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针对300MW电站锅炉低温省煤器烟气入口及本体进行三维流场数值模拟,获得了低温省煤器内部三维压力场和速度场分布,分析了烟道变径入口处分流挡板的分流效果,并对其烟气入口分流挡板进行结构优化,进而获得流量更加均匀的烟气入口流场。研究结果表明,经过结构优化后的低温省煤器烟道变径入口分流均布效果可以获得显著提升。 相似文献
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针对某糖厂烟道气变压吸附塔内气体分布不均的问题,采用计算流体动力学CFD相关软件对其流场进行数值模拟,重点对进口区(进口管到吸附剂之间的区域)进行流场优化。通过对原始板式分布器流场模拟,发现吸附塔中心区域速度较大,导致进口区末端截面的轴向和径向速度分布不均,同时也有一定的漩涡。比较板式分布器在不同倾角下的布气效果,发现当板式分布器的倾角在25°~40°有较好的布气效果;比较4种板式分布器,即原始分布器(Ⅰ)、中间挡板不开孔的分布器(Ⅱ)、中间挡板改为小孔的分布器(Ⅲ)及原始分布器中间加挡板(Ⅳ)的布气效果,结果发现中间挡板不开孔的分布器和中间挡板改为小孔的分布器的布气效果都优于原始分布器,其中中间挡板改为小孔的分布器的布气效果最好。通过对吸附塔进口区分布器结构优化,明显提高了吸附塔内流体的分布均匀度。 相似文献
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气动钉枪外缸充气过程数值模拟及特性参数 总被引:4,自引:4,他引:0
以数值模拟技术为基础,采用三维可压k-ε湍流模型对气动钉枪工作过程中外缸充气流场进行瞬态数值模拟,并对流场重要结构-阻尼孔的设计参数进行了讨论。研究表明,阻尼孔的大小和数量对外缸流场流动参数分布及充气时间有重要影响,增大阻尼孔直径或增加阻尼孔数量都可以显著缩短充气时间,提高打钉效率,但同时流场的不稳定性和能量损耗都将增加。采用三维瞬态数值模拟技术可获得不同时刻流场中每一点的压力、速度等流动参数分布,据此可以为气动钉枪气道结构参数的优化设计提供可靠依据,从而提高气动钉枪的气动性能。 相似文献
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针对实验中模拟的两种稀释水调节阀模型,命名为调节阀A和调节阀B,采用计算流体动力学方法,通过改变稀释水阀的阀门开度对阀芯流场进行了数值模拟和分析计算。模拟结果生动地表现出了阀芯流场稀释白水的流动特性,同时研究分析表明调节阀B具有更好的线性调节流量的性能。 相似文献
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为探究织物在烘干定型过程中存在的织物烘干不均匀霉变、织物泛黄过硬和织物存在条纹亮斑等现象,以棉织物烘干定型的风道结构为仿真模型,利用Fluent软件对风道锥度及喷嘴处挡板高度2个参数进行了仿真模拟。仿真分析结果表明:风道锥度φ对喷嘴处气流的均匀性影响较大;喷嘴处挡板高度hf对喷嘴处气流的方向影响较大。 相似文献
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基于国内外已有的相关专利和应用的立式水力碎浆机结构,提出了一种高效、节能和运行平衡稳定的新型鼓槽体结构;然后,运用FLUENT软件对新型鼓槽体内部浆浓为5%的浆料流场进行数值模拟,以得到其内部浆料流场的压力、流速和湍流强度的分布情况,并与O形和D形槽体进行分析对比;最后,通过小型碎浆装置碎浆实验验证数值模拟结果。实验结果表明,新型鼓槽体螺旋返流板立式水力碎浆机的结构特征为槽体采用鼓形结构,并且在槽壁上焊有反流向、45°螺旋线、间断排布、带凹槽的梯形截面返流板;椭球弧形收口和返流板的合力作用可将浆料同时向槽体中心和槽底转子区域推送,同时返流板附近湍流强度平均增强100%,有效提高了碎浆效率;倒锥体部壁面处的浆料速度为5 m/s,能够有效降低因径向撞击壁面造成的能量损失;碎浆过程中,鼓槽体的振幅有效值远低于具有不对称结构的D形槽体,保证运行时的安全性和稳定性。 相似文献
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研究了在入口风速不变的条件下,通过改进结构和改变冻品参数,增大流场气流平均速度,达到降低装置能耗、提高冻结效率的目的。建立二维紊流模型,采用SIMPLE算法,对未放冻品原有结构的流场、开孔和增设隔板后的流场、食品不同摆放密度的流场以及不同食品高度的流场进行模拟计算分析,结果表明:网带的对螺旋塔内流场的平均速度影响小。增设隔板和开孔有利于提高流场内气流的平均速度,增加热交换的充分性。冻品摆放密度增加需要综合考虑气流平均速度、压力、和风机功率等因素。冻品高度在满足不超过孔的位置高度下,增高能增加气流平均速度。 相似文献
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In recent years, several foodborne illness outbreaks have been associated with the consumption of cantaloupe. Cantaloupes can be contaminated with pathogens anywhere from the field to the packing line. In the United States, cantaloupes are handled and packed differently in each state. Georgia-grown cantaloupes are brought to sheds, washed, and packed, whereas California-grown cantaloupes are field packed. In this study, the microbiological status of cantaloupes produced by four Georgia growers that use various washing and packing practices was assessed to determine the influence of these different practices. The facilities were visited four times during the harvest season. Aerobic bacteria, Escherichia coli, and coliforms on these Georgia-grown cantaloupes were enumerated in transport trailers, after washing, and after packing. Samples also were analyzed for the presence of Salmonella and E. coli O157:H7. In sheds 1 and 4, a chlorinated dump tank was used to wash melons. In sheds 2 and 3, heated water with chlorine was used in the dump tanks. Although there was a significant reduction (P < 0.05) in the populations of the aerobic bacteria and E. coli between the transport trailer and the dump tank for sheds 1 and 4, the reduction was less than 0.5 log CFU/cm2. The temperatures of the water in the dump tanks at sheds 2 and 3 were not high enough to effectively reduce the microbial populations evaluated. Populations on the melons increased slightly (< 0.5 log CFU/cm2) after the melons were removed from the dump tank, suggesting possible contamination after washing. 相似文献
