双介质喷嘴气相流速对雾化效果的影响

烟草香料的雾化是烟草加料的重要环节,为了提高雾化均匀性和降低雾化成本,首先通过inventor软件对双介质雾化喷嘴进行等比例三维建模,并通过icem软件对其进行网格划分,其次采用Fluent软件的k-ε湍流模型以及vof多相流模型进行雾化模拟。研究表明:当气相流速为0,即喷嘴为单相流时,雾化效果最差,这也验证了双介质喷嘴相对于单介质喷嘴的优越性。当液相流速保持不变时,随着气相流速的增大,在一定范围内扩散效果变好,雾化效果越好。

倾斜气井积液临界气相流速预测新模型

井筒积液是气井生产过程中常见的现象,特别对于页岩气、致密气等低渗透性气井,积液产生一定的背压会使得气井产量进一步降低,严重情况下会导致气井停产。准确预测气井积液临界气相流速可以指导生产者及时采取积液防治措施。斜井中液膜在重力作用下不均匀分布,使得其内部的积液研究较为复杂。通过对比已有的实验和理论研究,分析认为液膜的反向流动是积液的主要原因,并且起始于井筒横截面底部最厚处的液膜;通过分析斜井井筒中液膜速度分布规律,确定以液膜与井壁剪切应力为0作为积液判定条件。基于环雾流型并考虑斜井井筒中液膜周向不均匀分布、气芯液滴夹带的影响,建立适用于不同管径、不同液相流量的全倾角气井积液预测新模型。利用井斜角为0°~88°的实验数据、直井和斜井的现场生产数据对新模型及已有的6种积液预测模型进行分析验证的结果显示,基于零液壁剪切应力的新模型相比于其他模型更能准确地预测全倾角气井积液临界气相流速。

气井积液临界气速预测新方法

气井产生积液后,气体流速不足以将液体完全提升到地面,可能导致气井停产。准确预测气井临界气速可以提醒操作人员及时采取措施以预防积液发生。基于环状流最小气液界面剪切应力准则,结合管壁均匀液膜速度流场解析解,建立了临界气速预测新模型。该模型通过联立环状流的液相流量与气相动量方程得到气液界面剪切应力表达式,令其导数为零求解临界气速,简化了积液模型的求解流程。新模型考虑了井斜角、管径、压力和气芯中液滴夹带等因素对积液临界气速的影响。收集国内外不同文献中的室内实验数据以及现场生产数据,评估新模型和其他具有代表性的积液模型预测临界气速的精度,表明新模型要优于其他积液模型。对于管径为1 in、2 in、3 in、4 in、6 in垂直和倾斜管道实验室积液实验,新模型预测平均相对误差为1%;对于管径为2.441 in~4.28 in的直井和管径为1.75 in~6.18 in、井斜角为13°~64°的斜井,新模型预测的临界气速较生产数据平均相对误差不超过23%。

加工高酸原油的常压塔塔顶挥发线腐蚀及防护

某加工高酸原油的常减压装置的常压塔塔顶(常顶)挥发线,在线腐蚀探针监测数据长时间超过控制指标,检修发现常顶挥发线有较多蚀坑减薄部位,存在腐蚀泄漏风险。通过分析定点测厚情况、探针腐蚀速率、探针腐蚀垢物、常顶含硫污水腐蚀介质,结合常顶挥发线中介质流速的计算,识别出两个加剧腐蚀过程的主要因素:常顶挥发线介质中存在浓度高达390~600 mg/L的多种小分子有机酸,以及塔顶介质的高流速。针对常顶挥发线的腐蚀问题,采取了两项有针对性的措施:控制常顶石脑油流量不超过150 t/h,以减少腐蚀介质在系统内的积累;优化中和剂的选型,确保中和剂能够有效中和系统中的酸性物质,从而显著降低腐蚀速率。通过实施这些工艺措施,改善了常顶挥发线的腐蚀情况,延长了设备的使用寿命,确保了装置能够长期、稳定、安全地运行。

严重段塞流周期特性实验研究

为探索流动参数对周期特性的影响规律,在中国石油大学(华东)油气储运实验室的下倾-立管实验系统上对严重段塞流进行了实验研究。实验管道的内径为0.051m,其中下倾管段长10.4m,立管高度4.0m。实验介质为水和空气。实验发现,严重段塞流的周期随气相折算流速的增大而减小;随液相折算流速的增大而减小;随下倾管倾角的增大而减小。气相折算流速较大的工况下液相折算流速和下倾管倾角变化对严重段塞流周期的影响要小于气相折算流速较小的工况。气相折算流速变化对严重段塞流周期的影响大于液相折算流速和下倾管倾角变化产生的影响,是严重段塞流周期的主要影响因素。文中还给出了严重段塞流周期的实验关联式,与实验数据符合很好。

Review of gas-solid two phase flow rate-concentration detection technology

The indirect detection method basic principle of rate and concentration,application range and research results on gassolid two phase flow were discussed.The present development situation and the existing problems of rate and concentration detection technology were analyzed and summarized.Emphatically analyzed the existing problems in the industrial application and research status of electrostatic method in measuring phase concentration.Design criterion of electrostatic phase concentration sensor is given,the superiority and wide industrial application prospect of the sensor used for phase concentration measurement are clarified.

