the region and the local exhaust hood reduces.As the flow rate decreases,the maximum concentration on the Y-axis direction gradually moves toward the local exhaust hood.(4)When?d(The horizontal distance between discontinue buoyant jet and the plume)icreases,the temperature and concentration values on the horizontal direction that parallel to the local exhaust hood and the vertical direction that located on the surface of discontinue buoyant jet increase.On the horizontal direction that perpendicular to local exhaust hood,the maximum temperature and concentration points located above plume and gradually decrease as?d increases.(5)When discontinue buoyant jet is stepped growth,the dynamic capture efficiency of the local exhaust hood has similar trendency.With volume of the local exhaust hood increases,the capture efficiency in different emission stages is also increasing.As for the emission speed and concentration of discontinue buoyant jet,the capture efficiency with the same exhaust volume sharply decreases.At the meantime,the empirical formula of capture efficiency of discontinue buoyant jet is obtained through regression analysis.The coefficient of function can determine the influence of different factors on the capture efficiency.The result is same as that of the orthogonal analysis.(6)The article gave the relationship between the axial trajectory of discontinue buoyant jet and Ar number,R(flow rate),?d(The horizontal distance between discontinue buoyant jet and the plume),and h(vertical distance between the bottom of the local exhaust hood and the surface of discontinue buoyant jet).