Application of a screw conveyor with axial tilt blades on a shearer drum and investigation of conveying performance based on DEM

Screw conveyors are widely employed in industrial fields for conveying bulk materials. The shearer drum which uses the screw conveying principle is responsible for excavation and conveying coal particles onto the chain conveyor. Screw conveyor performance is affected by potential factors, such as the blade axial tilt angle and style, core shaft form and diameter. The effect of blade axial tilt angle on the conveying performance was investigated with the help of DEM. In the case of the screw conveyor, the mass flow rate, and particle axial velocity increased with increasing positive axial tilt angle, and declined with increasing negative axial tilt angle. In the case of the drum, the mass flow rate, particle axial velocity, and loading rate first increased and then decreased with increasing positive axial tilt angle, and decreased with increasing negative axial tilt angle. These results can be considered as a benchmark for screw conveyor and drum structural designs with axial tilt screw blades.     

Transportation characteristics of gas-solid two-phase flow in a long-distance pipeline

In this study,experiments on fly ash conveying were carried out with a home-made long-distance positive-pressure pneumatic conveying system equipped with a high performance electrical capacitance tomography system to observe the transient characteristics of gas-solid two-phase flow.The experimental results indicated that sol ids throughput increased with increasing solids-gas ratio when the conveying pipeline was not plugged.Moreover,the optimum operating state was determined for the 1000 m long conveying pipeline with a throttle plate of 26 orifices.At this state the solids throughput was about 12.97 t/h.Additionally,the transportation pattern of fly ash gradually changed from sparse-dense flow to partial and plug flows with increasing conveying distance because of the conveying pressure loss.These experimental results provide important reference data for the development of pneumatic conveying technology.     

Transportation characteristics of gas–solid two-phase flow in a long-distance pipeline

In this study, experiments on fly ash conveying were carried out with a home-made long-distance positive-pressure pneumatic conveying system equipped with a high performance electrical capacitance tomography system to observe the transient characteristics of gas–solid two-phase flow. The experimental results indicated that solids throughput increased with increasing solids–gas ratio when the conveying pipeline was not plugged. Moreover, the optimum operating state was determined for the 1000 m long conveying pipeline with a throttle plate of 26 orifices. At this state the solids throughput was about 12.97 t/h. Additionally, the transportation pattern of fly ash gradually changed from sparse–dense flow to partial and plug flows with increasing conveying distance because of the conveying pressure loss. These experimental results provide important reference data for the development of pneumatic conveying technology.     

宾汉姆体的缓凝砂浆在单螺杆挤出机中的流动

在实验的基础上，研究了宾汉姆体的缓凝砂浆在单螺杆挤出机中的流动；运用流变学理论， 建立了缓凝砂浆螺旋输送物理模型；对缓凝砂浆螺旋输送与包裹机构的工作机理进行了分析 与研究，得出了缓凝砂浆连续输送的条件，螺杆转速必须大于临界转速. 实验发现：宾汉姆 体的缓凝砂浆在螺旋输送与包裹机构中当螺杆转速在78$\sim$240\,r/min范 围内可实现连续输送和包裹.     

The effects of Knudsen-dependent flow velocity on vibrations of a nano-pipe conveying fluid

In this paper, we investigate the effect of nano-flow on vibration of nano-pipe conveying fluid using Knudsen (Kn). We use Euler–Bernoulli plug-flow beam theory. We modify no-slip condition of nano-pipe conveying fluid based on Kn. We define a Kn-dependent flow velocity. We consider effect of slip condition, for a liquid and a gas flow. We reformulate Navier–Stokes equations, with modified versions of Kn-dependent flow velocity. We observe that for passage of gas through nano-pipe with nonzero Kn, the critical flow velocities decreased considerably as opposed to those for zero Kn. This can show that ignoring Kn effect on a gas nano-flow may cause non-conservative design of nano-devices. Furthermore, a more impressive phenomenon happens in the case of clamped-pinned pipe conveying gas fluid. While we do not observe any coupled-mode flutter for a zero Kn, we can see the coupled-mode flutter, accompanying the second-mode divergence, for a nonzero Kn.     

A parametric study on nonlinear flow-induced dynamics of a fluid-conveying cantilevered pipe in post-flutter region from macro to micro scale

A mathematical formulation is proposed to investigate the nonlinear flow-induced dynamic characteristics of a cantilevered pipe conveying fluid from macro to micro scale. The model is developed by using the extended Hamilton's principle in conjunction with the inextensibility condition and laminar and turbulent flow profiles as well as modified couple stress theory. The current model is capable of recovering the classical model of cantilevered pipe conveying fluid by neglecting the couple stress effect. The governing equation of motion is presented in dimensionless form in a convenient and usable manner. To solve the problem at hand, the integro-partial-differential equation of motion is discretized into a set of ordinary differential equations via Galerkin method. Afterward, a Runge–Kutta's finite difference scheme is employed to evaluate the nonlinear dynamic response of the cantilevered pipe conveying fluid. A parametric study is carried out to examine the influences of mass parameter and dimensionless mean flow velocity on the nonlinear dynamic characteristics of the cantilevered pipe conveying fluid in post-flutter region. The role of size-dependency in the nonlinear behavior of pipe is explored by converting the new set of dimensionless parameters into the conventional one. Eventually, some convergence studies are performed to indicate the reliability of present results.     

