Research On Key Technologies Of Wood Drying Based On High Power Microwave

With the gradual reduction of global forest resources, how to make effective use of tree resources has become the focus of people’s growing concern, the wood drying is a key link of trees utilization, while the disadvantages of high energy consumption,poor drying effect and low utilization rate exist in the process of wood drying, so the wood drying has been a focus of research in the field of drying. The conventional drying method has the defects of long preheating time, heating state of inertia long time, uneven heating, microwave heating drying has the advantages of short drying time, uniform heating and high permeability, therefore, the study of microwave drying for the conservation of timber resources has practical significance.In this paper, based on the theory of microwave heating, the key technologies of timber drying are studied, the main work of this paper is as follows:1. For the single-source indirect coupling method, this paper designs a waveguide branching element, which needs to be tuned by tuning elements such as pins, After the microwave is fed into the resonant cavity, the uniformity of the electric field is better than that of the single-source direct feed, both the simulation and the actual test results demonstrate the effectiveness of the design,the reflection coefficient is less than -15dB in the range of 2.4GHz-2.5GHz; In the multi-source coupling method, the coupling coefficient between the feeders are not only related to the number of microwave sources, but also to the placement of the feeds, multi-source coupling method improves the uniformity of the electric field to a certain extent.2. In this paper, I design a U-shaped waveguide feed wave crack antenna based on slot array antenna and equal power radiation. In this paper, the waveguide array antenna shape, slot correlation parameters, U-shaped waveguide radius and other factors are analyzed in detail, the design of the feed wave antenna combines the advantages of resonant and non-resonant two different waveguide array antennas, it has many superiorities, such as high radiation efficiency, small coupling coefficient between slots, wide resonance range and so on, compared with the direct coupled resonator method, the design can achieve the goal of uniform electric field in the case of a small number of microwave sources. The simulation results show that the reflection coefficient is less than -17dB in the range of 2.4GHz-2.5GHz, the matching effect is good.3. In this paper, the uniformity of the electric field on the wood surface under different wave feeding methods is analyzed and compared by introducing the uniformity index, the results show that the electric field uniformity index of U waveguide slot antenna fed wave method is smaller than that of other methods,indicating that the U waveguide slot antenna designed in this paper is feasible in theory,this paper also analyzes how the dielectric properties of wood affect the uniformity of the electric field on the wood surface and the ability of the wood to absorb the microwave.