气力输送闭式管路系统特性分析

提出了气力输送闭式管路系统这一新的思路，给出了气力输送闭式管路系统除法特性的计算方法，分析结果表明，气力输送闭式管路系统较 开式管线系统具有能循环利用气流功能、不需高效除尘器、总排尘量大幅度减少等优点。     

粉体性能对浓相气力输送特性的影响

气力输送过程中物料性能是确定输送特性的重要因素．因此．粉料气力输送技术的实现要以对粉料的性能研究为基础．文中对影响气力输送的粉体基本性能及其相关参数做了较全面分析．其中粒子尺寸、粒径分布、形状是影响粉料是否可适用于浓相气力输送的关键参数．其它特性都与这3种特性相关联。介绍了几种应用广泛的粉料气力输送特性分组方法．并进行了简要评述．同时指出了今后的研究方向。     

粉体性能对浓相气力输送特性的影响

气力输送过程中物料性能是确定输送特性的重要因素,因此,粉料气力输送技术的实现要以对粉料的性能研究为基础。文中对影响气力输送的粉体基本性能及其相关参数做了较全面分析,其中粒子尺寸、粒径分布、形状是影响粉料是否可适用于浓相气力输送的关键参数,其它特性都与这3种特性相关联。介绍了几种应用广泛的粉料气力输送特性分组方法,并进行了简要评述,同时指出了今后的研究方向。     

桥梁全寿命周期成本分析

桥梁从建设投资到运营再到拆除都影响着桥梁工程建设投资费用的管理控制,本论文从桥梁全寿命周期成本的角度详细探讨了桥梁在使用过程的各个阶段的成本费用,首先介绍了桥梁全寿命周期成本分析的基础流程,在此基础上重点从建设期成本、营运期成本、养护期成本和拆除成本等几个角度详细具体探讨了桥梁全寿命周期成本费用,对于进一步提高桥梁全寿命周期成本分析的应用及桥梁成本费用管理控制具有一定借鉴意义。     

小麦气力输送流场颗粒流化特性数值模拟

目的 探索仓泵式气力输送小麦颗粒时不同输送压力下罐体及引出管内颗粒的流化特性,从而得出最佳操作压力。方法 利用Solidworks建立简易的等比例发送装置三维模型,采用模拟仿真软件Fluent对0.25、0.3、0.35 MPa等3种不同输送压力进行数值模拟,并利用CFD–Post进行数据后处理。结果 当进气口压力为0.35 MPa时物料最先输送完毕,用时为10 s。整体发料过程从引出管入口至出口处三者压力分别降低了97.1%、96.8%、98.1%,其中当进气口压力为0.3 MPa时,压力降低最小,能量利用率最高。结论 输送压力越大输送速度越快,其压降也最大。考虑经济性与高效性可得,最佳进气口压力为0.3 MPa。     

炭黑在气力输送系统中的破碎原因的分析

分析了炭黑在气力输送过程中的破碎机理．通过实验．介绍了气力输送系统中炭黑的种类和炭黑的物性对炭黑的破碎的影响．指出气力输送系统的输送管路长度和布置以及输送参数如输送压力和输送速度等的变化直接影响着炭黑的破碎率的大小．为更好地解决炭黑在气力输送中存在的问题,优化炭黑气力输送系统的设计提供了依据．     

炭黑在气力输送系统中的破碎原因的分析

分析了炭黑在气力输送过程中的破碎机理。通过实验,介绍了气力输送系统中炭黑的种类和炭黑的物性对炭黑的破碎的影响,指出气力输送系统的输送管路长度和布置以及输送参数如输送压力和输送速度等的变化直接影响着炭黑的破碎率的大小。为更好地解决炭黑在气力输送中存在的问题,优化炭黑气力输送系统的设计提供了依据。     

用周期倍差法评价数据采集系统的动态特性

数据采集系统的采样周期是有下限的,即其采集速率不可能无限高,这在实际应用中常常限了其瞬态响应特性的获得。本介绍了一种方法,通过对其加载特定周期性输入信号,利用采要周期的整数倍和信号周期的整数倍间的微小偏差,获得比实际采样周期小得多的等效采样周期,从而解决了数据采集系统瞬态响应特性的获取问题。     

气力输送系统中弯管耐磨性的研究

在气力输送系统在多个领域得到广泛应用的同时,系统弯管磨损问题也引起了人们的关注。基于这种情况,本文对气力输送系统中弯管的磨损机理进行了分析,然后对系统弯管耐磨性的影响因素和增强方法展开了研究,以期为关注这一话题的人们提供参考。     

石灰长距离气力输送系统的试验研究

基于气力输送理论,通过石灰的长距离输送试验系统的建立,研究输送过程中耗气量、管道压力损失、物料输送前后的状态等重要输送特性。结果表明,将气力输送应用在长距离的石灰输送上是完全可行的,可解决钢铁行业的高粉尘污染问题,极大地改善工作环境。     

