灰斗对旋风分离器气相流场的影响

本文采用fluent数值模拟的方法研究了中国石油辽河石化分公司聚丙烯装置在用旋风分离器内气相流场,将改造前和改造后两种结构旋风分离器内部流场进行了对比,研究发现,旋风分离器不设计灰斗时分离空间内最大切向速度减小,轴向速度中心上行流速度增大,旋转气流延伸到收料罐,大大降低了分离旋风分离器效率。     

灰斗抽气对旋风分离器分离性能影响数值模拟研究

 利用计算流体动力学软件FLUENT对旋风分离器内气固两相流动特性进行三维数值模拟,模拟气相流场采用雷诺应力模型,应用随机轨道模型模拟湍流流场中颗粒的运动轨迹,同时给出了不同抽气率下旋风分离器的速度、压力分布,计算出旋风器分级效率,模拟结果与文献实验数据吻合较好.结果表明,灰斗抽气可以提高锥体内旋转气流切向速度,轴向速度减少能够降低气流携带颗粒返混能力,并减小排气芯管下口短路流,提高旋风分离器分离效率.对于给定的旋风分离器,抽气率应有一最优值.     

新型旋风分离器的试验研究与流场分析

文章针对高温高压的条件对传统旋风分离器入口结构进行改进,提出了圆柱形径向插入、端面加导流板结构的新型旋风分离器结构。由冷态模型下对超细滑石粉和FCC催化剂颗粒的分离效率-压降对比试验结果表明,新型旋风分离器入口结构强度性能优良,虽然对超细粉料分离性能略有不足,但对大颗粒粉料的分离性能接近传统直切入口旋风分离器,可以满足要求。并且数值流场模拟结果表明,分离器压降与实验结果相一致。     

旋风分离器在冷镦机油雾处理中的应用探讨

借助计算流体力学软件Fluent,探讨旋风分离器分离冷镦机产生的油雾的可行性。运用雷诺应力二次压力应变模型和离散相随机轨道模型对旋风分离器进行数值仿真,分析了流场、颗粒轨迹、油雾内PM2.5分离效率。结果表明:旋风分离器可作为冷镦机油雾处理的初级分离设备。     

旋风分离器内气相数值模拟研究

旋风分离器内部进行的是两相流运动,是气相和固体颗粒相的分离过程,而固体颗粒的运动在很大程度上取决于分离器内湍流的运动.对湍流及其模型的研究具有十分重要的意义.在综述旋风分离器内湍流模型和数值模拟相关理论研究进展的基础上,着重分析了k-ε双方程模型和雷诺应力模型在旋风分离器流场预测方面的进步和不足,并展望今后湍流模型的发展趋势.     

不同侧向入口旋风分离器流场数值分析

利用雷诺应力模型(RSM)对直切单入口、直切双入口、斜切单入口、斜切双入口、斜切螺旋面单入口、斜切螺旋面双入口6种不同侧向入口旋风分离器内部气相流场进行了计算分析。结果表明:双入口结构旋风分离器内部压力场和速度场具有更好的对称性与稳定性;仅改变入口斜切角度对旋风分离器内部速度场和压力场的分布影响不大;当本文中6种分离器内部具有相近的切向速度径向分布时,斜切螺旋面入口结构分离器压力损失减少约25%,入口所需总压降低17%,处理相同气体量的能耗约下降17%;斜切螺旋面双入口(XS-L型)分离器是一种综合性能比较优的旋风分离器。     

芯管半切旋风分离器的实验研究

基于相当成熟的PV型旋风分离器的流场分析,对芯管做简单的斜切处理,并充分考虑芯管切口方向和芯管插入深度对旋风分离器的分离效率和压降的影响,实验结果表明半切式芯管能够提高旋风分离器分离效率并降低其压力损失,可以用于高温条件下的除尘使用.     

