扇块分区热磨机磨片的热应力分析与优化设计

通过对扇块分区热磨机磨片进行热应力分析,得到磨片的最大应力值和最大变形,并运用ANSYS的优化模块对磨片进行结构优化设计,得到了能够满足各项性能要求的新磨片,并最终达到了产品设计的轻量化要求.     

影响热磨机磨片齿形结构设计要素分析

阐述了热磨机磨片的主要功能,并对影响磨片齿形结构设计的三个主要因素进行了分析.研究表明,原料的纤维特性、热磨机的性能、磨片的制造工艺对磨片齿形的结构设计、纤维分离的机理及磨片综合性能等有不同程度的影响.     

热磨机磨片齿形结构的设计及静力学分析

热磨机磨片的齿形结构是磨片和原料间传递能量的主要方式,它与木片原料被研磨时的运动状态和研磨时间,以及纤维制备过程中纤维质量和设备的能耗密切相关。笔者根据磨片破碎区、粗磨区、精磨区的齿形结构、磨齿倾角、周向齿等参数对纤维分离能耗的影响以及磨片的设计要求,设计了一种有利于降低纤维分离能耗的热磨机磨片,并运用ABAQUS软件对磨片进行了静力学分析,分析结果表明磨片受到的静力作用对自身影响很小,设计满足要求。     

热磨机磨片齿刃比负荷对木纤维形态的影响

选择8种热磨机磨片,通过计算齿刃比负荷(SEL),并测量其加工纤维样本的长度及长径比,采用线性回归方法建立磨片齿刃比负荷与纤维长度、长径比之间的关联模型。分析结果表明,磨片齿刃比负荷对纤维长度和长径比有显著影响,均为负相关关系,其中对纤维长度的影响更为明显。这一特征可为生产中纤维形态质量预估、热磨机磨片选型及齿形结构设计提供参考。     

热磨机磨片间隙电液伺服控制原理与系统设计研究

通过对典型热磨机磨片间隙控制系统的功能分析,采用电液伺服系统对热磨机磨片间隙控制系统进行了原理与系统结构设计,建立了控制系统的传递函数与数学模型,对液压缸和伺服阀进行了设计计算与选型;通过对系统传递函数的校正,保证了系统的稳定性和较好的控制品质。热磨机磨片间隙电液伺服控制系统的设计研究有助于提高热磨机的解纤质量和工作性能,具有理论和实际应用价值。     

热磨法纤维分离能量耗散影响因素的分析

目前,我国纤维板生产进入了一个高速发展的时期,年产量位居世界首位,而生产状况总体上呈现"高能耗、低效率"的状态,其主要原因在于我国纤维板生产的工艺水平和技术水平还比较落后,对纤维板生产的工程应用性基础理论的研究还存在不足,因此笔者结合热磨法纤维分离的基本原理及纤维制备的工艺过程,从热磨机磨片和热磨工艺参数两个方面对热磨法纤维分离能耗进行分析,分别探索磨片齿形结构参数、原料预处理工艺等因素对纤维分离能耗的影响,从而揭示热磨法纤维制备中能量耗散的影响因素,建立磨片齿形结构参数与纤维分离能耗之间的内在联系,不仅可以为纤维分离设备的结构优化、提高纤维分离质量以及降低纤维分离能耗提供可靠的理论基础和技术支撑,也可以提高磨片的使用性能。     

热磨机磨片的材质与磨损

热磨法(TMT)是目前国内外纤维板生产中分离纤维的主要方法,作为对纤维直接起研磨作用的热磨机磨片的质量优劣,关系整个热磨工程系统技术性能的发挥,能耗的大小,效率的高低等,因此,许多国家十分重视磨片的研究工作。     

浅析影响热磨机磨片齿形结构设计的主要因素

纤维板生产原料的纤维特性、热磨机的性能、磨片的制造工艺对磨片齿形的结构设计、纤维分离的机理及磨片综合性能等有不同程度的影响。     

蒙特卡罗法在热磨机磨片优化设计中的应用

热磨机磨片生产加工木纤维的工作环境十分复杂,影响其齿形结构设计的因素较多,用传统的方法优化设计具有一定的局限性,而蒙特卡罗方法在优化设计方面具有极大的优越性。首先对其算法原理进行初步的研究,然后将其应用到热磨机磨片的优化设计中,设计出符合实际生产需求的磨片。     

