Development of steam injection drying method for lumber.

研制了将100℃以上的超蒸汽注入木材激光切割孔内的蒸汽注入干燥方法。与传统的窑炉干燥相比，这种新型的干燥方式能够快速、均匀地加热和干燥整个木材。此外，根据伯努利理论，木材中的水分会发生减压脱水。我们还检查了扩束器是否能控制孔的形状。本研究得到的结果如下：1。为防止木材在纤维含水率饱和点以下收缩导致蒸汽从缝隙泄漏，设计制作了注汽干燥夹具。结果，我们可以将木材干燥到15%的含水率而不泄漏蒸汽。木材在快速干燥后出现干燥检查。因此，为了达到完美的干燥效果，必须制定一个干燥计划。干燥速度随激光切割密度的增加而增加，但当激光切割密度为木材的四倍时，干燥效率提高了一倍。因此，很明显不能盲目地提高增加密度。只有纵向和横向间隔比分别为1:2和1:5的切割模式下，干燥速度才会下降。在较高和较低的切割密度（如2000孔/m^2或500孔/m^2.4）中都没有发现这种现象。在本研究中，1,000孔/m^2的切割密度对于木材的完美干燥是最有效的。使用本基金研制的光束扩展器，将入射到透镜的激光束直径扩大两到三倍，虽然聚焦深度较浅，但可以形成一个更细的孔。因此，该技术更适合于激光切割胶膜。

We developed the steam injection drying method in which super steam of over 100' was injected into laser incised holes of lumber. This new type of drying is supposed to be able to heat and dry whole lumber rapidly and evenly compared to conventional kiln drying. Furthermore, decompression and dehydration of water in lumber is supposed to happen by Bernoulli's theory. We also inspected whether a beam expander can control the shape of a hole or not. The results obtained in this research were as follows.1.We designed and made a jig for steam injection drying in order to prevent a leak of steam from a gap caused by shrinkage of lumber under fiber saturation point in moisture content. As the results, we could dry lumber to 15 % in moisture content without the leak of steam. Drying check was seen in lumber after quick drying. Therefore, a drying schedule must be developed even for this method to achieve a perfect drying.2.Drying speed increased with the laser incising density but the efficiency was doubled in case of lumber with four times of incising density. Therefore, it became clear not to raise the incising density blindly.3.The drying speed decreased only in case of incising pattern whose interval ratios are 1:2 and 1:5 for longitudinal and lateral directions. This phenomenon could not found both in higher and lower incising densities such as 2,000 holes/m^2 or 500 holes/m^2.4.The incising density of 1,000 holes/m^2 was most effective for perfect drying of lumber within this research.5.When an input diameter of a laser beam to a lens is expanded twice or three times compared to that of the original one with the beam expander made by this fund, a more slender hole could be made, though the depth of focus was shallow. Therefore, this technique is found to be more suitable for the laser incising of a lamina for glue lam.