雾化焙烧制备超细颗粒用旋风分离器优化模拟

旋风分离器是雾化焙烧制备稀土氧化物工艺中的常用分离设备之一。为了提高焙烧产物中超细颗粒的分离效率，采用Fluent数值模拟和实验验证相结合的方法，得到旋风分离器的优化构型，利用颗粒分离效率和流体压降2项指标进行评价，以探讨扩张结构旋风分离器的优化效果。结果表明：在锥筒高度为距旋风分离器顶板370 mm处，进行角度为10°的扩张改进后，分离器对粒径为1、 3、 5μm的颗粒分离效率分别提高13.25%、 42.33%、 44.02%,阻力系数减小3.6%;新改进结构旋风分离器在降低能耗的同时提高分离效率。     

旋风分离器内三维强旋湍流流动数值模拟的修正压力应变项模型

针对旋风分离器内强旋流动的数值模拟,改进了雷诺应力方程压力应变项的IPCM+wall模型,加入到FLUENT6.0软件平台上。分别用修正的和标准的IPCM+wall模型、IPCM模型以及SSG模型,对蜗壳式旋风分离器内三维湍流流动进行了数值模拟,给出了分离空间和灰斗内的时平均速度和雷诺应力分量的分布,并用LDV测量结果加以检验。研究结果表明,修正的IPCM+wall模型对切向和轴向速度、切向和轴向正应力以及轴-切剪应力的预报值与实测值的吻合比其他压力应变项模型的好得多。     

旋转直流内循环式旋风分离器流场测定与分析(Ⅰ)

采用五孔探针测试技术及相应的计算机数据采集与处理系统，测定了旋转直流内循环式旋风分离器的三维流场分布。对所测流场分4个区域进行了分析讨论，并对内循环气量进行了衡算。结果表明该新型旋风分离器设计合理，结构有利于气流中颗粒的分离。     

Organic impurity preconcentration by a multimembrane inlet system of a mass spectrometer

Using an inlet system comprising a series of membranes sequentially operating in a nonstationary flow regime, it is possible to increase the concentration of an organic impurity in a sample immediately before introduction into a mass spectrometer. The degree of preconcentration calculated in the approximation of a small response time of the membranes is proportional to (k _j /k _m )^N, where k _j and k _m are the membrane permeabilities for the impurity and matrix, respectively, and N is the number of membranes. For a butane admixture in air, the calculated relative effect for an inlet using two membranes instead of one is ∼40, while the experimental verification using 0.1-mm-thick poly(dimethylsiloxane) membranes showed an increase in the degree of preconcentration by a factor of ∼14. It is possible to approach the theoretical value by decreasing the time of impurity diffusion through the membrane at the expense of reduced membrane thickness. It is expected that multimembrane inlet systems will be especially effective in environmental monitoring, where a high sensitivity of the analysis is required with respect to toxic organic substances possessing k _j /k _m ratios much greater as compared to that of butane.     

进出口条件对多孔板流动特性影响研究

对不同进出口条件下液氮经多孔板流动特性进行了数值模拟与分析,主要研究了进口温度和出口压力对多孔板流出系数和压力损失系数的影响,以探索用做多孔板流量计时的稳定工作区域。结果表明,进口温度和出口压力不影响稳定区雷诺数下限值、稳定区内平均流出系数值和平均压力损失系数值;稳定区雷诺数上限值随出口压力降低而减小,随进口温度降低出现先增加后减小的现象;随着雷诺数进一步增大,流出系数将在空化区出现另一个稳定区域。     

Turbulent flow in a boundary layer on the inlet and outlet sides of a rotating channel

Expressions are obtained for approximately determining the shear stresses on the outlet and inlet sides of a rotating channel on the basis of a turbulence energy balance equation, A. N. Kolmogorov's hypothesis, and the Monin-Obukhov similitude theory.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 6, pp. 977–986, December, 1981.     

CFD simulation and experimental validation of a GM type double inlet pulse tube refrigerator

Pulse tube refrigerator has the advantages of long life and low vibration over the conventional cryocoolers, such as GM and stirling coolers because of the absence of moving parts in low temperature. This paper performs a three-dimensional computational fluid dynamic (CFD) simulation of a GM type double inlet pulse tube refrigerator (DIPTR) vertically aligned, operating under a variety of thermal boundary conditions. A commercial computational fluid dynamics (CFD) software package, Fluent 6.1 is used to model the oscillating flow inside a pulse tube refrigerator. The simulation represents fully coupled systems operating in steady-periodic mode. The externally imposed boundary conditions are sinusoidal pressure inlet by user defined function at one end of the tube and constant temperature or heat flux boundaries at the external walls of the cold-end heat exchangers. The experimental method to evaluate the optimum parameters of DIPTR is difficult. On the other hand, developing a computer code for CFD analysis is equally complex. The objectives of the present investigations are to ascertain the suitability of CFD based commercial package, Fluent for study of energy and fluid flow in DIPTR and to validate the CFD simulation results with available experimental data. The general results, such as the cool down behaviours of the system, phase relation between mass flow rate and pressure at cold end, the temperature profile along the wall of the cooler and refrigeration load are presented for different boundary conditions of the system. The results confirm that CFD based Fluent simulations are capable of elucidating complex periodic processes in DIPTR. The results also show that there is an excellent agreement between CFD simulation results and experimental results.     

