8管道材质、走向及弯头

8管道材质、走向及弯头 8 Pipeline Material, Orientation, and Bends管道材料、走向、及弯头 1 INTRODUCTION介绍 A major advantage that pneumatic conveying systems have over alternative mechanical conveying systems is in flexibility in continuous pipeline routing. Pipelines can run horizontally, and with bends in the pipeline, flows can go vertically up or vertically down, with little restriction on numbers of bends or distances. Pipelines inclined upwards are not generally recommended and so flow in inclined pipelines is examined.气力输送系统相对机械输送系统的一个重要的优点是是管道可以方便的布置。水 平管道通过弯头，可以垂直向上或向下，对弯头的数量或距离几乎没有限制。一般不建议管道倾斜向 上，因此要诊察倾斜管道内的流动。 Up to now pressure gradient has been discussed in global terms of pressure drop available and distance over which a material must be conveyed, with high pressure gradients being required for dense phase conveying. Data is included in this chapter to show how pressure gradient varies with conveying parameters for horizontal and vertical conveying in both dilute and dense phase flows. 截至目前，我们已经讨论了许可压 降及物料必须被输送的距离方面的压力梯度的问 题 快递公司问题件快递公司问题件货款处理关于圆的周长面积重点题型关于解方程组的题及答案关于南海问题 ，密相输送要求有高的压力梯度。本章中的数据将 用来说明压力梯度是怎样随稀相及密相流动中水平和垂直流动常数而变化的。 Conveying parameters were introduced in the previous chapter for pipeline bore and conveying distance. In this chapter scaling parameters are presented for other pipeline features including vertical flow. The influence of conveying parameters on pressure drop across bends is considered, for both dilute and dense phase flow, and losses are presented in terms of both a pressure drop and an equivalent length. Pipeline material is also considered, with particular reference to the use of flexible rubber hose.上一章中已经介绍了管道口径和输送距离等输送参数。在这一章将提出 其它管道特征，包括垂直流动的换算参数。将研究稀相和密相流动中输送参数对弯头压降的影响，压 损用压降和当量长度这两种形式来 表 关于同志近三年现实表现材料材料类招标技术评分表图表与交易pdf视力表打印pdf用图表说话 pdf 达。也将关注管道材料，特别是挠性软管的应用。 2 PRESSURE GRADIENT DATA压力梯度数据 All the conveying data presented so far has been for total pipeline systems. This is usually obtained from a test facility comprising a pipeline test loop that generally includes horizontal pipeline lengths, a number of bends and possibly an element of vertical lift. The pressure drop data in the conveying characteristics presented has been for the entire pipeline.迄今为止所有输送数据都是针对全体管道系统的。这通常是从一个试验装置获取， 试验装置由一个管道试验回路组成，通常包括水平管长，一些弯头，可能还有一个垂直提升部分。输送特 压降数据是针对整个管道的。 性中的 In order to isolate the effect of any individual element of pipeline, such as a straight section of horizontal or vertical pipeline, or a bend in the pipeline, pressure tappings must be fitted into the pipeline. Some of these issues are considered in this chapter but are considered in more detail in Chapter 23. 为了隔离管道中任何单个部分的影响，如水平或 垂直直管段，或管道弯头，必须从管道取压。其中的一些问题在在本章中讨论，但在第23章中有更详细的 论述。 2.1 Horizontal Conveying水平输送 Typical conveying data for flow in a horizontal section of pipeline is presented in Figure 8.1. The data is for barite, which is often used as a drilling mud powder. This material has a particle density of about 260 lb/ft3 but despite this it will be seen that the material could be conveyed at solids loading ratios in excess of 100 and at low velocity. For drilling purposes it is used as a very fine powder and so has very good air retention properties in this form. As a consequence of the air retention properties the material will convey in dense phase flow.管道水平段流动的典型输送数据显示在图8.1 中。这些是重晶石的数据，重晶石通常被用作钻井泥浆粉末。 这种物料的颗粒密度约为260 lb/ft3(注:约 4165kg/m3)，除此之外，还可看到，物料能超过100的混合比低速输送。用在钻井上，是一种非常细的粉 末，因此以这种形式它具有良好的。由于其存气性，它能以密相来输送。 Figure 8.1 Pressure gradient in horizontal flow for barite in 2 inch bore line.重晶石在2英寸口径管道中的水平流 动压力梯度。 