热磨机磨片的磨损,材质及经济分析

本文分析了磨片的磨损机理及对磨片材质的要求，对高铬铁和冷硬铸铁磨片与不锈钢磨片的技术经济指标进行了对比分析。结果表明，不锈钢磨片的技术特性和经济效益最好。     

基于太阳能利用的储能缓释地板模块的研制

为实现对能源的高效利用,研制了一种具有储热与热缓释的功能地板模块,对该地板模块的结构进行了设计,检测分析了5种隔热保温材料的导热系数,并对地板模块的热学特性进行了计算分析。结果表明,用挤塑板做隔热底板的保温材料热损失最少,而热源温度在60～70℃时,地板模块的吸热量最大,因此选择挤塑板做隔热底板的保温材料,地板模块的热源温度为60～70℃。     

三种速生建筑材树种制造中纤板的制浆工艺和磨片选型

研究了供制造中密度纤维板用的三种速生建筑材的制浆工艺和磨片齿形。试材树种为杉木、火炬松及湿地松；磨片齿形有中细齿、粗齿及中齿三种；木片蒸煮汽压固定为０４～０６５ＭＰａ，蒸煮时间分别为３，６，９及１２ｍｉｎ，磨盘间隙０１ｍｍ。研究结果表明，三种齿形制浆所得中长纤维（留于３２～１１５目）占总纤维量的５０％～７０％，尤以中齿形磨片制浆，效果更好；在３～１２ｍｉｎ的蒸煮时间内，纤维分离效果及制板后板的平面抗拉强度无明显差异，因此以采用３ｍｉｎ的蒸煮时间较为合理。     

A model of heat transfer in sapwood and implications for sap flux density measurements using thermal dissipation probes

A variety of thermal approaches are used to estimate sap flux density in stems of woody plants. Models have proved valuable tools for interpreting the behavior of heat pulse, heat balance and heat field deformation techniques, but have seldom been used to describe heat transfer dynamics for the heat dissipation method. Therefore, to better understand the behavior of heat dissipation probes, a model was developed that takes into account the thermal properties of wood, the physical dimensions and thermal characteristics of the probes, and the conductive and convective heat transfer that occurs due to water flow in the sapwood. Probes were simulated as aluminum tubes 20 mm in length and 2 mm in diameter, whereas sapwood, heartwood and bark each had a density and water fraction that determined their thermal properties. Base simulations assumed a constant sap flux density with sapwood depth and no wounding or physical disruption of xylem beyond the 2 mm diameter hole drilled for probe installation. Simulations across a range of sap flux densities showed that the dimensionless quantity k [defined as (ΔT(m) -ΔT)/ΔT, where ΔT(m) is the temperature differential (ΔT) between the heated and unheated probe under zero-flow conditions] was dependent on the thermal conductivity of the sapwood. The relationship between sap flux density and k was also sensitive to radial gradients in sap flux density and to xylem disruption near the probe. Monte Carlo analysis in which 1000 simulations were conducted while simultaneously varying thermal conductivity and wound diameter revealed that sap flux density and k showed considerable departure from the original calibration equation used with this technique. The departure was greatest for variation in sap flux density typical of ring-porous species. Depending on the specific combination of thermal conductivity and wound diameter, use of the original calibration equation resulted in an 81% under- to 48% overestimation of sap flux density at modest flux rates. Future studies should verify these simulations and assess their utility in estimating sap flux density for this widely used technique.     

高温热处理对杨木压缩板材物理力学性能的影响

采用高温热处理工艺固定杨木板材的压缩变形,比较分析了处理前后杨木板材的物理力学性能.结果表明:杨木板材的压缩变形得到很好的固定;杨木板材经过热压及高温热处理后,密度和尺寸稳定性得到提高,吸湿性降低,弯曲性能变化不大.     