Chlorine stable isotopes: a comparison of dual inlet and thermal ionization mass spectrometric measurements

Chlorine stable isotope ratios, 37Cl/35Cl, currently are measured using dual-inlet and thermal-ionization mass spectrometry. These two different analytical techniques, however, have never been cross calibrated. A set of samples with chlorine stable isotope delta values ranging from -4.4 to +0.3 % relative to standard mean ocean water chloride has been analyzed using both of these techniques. Our data show that both techniques can yield similar results within analytical uncertainty. CsCl thermal ionization data are extremely sensitive to the amount of chlorine being measured and cannot be used to determine absolute ratios without an independent means of correcting for machine-induced mass fractionation. As long as standards and samples are of equivalent size, however, the differences between samples measured by thermal ionization remain constant Dual inlet stable isotope mass spectrometry is suited best for samples of > 10 micromol Cl, yielding chlorine stable isotope data with < or =0.1% reproducibilities (2sigma). Thermal ionization mass spectrometry easily accommodates samples of approximately0.1-0.3 micromol Cl, with achievable uncertainties of < or =0.2% (2sigma).     

Hydromechanics of the inlet of heat-releasing apparatus

The article investigates the motion of liquid in an inlet with spiral channel, and a method is devised for calculating the design parameters of the inlet.     

Investigation of the gas inlet velocity distribution in a fixed granular bed filter

Granular bed filter (GBF) technology can be applied for high-temperature gas cleanup in integrated gasification combined-cycle (IGCC) and pressurized fluidized-bed combustion (PFBC) advanced coal-fired power plants. The design of the gas inlet component of the granular bed filter is important to achieve a uniform gas distribution and higher usage rate of the filter media. Previous studies show that the gas velocity at the inlet is not uniformly distributed. This non-uniformity may lead to a lower usage rate of the filter media. In this study a baffle device is introduced to the inlet system in order to achieve a more uniform gas velocity distribution. A more uniform gas inlet distribution can be obtained by adjustment of the lengths and angles of the baffles. The gas velocities along the inlet and filtration surfaces are measured using a pitot tube. The uniformity of the gas velocity distribution can be characterized by looking at the distributions of the standard deviation of the gas velocity and the differences in the mean velocities between the two filtration surfaces.     

Influence of inlet conditions on vortex characteristics

Vortex chambers are normally used for arc stabilization in linear plasma torches. In the present work, the effect of uniformity of the gas inlet channel distribution on the stabilizing characteristics of a swirled flow is studied numerically. The formation of a complex flow pattern with a toroidal recirculating flow area inside the vortex chamber is observed. For some regimes, two local maxima of the tangential velocity are observed in the middle section of the chamber. It is shown that an increment of the number of gas inlet channels leads to a more uniform gas input with disappearance of the second maximum, which increases the velocity amplification coefficient and, correspondingly, results in a better stabilizing effect. The obtained profiles of the radial distribution of the tangential velocity are compared with the results of Oseen’s equation for an unconfined vortex.     

Characteristics of the double inlet pulse tube

The performance of the double inlet pulse tube (DIPT) is analyzed using a linearized model that takes account of the void volume of the regenerator. The maximum rate of refrigeration obtainable with the regenerator is determined as a function of frequency and void volume. This rate can be achieved by a DIPT with infinitely large reservoir volume. Corrections resulting from a finite reservoir volume are important only at low frequency. The coefficient of performance of a DIPT with optimized rate of refrigeration is less than half of the thermodynamic maximum. The results obtained for the DIPT are compared with corresponding results for the optimized orifice pulse tube refrigerator (OPTR). The large improvements in performance obtained with the DIPT over the OPTR are due primarily to an increase in the pulse tube pressure. The maximum rate of refrigeration decreases as the temperature at the cold side decreases. This is caused primarily from the resulting decrease in cold side flow rate. At given temperature ratio, addition of the second inlet reduces the flow rate through the regenerator over a range of intermediate frequencies.