气力输送中弯管磨损原因分析及预防措施

分析气力输送中弯管磨损的机理,指出影响气力输送弯管磨损量的主要因素为:输送气流速度、撞击角度,料气比和输送物料的物性.为防止磨损,应采取以下措施:注意弯管选材、调整弯管结构和使用短半径弯管.采用这些措施后,可减少气力输送过程中的弯管磨损或降低由于弯管磨损而造成的对生产的影响.     

气力输送中影响弯管磨损的因素及解决办法

概述了气力输送中弯管磨损的机理,详细阐述了气力输送过程中影响弯管磨损的因素,如物料的物性,输送气速,料气比,弯管的结构及形状等主要因素对气力输送过程中弯管磨损的影响.并从弯管材料和结构两方面论述了减少弯管磨损的预防办法,并建议用短半径和一端不通T型弯头代替长半径弯头.     

气力输送系统中弯管的易磨损位置及其机理分析

气力输送技术应用广泛,但管件磨损问题影响安全性和经济性,其中弯管磨损问题是关键的磨损问题,因此确定弯管易磨损位置具有重要意义.本研究通过实验方法采用涂层模型并结合电容层析成像(ECT)测量,考察了表观气速、固体流率和颗粒粒径对不同弯径比(R/D)弯管的易磨损位置的影响.研究结果表明:在低气速时(约11 m/s),磨损位...     

气力输送中弯管压力降的研究

讨论了气力输送中弯管的压力损失,详细阐述了输送过程中各种参数,如输送气速、料气比和弯管弯曲半径、弯管结构及形状对气力输送压降和输送能力的影响,指出不同的物料在弯管结构选择上也应不同。     

气力输送系统中弯管磨损分析及应对措施

在气力输送系统中,设置弯管的主要作用是改变输送物料的运动方向,可为气力输送路径布置提供极大的灵活性。但也导致系统压力降增加,弯管磨损,以及物料破碎率增加。从物料在弯管内运动形式的角度,分析了影响弯管磨损的因素。从弯管设计的角度,提出了避免或减少弯管磨损的措施。     

在气力输送弯管中炭黑的输送特性分析

研究炭黑(固相颗粒)在气力输送通过弯管时,弯径比(δ)对输送弯管内压力损失和固相颗粒运动速度以及弯管内壁磨损的影响。当δ小于5时,随着δ的增大,输送弯管内压力损失减小和固相颗粒运动速度增大,弯管内壁磨损程度降低;当δ增大到5后,输送弯管内压力损失和固相颗粒运动速度以及弯管内壁磨损速率变化放缓。设计炭黑气力输送弯管时,δ在5～7范围内既可以使输送弯管内壁磨损程度和输送能耗降低,又可满足输送管道布局和工艺要求。     

陶瓷钢复合弯管在气力输送管道中的应用

目前,粉状物料气力输送管道的弯管通常采用无缝钢管或铸石弯管,其磨损一直是难以解决的问题。去年,牡丹江水泥厂在粉状物料气力输送管道中采用了一种陶瓷钢复合弯管,使用效果良好,使用寿命远远超过铸石弯管,现介绍如下。     

弯管气力输送炭黑的数值模拟与分析研究

建立炭黑浓相气力输送的数学模型,对炭黑在弯管中的流动状态进行数值模拟分析。结果表明,炭黑颗粒在弯管中的流动状态不稳定,应尽量减少弯管数量,且两个弯管的距离不宜太短;弯管最易磨损,弯管30°～60°外壁面处的压力最大,磨损也最大,可在弯管的易磨损部位附加可更换衬板来延长弯管的使用寿命;炭黑在弯管中的输送压降与弯径比（R/D）有关,当R/D=5时输送压降最小,最有利于炭黑的稳定输送和节能输送。     

中浓度气力输送弯管压力降数值模拟研究

对于中等浓度气力输送90°弯管内的气固流动状态进行数值模拟研究,并对水平转垂直、垂直转水平,不同弯径比(R/D=1.5~6.0)的90°弯管,均匀和非均匀粉体颗粒流过弯管的压力降Δp进行了模拟计算。结果表明,在同一气体流速下,不同R/D的弯管的Δp变化显著;存在一个使Δp最小的R/D值。在模拟的条件范围内,弯管内粉体颗粒的速度分布随R/D变化。并讨论了不同R/D的粉体颗粒流动对弯管压力降及管壁磨损的影响。在同样操作条件下,对煤粉输送进行了弯管压力降数据模拟,其模拟计算结果与周建刚等人的试验结果吻合良好。     

