共查询到18条相似文献,搜索用时 140 毫秒
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采用雷诺应力模型对旋风分离器内三维非稳态流场进行了模拟计算。结果表明,旋风分离器全空间内都存在旋进涡核现象。对旋进涡核现象和旋进涡核中心的运动规律进行了详细的描述,分析了不同轴向位置的旋进涡核区域内不同点的速度波动幅值和频率,得到了旋进涡核影响范围以及速度波动规律;通过分析旋进涡核中心的运动频率,得到了旋进涡核出现的强度。模拟结果与采用热线风速仪以及激光粒子成像技术(PIV)测定的实验结果基本吻合。研究结果可以分析旋进涡核对分离效率和压降的影响。 相似文献
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旋进涡核(PVC)现象会削弱旋风分离器对细颗粒的捕集效率。利用数值模拟方法研究纯气相流场中涡核的运动频率和偏心程度。结果表明:随着蜗壳包角的增大,排尘口截面涡核的运动频率和偏心程度都逐渐减小,PVC现象被削弱,蜗壳包角大于270°以后,纯气相流场中的PVC现象基本消失。入口切进度对排尘口截面涡核运动特性的影响会因蜗壳包角而有所不同。相比于入口结构的对称性,涡核偏心程度与下行气流的能量损失相关性更强。下行气流的能量损失越多,下行期间汇入内旋流的气流能量越高,内旋上行气流受到的横向扰动越大,汇入气流的能量超过某一阈值后,引发涡核摆动。而涡核旋转频率受下行气流能量损失的影响则较小。 相似文献
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旋进涡核(PVC)现象会削弱旋风分离器对细颗粒的捕集效率。利用数值模拟方法研究纯气相流场中涡核的运动频率和偏心程度。结果表明:随着蜗壳包角的增大,排尘口截面涡核的运动频率和偏心程度都逐渐减小,PVC现象被削弱,蜗壳包角大于270°以后,纯气相流场中的PVC现象基本消失。入口切进度对排尘口截面涡核运动特性的影响会因蜗壳包角而有所不同。相比于入口结构的对称性,涡核偏心程度与下行气流的能量损失相关性更强。下行气流的能量损失越多,下行期间汇入内旋流的气流能量越高,内旋上行气流受到的横向扰动越大,汇入气流的能量超过某一阈值后,引发涡核摆动。而涡核旋转频率受下行气流能量损失的影响则较小。 相似文献
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《高校化学工程学报》2021,(2)
针对旋风分离器的内部涡核随时间发生周期性振荡,采用雷诺应力模型(RSM)对两级串联旋风分离器内三维非稳态流场进行模拟计算,对比分析1、2级分离器内压力脉动规律。结果发现:1、2级分离器内脉动主频一致,但第2级分离器内存在较高的二倍频和三倍频;随着轴向高度的降低,1、2级旋进涡核的摆动幅度逐渐减小;入口气速的提高会增加1、2级分离器旋进涡核的频率及幅度。模拟结果与工业现场测得结果基本吻合。研究结果对两级串联旋风分离系统的改进有重要意义。 相似文献
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防返混锥可用于常规旋风分离器的改造以提升分离性能。基于大涡模拟(LES),从平均流场、湍流脉动和流场稳定性等方面,系统地研究了配置防返混锥后旋风分离器全局流场的变化情况。具体结论如下:圆筒段和圆锥段的平均切向速度略有提升、中心平均轴向速度轻微上移,灰斗壁面附近的切向速度几乎不变、轴向速度有所提升,灰斗底部中心区域的切向速度和轴向速度均明显降低;防返混锥附近切向与轴向的湍流脉动轴对称性有所恶化,且局部位置脉动数值增幅较大,但灰斗底部区域的脉动得以削弱;尽管在临近防返混锥的区域内旋进涡核(PVC)摆动有所增强,但全局流域的涡核平均偏心距仍降低了近21.3%。 相似文献
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为了探究局部磨损对旋风分离器性能的影响,采用Oka磨损方程以及计算流体动力学(CFD)对旋风分离器壁面磨损以及内流场特性进行数值模拟,考察旋风分离器内流场等参数随磨损厚度增大的变化规律。结果表明,旋风分离器壁在锥体底部排尘口附近壁面局部磨损严重,形成螺旋形冲蚀磨损带。磨损引起设备几何结构的改变会导致切向速度降低,颗粒所受离心力降低,锥体内局部涡强度及影响范围增大,涡核旋进(PVC)的影响加大,不利于主流的稳定与固体颗粒的分离。与未磨损时相比,当局部磨损厚度为20 mm时,粒径为4μm的颗粒分离效率由100%降低至93%,分割粒径由1.3增大至1.9μm,设备压降降低了约40%。研究工作对保障旋风分离器的长期安全稳定运行具有重要理论指导意义。 相似文献
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目前大庆油田采油三厂天然气湿气计量主要采用两种仪表:一种是孔板阀配差压变送器的测气,这种测气精度高可达0.5级,被应用在天然气贸易结算口。另一种是旋进旋涡气体流量计,这种流量计因其无机械可动部件,耐腐蚀,使用寿命长,线性测量范围宽,稳定可靠,长期运转无需维护等优点而被广泛应用在油气中转站和联合站的湿气计量中。本文针对非智能型旋进旋涡流量计和智能旋进旋涡流量计,在现场应用中所出现的问题来阐述流量计的应用情况。 相似文献
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杜清府 《化工自动化及仪表》2005,32(1):69-71
通过对涡街流量传感器的信号分析,发现涡街信号的幅值和流体的密度及其流速的平方成正比,而涡街信号的频率与流体的速度成正比,所以,涡街信号中包含了流体的流速和密度的信息,提出用涡街信号的幅值进行密度补偿的方法,并通过实验加以验证。 相似文献
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Experimental study of the vortex end in centrifugal separators: The nature of the vortex end 总被引:1,自引:0,他引:1
W. Peng A.C. Hoffmann H.W.A. Dries M.A. Regelink L.E. Stein 《Chemical engineering science》2005,60(24):6919-6928
The nature of the vortex end (or the “tail end” or “tip”) in reverse-flow centrifugal gas cleaning equipment, cyclones and swirl tubes, has been studied by visualization using a stroboscope and high-time-resolution pressure measurements. The core of the vortex is shown to bend to the wall of the separator, and rotate around the wall, forming the ring-shaped pattern normally observed at the vortex end. The end of the vortex was found to occur higher in the swirl tube (“less stable vortex”) when the solid loading is increased, and when the volumetric flow rate to the tube is decreased. The frequency with which the vortex core rotates varies with the gas flow rate and was found to be about the same as the frequency with which the gas rotates higher in the separator. The time-averaged wall pressure suddenly decreases in the separator body at the point where the vortex end attaches to the wall. 相似文献
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When water was rotated by means of a “horse-shoe” stirrer in a vertical, cylindrical tank and a stream was withdrawn from the bottom through a central exit pipe, a pronounced filament-like vortex was formed under certain conditions. Experiments were performed to determine the factors which influenced the height of the vortex. The effects of vessel sue, stirrer geometry, rotational speed, exit flow rate and exit pipe diameter on vortex depth were studied. It was found that the vortex depth was highly dependent on the rotational speed, exit flow rate and exit pipe diameter. It was also found that under certain flow conditions the vortex penetrated the exit pipe. A relationship between the vortex depth and the pertinent variables was developed using dimensional analysis. The relationship resulting from a regression analysis of the dimensionless groups affecting the vortex depth was found to be: Motion picutes were taken showing the flow characteristics in the vicinity of the vortex by using a dye tracer technique. Ways of inhibiting vortex formation were also examined. 相似文献
