导向叶片角度对柱面笼型粉体分级机流场影响的研究

为柱面笼型粉体分级机的导向叶片角度会对分级机内速度和压强产生影响,直接影响了分级机的性能。为了研究不同角度的导向叶片对柱面笼型粉体分级机流场的影响,设计了3种不同角度的导向叶片来进行对比研究,利用计算流体动力学对柱面笼型粉体分级机内部流场特性进行数值模拟.。模拟结果表明导向叶片角度变小后虽然可以使速度增加,但破坏了流场的稳定性;角度增大,则会减小分级区域的速度.通过对计算数据的分析,发现分级机存在一个最优导向叶片角度,此时分级机内流场最为稳定,分级性能最佳。     

基于数值分析的前向多翼离心风机叶轮的改进

对某双进气前向多翼离心风机进行了数值模拟,分析了此类风机内部流动沿转轴方向的不均匀性,并针对这种特性提出了沿轴向改变叶轮叶片进口角、沿轴向改变叶轮叶片内径2种对叶轮的改进方法。分析结果表明,变角度处理可以改善盖侧叶轮叶片进口的正冲角,减小叶轮内的冲击损失;变内径的处理可以改善叶轮出口速度的不均匀性,有助于减小蜗壳内二次涡流。     

基于CFX的新型打散分级机结构改进分析

对应用于辊压联合粉磨系统的新型打散分级机的理论分级粒径公式进行了详细推导,并利用流体力学数值分析软件ansys cfx 11.0,采用k-ε湍流物理模型对其进行数值模拟分析.在处理风量以及转子工作转速一定的条件下,分别研究了分级机不同的蜗壳偏心距,不同出风管位置及结构形式进行了优化研究,通过改变结构的方式明显提高了分级区域内流场的稳定性以及均匀度,经过实验验证,采用数值优化的方法,有利于提高该分级设备的分级效率与分级精度.     

O-sepa选粉机叶片结构对分级区流场影响研究

O-sepa选粉机环形区域的速度场是影响其分级效率的主要因素之一,建立了3种不同结构的叶片来研究不同结构的转笼叶片对O-sepa选粉机流场的影响。使用Fluent软件对选粉机内流场进行模拟分析,分析结果表明转笼叶片采用流线型结构流场分布最好。     

主要结构参数对微型旋风分级器性能的影响

颗粒的分级作为目前粉体材料加工与应用的基本技术之一,已被广泛的应用于各个领域,如矿物加工与分选、冶金等方面。旋风分离器的主要结构参数对旋风分离器内的流场影响最大,但目前鲜有人研究其对分级的影响。通过对旋风分离器的锥角与排气管插入深度进行数值模拟研究,采用非稳态离散项模型与雷诺应力模型的方法研究其对压力降与分级性能的影响。结果表明:排气管插入深度对分级粒径和分级精度都有显著的影响,插入深度过小甚至没有插入深度都对分级精度的提高不利,但插入深度增大会增大分级粒径和压力降;对于分级精度,锥角存在最佳值,但分级粒径和压力降都随锥角的增大而增大;最佳锥角值与溢流管插入深度有关,其随着溢流管插入深度的增大而减小;自然旋风长在分级精度曲线峰值处保持在一个稳定的范围内,对于柱段长度与入口结构不变的情况,自然旋风长在3.2 D～3.5 D之间分级精度较高。     

贯流风机性能参数实验与扭曲角优化

介绍了一种自行研制的电壁炉用贯流风机性能参数检测台,详细描述了检测台中关键部件的实验测试原理,并对直叶片和扭曲叶片贯流风机在热风状态下的性能参数(出风口风速、风量和风机转速等)进行了对比实验研究,得出了扭曲角为60°的扭曲叶片贯流风机的性能明显优于直叶片贯流风机。同时对扭曲叶片贯流风机流场进行了数值模拟,并对扭曲角进行了优化。结果表明:数值计算和实验结果基本吻合,这两者的结合是研究贯流风机结构和改进其性能的有效手段。     