Effect of moisture content on conveying characteristics of pulverized coal for pressurized entrained flow gasification

During the pneumatic conveying, pulverized coal with different moisture contents may develop substantial difference in flow characteristics, whose cause is not fully understood. This study focused on influence of moisture content on conveying characteristics in an experimental test facility with the conveying pressure up to 4 MPa. The experiments included soft coal and lignite with similar density and particle size. With the increase in moisture content, the mass flow rate decreased for lignite (3.24% < M < 8.18%) but increased at first and then decreased for soft coal (0.4% < M < 6.18%) at same operating parameters. The flowability of soft coal was worse than that of lignite at similar operating parameters and external moisture content. The extremal conveying moisture contents of two coal types were obtained. The particle charge and surface moisture content were investigated to indicate influence mechanism of moisture content on mass flow rate in pneumatic conveying at high pressure. Pressure drop of soft coal was greater than that of lignite for same test section. The conveying phase diagram of dense-phase pulverized coal at high pressure was obtained and the pressure drops through different test sections were compared and analyzed. The bend loss factor rose with the increase in moisture content and was independent of conveying velocity and solid-gas ratio in dense-phase pneumatic conveying at high pressure.     

Experiments on the Onset of Impacting Motion Using a Pipe Conveying Fluid

The transition from stable periodic nonimpacting motion to impacting motion, due to variations of parameters, is observable in a wide range of vibro-impact systems. Recent theoretical studies suggest a possible scenario for this type of transition. A key element in the proposed scenario is fulfilled if the oscillatory motion involved in the transition is born in a supercritical Hopf bifurcation. If the onset of impacting motion is close to the Hopf bifurcation, the impacting motion is likely to be chaotic. A numerical simulation of a system of articulated pipes conveying fluid is used to illuminate the theory. An experimental setup is presented, where a cantilevered pipe conveying fluid is unilaterally constrained. Results from experiments are found to be in good qualitative agreement with the theory.     

粘弹性地基上粘弹性输流管道的稳定性分析

从Winkler假设和单轴线性粘弹性本构方程出发,推导了Kelvin-Voigt粘弹性地基上三参量固体模型输流管道的运动微分方程,采用改进的有限差分法,分析了管道和地基的粘弹性参数对输流管道无量纲复频率和无量纲流速之间的变化关系的影响。     

Impact of sorption phenomena on multiphase conveying processes

Twin-screw multiphase pumps are employed increasingly to convey multiphase mixtures of crude oil, accompanying fluids, associated gas and solid particles. They are positive displacement pumps and suitable for handling products containing liquid accompanied by large amounts of gas. Experimental investigations on the conveying characteristic, namely measuring the delivered volume flow as a function of the pressure difference, provide results for selected mixtures. By means of the on hand work, the influence of sorption phenomena occurring due to pressure variations alongside the conveying process on the conveying characteristics of twin-screw pumps delivering mixtures of oil and gases is measured. The employed gases are air and carbon dioxide, which differ strongly in solubility in oil. All experiments are conducted in a closed loop test facility, where oil and gas volume flows are mixed before the inlet and separated after the outlet of the multiphase pump. In order to simulate the influence of the suction side pressure drop in the reservoir on the conveying characteristic, packed beds are employed as oil-filed model. Sorption processes inside of the oil-field model and within the multiphase pump affect the conveying behaviour significantly. The two-phase flow in the inlet and outlet pipe is visualised by means of a capacitance tomography system. Results show that the oil fraction of the total delivered volume flow is decreased due to desorption at the pump inlet. The gas fraction at the pump outlet is further decreased due to absorption. Experimental results are compared to calculated solubilities of the on-hand gases in oil and to the theoretically derived gas volume flow fraction expected at the multiphase pump.     

Influence of a Wieghardt foundation on the dynamic stability of a fluid conveying pipe

This article considers the behaviour of a fluid conveying pipe on a partial elastic foundation. The model of the pipe is that of a Timoshenko beam; the foundation response is of Wieghardt type. Both material and environmental damping are taken into account. The critical value of the velocity of the fluid inducing dynamical instability of the system is evaluated as a function of the attachment ratio of the foundation for various values of the physical quantities involved. It is shown that this dependance is not always monotonic.     