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Nicolai Szeliga Lando Helmrich von Elgott Daniel Bezecny Steffen Richter Marko Hoffmann Michael Schlüter 《化学,工程师,技术》2019,91(12):1802-1811
Experiments were carried out in a 50‐m3 cylindrical tank to determine the influence of strong momentum on the formation of large‐scale gas‐core vortices. Gas‐core lengths were measured for varying volume flow rates and submergence depths. The critical Froude numbers were also determined and the efficiency of different vortex suppressors on the gas‐core formation was investigated. The horizontal velocity field inside the vortex core region was additionally recorded using particle image velocimetry. The experimental results were used to verify numerical simulations and compared to vortex models and correlations from literature. 相似文献
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The characteristics of the trailing vortex systems generated behind the blades of a fan turbine (denoted here as discharged wake vortex) were elucidated through a simultaneous measurement of the three components of velocity of the impeller discharge stream. A conditional sampling technique was applied to extract the well developed vortex signals. Totally 373 vortex signals were sampled. It was found that in spite of the scale of the vortex core being small (about one fourth of the impeller blade width), its rotational and axial velocities reach equal to and higher than the blade tip velocity, respectively. From these results, it was estimated that the discharge velocity of the vortex core is 2.4 times the impeller mean discharge velocity and the kinetic energy carried by the vortex core per unit area is 14.5 times larger than that of the impeller discharge stream. These results demonstrate how much the vorlex contributes not only to gas or liquid dispersion but also to mixing in the impeller region. 相似文献
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A. M. Ali H. H. S. Yuan D. S. Dickey G. B. Tatterson 《Chemical Engineering Communications》1981,10(4):205-213
An oil into water dispersion, created by a pitched blade turbine, was observed using high speed, stereoscopic motion pictures. Two different dispersion mechanisms were responsible for the break-up of the oil drops, even though both mechanisms occurred in the vortex system trailing from the impeller blade tips. The first mechanism could be described as ligament stretching, since large oil drops were stretched by fluid shear to form elongated ligaments, which subsequently ruptured into small drops. The second mechanism was turbulent fragmentation, where large oil drops were shattered into large droplet clouds the instant they entered the trailing vortex system. Observations of the oil drops undergoing ligament stretching also indicated that velocities in the trailing vortex system were proportional to impeller tip speed. 相似文献
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A.M. ALI H.H.S. YUAN D.S. DICKEY G.B. TATTERSON 《Chemical Engineering Communications》2013,200(4-5):205-213
An oil into water dispersion, created by a pitched blade turbine, was observed using high speed, stereoscopic motion pictures. Two different dispersion mechanisms were responsible for the break-up of the oil drops, even though both mechanisms occurred in the vortex system trailing from the impeller blade tips. The first mechanism could be described as ligament stretching, since large oil drops were stretched by fluid shear to form elongated ligaments, which subsequently ruptured into small drops. The second mechanism was turbulent fragmentation, where large oil drops were shattered into large droplet clouds the instant they entered the trailing vortex system. Observations of the oil drops undergoing ligament stretching also indicated that velocities in the trailing vortex system were proportional to impeller tip speed. 相似文献