共查询到18条相似文献,搜索用时 203 毫秒
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提出一种将涡流搜索算法用于支持向量机参数选取的新算法,利用该算法不必遍历搜索空间内所有的参数点即可找到全局最优解。给出了具体的算法流程,并进行了仿真。仿真实验结果表明涡流搜索算法是选取SVM参数的有效方法。 相似文献
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对不同初始旋流强度的空气介质在环形管内涡旋流动特性及传热机理的试验研究,得到了表示涡流喷嘴位置及方向的几何参数与传热系数及压力降的关系。实验表明,涡旋流动有明显的强化传热作用。 相似文献
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为寻求涡流空气分级机进口风速和转笼转速的最佳匹配,利用Fluent软件对涡流空气分级机内部流场进行模拟分析,得出:当进口风速与转笼外缘的切向线速度相等或相近时流场最稳定。在流场较稳定的前提下,较高进口风速和转笼转速时,环形区湍流耗散率更大,更有利于物料的分散及分级。碳酸钙物料实验表明:转笼转速分别为800 r/min和1 200 r/min时,取进口风速分别为9 m/s和12 m/s,分级精度和牛顿分级效率都较高。其中进口风速为12 m/s,转笼转速为1 200 r/min时,分级精度和牛顿分级效率最优。该结论为利用涡流空气分级机进行分级合理调节进口风速和转笼转速提供理论依据。 相似文献
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利用热力学第二定律中的熵产理论对涡流空气分级机各不可逆因素引起的熵产进行分析,通过粉料分级试验对其分级性能进行验证,获得了黏性熵产、湍流熵产和壁面熵产分布特点及操作参数对熵产和分级精度的影响规律。熵产分析结果表明,涡流空气分级机内湍流熵产和壁面熵产占总熵产的比例高达56.41%和43.11%,湍流熵产主要产生于转笼叶片间和转笼内部,进风口和细粉出口壁面剪切引起较大壁面熵产;此外,转笼转速和进口风速变化分别仅对转笼区域和切向进风口区域内气流运动熵产影响较大,进口风速-转笼转速处于8.6m/s、 800r/min和18m/s、1200r/min操作工况附近时,涡流空气分级机内总熵产/总能变化率较小,分级流场稳定性较高,对粗、细颗粒分离有利,该工况下分级机的粉料分级试验效果较好,说明熵产理论可用于涡流分级机内流动分析及其操作参数的优化匹配。 相似文献
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采用正交试验设计法进行实验,得到缩聚改性最佳条件,合成出性能比国标GB12216合脂粘结剂更优越的铸造粘结剂。 相似文献
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Vortex diodes are used as leaky non-return valves in applications where it is desirable to avoid valves with moving parts. Despite their use in practice for several decades, no clear guidelines for design and optimization of vortex diodes are available. Detailed experimental study on flow and pressure drop characteristics of vortex diodes was therefore carried out to evolve such guidelines. The study covered a wide range of vortex diodes. The variation of diodicity (ratio of pressure drop for reverse and forward flow for the same flow rate) with respect to diode geometry, diode size (dC), aspect ratio (dC/h), nozzle configuration and Reynolds number (Re) was studied. The experimental results were critically analyzed to develop a design methodology. The methodology is shown to be useful for obtaining the diode dimensions that would yield the desired diodicity for the required operating flow rate. 相似文献
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To address the gas flow pattern and pressure drop characteristics for small long‐cylinder cyclones (SLCCs) in the high operating flow rate range, experimental investigation and computational fluid dynamics (CFD)‐based simulation were performed. The pressure drop coefficient depends insignificantly on the Reynolds number at high flow rates. The tangential and axial velocities present the Rankine vortex and the roughly inverted V‐shaped distribution, respectively, similar to those in typical cyclones. The CFD simulation approximated well the experimental data of pressure drop. The pressure drop caused by vortex loss, turbulent energy loss, and resistance loss accounted for 72.5 % of the total pressure drop. The Stairmand model was found to be relatively accurate among the classical pressure drop models for the proposed cyclone. The results may help in the design and applications of cyclone separators and reactors. 相似文献