On global motions of articulated tubes carrying a fluid

Global three-dimensional motions of articulated tubes conveying a fluid are studied by analytical as well as numerical methods. Several different kinds of limiting configurations and bifurcation phenomena are shown to occur in this system.     

含非线性能量汇的简支输液管非线性振动控制研究

论文建立了一个含有非线性能量汇(NES)装置并输运脉动内流的简支输液管道理论模型, 研究了NES装置对管道的非线性动力学特性与振动控制的影响. 利用Galerkin和龙格库塔法, 得到了在含NES和不含NES装置时管道动力学响应的数值结果. 研究表明, NES装置能有效地抑制管道振动. 通过对比可知, NES对管道系统的稳定性和非线性振动控制有着明显的影响. 此外, 本文还详细讨论了NES装置相关参数对系统的动力学影响. 结果表明, 增大NES的弹簧刚度、阻尼和质量比有利于管道减振, 且最佳安装位置在管道中点. 此外, 增大阻尼?能缩小失稳激励频率区域, 而其他参数的变化对失稳激励频率区域影响较小.     

气流特征对水平长管内石松子粉尘爆炸火焰结构的影响

为探索气流特征对水平长管内粉尘爆炸火焰结构的影响, 对采用加压送气传输方式形成的石松子粉尘云经静电引燃后其火焰在水平长管内的传播特性进行实验。利用热线风速仪测量不同气流条件下沿管径方向的速度分布和湍流强度分布, 采用高速摄像系统记录了火焰在水平管道内的传播过程。实验观察到, 即使管内石松子粉尘质量分数相同, 仍然会出现2种不同类型的火焰结构:一种类型火焰轮廓规则、清晰, 火焰中心为连续的黄色发光区并由红色边缘火焰包裹; 另一种类型火焰空间离散, 火焰发光区局部存在, 散乱地呈现不规则状态。详细分析不同气流条件对火焰结构的影响。     

Nonlinear vibration control of a cantilevered fluid-conveying pipe using the idea of nonlinear energy sink

Nonlinear Dynamics - Different from the both-end supported pipe conveying fluid as a conservative system, the cantilevered fluid-transporting pipe is a non-conservative system and its dynamic...     

具有弹性支承的圆管在内外部流激发下动力特性及实验研究

本文建立了具有弹性支承的圆管在内外部流激发下的力学模型.推导了内部流与静止外部流作用下圆管的耦联振动方程.提出了确定弹性系数的方法.采用振型叠加法分析圆管动力特性问题.对内部流与静止外部流情况下圆管固有频率进行了计算和测量,计算值与实验值吻合较好.另外,对内外流同时激发下圆管的固有频率进行了测量,得到若干对工程实际有用的结论.     

输流管道系统振动研究进展

从5个方面评述了近年来输流管道流固耦合振动的研究进展.概述了输流管道线性振动的动力学建模与分析方法;非线性振动及分析方法;输流管的振动试验方法、输流管的振动控制以及管道动强度设计.并提出了进一步的研究方向以及采用的相应的对策.      

Method of experimentally identifying the complex mode shape of the self-excited oscillation of a cantilevered pipe conveying fluid

Nonlinear Dynamics - The dynamics of a flexible cantilevered pipe conveying fluid have been researched for several decades. It is known that the flexible pipe undergoes self-excited vibration when...     

DEM investigation on conveying of non-spherical particles in a screw conveyor

Screw conveyors are extensively used in modern industry such as metallurgy, architecture and pharmaceutical due to their high-efficiency in the transportation of granular materials. And substantial efforts have been devoted to the study of the screw conveyors. Numerical method is an effective way to study screw conveyor. However, previous studies have mainly focused in the regime of spherical particles while the in-depth investigations for non-spherical particles that should be the most encountered in practical applications are still limited. In view of the above situations, discrete element method (DEM), which has been widely accepted in simulating the discrete systems, is utilized to investigate the conveying process of non-spherical particles in a horizontal screw conveyor, with particles being modeled by super-ellipsoids. In addition, a wear model called SIEM (Shear Impact Energy Model) is incorporated into DEM to predict the wear of screw conveyor. The DEM simulation results demonstrate that the particle shape is influential for the flow behaviors of particles and the wear of conveyor. The conveying performance evaluated quantitatively of both mass flow rate and power consumption is subsequently obtained to investigate the effect of sphericity of particle with different operation parameters. Moreover, particle collision frequency and collision energy consumption are acquired to investigate the possible particle breakage between particles and screw blade. The comparisons between particle–particle collision and particle–wall collision reveal that particles with large shape index have more possibility to be damaged in particle–wall impingement.     

Stability Analysis of Maxwell Viscoelastic Pipes Conveying Fluid with Both Ends Simply Supported

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