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通过对浅圆仓围护结构的热工性能的计算、比较,分析了围护结构对储粮的影响,提出适当保温可实现多种目的,有利安全储粮 相似文献
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不同卸料流态对仓壁侧压力影响的试验研究 总被引:1,自引:0,他引:1
为了观察筒仓卸料过程中内部流态及其相对应的仓壁压力变化进行研究,现基于物理模型试验,自主设计并制作半圆形筒仓,采用压实和松散两种装料方式,观察卸料过程中不同的物料流态。结果表明,当采用压实装料时,物料表现为管状流,采用松散装料时,物料表现为整体流与漏斗流共存。通过自主设计定制的土压力盒传感器来测定贮料及卸料工况下仓壁压力数值,将仓壁压力数值与物料流态联合分析,结果显示:在贮料工况下,压实装料时仓壁压力数值与Janssen公式计算值具有较好的一致性,松散装料时,内部力链网络疏松,仓壁压力数值较大。在卸料工况下,物料流态为管状流和漏斗流时,仓壁压力变化稳定,物料流态为整体流时,仓壁压力具有较大的波动性变化。对两种不同装料方式下,仓壁压力进行超压分析,发现物料表现为管状流和漏斗流时,无较大的超压变化,物料表现为整体流时,有较大的超压现象,最大超压系数为1.85,且仓壁压力波动性最大点与超压现象最大点一致。在筒仓卸料过程中,不同的装料方式具有不同的流态,同时,仓壁具有不同的压力变化规律,该研究可为构建和完善筒仓结构安全设计提供参考。 相似文献
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Design and development of low-cost farm silos call for a strong understanding of its structural performance and loads. Limited studies address the effect of stored grains on silos. A farm level bamboo reinforced concrete (BRC) silo with a flat bottom has been designed for the storage of rough rice. A full-scale 3D finite element (FE) model of the BRC silo has been developed and the grain filling in progressive layers simulated in the ANSYS® software. The stored grain and silo body interactions have been modeled considering the characteristic properties of both rough rice as well as the BRC, with minimal simplifications. The numerical results have been compared with the outcomes of classical theories (Jannsen’s and Reimbert’s) and design code (IS 4995-1974). While a significant difference was observed between the lateral stress magnitudes predicted by the numerical and analytical methods, the axial wall stresses from FEM approach deviated from the IS code values by 16%. Contrary to the analytical approaches, FEM predicted non-uniform stress distribution due to the bulk grain at the silo bottom. The numerical approach could also identify the localized peak pressures and stress distribution patterns within the grain layers, which is usually beyond the scope of analytical techniques. Possible reasons for fluctuations in stress patterns are discussed in detail. The study unveiled the intricacies involved in the FEM and the analytical outcomes while predicting the stresses in small and medium scale silos intended for use on farms. 相似文献
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作为一种新仓型,半地下双层浅圆仓具有节约用地、节约能源、机械化程度高的优势,并可保证储粮品质。论文采用实体单元建立数值模型,根据场地地质条件与实际状态设置边界条件,构建了半地下双层浅圆仓的数值分析方法;经与地下粮仓的足尺试验结果进行对比,验证了数值模拟方法的可行性。通过对半地下双层浅圆仓施工过程中回填前后的受力性能进行分析,研究表明:仓底在回填前距锥底2/3处径向、环向应力达到峰值;首层仓壁在回填后距锥底1/3处径向、环向应力达到峰值。该研究可为半地下双层浅圆仓工程设计与施工提供理论支持。 相似文献
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为探究粮食颗粒内部之间的应力分布及颗粒与仓壁之间相对静摩擦力的分布规律,在考虑粮食颗粒压缩性对粮堆剪胀参数影响的情况下,通过理想弹塑性本构关系和Drucker-prager屈服准则,并采用非关联流动法则来模拟储料,建立了粮仓仓壁与粮食之间正压力、相对静摩擦力的有限元模型,分别模拟不同装粮高度下仓壁与粮食之间的相对静摩擦力、正压力等,找到不同装粮深度处仓壁的相对静摩擦系数分布规律。结果表明,不同装粮高度处的相对静摩擦系数是不同的,伴随深度的增加,系数呈先增加后减小趋势。可见,粮食颗粒相互间的作用力及颗粒与仓壁之间的静摩擦力对粮食重量测量具有十分重要的指导意义。 相似文献
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世界各国因储粮害虫对粮食造成的损失非常严重,为了降低粮食在储藏期间的损耗,所以研究储粮通风过程中害虫增长量的变化至为重要。文章基于多孔介质热湿耦合理论,建立了浅圆仓的粮堆内部热湿传递和流动的数学模型以及害虫和熏蒸经验模型,并基于Fortran语言编程,模拟分析了通风状态下粮堆温度、水分含量、储粮害虫增长量以及杀虫剂浓度衰减的变化。结果表明:通风对粮堆内部温度和水分以及害虫生长影响明显。粮堆的水分含量近似对称分布,而受太阳辐射的影响,粮仓不同方向壁面的温度分布并不对称。储粮害虫在粮仓内的数量分布与温度、水分等因素有关,在壁面附近害虫分布较多,且在筒仓中心区域出现分层现象。杀虫剂浓度衰减也受温度的影响,温度高会影响杀虫剂的降解,导致杀虫剂浓度较低 相似文献
