| Environmental pollution has become one of the major problems that hinder our economy development and affect people's quality of life,and one of the main producers of environmental degradation is automobile exhaust.According to statistics,our vehicle fleet capacity amounted to 264 million by 2015! So the whole society are concerned about energy conservation vehicles.Automotive lightweight is one of the important means of achieving energy saving and replace steel with aluminum is the most effective way to achieve automotive lightening.However,due to the key equipment production for aluminum automotive sheet-floatation furnace's manufacturing technology has been monopolized by foreign companies,this has seriously harnpered the application of aluminum sheet and strip in the car.In view of this,this paper combined theoretical analysis and numerical simulation technology,study on the air system stability,plenum flow field uniformity,convective heat transfer effect and strips deformation etc.It aims to draw a variety of structures and processes'parameters on air furnace using effect,which provides the appropriate basis for the design and manufacture of air furnaces.The thesis work and achievements are as follows:(1)Floatation furnace nozzles stability were studied.The theoretical model of air pressure and the pressure coefficient were put forward,which coincide with the experimental and simulation results;Research crevice nozzle length,the opening degree,inclination angle,strip cushion height,air bars internal pressure and the inlet air temperature on air pressure distribution.The results showed that:the smaller the degree of the nozzle opening,the smaller strip cushion height and air bars internal pressure,the lower inlet air temperature the greater the value of the air pressure stable;take six times the length of the slit nozzle opening degree and the angle is from 45° to 60° can get better stability.The influence of the number of opening holes on the pressure distribution was also studied,the results show that as the number of holes increases air pressure distribution became more stability and the pressure coefficient increases.(2)Air furnace plenum flow field uniformity were studied.Analyzed the influence of different structures plenum on the flow field and pressure distribution and studied the flow field distribution of rectangular and circular plenum,the results show that the arc-shaped structure enables each air bars pressure distribution more uniform which conducive to the stability of the entire air furnace and ensure uniformity of heating.(3)High-speed floatation furnace forced convection were researched.The traditional slot nozzle,crevice nozzle single row of holes and crevices three rows of holes nozzle heating characteristics were studied respectively.The results show that the conventional slit nozzle due to the relatively closed air area its flow rate of fluid is low,resulting in the position of the aluminum plate in temperatures is low than other position and the temperature uniformity 'is poor;slit nozzle with a single row of holes heating effects are significantly improved because the center holes' jet action and faster heating rates and temperature uniformity are better;compared with the previous air bars slit nozzle with three single row of holes heating effect has the best heating effect:the fastest heating rate and temperature uniformity which able to meet the requirements for production.In addition,for these three conditions experimental correlations were established for the average Nusselt number and Reynolds.(4)The bending of the strip running in the furnace were researched.A deflection theoretical model without tension on strip were established,and compared with the simulation results and the results show a good agreement;for the case of tension exists,studied the influence of size of the rally,the average air pressure,the size of the strip on the deflection of the strip and established model which reflected the relation of maximum deflection and tension,air pressure and strip-sectional moment. |
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