The data in Figure 8.1 is presented in exactly the same form as the conveying characteristics, with material flow rate in Ib/h plotted against free air flow rate in fVVmin. The family of curves plotted is now of pressure gradient in lbf/in2 per 100 ft length of pipeline rather than a pressure drop for the total pipeline. Lines of constant solids loading ratio are also included as these are simply straight lines through the origin as before. The juxtaposition of these two sets of curves on the one plot is particularly useful for illustrating once again the problem of maintaining flow in dense phase with increase in conveying distance.图8.1中的数据与输送特性具有完全一样的形式， 图中横坐标为自由空气流量(ft3/min)，纵坐标为物料流量(lb/h)。现在用压力梯度(lbf/in2每100 ft) 的一组曲线来替代总管线的压降。恒定混合比线也列入其中，像以前一样它们是通过原点的直线。这 两组曲线并列显示在一个图上，对再次说明随输送距离增加维持密相流动的难题特别有用。 2.1.1 Long Distance Conveying长距离输送 As expected, it will be seen that as the solids loading ratio increases, the pressure gradient increases. At a solid loading ratio of about 100 the pressure gradient is approximately 10 lbf/in2 per 100 ft length of pipeline. With a limit on air supply pressure because of air expansion problems, and the consequent need to step the pipeline, the scope for long distance dense phase flow is strictly limited. This does not take account of the additional pressure drop due to bends and sections of vertically upward pipeline that might need to be included either. 正如预期的那样，可以看到，随着混合比的增加， 压力梯度也增加。混合比约100时的压力梯度大约为10 lbf/in2每100 ft长度的管道。因为空气膨胀的问 题对供气压力有一定的限制，而且需要对管道扩管，长距离密相输送的范围受到了严格限制。这并不 没有考虑到可能需要列入的由于弯头和垂直向上管段生产的附加压降。 For longer distance conveying there must be a compromise and this is to convey at a lower value of solids loading ratio where the pressure gradient is lower. In Figure 7.2Id, magnesium sulfate conveyed over a distance of 2500 ft is presented and the maximum value of solids loading ratio, with a conveying line pressure drop of 30 lbf/in2, is only about 1 '/2. 对于长距离输送，必须要折衷考虑，压力梯度更低时的输 距离为2500 ft，输送线压降为30 lbf/in2 ，而最大送混合比也就更低了。在图7.21d中 ，输送硫酸镁的 混合比只有约1 '/2。 3 VERTICAL CONVEYING垂直输送 Apart from the difficulty of finding a suitable wall or structure on which to mount a vertical pipeline for testing purposes, a test loop needs to be used, unless two conveying systems are available, one conveying to the other. The former was used for the test work reported here [1]. An advantage of this method is that the pipeline must go down as well as up and so data can be obtained for both sections of pipeline in every test run. 除了难以找到合适的墙壁或结构来支撑进行试验的垂直管道之外，需要使用一个试 验回路，除非有两个输送系统，一个输送到另一个。用于试验工作所使用的模型回报于此[ 1 ] 。这种 方法 快递客服问题件处理详细方法山木方法pdf计算方法pdf华与华方法下载八字理论方法下载 的一个优点是，管道必须下降和上升同样的高度，因此在每次测试运行中可以同时测得两段管道 中的数据。 A sketch of the test pipeline is given in Figure 8.2 together with dimensional details. A high pressure top discharge blow tank was used to feed material into the pipeline. The layout of the test facility was such that the material was conveyed vertically down first and then vertically up. The fall and rise elements of the pipeline were both 53 ft long. The total pipeline length was about 185 ft. Two pipelines were available; one of two inch and another of three inch nominal bore, both following an identical routing.图8.2给出了试验管道的示意图与三维细节。采用一个高压上引式发送罐 来供料。试验设施的布局是这样的，物料先是垂直向下输送，然后垂直上升。下降和上升管道均为53 ft长。管道总长度约185 ft。有两条管道，一个的名义直径为两个英寸，另一个为两个英寸，它们的走 向是一样的。 Typical conveying characteristics for the total pipeline system are presented in Figure 8.3 [2]. These are for barite conveyed through the three inch bore pipeline. Barite can be conveyed in dense phase, as was illustrated in Figure 8.1 and so conveying with air supply pressures up to 30 lbf/in2 was possible and solids loading ratios of well over 100 were achieved.图8.3介绍了总的管道系统典型的输送特性 [ 2 ]。这些都是通过三 个英寸口径管道输送重晶石。如图8.1所示，重晶石可以密相来输送，因此当输送空气供应压力高达 30 lbf/in2时，混合比远远超过100。 Figure 8.2 Details of test pipeline试验管道详图。 Figure 8.3 Conveying characteristics for barite in figure 8.2 pipeline of 3 inch bore.