CN-122020994-A - Asphalt pavement in-situ thermal regeneration heating optimization method based on multi-field coupling simulation

Abstract

The invention provides an on-site thermal regeneration heating optimization method for an asphalt pavement based on multi-field coupling simulation, belongs to the field of road maintenance engineering, and solves the problems that heating parameters are difficult to quantify by experience setting, a temperature field is difficult to quantify, local overheat aging is high and energy consumption is high. The method comprises the steps of firstly establishing an infrared heating device-air domain-three-layer asphalt pavement model in multi-physical-field software, setting construction parameters, secondly endowing each layer with thermal physical properties changing along with temperature, setting a pavement bottom heat insulation and air domain convection heat exchange boundary, then coupling solid heat transfer, fluid flow and surface radiation, adopting a mobile heat source simulation unit to carry out running heating to obtain a pavement transient temperature field, finally carrying out parameterization scanning by taking heating power, running speed, heating height and heating times as variables, calculating target depth average temperature, road surface peak value, temperature uniformity and unit area energy consumption, and screening optimal parameter combinations. The invention can guide the on-site heating construction, realize uniform temperature rise, save energy and reduce consumption and inhibit asphalt aging.

Inventors

• XU TAO
• PENG YONGCHENG
• XIA WENJING
• LIU SONG

Assignees

• 南京林业大学

Dates

Publication Date

20260512

Application Date

20260113

Claims (1)

1. 1. An on-site thermal regeneration heating optimization method for an asphalt pavement based on multi-field coupling simulation is characterized by comprising the following specific steps of: (1) In COMSOL Multiphysics simulation software, a three-dimensional geometric model of an asphalt pavement in-situ heat regeneration heating system is established, wherein the three-dimensional geometric model comprises an infrared heating plate, a heating cavity, a guide cover of the heating cavity, an air area above and around the heating plate, an upper surface layer, a middle surface layer and a lower surface layer of the asphalt pavement, wherein the length of the heating plate is 2.0m, the width of the heating plate is 2.0m, the length of the heating cavity is 2.0m, the width of the heating cavity is 2.0m, the height of the heating cavity is 0.30m, the length of the asphalt pavement model is 3.0m, the width of the heating cavity is 2.0m, the total thickness of the heating cavity is 0.18m, the thicknesses of the upper surface layer, the middle surface layer and the lower surface layer are respectively 0.04m, 0.06m and 0.08m, and working condition parameters in a typical in-situ heat regeneration construction process setting model are combined, the air inlet speed is 2.0m/s, the inlet air temperature is 25 ℃ and the equivalent temperature of the heating plate surface is 450 ℃ so as to ensure that the simulation model is matched with actual heating equipment and the pavement structure in geometric dimension and working condition, and the actual heating process can reflect the actual heating process in a simulated range; (2) Giving material properties and initial conditions to each component in the geometric model, respectively setting heat conductivity, density and specific heat capacity functions which change along with temperature for an upper layer, a middle layer and a lower layer of asphalt, setting heat conductivity coefficients and surface emissivity for a heating plate and a cavity structure, setting density, viscosity, specific heat capacity and heat conductivity coefficients for an air domain, uniformly setting the initial temperature and the ambient temperature of a road surface to 25 ℃, adopting an adiabatic condition for the bottom boundary of the road surface, adopting a convection heat exchange boundary for the outer surface of the air domain, and setting the upper boundary of the air domain at a position 1.0m away from the road surface so as to reduce the influence of the outer boundary on the distribution of a temperature field of a calculation region; (3) Establishing an asphalt pavement in-situ thermal regeneration multi-physical field coupling heat transfer model, enabling a solid heat transfer physical field in a pavement structure in the model to simulate heat conduction in each structural layer, enabling a fluid heat transfer physical field between a heating plate and the pavement and in an air field around a heating cavity, adopting a fluid flow module to simulate hot air flow movement and convective heat transfer generated by combustion, enabling a surface radiation physical field between the heating plate and the pavement, setting the surface emissivity of the heating plate, equivalent heating power and surface temperature to simulate heat radiation, and coupling the solid heat transfer, the fluid heat transfer and the surface radiation physical field through a multi-physical field coupling node so as to form the multi-field coupling model of the asphalt pavement in-situ thermal regeneration heating process; (4) After the geometric modeling and the setting of multiple physical fields are completed, the multiple field coupling models are subjected to grid division, grid encryption is carried out on road surfaces, interlayer interfaces, the vicinity of heating plates and air inlet areas, relatively larger unit sizes are adopted in other areas, so that the calculation accuracy is improved, the calculation efficiency is considered, a transient solver and a time step size 1fs are set, the heating plates are regarded as heat sources for setting the moving speed to move along the advancing direction of the in-situ thermal regeneration construction unit, and the change of the temperature field of the asphalt pavement along with time in the heating process is calculated; (5) By means of parameterized scanning, heating power, moving speed, heating height and heating times are selected as working condition parameters, multiple groups of working conditions are set in a given parameter range, simulation calculation is conducted respectively, influences of different working condition parameter combinations on road surface temperature field distribution are analyzed, average temperature, road surface highest temperature, temperature uniformity indexes and unit area energy consumption of a designated road surface depth range are calculated mainly, according to requirements of asphalt road surface on-site thermal regeneration construction on the temperature range and the temperature distribution uniformity, comprehensive comparison and analysis are conducted on calculation results of all groups of working conditions, optimal heating process parameter combinations are determined, accordingly, the requirements of asphalt road surface on-site thermal regeneration heating temperature are met, the distribution uniformity of the temperature field is improved, the energy consumption is reduced, the ageing degree of asphalt road surface is reduced, and an asphalt road surface on-site thermal regeneration heating process is optimized.