Thermal constants of wood during the heating process measured with the laser flash method

The thermal diffusivity, specific heat, and thermal conductivity of 13 species of wood were measured by means of the laser flash method to investigate the thermal properties of wood during the heating process. The temperature ranged from room temperature to 270°C in air or under vacuum. The thermal diffusivity varied little during the heating process up to 240°C. The values in air were larger than those under vacuum. There was a linear relation between the specific heat and the ambient temperature, and the specific heat under vacuum was larger than that in air at high temperature. The thermal conductivity increased with density and the ambient temperature. To discuss the effects of the atmospheric conditions on the thermal constants of wood, a theoretical model of thermal conductivity was proposed and its validity examined, where the wood was assumed to be a uniformly distributed material composed of cell walls and air.Part of this paper was presented at the 47th annual meeting of Japan Wood Research Society at Kochi, April 1997     

Measurement of the refining degree of bamboo charcoal by an alternating current method

We investigated a method for measuring the refining degree of bamboo charcoal using an alternating current. The bamboo charcoal was made under heating conditions of 400°–900°C (set temperature) and 0—3 h (holding time at each set temperature). The qualities of the bamboo charcoal could not be estimated from the yield, and electric tests were required. The effect of the variation in sample thickness on the impedance could be ignored. Attaching two plate electrodes to the same surface of a specimen enabled high accuracy and practical use. The impedance was found to be a suitable index for estimating the refining degree of the bamboo charcoal, such as the specific electric resistance. We believe that bamboo changes from an insulator to a conductor suddenly when processed at 600°–750°C for 0–2 h. It is possible that the integral of temperature with time in a specimen during heating is useful for approximately estimating impedance.     

Effects of temperature and sulfonation on shear deformation of spruce wood

Summary The effects of temperature and sulfonation on the deformation of spruce wood at conditions comparable to those during screw press impregnation prior to mechanical pulping were studied using a dynamic testing method. In addition to the physical properties of wood, shear fracture surfaces obtained at different deformation temperatures and at different sulfonation levels were studied using scanning electron microscopy (SEM).The results showed that the failure energy of wood decreased gradually with increased deformation temperature in the tested range of 20–95 °C, due to thermal softening of the material. In addition to thermal treatment, the failure energy could also be reduced by sulfite treatment of the wood before deformation, and decreased with increasing sulfonation degree.The SEM analysis showed that increasing the deformation temperature causes the fracture plane to travel around the fiber walls instead of through them, thus exposing a smoother wood surface with less fiber damage. At a given deformation temperature, particularly at the lower temperatures, sulfonation improves fiber separation.Financial support from the Swedish National Board for Industrial and Technical Development (NUTEK) is gratefully acknowledged     

基于Landsat 8的东莞市热岛效应研究

以2014年广东省东莞市Landsat 8卫星的热红外波段数据建立模型,反演东莞市地表温度,研究东莞市热岛效应分布情况,从优势度指数、分维数指数和形状指数来分析热力场景观格局,根据热岛效应的不同影响因素分析东莞市热岛现象的成因。结果表明：Landsat 8卫星影像反演2014年东莞市地表温度是可行的;东莞市热力景观以中热岛为主,热岛效应不明显,分布呈西北偏高,中部地区和东南区域偏低;热力景观斑块较复杂、热力场呈条带状零星分布;受绿化、水体影响区域的热岛强度较小,而受人为热源、道路、城市下垫面和建筑等因素影响的区域,热岛强度较大。     

热脉冲技术测定土壤热通量的原理和方法

正土壤热通量是地表能量平衡的重要组成部分,是研究陆-气能量交换的主要物理量。在农林业研究上,大部分土壤热通量研究主要关注于土壤热通量对种子萌发、植物根系生长、小气候效应、土壤碳氮循环过程的影响[1-3];在地球物理学和土木工程学研究上,重点研究土壤热通量在大地热流、埋地管道、地铁工程等方面的应用[4-5]。传统的土壤热通量测定方法主要是土壤热通量板直接测定法,但对土壤的扰动比较大。由于存在一定的厚度,土壤热通量板其自身导热材料的传热性能和土壤会存在差异,导致热通量