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开发了一种双波纹流道结构,基于正交实验方法设计了9组不同结构参数的双波纹流道,采用计算流体力学(CFD)方法,研究了一定Reynolds数范围内(25≤Re≤200),9组双波纹流道内的流体充分发展层流流动和传热性能。研究结果表明,流道的波纹波幅对于流体流动和传热性能的影响较大。设计制作了流体在双波纹流道中流动的冷模实验装置,采用激光多普勒测速仪(LDV)对于流道内特殊位置点的速度进行测量,将实验测量结果与数值模拟计算结果进行对比。结果表明,实验测量结果与数值模拟计算结果变化趋势一致且吻合较好,主流速度的最大相对误差为28.7%,由此验证了数值模拟计算的可靠性和准确度。 相似文献
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穆道彬 《中国石油和化工标准与质量》2023,(10):113-115
环管轴流泵是应用在聚丙烯装置上特殊用途的泵,固液气介质特性决定了轴流泵设计研究的特殊性,导叶改变着流体内部流动方向,导叶结构参数的设计研究尤为重要。应用流体数值模拟软件对两种导叶数、相同叶轮的不同流量进行内外特性的研究,采用SST湍流模型,首先模拟两种导叶数在0.2~1.4Q t流量的外特性,结果显示七叶片导叶的泵性能优于五叶片导叶的泵;同时对两种导叶数的导叶进行内特性研究,通过出口断面压力和出口断面流线模拟分析,导叶片数对泵水力性能影响很大,采用七叶片导叶的泵内部流动平稳,水力损失小,效率更高;内外特性分析研究表明,相同性能参数相同叶轮的条件下选取七叶片导叶水力性能更佳。本文的研究对环管轴流泵的设计应用具有借鉴意义。 相似文献
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针对轴流泵叶顶区空化流气液混合区域密度变化,以SST k-ω湍流模型为基础,对湍流黏度项进行了修正。基于输运方程的完全空化模型对轴流泵NPSH曲线、空化特性及其叶片载荷进行了数值模拟和分析,并与实验结果进行了对比。研究结果表明,修正的SST k-ω湍流模型和空化模型较准确地预测了叶顶区空化流,临界空化数预测误差为7.79%。通过高速摄影实验观测到轴流泵的初生空化为刮起涡空化、间隙附着空化和涡带区空化,空化区域也随着空化数的降低而不断扩大,直至在叶片后缘脱落和爆破,爆破位置也不断向叶片中部移动;叶片吸力面的低压区主要集中在叶顶翼型间隔角为-13°~+13°的区域;在叶轮叶顶间隙的3%区域,随着半径系数增大,叶片压力面压力逐渐减小,叶片载荷不断降低,且越接近间隙边缘,叶片载荷降低越明显,从机理上找到了空化诱导轴流泵性能下降的原因。 相似文献
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印刷电路板换热器换热性能好、紧凑性高,在超临界CO2布雷顿循环等领域有着广阔的应用前景。本文通过数值计算,首先比较了湍流条件下15°~30°范围内不同波纹角对正弦波纹流道流动换热性能的影响,结果表明,波纹流道内的换热效果随波纹角的增大而增强(换热量最大增长了7.1%),且热侧的压降相对于冷侧增大更明显。其次,分节研究并分析了流道内不同区域的局部流动换热特性,发现了在热侧和冷侧入口区域各存在着1个大、小温差区,同时,需要对入口处进行合理的优化设计以减小入口处的压降。最后,进一步设计了一种“正弦波纹+直通道”的复合结构并初步探究了该结构的流动换热性能。 相似文献
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两端进料式宽幅片材挤出机头流道流场分析 总被引:1,自引:0,他引:1
建立两端进料式宽幅片材挤出机头流道三维几何模型,并对物料在流道内的流动进行数值模拟.模拟结果表明,流道内部压力在沿挤出方向递减的同时逐渐趋于横向均匀.高度分别为5和8 mm的阻尼部分对比分析表明,适当调整阻尼部分高度,可影响出口区域挤出速度横向分布,使横向挤出压力和速度更均匀. 相似文献
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针对目前管壳式换热器中微小流路建模和分析的缺失,采用“分段建模,整体综合”的模拟方法成功地开发了小间隙流路A和E的建模技术,建立了既包含主体流路(B、C),也包含微小泄漏流道(A、E)的全流路管壳式换热器流动与传热模型,得到了与实际换热器相适应的几何模型。通过应用CFD软件Fluent进行分段模型的流动与传热研究,对各流道在折流空间中对传热和流动的影响进行了分析讨论。同时,采用整体综合技术,将数值模拟获得的局部流动与传热数据综合整理得到了换热器传热和阻力系数的整体法关联式。并将模拟结果与几种著名的壳程计算方法(Donohue、Kern和Bell-Delaware,流路分析)进行了对比,结果发现数值模拟与Bell-Delaware法和流路分析法的结果吻合良好,最大偏差小于20%。 相似文献
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结合钢塑复合共挤工艺特点,建立了复合共挤出流动的数学模型。采用有限元分析软件Ansys对钢塑复合中空异型材共挤流道内熔体的三维等温非牛顿流动进行了数值模拟;讨论了内部芯材以不同速率移动时,流道内熔体压力、速度和粘度的分布特点及变化规律,并与普通异型材挤出进行了对比。结果表明:随着芯材移动速率的提高,流道内压降减小;在熔体与芯材接触结合区域,压力和速度梯度明显增加,粘度减小,易出现不稳定流动;流道内熔体有较高的轴向速率,径向速率对称分布,其流动特征为典型的收敛流动;由于芯材在牵动,熔体最大流速出现在口模成型段,即挤出熔体与芯材的会合处。 相似文献
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为了提高输油转子泵腔内部流动稳定性,同时提高泵的容积效率,建立了5种啮合间隙、3种转子叶数的输油转子泵模型进行对比分析。基于动网格技术和SSTκ-ω湍流模型对输油转子泵腔内部进行数值模拟,并通过试验验证了研究方法的可行性,分别研究了啮合间隙、转子叶数对输油转子泵性能影响规律,并对输油转子泵的啮合间隙、转子叶数进行了优化设计。结果表明,啮合间隙从0.1 mm增至0.3 mm,2叶输油转子泵腔内高速流动区域扩大,转子腔内漩涡强度增大,泵腔内流体流动的平稳性和容积效率降低;转子叶数由2增加为4,转子腔内压力变化的多样性增加,3叶转子泵腔内流体流动最平稳。优化设计的输油转子泵腔内流动平稳性得到提高,同时容积效率提高了2.1%,能更好地满足油田输油的需要。 相似文献
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We made a theoretical analysis for an axial flow of a working liquid of low viscosity without concern for the thermal effects. Variables studied were rotational speed of wiping blades, volumetric flow rate and viscosity.