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为改善熔喷流场和降低纤维直径,在普通双槽形气流模头的基础上设计了新型模头,并对其进行数值研究。借助Gambit软件建立新型模头的几何模型,采用Fluent软件对其流场进行模拟,分析了纺丝线上的速度、温度、湍流强度分布规律及其对纤维牵伸细化的影响。结果表明:与普通的双槽形模头相比,带有内稳定器的新型双槽形熔喷模头可有效地减小回流区的面积,增大纺丝线上的速度极大值,降低纺丝线上的速度波动和温度衰减速率;带有空气压缩器的新型气流模头可提高纺丝线上的流场速度和温度,但对模头附近的逆向速度和湍流强度峰值几乎没有影响;综合对比,同时带有内稳定器和空气压缩器的新型熔喷气流模头性能最佳,更有利于细化纤维。 相似文献
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为确保乳酸菌活菌奶的食用安全 ,预防食物中毒的发生 ,选择深圳市日产 2 0t以鲜乳、糖类为主要原料 ,经乳酸菌发酵而制成活菌奶的生产厂家为研究对象。通过危害分析 ,确定原料乳及辅料采购 ,生产加工管道与贮存罐的清洗消毒 ,溶解糖及脱脂奶粉 ,灭菌 ,乳酸菌的接种 ,灌装为活菌奶生产加工的 6个关键控制点 (CCP) ,采取相应的干预措施 ,达到预期效果。结果显示该系统简单易执行 ,可在同行业内推广。 相似文献
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仿生非光滑表面纺杯减阻性能的数值模拟 总被引:2,自引:0,他引:2
基于仿生微小非光滑表面具有减黏降阻特性的基本思想,将高速纺杯表面布置不同形状和尺寸的非光滑沟槽。采用RNG k ~ ε模型对其三维流场进行模拟,分别计算光滑纺杯与非光滑纺杯壁面阻力系数。对比二者壁面剪应力大小与周围速度流场可知,将微小非光滑仿生沟槽表面布置于高速纺杯表面,可降低纺杯在纺纱器内高速气流对壁面的空气阻力,从而降低转杯纺纱机的动力消耗,并且沟槽形状和深度均对纺杯壁面阻力产生不同影响。与光滑纺杯相比,三角形、半圆形、矩形3种沟槽纺杯最大减阻率分别为1.271%、1.261%和1.385%。 相似文献
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When white chocolates are kept molten in storage tanks, problems can arise due to uncontrolled thickening and solidifying of the chocolate mass. The thickening of molten white chocolate was simulated on a laboratory scale using a rotational rheometer under static conditions, interrupted by short shear periods to measure the increasing viscosity. Several chocolates having different dairy components and fat contents were investigated for their tendency to thicken. In addition, sorption isotherms for white chocolates were obtained using Dynamic Vapour Sorption at different temperatures. The sorption isotherms showed the presence of amorphous lactose in all the chocolates that were manufactured from milk powders. Moisture that is released during the crystallisation of amorphous lactose causes stickiness and agglomeration of the neighbouring particles and starts the thickening process. This process is highly temperature-dependent. On elevating the temperature the lactose crystallisation occurs at lower relative humidities. In order to reduce the tendency of white chocolate to thicken, a high free fat level should be maintained, based on a high total fat content and on the use of high free fat milk powders, preferably roller-dried whole milk powders or the combination of skimmed milk powder and anhydrous milk fat. 相似文献
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When white chocolates are kept molten in storage tanks, problems can arise due to uncontrolled thickening and solidifying of the chocolate mass. The thickening of molten white chocolate was simulated on a laboratory scale using a rotational rheometer under static conditions, interrupted by short shear periods to measure the increasing viscosity. Several chocolates having different dairy components and fat contents were investigated for their tendency to thicken. In addition, sorption isotherms for white chocolates were obtained using dynamic vapour sorption at different temperatures. The sorption isotherms showed the presence of amorphous lactose in all the chocolates that were manufactured from milk powders. Moisture that is released during the crystallization of amorphous lactose causes stickiness and agglomeration of the neighbouring particles and starts the thickening process. This process is highly temperature-dependent. On elevating the temperature the lactose crystallization occurs at lower relative humidities. In order to reduce the tendency of white chocolate to thicken, a high free-fat level should be maintained, based on a high total fat content and on the use of high free-fat milk powders, preferably roller-dried whole milk powders or the combination of skimmed milk powder and anhydrous milk fat. 相似文献
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针对造纸厂现有废水沉淀设备不能很好地去除废水中的有害物质的情况,通过对造纸厂废水中有害颗粒沉淀过程的具体分析,提出可采用异流型布水方式和较密集斜管沉淀相结合的方法,设计一种新型的异流型斜管沉淀池。该设备增加了沉淀池的沉淀面积,比一般沉淀池的处理能力高出7倍以上。 相似文献