图8.2的3英寸口径管道输送重晶石的输送特性。 Once again this illustrates the conveying potential of relatively small bore pipelines in that material flow rates of over 100,000 Ib/h were achieved. For the total pipeline the form of the conveying characteristics is little different from that for other pipeline systems presented in earlier chapters. 这再次说明了相对较小口径管道输送这种物料的输送 潜力能超过100,000 Ib/h(注:约45t/h)。对于总的管道，输送特性的形式和前面几章中的其他管道系统没 有什么不同。 In order to obtain pressure gradient data for the two test sections there were 15 pressure tappings (seven along the down section and eight along the up section). The first and last tappings at each section were placed about five feet from the bends in order to ensure that any upstream or downstream effects would have minimum influence on the pressure readings. At each location a ring of four tappings was used and all four were coupled to a common point. 为了获得这两个测试段的压力梯度数据，共有15个取 压点(七个在下降段，八个在上升段)。每个管段上的第一次和最后一个取压点都放在离弯头约五英尺远 处，以确保任何上游或下游对压力读数的影响最小。在每个地点都有一圈四个取压口，这四个都是相对同 一点对称布置。 Results from two tests carried out with a fine grade of pulverized fuel ash (fly ash) in the two inch bore pipeline are presented in Figure 8.4 [2, 3]. The horizontal xis represents the length of pipeline (see Figure 8.2) from the bend in a which the flow is horizontal to vertically down (bend number 4), to the bend in which the flow is vertically up to horizontal (bend number 7).在两英寸口径管道中对细粉级粉煤灰(飞灰)进行 的两次试验的结果显示在图8.4 [2, 3]中 。横轴代表从水平转为垂直流动的弯头(弯头4)开始的管道的长 )为止 。 度(见图8.2 )到从垂直转为水平流动的弯头(弯头7 The first section, therefore, represents the flow vertically down, along which there were seven pressure tapping locations, and the second section represents the flow vertically up, along which there were eight pressure tapping locations. The vertical axis represents the pressure of the conveying air.因此，第一部分代表垂直向下的流动，在这一段上有 七个取压点，第二部分代表垂直上升的流动，在这一段上有八个取压点。垂直轴表示的是输送空气压力。 The solid lines drawn represent the linearized dependence, from the measured values of pressure, while the dotted lines represent an approximate development of the pressure in the region where the pressure was not measured.实线代表压力测量值的线性关系，而虚线代表 没有测量点的区域的大致压力。 Figure 8.4 Typical pressure gradient results obtained with pulverized fuel ash.输送粉煤灰的典型的压力梯度。 It will be noticed that in one case the pressure gradient in the vertically down section was negative, while in the other it was positive. In the vertically up flow the pressure gradient was negative in each case, but there was a significant difference between the two tests. The influence that conveying conditions can have on the values of pressure gradient are considered below. 应注意到，在其中一个案例中，垂直向下段的压 力梯度为负，而另一个中为正。而两个案例中垂直向上段的压力梯度都为负，但这两次试验中有明显的不 同。后面会论述输送条件对压力梯度产生的影响。 3.1 Flow Vertically Up垂直向上流动 Pressure gradient data obtained in this way for the vertically upward flow of barite in the three inch bore pipeline is presented in Figure 8.5. The barite was conveyed over a wide range of both air and material flow rates, and some forty to fifty individual tests had to be carried out in order to provide the necessary pressure gradient data to obtain the plot or performance map shown in Figure 8.5. Once again solids loading ratios well in excess of 100 were achieved with this material.在图8.5所示的三英寸口径管道中重 晶石垂直向上流动，由此获得其压力梯度数据。在范围广泛的空气和物料流量下输送重晶石，进行了40到 50次的独立实验，以便为图8.5所示的性能图提供必要的压力梯度数据。再次达到了输送这种物料远超过100 的混合比。 The data is plotted in terms of a pressure gradient in lbf/in2 per 100 feet of vertically up pipeline. If the data is compared with that for the horizontal pipeline in Figure 8.1, which also relates to the conveying of barite, it will be seen that the pressure gradient values are significantly higher. 这些压力梯度数据表示为lbf/in2每100英尺垂直上升管道。如 果将这些数据与图8.1中涉及到的输送重晶石的数据相比，将会发现，压力梯度值明显要高。 