气力输送弯管结构替代装置流场特性数值分析

气力输送弯管转向过程中磨损和固相滞留等问题较为严重。本研究设计了一种新型连接装置,对结构进行了优化设计以减少磨损,用扩容仓代替弯管,在底部增加增压风,并利用计算流体动力学(CFD)数值方法,采用k-?标准型湍流模型,分析进出口中心线上速度比(V_a/V_0)和总压变化,及两相流颗粒分布,模拟结果表明,采用新型输送装置,将主流转向提前至垂直管道下方,利用风膜隔开主流与壁面,减少了磨损和固体颗粒滞留;增压风和主流风速比3.4时,出口速度差值最小,形成的额外阻力最小,该比例下增压风综合效果最好。     

高密度聚乙烯缠绕增强管的应用

介绍了高密度聚乙烯（HDPE）缠绕增强管的种类，性能，生产工艺及特点等。因HDPE缠绕增强管具有输水量大，铺设简便等优点，可适用于远距离低压输水，城市给排水，海水输送，以及农田灌溉等输送工程。举例阐述了使用HDPE缠绕增强管的优化，并展望了HDPE缠绕增强管的发展前景。     

炭黑在气力输送系统中的压力损失试验研究

炭黑在气力输送过程中的输送参数的确定大多以经验为主,极易造成输送效率的降低以及输送过程的不稳定对炭黑在输送管道中进行气力输送试验,分析了其在水平管、垂直管和弯管中的输送压力损失,分别得到了在这三种输送管道中的压力损失计算公式：该公式可作为工程上分析炭黑与气体混合流在输送管道中压力损失的经验公式。     

金刚石材料钻杆接头防磨带可行性研究

通过分析钻杆井下运动状态得出钻杆接头磨损机理,从理论上分析了聚晶金刚石作为钻杆接头耐磨材料的可行性。利用摩擦磨损试验机,模拟钻杆接头井下工况;通过防磨带试件分别与套管或岩样进行摩擦试验,模拟钻杆与套管或钻杆与裸眼段井壁的摩擦。通过使用水和钻井液两种不同的润滑液模拟不同润滑条件,得出润滑液对金刚石防磨带耐磨性的影响效果。试验结果表明,长方形金刚石防磨带设计合理,有良好的耐磨性能及保护套管的作用。     

石灰石粉密相气流输送中试研究

用石灰石粉进行长度分别为62m和167m两种不同输送距离、管径为80mm的中试研究，通过获得的有关水平管、垂直管、弯管的压降数据及不同输送距离条件下的固气比数据，提出了密相技术输送这种粉料的压降的关联式和固气比关联式，再通过计算程序，可以较好地模拟实验过程，说明所获得的计算关联式可以用于石粉输送的工艺设计，为石粉的输送工程设计奠定了基础。     

煤粉高压密相气力输送稳定性分析

在自主研发的密相气力输送实验装置上,以N₂作输送载气,以3种不同粒径的褐煤作输送物料进行输送实验,运用域重标分析方法对水平管差压信号和料罐质量脉动序列进行了Hurst指数分析,并采用统计学方法对料罐质量脉动序列进行了标准差分析,从管内流动和料罐出料出发,对整体输送稳定性进行了探讨。结果表明：水平管差压信号Hurst指数H_dp能较好地表征管内流动稳定性,而料罐质量脉动Hurst指数H_ma则需结合标准差分析才能更好地表征料罐出料稳定性。以表观气速与跃移速度比值K为特征参数进行探讨,在K=1.5左侧,随着K值减小,H_dp减小,管内流型发生转变,甚至可能发生堵管,管内流动稳定性变差,料罐质量脉动标准差增大,出料稳定性变差,整体输送稳定性变差;在K=1.5右侧,随着K值增大,H_dp减小趋势不明显,管内流动稳定性虽有变差的趋势,但不会发生堵管,而结合对料罐质量脉动序列的标准差分析,发现出料稳定性变差,甚至可能出现出料中断的情况,整体输送稳定性变差。     

