Simulation Study On Electromagnetic Field And Temper Ature Field Of Microwave Treatment Wood

Functional application is an effective way to achieve high value-added utilization of wood.The permeability of wood is a major difficulty that plagues functional applications.High-field-intensity microwave treatment can effectively improve the internal permeability of wood,but high-field-intensity microwave treatment wood of the research on the coupling mechanism in the process is unknown,so that the workload of process exploration in the actual industrial equipment production process will be huge.In this paper,the plantation wood Pines is used as the research object to study the coupling mechanism of high-field-intensity microwave-treated wood,the dielectric characteristics of Pines var.The coupling mechanism and multi-physical field coupling simulation of wood treated by high-field microwave were carried out,and the process standards of treated wood were summarized from macroscopic and microscopic aspects.The research contents of this paper include the following aspects: 1)Systematic study on the mechanism of microwave wood treatment with high field strength.Combined with the reaction of test materials under the coupling of electromagnetic field and heat and mass transfer mechanism,the coupling mechanism of Pines test materials under different water content was determined;2)Test the dielectric properties of the artificial forest Pines var.The high-performance simulation software Comsol Multiphysics was used to study the multiphysics simulation technology of the specimens under microwave field.3)CST software and Creo 2.0 software are used to simulate and analyze the electromagnetic field inside the heating cavity of high field microwave treated wood equipment,and to provide the parameters of the cavity for the simulation of multi-physical fields in the early stage.4)Experiments on plantation wood Pines var in a 200 k W high-power continuous microwave processing equipment,and using the actual absorption of microwave energy of Pines var.Corresponding standards are made for the damage situation and microdamage situation to provide an experimental basis for later functional applications.The following conclusions are drawn from the research in this paper:1.The theoretical decomposition of the sample is mainly composed of three combinations of free water,combined water,and wood itself.Under the condition of high field intensity microwave and different water content,the water migration method in the sample is different.The form of water migration inside the material is mainly Darcy's law,and the form of water migration inside the material below the fiber saturation point is mainly Fick's law;2.Regardless of the frequency of 2450 MHz or 915 MHz,as the temperature of the wood increases,the dielectric constant and loss tangent value inside the wood show an upward trend.The dielectric constant and loss tangent value of Pines var.Relative to water,the dielectric constant and loss tangent are much smaller,so the node constant of wet wood mainly depends on its moisture content.The higher the moisture content,the higher the proportion of moisture in the sample,and the corresponding dielectric The larger the electric constant.3.The optimal size of microwave cavity is 550 mm × 340 mm × 280mm(length ×width × height)for the large size wood with the cross-section of 220 mm × 120mm;the four feed port is the best in the microwave equipment,and the vertical distribution is adopted for the upper and lower cavity feed port and the left and right cavity feed port.4.The higher the moisture content is,the larger the dielectric constant and the tangent of dielectric loss angle are,so the wavelength of the medium in the test material becomes shorter.The change of the wavelength of the medium in the test material will affect the change of the electromagnetic field distribution of the whole test material5.The effect of microwave treatment on the macro cracks of Pines var was studied.The quality standard of the treated material was established.Under the same moisture content of the test material,the larger the microwave energy absorbed by the test material,the longer the treatment time,the larger the area expansion rate and the crack area ratio of the test material with the corresponding moisture content;the treatment time of the test material was 80 s,and the microwave input power was 100 k W When the moisture content is 40%-60%,the processing time is 120 s,and the microwave input power is 140 k W,the crack area ratio and the number of cracks in the cross-sectional area of Pines var.6.The damage of internal structure of Pines var was studied,such as the damage of wood pit membrane,ray cell,and main cell(tracheid,vessel,.),resin,etc.Under the condition of the same moisture content and microwave output power,the treatment time of the test material increased.The damage of the ray parenchyma cell began only after the initial pits were not destroyed,the pits were destroyed and the ray parenchyma cell was destroyed;...