Figure 8.5 Pressure gradient data for barite conveyed vertically up in 3 inch bore pipeline.在3英寸管道中垂直向 上输送重晶石的压力梯度数据。 Material flow rates are also very much higher but this is because the data is for a larger bore pipeline. It is by comparing sets of data such as this that scaling parameters can be determined, but ideally they need to be of the same bore pipeline, and so this is considered later in this chapter.因为管径更大，物料流量也高出很多。通过比较如上所示的这些 不同的数据，才能确定放大参数，但理想的情况是采用相同口径的管道，这些将在本章后面进行论述。 The data can also be compared with the conveying characteristics presented in Figure 8.3. Figure 8.3 was generated from exactly the same test program as that for the data in Figure 8.5. One was plotted from the total pipeline pressure drop data and the other from the pressure gradient data derived from the pressure tapping readings. 这些数据也可以与图8.3所示的输送特性相比较。图8.3与图8.5中的数据是根据完全相同的实验步 骤产生的。一个是根据总管道压力降数据来绘制，另一个的数据来源于取压口读数。 A comparison of the two will show that the slope of the pressure gradient lines on Figure 8.5 is very different from the slope of the lines of constant pressure drop on Figure 8.3. Figure 8.5 is for the vertically upward section of pipeline in isolation, while Figure 8.3 is for the total pipeline system, including nine bends. The influence of bends is also considered later in this chapter. 将两者进行比较，将会发现，图8.5中的压力梯度 线的斜率与图8.3中恒定压力降线的斜率有很大的区别。图8.5是单独测量垂直向上的一段管道，而图8.3是 总管道系统，其中包括9个弯头。本章后面部分也会将论述弯头的影响。 Two additional sets of data are included to reinforce the nature of the curves. These are for cement and fly ash, both conveyed vertically up through a two inch bore pipeline. There are clearly differences between the two sets of data but following the comparative data presented in Chapter 4 this will not come as a surprise. 其中包括了两组额外的数据以加强 对曲线性质的说明。它们是通过通过两英寸口径管道垂直输送水泥和粉煤灰的数据。这两组数据有明显区 别，但根据第4章中数据的比较，这并不令人感到意外。 The unknown factor is how the different elements of the pipeline contribute to the overall differences observed. Data for the cement is presented in Figure 8.6a and that for the fly ash in Figure 8.6b. 未知因素是管道的不同组成部分对所观测到得整体差别各有什么影 响。水泥的数据显示在图8.6a中，图8.6b为粉煤灰的数据 。 Figure 8.6 Pressure gradient data for flow vertically up in a two inch nominal bore pipeline, (a) Cement and (b) a fine grade of fly ash.两英寸管道中垂直向上流动的压力梯度数据，(a) 水泥 and (b) 细粉级粉煤灰。 3.1.1 Scaling Parameter放大参数 In the majority of pneumatic conveying system pipelines the proportion of horizontal conveying is very much greater than that of vertical conveying. A scaling parameter, therefore, is required in terms of an equivalent length of straight horizontal pipeline. 在大多数气力输送系统中，水平输送管道所占比例远大于垂直输送管道的比例。因此，放大 参数要求根据水平直管当量长度的形式来进行比较。 In order to provide a comparison between the data for conveying vertically up and conveying horizontally, and hence to obtain the necessary scaling parameter, a rectangular grid was placed on the various sets of pressure gradient data. The grid was set at corresponding values of air and material flow rates, and the ratio of the pressure gradient values obtained from the vertical and horizontal data were determined. 为了对垂直向上输送和水平输送的数据提供一个比较，从而获得必要的放大参数，在各 套压力梯度数据上放置一个矩形网格。那个网格定为空气和物料流量的相应值，根据垂直和水平数据 获得的压力梯度值之比得到确定。 The results of this process, carried out for barite in two inch bore pipeline, are presented in Figure 8.7a. They are presented on the same axes, together with the solids loading ratio lines, so that any pattern in the values with respect to conveying conditions could be determined. From this it will be seen that the ratio of the pressure gradient for vertically upward flow to that for horizontal flow varies from a minimum of about 1-9 to a maximum of about 2-4 and that the predominant value is about two. 进行上述步骤，在两英寸口径管道输送重晶石所得到的结果显示在图8.7a中。它们 显示在同样的坐标图中，加上混合比线，因此能够确定代表输送条件的任何模式的值。从中可以看出， 垂直向上流动与水平流动的压力梯度之比在最小约1.9最大约2.4之间变动，普遍值约为2 。 