Research On Temperature Uniformity Of Vehicle-Mounted Heated Stirring RAP Based On Temperature Field Analysis

The hot recycled pavement maintenance vehicle is a comprehensive maintenance equipment to complete the hot in-place recycling technology.Under the action of the heating and stirring device of the maintenance vehicle,RAP is easy to cause the heating rate of the mixture in the mixing pot to be low and uneven due to its complex motion mechanism and heat transfer,which affects the quality of RAP regeneration.Therefore,in order to obtain RAP with good temperature uniformity,this thesis relies on the project of Zhejiang Meitong Road Machinery Co.,Ltd.,and takes the LMT-5180 hot recycled asphalt pavement maintenance vehicle as the research object.The structure of the heating and stirring device was improved,and the heating and stirring process was theoretically analyzed.With the help of discrete element software EDEM,combined with indoor and outdoor experiments,the temperature uniformity of RAP heated and stirred by road maintenance vehicle is studied.The main research conclusions are as follows :(1)According to the stirring regeneration mechanism under different motion modes,the stress and heat transfer mode of the mixture particles under heating and stirring are analyzed,and the constitutive equation between the heat inside the particles and the temperature gradient is established.The range of the installation angle of the mixing blade is calculated,and the structural improvement scheme of the mixing chamber and the combustion chamber in the heating mixing device is proposed.The force and test analysis of the mixture particles in the improved heating mixing device are carried out.The results show that the contact between the particles is more sufficient,the heating area is larger,and the movement of translation,rotation and rolling can be realized on different mixing planes and different mixing rings.(2)According to the basic principle of discrete element method,the motion process of stirring heating device is analyzed,and the contact model between particles and particles and between particles and model is determined as Hertz-Mindlin with JKR model and Heat Conduction model.The mixing heating device model of pavement maintenance vehicle and the geometric model of RAP particles were established.The relevant working parameters of the stirring heating device and the setting of the solver were completed.(3)The evaluation index of temperature uniformity,namely temperature uniformity K,Based on the discrete element software EDEM,the temperature uniformity of RAP heating and stirring process under different stirring structures,different heating structures,different ratios of old and new materials,different heating temperatures and different stirring speeds was studied.The results showed that the temperature uniformity K value was smaller,the temperature dispersion was lower and the temperature uniformity was better when 35° three-blade spiral stirring knife was used,45° two-blade flame scattering device was installed,the ratio of old and new materials was 1:1,the heating temperature was 170°C and the stirring speed was 30 rpm.Whether it is under different structural parameters,different RAP material parameters,and different working parameters,the variation law of RAP temperature uniformity K in the stirring pot and after paving is in good agreement,indicating that the uniformity of RAP temperature distribution in the pot can be verified by the uniformity of RAP temperature distribution after paving.(4)Based on the Meitong cooperation project,indoor and outdoor tests were carried out on the LMT-5180 hot recycled asphalt pavement maintenance vehicle,and engineering measurements were carried out for different mixing structures,different heating structures,different heating temperatures,and different mixing speeds.The measured data show that the heating rate is faster when using 35° three-blade spiral stirring knife and 45° two-blade flame dissipation device.When the heating temperature is 170°C and the stirring speed is 30 rpm,the temperature dispersion of the mixture particles is lower and the RAP temperature distribution uniformity is better,which further verifies that the simulation results are in good agreement with the engineering measured results.