Description

Asphalt pavement in-situ thermal regeneration heating optimization method based on multi-field coupling simulation Technical Field The invention provides an on-site thermal regeneration heating optimization method for an asphalt pavement based on multi-field coupling simulation, and belongs to the field of road maintenance engineering. Background With the increasing perfection of the road traffic network and the continuous increase of road mileage in China, a large number of asphalt pavements enter the key stages of periodic maintenance and repair. Asphalt pavement is used as a main pavement form, and various diseases such as cracks, ruts, looseness, aging and the like can be inevitably generated under the multiple actions of traffic load, environmental factors, material aging and the like in the designed service life period. These diseases not only affect the safety and comfort of driving, but also significantly shorten the service life of the road surface. The traditional maintenance mode, such as paving new asphalt mixture after milling, has the problems of resource waste caused by waste of old materials, increased energy consumption and carbon emission due to material transportation, longer construction period, traffic influence and the like although the technology is mature. Under the background, asphalt pavement regeneration technology, especially in-situ thermal regeneration technology, which has both environmental protection and economy is increasingly emphasized and widely used. The in-situ heat regeneration technology is a complete set of technology that original old asphalt pavement is heated and scarified on a construction site, a regenerant or new asphalt mixture is added according to the requirement, and then the mixture is mixed, paved and rolled to form. The technology can realize 100% recycling of the old asphalt mixture, saves non-renewable resources such as stone, asphalt cement and the like to the maximum extent, and obviously reduces the damage and pollution to the environment caused by stone exploitation and asphalt refining. Meanwhile, as the old materials are not required to be transported to a fixed site, the demand of new materials is greatly reduced, and the energy consumption and the carbon dioxide emission are effectively reduced. However, despite the outstanding technical advantages of in-situ thermal regeneration, the level of process control of the heating process is a key element in determining the final regeneration quality and engineering benefits. The existing in-situ heat regeneration unit generally adopts a plurality of heating plates or radiation heaters, takes liquefied petroleum gas or diesel oil as fuel, and heats the pavement by generating high-temperature flame or infrared radiation through combustion. The process is a complex transient heat transfer process involving three heat transfer modes, convection, conduction and radiation, and being affected by a variety of factors such as environmental conditions, road conditions, equipment parameters, etc. In practical engineering applications, the heating process presents a significant challenge. First, uniformity of heating is difficult to ensure. Due to uneven heat distribution of the heating equipment, thermal property space variability of pavement materials and random disturbance of an environmental wind field, the pavement is extremely easy to have temperature gradient in the transverse direction and the depth direction. The too low local temperature can make the old asphalt mixture difficult to rake, the regenerant is unevenly mixed with the old asphalt, so that interlayer bonding is weakened, and quality hidden trouble is formed, while the too high local temperature can accelerate aging of asphalt, so that the asphalt becomes hard and brittle, road performance is reduced, and even harmful substances such as asphalt smoke are generated. Secondly, the temperature control accuracy is insufficient. At present, the control of the heating temperature in construction depends on the experience of operators, and the real-time and accurate monitoring and feedback control of the whole heating surface temperature field are lacked by observing the road surface color or roughly judging by using a handheld point thermometer. The rough control mode is difficult to adapt to complex and changeable working conditions, and accurate temperature regulation and control cannot be realized. Furthermore, the energy utilization efficiency is generally low. To ensure that the coldest areas also reach the minimum temperature required for construction, operators tend to use higher heating power or slower travel speeds, which necessarily results in overheating of other areas, resulting in a great deal of energy waste, increased construction costs, and contrary to the original purpose of being green and low-carbon. In order to solve the above problems, researchers and engineering technicians in the industry have made a series of researches. Ea