Figure 8.7 Ratio of vertical to horizontal conveying line pressure drop data for flow in two inch nominal bore pipeline, (a) Barite and (b) fly ash.在两英寸名义口径管道中垂直与水平输送线压 降之比，(a) 重晶石 and (b)粉煤灰。 It can be seen that the relationship obtained covers a very wide range of conveying conditions. A similar analysis, carried out with fly ash in a two inch bore pipeline is presented in Figure 8.7b. It will be noticed that there is very little variation in this ratio from minimum to maximum values of conveying air velocity and from minimum to maximum values of solids loading ratio. The only deviation from a mean value of about two would appear to be at the two extreme limits of the pressure gradient curves, where the data is least reliable. This, therefore, shows that the pressure drop in conveying vertically up is approximately double that in horizontal conveying, for given conveying conditions, over the entire range of conveying conditions. 可以看出，所得到的关系，涵盖了非常广泛的输送条件。在两英寸口径管道中 对粉煤灰进行的类似的 分析 定性数据统计分析pdf销售业绩分析模板建筑结构震害分析销售进度分析表京东商城竞争战略分析 ，显示在在图8.7b中。应注意到，从最低到最高输送空气流速及从最小到 最大混合比，这一比值变化很小。唯一的偏差是在压力梯度曲线的两个极端处，，那里的数据可靠性 不高。因此，这表明在整个输送条件范围之内，垂直输送的压降约为水平输送压降的2倍。 3.2 Flow Vertically Down垂直向下流动 In the majority of pneumatic conveying systems, flow vertically down usually occurs only when the pipeline is routed over some obstruction such as a road or railway line. In these cases the influence of the vertically downward section is generally disregarded. It is essential, however, that the additional bends required are taken into account. 在大多数气力输送系统中，通常只有当管道要越过某些阻碍，如公路或铁路时， 才会出现垂直向下流动。在这些场合中，一般忽略垂直向下段的影响。然而，必须考虑到附加的弯头 的影响。 It is with mining that long vertical pipelines come into their own, both for conveying vertically down as well as vertically up. The removal of muck from the boring of vertical mine shafts is often undertaken pneumatically. Much of the coal mined around the world is obtained from deep mines. With mechanization of coal face operations in the 1970's the mining capability exceeded the hoisting capability of winding gear and so additional means had to be found for extracting the additional capacity. Pneumatic conveying was widely used for this purpose and the conveying of coal 1650 feet vertically upwards at 110,000 Ib/h was quite common in the 1970's [4].采矿中常用到长距离垂直管道，包括垂直下降以及垂直上升输送管道。从垂直矿井 中清除淤泥往往采用气力输送。世界上大部分的煤都是从很深的矿井中开采。在二十世纪七十年代，随着 机械化采煤面的开采能力超过了卷扬设备的吊装能力，必须找到其它的手段来适应需求。气力输送被广泛 用于这一目的，在二十世纪七十年代，以110,000 lb/h(注:约50t/h)的输送量垂直向上1650英尺(注:约 500m)输送煤炭已经相当普遍了。 Back-filling of mined out areas is generally a requirement and cement and fly ash are widely used for this purpose. These materials, therefore, are often conveyed vertically down mine shafts. Because of the vast quantities of fly ash being produced around the world from power generation with coal, and the environmental problems associated with the material, the disposal of fly ash in this way is being considered more widely [3]. The longest pipelines conveying material vertically down are probably in South Africa. Ice is used in many deep gold mines as a heat transfer medium for cooling ventilation air. Ice making plant is located at the surface level and the ice produced is pneumatically conveyed over distances up to three miles, with vertically down distances up to about 7900 feet [5].一般都要求回填采空区，水泥和粉煤灰在这 一方面有着广泛的应用。因此这些物料往往要顺着矿井垂直向下输送。由于在世界各地燃煤发电产生大量 的粉煤灰，而这种物料会污染环境，因此更多的考虑以这种方式来处置粉煤灰 [ 3 ] 。垂直向下输送粉煤 灰最长的管道可能是在南非。在许多深的金矿矿井中用冰作为冷却通风空气的传热介质。制冰厂位于地面 而冰产品要送到高达三英里远的地方，垂直下降的距离达到约7900英尺(注:约2400m)[ 5 ] 。 Pressure gradient data for the pneumatic conveying of cement vertically down in the Figure 8.2 pipeline of two inch nominal bore is presented in Figure 8.8. Although the form of the data is similar to that for the other pressure gradient data presented, it will be seen that signs have been added to the values.