Development of steam injection drying method for lumber.

我们开发了将100‘以上的超强蒸汽注入激光切割的木材小孔内的蒸汽注射干燥方法。与传统的窑炉干燥相比，这种新型的干燥方式应该能够快速、均匀地加热和干燥整个木材。此外，根据伯努利的理论，木材中的水分应该发生减压和脱水。我们还检查了扩束器是否可以控制孔的形状。本研究取得的主要成果如下：1.针对纤维含水率饱和点以下木材收缩产生的缝隙，设计制作了注汽干燥夹具。结果是，我们可以将木材干燥到含水率的15%，而不会发生蒸汽泄漏。在快速干燥后的木材中可以看到干燥的痕迹。2.干燥速度随激光切割密度的增加而提高，但在切割密度为4倍的情况下，干燥效率增加一倍。因此，不能盲目提高切割密度。3.只有在纵横向间隔比为1：2和1：5的切割方式下，干燥速度才会降低。这一现象在较高和较低的切割密度下都没有发现，如2000孔/m^2或500孔/m^2.4。在本研究中，1000孔/m^2的切割密度对于木材的完美干燥是最有效的。5.当激光到透镜的输入直径与使用该基金制造的扩束器的原始直径相比扩大两到三倍时，可以制造出更细长的孔，尽管焦深较浅。因此，这项技术被发现更适合于激光切割胶合板。

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.