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The gas flow fields of a cyclone with different inlet section angles have been studied numerically. The gas flow fields were simulated by means of the Reynolds Stress Transport Model (RSTM). The velocities and pressure drop profiles of these cyclones were investigated. The shortcut flow rates at the bottom of the vortex finder were calculated with different inlet section angles. To analyze the relationship between the inlet section angle and the vortex finder insertion deepness, this paper details the shortcut flow rates at the bottom of the vortex finder for three vortex finder insertion depths. The results indicate that the inlet section angle can decrease the shortcut flow from the bottom of the vortex finder, which has practical importance for the improvement of the separation efficiency. The inlet section angle can also decrease the pressure coefficient of a cyclone. When the inlet section angle is 45 °, the level of decrease is up to 30 %. However, the effect of the inlet section angle on the separation performance is related to the dimension of the vortex finder, i.e., the insertion depth and diameter of the vortex finder, and the effect is different when the cyclone has different vortex finder insertion depths. 相似文献
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为强化气液离心分离过程,实现在大直径分离器内的气液旋流高效分离,设计构思了一套多旋臂气液旋流分离设备,为气液分离大型化设计提供了一种新思路。在纯气流条件及不同的旋流臂喷出气速下对该分离设备进出口静压差进行了测量,实验结果表明,旋流分离设备静压差在整个运行过程中较为稳定,有较强的可预测性,无量纲标准偏差维持在2%以内,总压降与旋流臂出口气速呈现出良好的平方关系。进一步将总压降分解为入口及旋臂摩擦损失、分离器空间内摩擦损失和出口管路摩擦损失三个部分进行详细测量,获得了各部分压降与旋流臂出口速度头的定量关联模型,发现分离器空间内摩擦阻力损失在总压降中占比最大。GLVS总压降主要受旋流臂出口气速影响,加入液相后对压降影响很小。该旋流分离设备的阻力系数与普通旋风分离器相当,根据四组不同结构尺寸的旋流头得到了阻力系数与旋流头关键设计参数的关联式,为进一步结构优化提供了参考。 相似文献
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为降低翅翼型纵向涡发生器与螺旋片复合强化的套管式换热器壳侧传热阻力,提出一种新型翅翼型纵向涡发生器,即流线型涡发生器。采用实验和数值模拟方法研究了流线型涡发生器与螺旋片复合强化的换热器壳侧的传热和阻力特性并与三角翼型涡发生器(DWP)的强化效果进行比较,考察了流线型涡发生器common-flow-down(CFD)和common-flow-up(CFU)两种安装方式的强化效果,分析了流线型涡发生器的减阻机理。结果表明,在涡发生器面积和迎流角相同的情况下,流线型涡发生器可以取得与三角翼型涡发生器相同(Re<8000)或略低(Re>8000)的传热系数,但其产生的流动阻力比三角翼型涡发生器低21%;在相同压降条件下,common-flow-up安装方式的综合传热效果优于common-flow-down;流线型涡发生器减阻机理在于提高了速度场与压力场的协同性。 相似文献
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In this article we examine confined swirling flows using the integral equations of continuity and energy, along with the minimum pressure criterion. The pressure drop and the core size have been studied in the swirling confined vortex chamber. Both the n = 2 vortex model, with reverse and non‐reverse flow, and the free vortex model have been used at the vortex chamber exit plane. The influence of vortex chamber geometry, such as contraction ratio, inlet angle, area ratio, aspect ratio, and Reynolds number, on the flow field has been analyzed and compared with the present experimental data. The pressure drop across the vortex chamber differs from that in pipe flow, due to the mechanism of swirl flow that depends mainly on the intensity of tangential velocity. If the chamber length is increased, the vortex decays producing a weaker tangential velocity (less centrifugal force) that leads to less pressure drop. Based on the present theory, a new approach to determine the tangential velocity and radial pressure profiles inside the vortex chamber is developed and compared with the available experimental data. It shown that the n = 2 vortex model with reverse flow gives better results for strongly swirling flow. 相似文献
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采用计算流体力学三维层流模型模拟,研究了温度50~75℃、雷诺数Re=300~800、弯管内径D=50.7~131.7 mm、弯径比B=0.75~3.0条件下稠油在90°弯管内的阻力特性,分析了弯管局域阻力系数波动的机理。结果表明,随温度升高、入口雷诺数下降、弯管直径增加,局域阻力系数提高;在弯管0~15°范围内阻力下降,原因是弯管内形成双纵向涡,75°到弯管后0.5D范围内阻力下降,原因是弯管内形成4个纵向涡;弯管的弯径比对局域流动阻力影响很大,B=0.75时相邻截面最大落差达B=3.0时的28.35倍,但管道进出口阻力仅为1.68倍,原因是弯径比B≤1.0时,弯管后1.0D范围内侧形成了局域低压区,对应位置出现流向涡旋,同时弯管后0.5D截面稠油剪切速率达到峰值。 相似文献
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为促进旋流快分(SVQS)系统的工业应用、准确评估其性能,参照国家标准设计了一系列不同密度、黏度的油气模型,并采用商用软件FLUENT 2019 R3对一套Φ600 mm×3150 mm的SVQS系统进行了流动模拟和可行性验证。用单因素变量法分别研究了油气性质对系统无量纲切向速度和压降的影响;用标量输运方程分析了油气在系统内的停留时间分布规律。结果表明,无量纲切向速度随油气密度增加或黏度降低而变大;无量纲最大切向速度随油气密度增加或黏度减小而呈对数递增,最大为0.912;密度越大、黏度越小的油气在SVQS系统内的平均停留时间越短,最短可达6.279 s;压降、阻力系数不仅与系统的结构参数相关,也与油气黏度呈对数关系。拟合得到了与油气参数相关的无量纲切向速度、压降和阻力系数函数式,具有较好的普适性,可为SVQS系统的结构优化提供参考。 相似文献