用图8.2所示的2英寸名义口径管道垂直向 下气力输送水泥的压力梯度数据显示显示在图8.8中。虽然数据的形式类似于其他压力梯度数据，可以看到 在数值上添加了记号。 Figure 8.8 Pressure gradient in vertically down flow for cement in two inch nominal bore pipeline.在两英寸名义口径管道中垂直向下输送水泥的压力梯度。 At high values of solids loading ratio the pressure gradient is negative which means that there is a rise in pressure along the length of the pipeline, rather than a pressure drop. Where the pressure gradient is 16 lbf/in2 per 100 ft of pipeline, for example, it means that at the bottom of the 53 ft vertical fall in the test facility the pressure will have risen by about 8'A lbf/in2. It will also be seen that some of the pressure gradients are positive which means that there is a pressure drop along the length of the vertical fall. 在高的混合比下，压力梯度为负，也就是说，沿管道长度压力是上升了，而 不是下降。例如，在压力梯度为-16 lbf/in2每100英尺的管道时，这意味着在试验装置的53 ft 长垂直下 降管道的底部，压力将上升约8-1/2 lbf/in2 。这可看到有一些压力梯度是正的，这意味着有沿垂直下 降管道有一个压降。 The magnitude of the pressure gradient varies with solids loading ratio, and pressure rise for the flow vertically down increases with increase in solids loading ratio. At a solids loading ratio just below about forty the pressure gradient is zero, which means that the material is conveyed with no pressure drop whatsoever under these conditions. At lower values of solids loading ratio there is a pressure drop and this covers the entire range of dilute phase conveying.压力梯度的量值随混合比而变化，并且垂 直向下流动的压力随混合比的增加而增加。当混合比刚低于40时的压力梯度为零，这意味着在无论什 么输送条件下，该物料的输送没有压力下降。但混合比更低的时候有压降，这涵盖了所有的稀相输送。 Two additional sets of data are included to reinforce the nature of the curves. These are for barite and fly ash, both conveyed vertically down through the same two inch bore pipeline. Data for the cement is presented in Figure 8.9a and that for the fly ash in Figure 8.9b. It will be seen that all three materials follow a very similar pattern, although material flow rates differ, as might be expected. The zero pressure gradient curve is also consistent in occurring at a solids loading ratio of about 35 in each case. 两组额外的数据包括在其中，强调了曲线的特性。 它们是通过同样的两英寸口 径管道输送重晶石和粉煤灰的数据。水泥的数据显示在图8.9a中 ，而粉煤灰的数据显示在图8.9b中 。 可以看出，所有这三种物料都遵循非常相似的模式，虽然物料流量各不相同，这种情况是可以预见的。 在每一种情况下，混合比约35时都出现了零压力梯度曲线。 Figure 8.9 Pressure gradient data for flow vertically down in a two inch nominal bore pipe, (a) Barite and (b) fly ash.在两英寸名义口径管道中垂直向下流动的压力梯度数据，(a) 重晶石 and (b) 粉煤灰 For conveying vertically down, therefore, materials capable of dense phase conveying could be conveyed very long distances with a relatively low air supply pressure. A particular advantage is that in conveying materials such as cement and fly ash down a mine shaft, the pressure generated at the bottom could be high enough to automatically convey the material to underground mine workings another 5000 ft distant.因此，对垂直向下输送，具有密相输送能力的物料可以在相对较低的供气压力下输送很 远的距离。沿矿井向下输送如水泥和粉煤灰这些物料的一个优势是，在底部产生的压力可以高到足以 输送到5000 ft 远的井下工作区。 A problem with this, however, is in the sizing of the pipelines, for the velocity of the material at the start of the horizontal run may be too low as a result of the high pressure generated. This point is considered further in the next chapter on Stepped Pipeline Systems.不过，这种输送的一个问题是管道的尺寸选择，因为可能会由于产生的高压 力而在水平运动的起点处物料过低。这一点在下一章的扩管系统中会进一步考虑。 3.3 Minimum Conveying Air Velocity最小输送空气速度 Much has been said about minimum conveying air velocities and conveying line inlet air velocities. The data presented so far has essentially been for total pipeline systems comprising horizontal and vertical sections of pipeline, and bends. Minimum conveying air velocities in vertically upward flow are lower than those for horizontal conveying but in a mix of orientations in the one pipeline it is usually difficult to take the benefit of this into account and so the worst case of velocity requirements for horizontal conveying are usually specified.