基于砂丘模型的气力输送粒子运动特性

针对气力输送过程中存在严重能量损失问题,在水平管气力输送系统的粒子入口附近安装砂丘模型,探讨系统最小压力损失和最小输送速度;为了揭示砂丘模型的节能机理,采用粒子图像测速(PIV)技术和快速傅里叶变换(FFT)分别对各个工况加速区的粒子平均速度和粒子脉动速度进行测量与分析。结果表明:同样的空气输送速度下,安装砂丘模型进行输送时,粒子平均速度和粒子脉动速度的功率谱密度峰值明显大于传统气力输送系统,并且自相关系数呈现准周期变化;粒子脉动速度的两点相关系数明显大于传统的气力输送系统;在管顶部附近,粒子速度脉动强度大于传统的气力输送系统。     

Particle dynamics analysis in bend in a horizontal-vertical pneumatic conveying system with oscillatory flow

The pneumatic system is frequently operated in the high air velocity region, which aggravates the power consumption and erosion of bend, and the intensive study of the particles motion characteristic on a horizontal-vertical pneumatic conveying in various curved 90° bends is necessary. This experimental study focuses on the particles motion characteristic of bend on the horizontal-vertical pneumatic conveying with oscillatory flow (generated by installing the oscillator) in terms of on pressure drop, powder consumption, the evolution of particle velocity and particle fluctuating intensity during flowing through bends. The results indicate that powder consumption can be reduced by using oscillatory flow, which is more obvious with a larger radius ratios bend. Meanwhile, the pressure drop proportion of bend is higher than average pressure drop of the system within the same distance. Otherwise, the total reduction particles velocity through bend is less while using oscillatory flow, which is more obvious using larger radius ratios bend. The particle velocity using oscillatory flow is higher than that of the conventional pneumatic conveying for the cases of larger radius ratios bend, and this effect is less evident while through a smaller radius bend.     

Wavelet multi-resolution analysis on particle dynamics in a horizontal pneumatic conveying

The particle velocities are measured by the high-speed particle image velocimetry (PIV) in the acceleration and fully developed regimes of a horizontal pneumatic conveying. Based on the measured particle fluctuation velocities, continuous wavelet transform and one-dimensional orthogonal wavelet decomposition were applied to reveal particle dynamics in terms of time frequency analysis, the contribution from wavelet level to the particle fluctuation energy, spatial correlation and probability distribution of wavelet levels. The time frequency characteristics of particle fluctuation velocity suggest that the small-scale particle motions are suppressed and tend to transfer into large scale particle motions from acceleration regime to fully developed regime. In the near bottom part of pipe, the fluctuation energy of axial particle motion is mainly contributed from the wavelet levels of relatively low frequency, however, in the near top part of pipe, wavelet levels of relatively high frequency make comparable contribution to the axial particle fluctuation energy in the suspension flow regime, and this contribution decreases as particles are accelerated along the pipe. The low frequency wavelet levels exhibit large spatial correlation, and this spatial correlation increases as the particles flow from acceleration regime to fully developed regime. The skewness factor and kurtosis factor of wavelet level suggest that the deviation of Gaussian probability distribution is associated with the central frequency of wavelet level, and the deviation from Gaussian distribution is more evident as increasing central frequency. The higher wavelet levels can be linked to small sale particle motions, which lead to irregular particle fluctuation velocity.     

基于全寿命周期费用分析法的风管系统的选择

针对目前国内还没有一种有效的方法用于选择和评价风管系统的现状,提出采用全寿命周期费用分析法来选择和评价风管系统,并在实际工程中,采用该方法比较和分析国内4种常见风管系统的一次性投资、能耗费和维护费,重点对各风管的全寿命周期费用进行评估,认为酚醛铝箔复合风管的费用最低,是一种值得推广的风管系统。     

An experimental study on a horizontal-vertical pneumatic conveying system using oscillatory flow

To reduce the power consumption of a horizontal-vertical pneumatic conveying system, an oscillator is mounted with a 45° oblique plane through the pipe axis in this study. This experimental study focuses on the effect of oscillatory flow using the oscillator on the horizontal-vertical pneumatic conveying system in terms of the overall pressure drop of the system, power consumption, local pressure drop, and particle velocity. Compared with conventional pneumatic conveying (axial-flow), the pressure drop and power consumption can be reduced using the oscillatory flow in a lower air velocity range. Meanwhile, the particle axial velocity of the oscillatory flow is higher than that of the axial-flow near the bottom of pipe. This outcome indicates that the accelerating effect of oscillatory flow is obvious near the bottom of the pipe, and the particle vertical velocity of the oscillatory flow is positive, whereas the particle vertical velocity of the axial-flow is almost negative. This result shows that the particles of the oscillatory flow are suspended sufficiently, but the particles of the axial-flow have a tendency of deposition. Furthermore, the fluctuation intensity of the particle velocity of the oscillatory flow is higher than that of the axial-flow, especially near the bottom of the pipe.     

