Simulation And Experimental Research On Hot Air Heating Asphalt Pavement

Hot in-place recycling(HIR)as a kind of good pavement maintenance technology has been widely concerned by the highway maintenance industry,which has the advantages of economy,environmental protection and high efficiency,it can heat and mill old asphalt pavement in place,and then compacting again.The hot air circulation heating is mainly achieved by heat convection between the high temperature flue gas with a certain velocity which from the nozzle of heater and road surface.However,there is a lack of research on hot air's velocity field,temperature field when it working and arrangement of nozzles.The thesis firstly introduced the principle of hot air circulation heating which based on heat transfer theory,established the heat transfer inner model of asphalt pavement,and then deduced and solved the heat transfer equation of asphalt pavement.According to the existing heater equipment,established the fluid-solid coupling model of hot air heating pavement under a single-hole nozzle and used Fluent software to simulated the continuous and intermittent heating conditions.According to the difference of heating clearance between the heater and the asphalt pavement,established the heating clearance model of hot air single-hole,and by virtue of Fluent software,analyzed and studied temperature field of hot air with different clearances.In order to qualitatively research the influence of different nozzle arrangements on the heating effect,the relative area of the nozzle is introduced,and put forward three kinds of nozzle arrangement: rectangle,triangle and diamond.Though theoretical calculation got the conclusion: The convective heat transfer coefficient of rectangular and triangular arrays is larger,while that of rhombic arrays is smaller.Then established the fluid-solid coupling model that nozzles arranged in a rectangle or triangle arrays.Through Fluent software,researched the heating effect of these two arrangements and the interaction between temperature field of adjective nozzles.Lastly,building a hot air heating test bench to test the surface temperature field and heat flow density of the pavement specimen.The test results show that intermittent heating can meet the actual heating requirements better than continuous heating.With the increase of heating gap,the temperature field of hot air will change correspondingly.When the nozzles are arranged in multiple orifices,adjacent hot air jets will interfere with each other's temperature field and velocity field,which can impact on heating effect.Relevant test results show that the hot air heating under thesingle-hole nozzle has non-uniformity,and the measured value of heat flux delivered to the surface of the specimen is close to the simulation value,which verifies the correctness of the simulation and provides a certain reference for the actual construction.