关于最低输送空气速度和输送线进气速度已 经讲了很多。迄今列出的数据基本上都是对包括了水平和垂直段，以及弯头的总管道系统的。垂直向 上流动所需的最低输送空气速度是低于水平输送的，但在一个包含两者的管道中，通常很难取舍，所 以一般指定最坏的情况下水平输送要求的速度。 In horizontal pipelines particles that drop out of suspension, or saltate, will come to rest on the bottom of the pipeline. With an increase in the thickness of the saltated layer the cross sectional area will reduce and there will be a corresponding increase in conveying air velocity. Depending upon the nature of the material this may result in a steady equilibrium situation. More often than not, however, the saltated layer will be formed into dunes and these will be swept up and block the pipeline, often at a bend in the pipeline. 在水平管道中颗粒从悬浮态沉降，或跳跃，将会沉积在管道底 部。随跳跃层厚度的增加，横截面面积将减少，相应的输送空气流速会增加。根据物料的性质，这些 可能导致稳定平衡的状态。当更多时候不是这样，跳跃层将形成沙丘，并且他们会滑行并堵塞管道， 往往是在管道弯头处。 In vertically upward flow this process is referred to as choking. When particles drop out of suspension, usually in the boundary layer at first, where the velocity is lowest, they will enter into free fall. At velocities at which particles will settle on the bottom of the pipeline in horizontal flow, particles are likely to be reentrained in flow vertically up because of impact with other particles moving up and the general turbulence. As a consequence minimum conveying air velocities can be lower for vertically upward flow. In mining situations, as discussed earlier, this can be used to advantage where there will be very long runs of vertical pipeline. Where the majority of a pipeline runs horizontal it is more difficult to take advantage of this fact. 在垂直向上流动中这一过程被称为噎塞。当粒子脱离悬浮态，通常首先出现在 边界层，那里的速度是最低的，他们将进入自由落体。在某速度下，水平流中的物料会沉积在管道底 部，而同样速度上的粒子在垂直流动中由于其他粒子的碰撞和通常的激流，粒子有可能重新起动。因 垂直向上流动的最低输送空气流速要低一些。如前文所述的采矿的情况下，这一点可以得到利用，此 那里有很长的垂直运行管道。在大多数管道是水平运行时更难利用这一点。 4 INCLINED PIPELINES倾斜管道 There is little published information on the advisability of using inclined pipelines. Much of it is anecdotal, but as it is generally experiential it would generally be wise to avoid pipelines that incline upwards. An inclined section of pipeline may well reduce the overall length of a pipeline but their use is not recommended. 很少有关于使用倾斜管道的 发表的资料。 大部分都是传闻，但人们普遍认识到避免管道倾斜向上是明智的。倾斜管道可以减少 管道的总长度，但不推荐使用。 4.1 Upward Incline向上倾斜 The general consensus of opinion is that pipelines inclined upwards should be avoided and that for any vertical rise, a combination of horizontal and vertical sections only should be used. The problem relates essentially to low velocity conveying and the influence that an inclined line might have on the minimum velocity. There is, of course, the additional issue of pressure drop普遍的共识是，应当避免管道倾斜上升，对任何 垂直上升，只应使用水平与垂直管道的组合。这个问题主要涉及低速输送，倾斜管道可能对最小速度 有影响。当然，也有关于压力降等其它问题。 When saltation occurs in a horizontal pipeline, particles will be deposited on the bottom of the pipeline, as mentioned above. In a pipeline inclined upwards, however, particles dropping out of suspension will be more mobile and will tend to roll backwards. The saltated layer will readily form dunes and these will result in pipeline blockage如上所述，当在水平管道中产生跳跃时，粒子会堆积在管道底部。但在倾斜向上管 道中， 粒子将更频繁地脱离悬浮态，并会滚落下来。跳跃层将会容易地形成沙丘，而这将导致管道 堵塞。 Although the minimum conveying air velocity for vertically upward flow is lower than that for horizontal flow, the minimum conveying air velocity for pipelines inclined upward is higher than that for horizontal pipeline. If it is known that the velocity in an inclined section of pipeline will be high there should be no risk of blockage. 虽然垂直向上流动的最低输送空气流速低于水平流动，而倾斜向上管道的最低输送空气 流速高于水平管道。如果已经知道管道倾斜段内的速度很高，那么不会有堵塞的风险。 