Hydrodynamic Behavior in a Rotating Zigzag Bed

As a high gravity(HIGEE)unit,the rotating packed bed(RPB)uses centrifugal force to intensify mass transfer.Zigzag rotating bed(RZB)is a new type of HIGEE unit.The rotor of RZB consists of stationary discs and rotating discs,forming zigzag channels for liquid-gas flow and mass transfer.As in RPBs,some hydrodynamic behavior in RZB is interesting but no satisfactory explanation.In this study,the experiments were carried on in a RZB unit with a rotor of 600 mm in diameter using air-water system.The gas pressure drop and power consumption were measured with two types of rotating baffle for RZB rotors,one with perforations and another with shutter openings. The circumferential velocities of gas were measured with a five-hole Pitot probe.The pressure drop decreased rapidly when the liquid was introduced to the rotor,because the circumferential velocity of the liquid droplets was lower than that of the gas,reducing the circumferential velocity of gas and the centrifugal pressure drop.The power consumption decreased first when the gas entered the RZB rotor,because the gas with higher circumferential velocity facilitates the rotation of baffles.

Turbulent Liquid Flow in a Gas-Liquid Bubble Column

The radial distribution of the axial component of time-average liquid velocity and turbulent intensity in a gas-liquid bubble column was investigated experimentally using Laser Doppler Anemometer (LDA). The effects of operating parameters on liquid turbulent intensity are studied and an empirical relationship between turbulent intensity and viscosity was established. Such a relationship can be used conveniently in the calculation of liquid velocity profiles in bubble columns.

Velocity Slip and Interfacial Momentum Transfer in the Transient Section of Supersonic Gas-Droplet Two-Phase Flows

Modelling and simulations are conducted on velocity slip and interfacial momentum transfer for supersonic two-pha.se (gas-droplet) flow in the transient section inside and outside a Laval jet(LJ). The initial velocity slip between gas and droplets causes an interfacial momentum transfer flux as high as (2.0-5.0) x 104 Pa. The relaxation time corresponding to this transient process is in the range of 0.015-0.090ms for the two-phase flow formed inside the LJ and less than 0.5ms outside the LJ. It demonstrates the unique performance of this system for application to fast chemical reactions using electrically active media with a lifetime in the order of 1 ms. Through the simulations of the transient processes with initial Mach number Mg from 2.783 to 4.194 at different axial positions inside the LJ, it is found that Mg has the strongest effect on the process. The momentum flux increases as the Mach number decreases. Due to compression by the shock wave at the end of the LJ, the flow pattern becomes two dimensional and viscous outside the LJ. Laser Doppler velocirneter (LDV) measurements of droplet velocities outside the LJ are in reasonably good agreement with the results of the simulation.

The Effect of Eddy-bubble Interaction Model on the Turbulent Dispersion of Gas Bubbles in Stirred Tanks

Based on trajectory equations of gas bubble,an eddy-bubble interaction(EBI)model was developed. This model considered the effect of non-drag forces and took the eddy-bubble interaction time as the refreshing time scale of turbulent fluctuations.The relationship between the crossing-eddy time and the eddy lifetime was discussed,and the predicted distributions of radial,axial velocities of bubbles and gas holdup were also given. Compared with eddy lifetime(EL)model,the EBI model gives somewhat smaller axial velocity in the upper circulation region and larger velocity in the lower circulation region,causing that fewer bubbles reach the lower circulation region and gas holdup becomes higher in the upper circulation region.The predicted gas holdup by the EBI model approaches closer to the experimental data in the discharge stream region.

Turbulent Characteristic of Liquid Around a Chain of Bubbles in Non-Newtonian Fluid

The turbulence behavior of gas-liquid two-phase flow plays an important role in heat transfer and mass transfer in many chemical processes. In this work, a 2D particle image velocimetry (PIV) was used to investigate the turbulent characteristic of fluid induced by a chain of bubbles rising in Newtonian and non-Newtonian fluids. The instantaneous flow field, turbulent kinetic energy (TKE) and TKE dissipation rate were measured. The results demonstrated that the TKE profiles were almost symmetrical along the column center and showed higher values in the central region of the column. The TKE was enhanced with the increase of gas flow and decrease of liquid viscosity. The maximum TKE dissipation rate appeared on both sides of the bubble chain, and increased with the increase of gas flow rate or liquid viscosity. These results provide an understanding for gas-liquid mass transfer in non-Newtonian fluids.