布袋除尘器气固两相三维流场分析

本文对一台用于净化氧化铝烟气的布袋除尘器进行了气固两相三维流场数值模拟。分析结果表明,其流场分布不够理想。为了改进除尘区流场分布,需了解除尘器流场分布规律。本文在原分析的基础上,分别改变颗粒粒径、布袋渗透率以及气流入口速度等边界条件,进行了多次分析。结果表明粒径越小,颗粒在除尘室分布越均匀;在允许的条件下,增大布袋渗透率并适当增加入口风量有利于使流场分布均匀。该分析结论为布袋除尘器的实验和改进提供了依据。     

核电站三级循环给水混流泵的数值模拟与试验分析

针对某在建核电站三级循环给水混流泵要求在多工况高效率运行的情况,基于N-S方程、标准k-ε湍流模型和SIMPLE算法,对叶轮及蜗壳内部流场进行了数值模拟,并预测了扬程效率曲线.在清水试验台上进行了性能测试,数值模拟与试验结果吻合较好,但CFD分析与试验结果均显示已生产的样机效率不达标,可通过增大蜗壳断面面积以及减小叶片进口冲角来进一步提高整机效率.     

选粉机分级进料方式的试验研究

为研究进料方式对分级机分级性能的影响,分别对上进料和下进料式的SCX型选粉机进行试验研究。对比分析了两种进料方式下d10,d50和d90等特征粒径的变化规律,并考察了不同操作参数下分级机的产量和粒径分布,结果表明:随着下进料式分级机转速的增加,d10,d50,d90均减小;上进料式分级机转速为305r/min和415r/min时,特征粒径变化不大,当转速增加到590r/min时,d10,d50,d90明显减小;采用气流预分散的上进料式分级机和采用机械预分散的下进料式分级机都能得到较好的分级效果,分级后细粉的中位径较小,且粒径分布窄,主要集中在(1~30)μm,30μm以下的颗粒含量达到90%以上。     

三级选粉机的设计与仿真

针对燃煤固硫对碳酸钙粒径的特殊需求,设计了一种三级选粉机。在设计的过程中,运用Fluent软件,选用kepsilon标准模型和多重参考坐标系法,在稳态条件下,对三级选粉机分级腔内的流场进行了仿真,分析了不同转子结构和转速对选粉机内部流场的影响。模拟分析得到当转子叶片数量为48片,转子转速为1500转/每分钟时,选粉机内部流场较好。通过制造样机进行实验,实验结果表明,设计制造的三级选粉机能有效的分选出(0.125~1.2)mm粒径碳酸钙颗粒,满足设计要求。     

Flow Field Characteristics of the Rotor Cage in Turbo Air Classifiers

The turbo air classifier is widely used powder classification equipment in a variety of fields. The flow field characteristics of the turbo air classifier are important basis for the improvement of the turbo air classifier's structural design. The flow field characteristics of the rotor cage in turbo air classifiers were investigated under different operating conditions by laser Doppler velocimeter(LDV), and a measure diminishing the axial velocity is proposed. The investigation results show that the tangential velocity of the air flow inside the rotor cage is different from the rotary speed of the rotor cage on the same measurement point due to the influences of both the negative pressure at the exit and the rotation of the rotor cage. The tangential velocity of the air flow likewise decreases as the radius decreases in the case of the rotor cage's low rotary speed. In contrast, the tangential velocity of the air flow increases as the radius decreases in the case of the rotor cage's high rotary speed. Meanwhile, the vortex inside the rotor cage is found to occur near the pressure side of the blade when the rotor cage's rotary speed is less than the tangential velocity of air flow. On the contrary, the vortex is found to occur near the blade suction side once the rotor cage's rotary speed is higher than the tangential velocity of air flow. Inside the rotor cage, the axial velocity could not be disregarded and is largely determined by the distances between the measurement point and the exit.     

