Research On Heating Apparatus Of Asphalt Pavement Hot In-place Recycling Unit

Microwave heating was introduced to hot in-place recycling of asphalt pavementas a new heating method.By contrast, microwave heating has smaller thermal gradient,bigger heat penetration depth and lesser cost than conventional asphalt heating, andmicrowave heating also can avoid asphalt aging rapidly.However, microwave heating ofasphalt mixture also has its shortcomings, such as the uneven temperature of the surfacelayer, relatively small dielectric loss of asphalt mixture and microwave leakage andother problems.This paper is supported by funded projects of Key Laboratory of RoadConstruction Technology and Equipment, Ministry of Education（Project number：2013G1502053）and Jiangsu "Innovation entrepreneurial talent plan" and Yangzhou"Green Yang Jinfeng plan" in2012. It is heating apparatus of asphalt pavement hotin–place recycling unit that have been taken as an object of study. With the fieldequivalence principle(Huygens’Principle), theory of array antenna and theory of heatand mass transfer in porous media under the condition of local thermal non-equilibrium,the uniformity of microwave heating power distribution, mechanism of heat and masstransfer in asphalt mixture under microwave heating and temperature control ofmicrowave heating are researched in this paper.The main research work of this paper are as follows:（1）To investigate the uniformity of microwave heating power distribution on thesurface of asphalt pavement, models of field intensity distribution of rectangularwaveguide and horn aperture secondary radiation field are established and solved withthe field equivalence principle(Huygens’ Principle) and other related theory ofelectromagnetic field, and the structure of microwave heater has also been considered.Field intensity distribution of pyramid horns with different dimensions and differentdistance have been analyzed and compared with numerical simulation, and fieldintensity distribution of multi-magnetron microwave heater radiation field has beenstudied in this paper as well. The influences of arranged location and phase ofmagnetrons to microwave heating uniformity are comparatively studied by numericalsimulation. The results can be used to the optimal design of microwave heater size andresearch on the influences of pyramidal horn size and magnetrons array distribution to uniformity of microwave heating as the theoretical guidance.（2）To study heat and mass transfer mechanism of asphalt mixtures undermicrowave irradiation, moisture migration model and heat and mass transfer model ofasphalt mixtures between each phase under microwave processing are established withthe mechanism of heat and mass transfer in porous media on the assumption of localthermal non-equilibrium and the influence of moisture migration to heat and masstransfer. Depending on the microwave attenuation theory in lossy dielectric materialsand calculus theory, the expressions of microwave power loss are modified. Models ofmoisture migration and heat and mass transfer are sovled numerically with the initialand boundary conditions, and the microwave heating processes of asphalt mixtures ofdifferent moisture content also are studied in this paper.（3）To achieve real-time control of the microwave heating process of asphaltmixtures, an adaptive fuzzy PID controller has been used to control the microwaveheating process. An adaptive fuzzy PID controller is designed with amount in advanceand small amount of adjustment. Delay time which is caused by response of system isshorten obviously, and energy consumption of temperature adjustment process isreduced. Real-time computer Automation control of microwave heating process ofasphalt mixtures is achieved.