When the viscosity is low, theoretical values are in proper accord with experimental ones. As a result, we can say that the residence time and the effective area for heat transfer are able to be controlled (when the viscosity is low) by selecting the rotational speed. 相似文献
When the viscosity is low, theoretical values are in proper accord with experimental ones. As a result, we can say that the residence time and the effective area for heat transfer are able to be controlled (when the viscosity is low) by selecting the rotational speed. 相似文献
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Abstract We made a theoretical analysis for an axial flow of a working liquid of low viscosity without concern for the thermal effects. Variables studied were rotational speed of wiping blades, volumetric flow rate and viscosity. When the viscosity is low, theoretical values are in proper accord with experimental ones. As a result, we can say that the residence time and the effective area for heat transfer are able to be controlled (when the viscosity is low) by selecting the rotational speed. 相似文献
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涡流分级机蜗壳内水平隔板对其流场的影响 总被引:2,自引:0,他引:2
为了探究蜗壳结构对涡流空气分级机流场特性的影响,文中利用Fluent软件对蜗壳内增加不同数目水平隔板的涡流空气分级机流场进行数值模拟。研究表明:蜗壳内水平隔板数目对流场速度以及环形区湍流耗散率有不同影响,存在临界隔板数使流场轴向速度分布均匀,在本文条件下的临界隔板数为3;在蜗壳中增加水平隔板可以对转笼外柱面处切向速度产生不同影响,在文中条件下增加1—3层水平隔板可以在一定程度上减小转笼切向速度与气流切向速度的差值,从而改善转笼叶片间的惯性反漩涡;随着隔板数的增加,湍流耗散率得到显著提高,物料分散性变好;涡流空气分级机的结构设计中应当考虑水平隔板对分级流场的影响。 相似文献
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M. I. Dorofeeva E. M. Koltsova L. S. Gordeev 《Theoretical Foundations of Chemical Engineering》2008,42(1):67-76
The growth mechanism of ammonium sulfate crystals is studied. A mathematical model for the process of continuous crystallization in an experimental FC-crystallizer based on the previously reported model of crystal attrition is developed. A mathematical model for the mass crystallization of ammonium sulfate in an industrial crystallizer with forced circulation by an axial three-blade propeller pump, which takes into account the impact of crystals onto its blades, is developed as well. Optimal operating conditions for an industrial crystallizer, the parameters of an axial propeller pump, and its operating conditions for producing crystals of a given size at minimal power consumption are chosen. 相似文献
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The Flow Simulation and Experimental Study of Low-Specific-Speed High-Speed Complex Centrifugal Impellers 总被引:1,自引:0,他引:1
1 INTRODUCTION Low-specific-speed high-speed centrifugal pumps are widely used in petrochemical, aerospace and chemical industries to deliver low flow rate and high-head liquids, but there exist many problems to be solved, such as low efficiency due to disc loss and low flow rate instability due to positive slope of head-capacity characteristic curve. Through the ex- perimental study on the low-specific-speed high-speed centrifugal pumps, it is found that complex impeller with long, mid an… 相似文献
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Based on the Navier-Stokes equations and the Spalart-Allmaras turbulence model, three-dimensional turbulent flow in four low-specific-speed centrifugal impellers are simulated numerically and analyzed. The relative velocity distribution, pressure distribution and static pressure rise at the design point are obtained for the regular impeller with only long blades and three complex impellers with long, mid or short blades. It is found that the back flow region between long-blade pressure side and mid-blade suction side is diminished and is pushed to pressure side of short blades near the outlet of impeller at suction side by the introduction of mid, short blades, and the size of back flow becomes smaller in a multi-blade complex impeller. And the pressure rises uniformly from inlet to outlet in all the impellers. The simulated results show that the complex impeller with long, mid and short blades can improve the velocity distribution and reduce the back flow in the impeller channel. The experimental results show that the back flow in the impeller has an important influence on the performance of pump and a more-blade complex impeller with long, mid and short blades can effectively solve low flow rate instability of the low-specific-speed centrifugal pump. 相似文献