Empirical study of classification process for two-stage turbo air classifier in series

The suitable process parameters for a two-stage turbo air classifier are important for obtaining the ultrafine powder that has a narrow particle-size distribution, however little has been published internationally on the classification process for the two-stage turbo air classifier in series. The influence of the process parameters of a two-stage turbo air classifier in series on classification performance is empirically studied by using aluminum oxide powders as the experimental material. The experimental results show the following: 1) When the rotor cage rotary speed of the first-stage classifier is increased from 2 300 r/min to 2 500 r/min with a constant rotor cage rotary speed of the second-stage classifier, classification precision is increased from 0.64 to 0.67. However, in this case, the final ultrafine powder yield is decreased from 79% to 74%, which means the classification precision and the final ultrafine powder yield can be regulated through adjusting the rotor cage rotary speed of the first-stage classifier. 2) When the rotor cage rotary speed of the second-stage classifier is increased from 2 500 r/min to 3 100 r/min with a constant rotor cage rotary speed of the first-stage classifier, the cut size is decreased from 13.16 μm to 8.76 μm, which means the cut size of the ultrafine powder can be regulated through adjusting the rotor cage rotary speed of the second-stage classifier. 3) When the feeding speed is increased from 35 kg/h to 50 kg/h, the "fish-hook" effect is strengthened, which makes the ultrafine powder yield decrease. 4) To weaken the "fish-hook" effect, the equalization of the two-stage wind speeds or the combination of a high first-stage wind speed with a low second-stage wind speed should be selected. This empirical study provides a criterion of process parameter configurations for a two-stage or multi-stage classifier in series, which offers a theoretical basis for practical production.     

高输送气流速度下竖直管道内物料的运动分析

分析在稀相气力输送中,输送气流速度超出最佳经济速度时,物料在竖直管道中的运动情况,并提出一种在输送气流速度大于最佳经济速度时,增加气流速度以加快输送物料的解决方法。利用Fluent软件对其进行仿真模拟分析,并对不同入口气流速度对物料运动的影响进行研究分析。结果表明：在高输送气流速度下,物料在给定高度竖直管道中一直处于加速状态,且在入口处加速度较大,随着运动高度的增加,加速度逐渐减小;在物料粒径和管道内径不变时,改变入口处气流速度,物料的运动速度随着入口气流速度的增大而增大,同时管道内的压力损失也随着增大。     

Numerical simulation of the hydrodynamically developing flow of a viscoelastic fluid

Hydrodynamically developing flow of OldroydB fluid in the planar die entrance region has been investigated numerically using SIMPLER algorithm in a non-uniform staggered grid system. It has been shown that for constant values of the Reynolds number. the entrance length increases as the Weissenberg number increases. For small Reynolds number flows the center-line velocity distributions exhibit overshoot near the inlet, which seems to be related to the occurrence of numerical breakdown at small values of the limiting Weissenberg number than those for large Reynolds number flows. The distributions of the first normal stress difference display the development of the flow characteristics from extensional flow to shear flow.     

进口速度畸变对轴流风机性能影响的全周数值研究

采用全通道数值模拟方法,通过设置周向角度相同、径向位置不同的速度畸变区域,分析了畸变条件下低压轴流风机性能及流场的变化规律。计算结果表明,该方法可以清晰描述流场参数的分布情况,设置的进口速度畸变方式会使风机效率降低,静压升变大,转子进口相对气流角分布与叶型极不匹配,造成进口冲角绝对值较大,叶栅通道内的流动恶化,流动损失增加,并且风机出口的压力沿周向分布的不均匀性增强。     

滚滑轴承滑块的油-气两相流润滑分析

为改善滚滑轴承的润滑,运用两相流理论对其滑块进行油气润滑设计,建立滑块的油-气两相流CFD模型,分析不同入口角度、进气速度、进油速度和润滑油黏度对流场油相分布的影响。结果表明:油-气混合润滑方式能在内外滚道接触区形成有效的润滑油膜;油气管道夹角影响油滴分布,角度过大时大量油滴会在滑块侧面上附着,角度过小时油滴会在外滚道入口处堆积,造成供油连续性不好,油膜稳定性下降;进气速度过大会降低油滴附着率,无法形成有效油膜,而进油速度过大会造成润滑油累积,出现搅油现象,因此选择合适的进气和进油速度,才能控制油滴的大小和保持润滑过程的连续性;润滑油黏度会影响油滴在滑块上的附着效果,合理地选择润滑油黏度,才能保证流场油相分布均匀。     