An Experimental Study of Air-Solid Two-Phase Flow in a 90° Bend Using LDV System

The measurements of the mean streamwise and radial velocities,the associated turbulence and the relative particle densities were made in an air-solid two-phase flow in a square sectioned (30mm×30mm)90°vertical to horizontal bend using laser Doppler velocimetry.The radius ratio of the bend was 2.0.Glass beads of 100μm in diameter were employed to form the solid phase.The measurements of air and solid phases were performed separately at the same bulk velocity 19.34m/s,corresponding to a Reynolds number of 3.87×10~4.The mass ratio of solid to air was 1.6%.The results indicate that the particle trajectories are very close to straight lines. The streamwise velocity profiles for the gas and the solids cross over near the outer wall with the solids having the higher speed.At θ=30°and 45°,particle-wall collisions happen mostly in the region from θ=30°to θ=75°,and cause a sudden change in solid velocity.The particles tend to move towards the outer wall in 90° bend.The particle concentration near the outer wall is much higher than that near the inner wall in the bend, and there are few particles in the inside of the bend.The bend leads to apparent phase separation:atθ=45°, the solids concentrate in the half of the duct near the outer wall.Afterθ=60°the second peak concentration appears,and goes gradually towards the inner wall.

Numerical Investigation of Influence of Rotor/Stator Interaction on Blade Boundary Layer Flow in a Low Speed Compressor

Numerical method was applied to the unsteady flow simulation at the mid span of a two-stage low speed compressor,and the blade boundary layer flow under rotor/stator interaction was investigated.By the model of wake/boundary layer interaction provided in this paper,the simulated blade frictional force and the boundary layer turbulent kinetic energy,the influence of wake/potential flow interaction on the blade boundary layer flow was analyzed in detail.The results show that under the condition of rotor/stator interaction,the wake is able to induce the stator laminar boundary layer flow to develop into turbulent flow within a certain range of wake interaction.In the stator suction boundary layer,an undisturbed region occurs behind the rotor wake,which extends the laminar flow range,and the wake with high turbulent intensity has the capability to control the boundary layer separation under adverse pressure gradient.

Experimental Study on Structural Optimization of a Supercritical Circulating Fluidized Bed Boiler with an Annular Furnace and Six Cyclones

Annular furnace CFBs with six cyclones represent new designs for large capacity CFB boilers over 660 MW. To investigate the gas-solid flow non-uniformity and its main influencing factors, an experimental study was carried out in the cold-test rig of an annular furnace CFB with six cyclones. The influence of furnace structure and cyclone arrangement on the non-uniformity of gas-solid flow was obtained. On the basis of these findings, the structure of the annular furnace CFB with six cyclones was optimized, and an optimal structure was obtained. The results show that for newly designed annular furnace CFBs, the non-uniformity of gas-solid flow among loops is no greater than that of traditional CFBs. In terms of uniformity, side cyclones rotating inward are superior to those rotating outward. The position of the side cyclones determines the basic solid circulating rate distribution trend and can dramatically improve flow non-uniformity. The middle cyclone positions and the symmetric modes of the cyclones do not determine the solid circulating rate distribution trend and have less effect on DEVGs. Forty-five degree chamfers of outer ring walls can reduce wall erosion and the non-uniformity of gas-solid flow in the circulating fluidized bed. Regarding the operating and structural conditions in this work, the optimal structure of annular furnace CFBs is Type 6: side cyclones rotating inward and b = a/2, d = 0.1c; the center of the middle cyclone inlet located at the centerline of the furnace cross-section; cyclones on the two sides of the furnace in an axisymmetric arrangement; and a furnace corner shape of 45° chamfers. Under the given operating conditions, the DEV_(Gs) for the optimal structure are approximately 4.0%~10.3%.

Solutions to Forced and Unforced Lin–Reissner–Tsien Equations for Transonic Gas Flows on Various Length Scales

The Lin–Reissner–Tsien equation is useful for studying transonic gas flows, and has appeared in both forced and unforced forms in the literature. Defining arbitrary spatial scalings, we are able to obtain a family of exact similarity solutions depending on one free parameter in addition to the model parameter holding the scalings. Numerical solutions compare favorably with the exact solutions in regions where the exact solutions are valid. Mixed wave-similarity solutions, which describe wave propagation in one variable and self-similar scaling of the entire solution, are also given,and we show that such solutions can only exist when the wave propagation is sufficiently slow. We also extend the Lin–Reissner–Tsien equation to have a forcing term, as such equations have entered the physics literature recently. We obtain both wave and self-similar solutions for the forced equations, and we are able to give conditions under which the force function allows for exact solutions. We then demonstrate how to obtain these exact solutions in both the traveling wave and self-similar cases. There results constitute new and potentially physically interesting exact solutions of the Lin–Reissner–Tsien equation and in particular suggest that the forced Lin–Reissner–Tsien equation warrants further study.