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During seed storage in tall silos the low layers of rape seeds are exposed to static pressure exerted by the upper layers. This may cause deformation and damage of seeds found in the lower layers and losses of biologically active compounds. The aim of this study was to simulate under laboratory conditions the actual ecosystem found in industrial plants and to evaluate the effect of not only the temperature and moisture content, but also static pressure on degradation of phytosterols contained in rape seeds in the course of storage. Changes in phytosterol levels were assessed using GC-MS. During storage in all samples of seeds (7–16% moisture content) under the adopted conditions of overpressure (20–60 kPa) and temperature (25–35 °C) the total content of phytosterols decreased by 3–57%. The smallest losses in the total phytosterol contents (3–4%) were recorded during storage of seeds with a 7% moisture content, irrespective of the applied storage temperature (25–35 °C) and overpressure variants (20–60 kPa). The greatest losses of phytosterols (43–57%) were observed during storage of seeds with a 16% moisture content at a temperature of 35 °C, while the higher the applied overpressure, the greater these losses were. The study showed that the greatest influence on sterol content during storage was increased seed moisture, and subsequently the temperature and the pressure. Experimental results also showed that for seeds with higher moisture contents (13 and 16%) an increase in storage temperature from 30 to 35 °C intensifies losses of individual phytosterols much more markedly that an increase in temperature from 25 to 30 °C. Moreover it was observed that overpressure over 20 kPa enhanced losses of investigated phytosterols. 相似文献
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针对真空辅助树脂传递模塑(vacuum assisted resin transfer molding,VARTM)工艺成型玻纤/环氧树脂复合材料存在气泡、聚胶等问题,采用PAM-RTM软件对该复合材料的VARTM成型工艺进行模拟仿真。通过改变流道的设计方案,控制树脂黏度,观测充模过程中树脂的压力分布及充模时间,优化实验工艺,进而对模拟结果进行实验验证。结果表明:最佳注射方案是平行于Y轴一侧线性注入,另一侧线性排出。多线性注射虽然可以提高效率但是同时会出现交汇、聚胶等现象。充模时间随树脂黏度的增加而增加,随着充模过程的进行,黏度过高的树脂会发生部分固化,影响纤维的浸润。因此,树脂黏度控制在0.5 Pa·s左右较为合适。根据模拟优化结果,采用VARTM工艺分别制备2种典型的玻纤/环氧树脂复合材料。发现最佳注射方案,制备的复合材料表面光滑,无明显气泡、聚胶等缺陷,注射方案较好。 相似文献
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为了开发营养丰富的多谷物面包预拌粉,本研究以杂粮粉为主要原料,添加谷朊粉构建面包网络结构,通过评价混合粉黏度特性,面团发酵流变特性和面包加工品质,研究多谷物粉含量对面团加工特性和面包品质的影响。结果表明:随着多谷物粉含量的增加,多谷物预拌粉的糊化黏度呈显著性上升,糊化温度呈显著性下降,面团的最大发酵高度和最终发酵高度显著降低(p<0.0.5)。当多谷物粉添加量从50%增加到80%时,面包的比容从5.10 mL/g降低到1.83 mL/g,体积降低,弹性下降,硬度和耐咀性增加。多谷物粉含量、糊化特性、部分发酵流变特性与面包质构特性、比容和颜色L*、a*之间均呈显著或极显著相关。当多谷物粉添加量在50%~60%之间,面包品质良好;添加量≥65%时,所制成的面包品质较差。 相似文献
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流动加速腐蚀现象广泛地存在于过程工业装置的流体输运管路中,通过在弯管前加装扰流子可以改善弯管内壁面的压力系数分布,降低弯管的流动加速腐蚀速率。文章应用CFD软件FLUENT6.3,对弯管前置扰流子进行数值模拟,研究其结构参数和安装尺寸对弯管内壁外弯侧面压力系数的影响,结果表明:加装扰流子之后,弯管中心面的最大压力系数随着叶片弦长的减小而降低;当安装攻角α在1°~2°之间,压力系数减小,当α大于2°时,弯管中心面的最大压力系数随着攻角的的增大而增大,从2°到6°增大了约100 Pa;当安装距离l在0~10 mm之间,弯管中心面外侧的最大压力系数减小,呈现良好的趋势。之后,随着安装距离的增大,最大压力系数反而增大了约90 Pa。 相似文献
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