Behavior of rotating stall cell in a high specific-speed diagonal flow fan

An experimental investigation was carried out to clarify unsteady flow fields with rotating stall cell, especially behavior of stall cell, in a high specific-speed diagonal flow fan. As its specific-speed is very high for a diagonal flow fan, its pressure-flow rate curve tends to indicate unstable characteristics caused by rotating stall similar to axial flow fan. Although for an axial flow fan many researchers have investigated such the flow field, for a diagonal flow fan little study has been done. In this study, velocity fields at rotor inlet in a high specific-speed diagonal flow fan were measured by use of a single slant hot-wire probe. These data were processed by using the ““Double Phase-Locked Averaging“ (DPLA) technique, i. e. phases of both the rotor blade and the stall cell were taken into account. The behaviors of stall cell at rotor inlet were visualized for the meridional, tangential and radial velocity.     

三叶片直线翼垂直轴风力机非定常流场速度分析

垂直轴风力机在回转过程中,叶片尾流的相互干涉和叶片攻角变化,使垂直轴风力机周围流场异常复杂。为探明直线翼垂直轴风力机在二维流场中速度分布及风力机叶片迎风角度变化关系,在风洞试验中采用激光多普勒测速仪(Laser Doppler velocimetry,LDV)技术,对所设计的三叶片直线翼垂直轴风力机流场风速进行试验研究,获得了该风力机叶片周围流场的速度分布情况。在建立直线翼垂直轴风力机在不同转速下叶片迎风角度变化的数学模型基础上,应用仿真软件对被测风力机流场进行分析计算。通过数学模型得知,来流风速夹角随回转角的变化情况可用正弦函数近似表示, 并且随着叶尖速比的增大逐渐减小。风洞试验和CFD结果表明,风力机在回转过程中,叶片前缘场域有乱流生成,并且该域风速值偏大;而在叶片旋转内部以及下流区域内会形成一个宽大的低速区域,并且伴随叶尖速比的增加,低速区域具有扩大趋势。     

Numerical Simulation of Unsteady Discharge Flow with Fluctuation in Positive Discharge Blower

The operating performance of positive discharge blower/s markedly influenced by the pulsation of the discharge flow, but difficult to be measured with experimental methods. The internal and discharge flow of positive discharge blower with involute type three-lobe are numerically investigated, both in air cooling and countercurrent cooling conditions by means of computational fluid dynamics (CFD). The unsteady compressible flow equations are solved using RNG κ-ε turbulent model. The finite difference method and the second order upwind difference scheme are applied into discrete equations. In the numerical simulation, the dynamic mesh techniques are used to approach the rotating displacement of cell cubage and the alterability of inlet, outlet flow area. The non-uniform mesh is applied to the rotor-stator coupled area. The reliability of the numerical method is verified by simulating the inner flow and comparing with the semi-empirical theory. The flow flux curves and the distributing of velocity vector showed obvious vortex motion in all the discharge process, both in air cooling and countercurrent cooling conditions. These vortexes with different positions, intension and numbers at different rotating angles have remarkable influences on the discharge flux. For air cooling, the vortex produced a second pulsation with big-amplitude in a cycle, and led to the early appearance of maximum of backflow. For countercurrent cooling, the frequency of pulsation increased due to the pre-inflow, but the hackflow at the outlet is prevented, also the pulsation strength has greatly decreased.     

迷宫密封-转子系统动力学特性的试验测量和数值模拟

针对迷宫密封内作涡动旋转的转子承受腔室内周向不均匀压力,从而导致振动特性发生变化的问题,通过建立迷宫密封-转子试验台,对密封进出口压比分别为1.5、3.0、6.0和7.0下的密封腔室内气流流动和转子振动特性进行同步试验测量,并基于振荡流体力学原理进行数值计算分析.通过对定转速条件下的密封齿腔平均压力、脉动压力周向分布以及转子临界转速等的对比分析,表明迷宫密封内气流流动对转子临界转速影响明显,试验测量和数值计算结果比较吻合.