Experimental and numerical study on the horizontal-vertical pneumatic conveying system with pulse excitation flow based on POD and recursive analysis

To solve the problem of energy loss during pneumatic conveying, a new energy-saving method of pneumatic transportation, pulse excitation flow, is proposed and applied to the transportation of petroleum coke. Firstly, the minimum pressure drop velocity of petroleum coke transported by pulse excitation flow is obtained through experimental research, and then the energy-saving mechanism of pulse excitation flow is explored through CFD-EDM coupling. The experimental results show that the energy loss coefficient of pulse excitation flow is reduced by 12.6% compared with axial flow. The numerical results show that the pulse excitation flow will produce alternating positive and negative vortices, and using the pulse excited flow conveying can make the particles enter the suspension region 6D earlier and reduce the energy loss, which further indicates that the gas–solid coupling effect of the pulsed excitation flow is more conducive to the dispersion and acceleration of the particles compared with axial flow.     

Computational model for prediction of particle degradation during dilute-phase pneumatic conveying: modeling of dilute-phase pneumatic conveying

A complete model of particle impact degradation during dilute-phase pneumatic conveying is developed, which combines a degradation model, based on the experimental determination of breakage matrices, and a physical model of solids and gas flow in the pipeline. The solids flow in a straight pipe element is represented by a model consisting of two zones: a strand-type flow zone immediately downstream of a bend, followed by a fully suspended flow region after dispersion of the strand. The breakage matrices constructed from data on 90° angle single-impact tests are shown to give a good representation of the degradation occurring in a pipe bend of 90° angle. Numerical results are presented for degradation of granulated sugar in a large scale pneumatic conveyor.     

Effect of particle size distribution on hydrodynamics of pneumatic conveying system based on CPFD simulation

The effect of particle size distribution on the hydrodynamics of dilute-phase pneumatic conveying system was analyzed using computational particle fluid dynamics (CPFD) simulation. The influence of a simulation parameter, i.e., correction factor of drag coefficient (k), on the hydrodynamics of pneumatic conveying system was determined via CPFD simulation. When results of simulation were compared with experimental data of previous studies, the average error of pressure drop per length predicted by the CPFD approach with the correction factor was below 4.4%. Saltation velocity and the pressure drop per unit length declined as the drag force coefficient increased. Simulation results also revealed that the pressure drop per length and the saltation velocity were decreased when the fine powder fraction in the particle size distribution was increased, although the width of particle size distribution was widened, and the standard deviation was increased. Finally, the Relative Standard Deviation (RSD) of pressure drop per length was measured and compared with median diameter (d₅₀), Sauter mean diameter, geometric mean diameter, and arithmetic mean diameter. The RSD of the Sauter mean diameter was 5.8%, approximately twice less than the RSD value of d₅₀ commonly used in pneumatic conveying.     

木质生物质热解二级脉冲式气力进料试验研究

为解决热解进料气体反喷问题,设计了二级脉冲式气力输送进料试验装置。为确定该装置颗粒质量流量的频率调控方法,以木质生物质锯末颗粒为物料,提出并优化了气力进料频率匹配调控方案。在自主设计搭建的试验台上,考察了A、B两级电磁阀的开闭频率对颗粒质量流量的影响。结果表明:减小喷嘴直径,每周期适当关闭电磁阀A,有利于提高颗粒质量流量,但关闭时间不宜超过滞留时间(约0.7~0.9 s);两级电磁阀最佳频率匹配方案为A开B闭(0.8~1.2 s)—A开B开(0.2~0.5 s)—A闭B开(0.7~0.9 s)—A开B开(0.8~1.0 s);在该方案下落叶松锯末平均颗粒质量流量约为21 g/min。     

正压开放式气力输送水泥的流动特性

针对目前大宗正压开放式气力输送粉体过程中出现的料位低于临界料位值后会出现大面积腾涌、输送效率大幅度下降的问题,以山东省莒县某大型水泥钢板仓为研究对象,通过相似理论模拟设计开发开放式气力输送仓泵,并据此建立开放式气力输送系统;在该系统上以水泥粉体为输送物料,压缩空气为输送动力进行实验研究。结果表明:正压开放式气力输送过程中,固体质量流率、压力损失随料位的减小出现先增大后减小的趋势,拐点处对应的料位为临界料位。同时,研究发现临界料位随气体表观速度与平均固气质量比的增大呈减小趋势。