Voidage waves in hydraulic conveying through narrow pipes

The nature of voidage waves in hydraulic conveying systems has been investigated computationally in this study. Voidage waves consisting of alternating regions of high and low solid fractions were observed to form spontaneously in hydraulic conveying through vertical pipes. The wavelengths of these voidage waves were found to be inversely related to mean solid fraction but independent of liquid conveying velocities for elastic solid particles. The wave structure in terms of the thickness and shape of the solid fraction profile over each dense phase was dependent on the mean solid fraction used. Pressure distributions along the longitudinal direction of the conveying pipe exhibited an interesting ‘step’ profile due to unequal pressure drops across the dense and dilute regions. With inelastic solid particles, a lower tendency for voidage wave formation was observed and a phase diagram was constructed to show combinations of operating conditions under which voidage waves would form. Finally, the study of voidage waves in hydraulic conveying systems was extended to the case of hydraulic conveying through horizontal channels. In addition to the various system parameters, voidage wave formation in this case was also affected by gravitational settling of the solid particles.     

Effect of mechanical properties of powder on pneumatic conveying in inclined pipe

Pneumatic conveying of fine powder has merits, such as no dust pollution and wide flexibility of pipeline layout. Thus, pneumatic conveying is widely used in industry. However, there is no information about the relation between the pressure drop for pneumatic conveying of fine powder and the mechanical properties of powder.We explained that the pressure drop of pneumatic conveying of powder in a horizontal pipe could be estimated from the dynamic friction coefficient of the powder in the previous paper. However, the relation between the pressure drop of pneumatic conveying in an inclined pipe and the mechanical properties of the powder is not cleared yet.The effect of mechanical properties and the angle of an inclined pipe on the pressure drop for pneumatic conveying of fine powder was examined and compared with the calculated results by our model. Based on these results, it is cleared that the pressure drop for pneumatic conveying of fine powder can be estimated from the dynamic friction coefficient of the powder and the inclined angle of the pipe.     

炭黑气力输送流动特性研究

对气力输送过程中炭黑的流动特性进行了试验研究.依据试验结果,分析了炭黑的粒径大小与输送管道阻力、输送压力与输送管道压力损失、气体流量与炭黑的质量流量、输送压力与炭黑粒子破碎率之间的关系,为炭黑气力输送系统的设计及其工艺参数的确定提供参考.     

Vertical pneumatic conveying of particle plugs

Dense-phase pneumatic conveying of solids offers many advantages over dilute-phase conveying. The lower air velocities, and, consequently, lower particle velocities, result in lower pipe wear and lower particle attrition. This paper describes an experimental program that has been undertaken to study the flow pattern of cohesionless solids in vertical transport and to measure the parameters influencing the pressure drop required to move a single plug of solids. Highspeed photographic techniques have been used to observe the flow pattern of polyethylene particles (diameter ? 3 mm) in the vertical riser section of a circulating unit constructed from pipes with an internal diameter of 50.8 mm. The flow pattern resembles that of square-nosed slugging in a fluidized bed. The solids move up as “plugs” of bulk solids that occupy the entire cross-section of the pipe. Particles are seen to “rain” down from the back of one plug and then to be collected by the front of the next plug. Collecting these particles causes a stress on the plug front which is transmitted by powder mechanics forces axially through the plug and radially to the wall. The pressure drop required to move a single plug of cohesionless solids through the transport pipeline was measured as a function of the plug length, particle properties, pipe diameter, and the frontal stress. The results of these experiments are compared with a theoretical model.     

The influence of particle shape on flow modes in pneumatic conveying

The transportation of particles along pipes or ducts using an imposed gas flow is known as pneumatic conveying. The type of granular flow in such systems is strongly dependent on the imposed gas flow rate, and can be categorised by a distinct set of modes. These modes range from dilute flow, where the grains are entirely suspended in the gas, to moving dunes and slug flow, in which the bore of the pipe is blocked by a slow moving plug of material. Understanding the transitions between these modes is critical to the design and application of pneumatic conveying systems. Particle shape is a crucial factor in systems with gas–grain interactions but has so far been overlooked in models of pneumatic conveying. We carry out a series of simulations using the discrete element method coupled to gas flow and show that particle shape is critical to the transition between different flow modes. Particles which are spherical, or nearly spherical, transition to slug flow at high gas flow rates, whereas non-spherical particles transition instead to dilute flow. We show the lower voidage fraction in beds of non-spherical particles is crucial to explaining this behaviour.