It is also understood, however, that the pressure drop in a pipeline inclined upwards is much greater and so on this basis it would be better to keep to horizontal and vertical sections for any vertical rise required. The scaling parameter is one for horizontal flow and two for vertically upward flow. At an angle of inclination of about 60? the scaling parameter is a maximum and is slightly greater than that for vertically up flow at 90? [6].但是，也要了解，倾斜向上管道的压降要大得多，基于这个原因，在任 何要求垂直上升的地方最好是采用水平和垂直上升段的组合。水平管道的缩放比例参数是一，而垂直 向上流动是二。倾斜角约60?时的缩放比例参数是最大的，要稍微大于90?垂直上升流动 [ 6 ] 。 4.2 Downward Incline向下倾斜 The mechanism of flow in downward inclined pipeline is somewhat different and so there should be little difference in minimum conveying air velocity from that in horizontal pipelines. Saltated particles will tend to roll in the direction of flow and be re-entrained in the gas flow, rather than form dunes, at velocities just above the minimum conveying air velocity for horizontal flow.向下倾斜管道中的流动机理有所不同，因而在最低输 送空气流速上与水平管道没有多少区别。 当速度只是略高于水平管道所需最低输送空气流速时，跳 跃粒子会试图沿流动方向滚落，并在气流中重新起动，而不是形成沙丘。 5 PIPELINE BENDS管道弯头 Although pipeline bends provide pneumatic conveying system pipelines with their flexibility in routing, they do have an impact on the performance of a conveying system. Determining the pressure drop due to bends in a pipeline, however, is not a simple matter. 虽然管道弯头使得气力输送系统的管道走向灵活，但它们确实影响了输送系统的性 能。但确定由管道弯头产生的压降并不是一件简单的事情。 Apart from the influence of the conveyed material, the location of the bend along the length of the pipeline and the geometry of the bend are also likely to have an influence on the pressure drop across the bend. Data on the influence of bends may be required as an equivalent length rather than a pressure drop value. These issues are considered as well as the general influence of bends on conveying performance. 除了被输送物料的影响之外，管道上弯头所处的位置及其几何形状也有可能对通过弯头 的压降具有影响力。弯头的影响数据可能需要用当量长度来表示，而不是压降值。 这些论题和弯头 对输送性能的总的影响一样被考虑到。 5.1 Classical Analysis经典分析 The difficulties of pressure measurement in pneumatic conveying system pipelines are highlighted most effectively with the problem of measuring the pressure drop across a bend in a pipeline. It is not just a matter of recording the pressure at inlet to and outlet from the bend and subtracting the two readings. This will give a totally false recording, being significantly lower than the actual value. It is necessary to record the pressure at regular intervals along the sections of pipeline both before and after the bend [3].气力输送系统管道的压力测量的难度最大体现在对通过管道弯头的压降的测量上。这 并不仅仅是测量弯头入口和出口的压力，并将两者的读数减去。。这会给出一个完全虚假的记录，它大大 低于实际值。有必要记录下在弯头前后管段上每隔一定间距的压力 [ 3 ] 。 Part of the problem lies in the complexity of the flow in the region of a bend. The conveyed particles approaching a bend, if fully accelerated, will have a velocity that is about 80% of that of the conveying air. This velocity, of course, depends upon the particle size, shape and density, and the pipeline orientation. At outlet from a bend the velocity of the particles will be reduced and so they will have to be re-accelerated back to their terminal velocity in the straight length of pipeline following the bend. The situation is depicted in Figure 8.10. 部分问题在于弯头区域流动的复杂性。如 果一个接近弯头的粒子已被完全加速，其速度约为输送空气速度的80%。当然这速度， 取决于粒子大小， 形状、密度，以及管道走向。在弯头出口处的粒子速度将会减少，所以他们在弯头后面的直管道上将被重 新加速会起必须重新回到他们的极限速度。在图8.10中对这种情况进行了描述 。 The pressure drop associated with this re-acceleration of the particles, therefore, is not registered in the bend, but occurs in the pipeline following, and so it must be taken into account as illustrated in Figure 8.10. The method by which the total pressure drop associated with a bend is determined is to instrument the pipeline before and after the bend with pressure transducers. Typical data for a white wheat flour is shown in Figure 8.11 [7].因此，与粒子重新加速相关的压降没有记录在弯头之中，但发生在后 面的管道上，因此如图8.10所示这也必须计算在内。由此，确定与弯头相关的压降时要在弯头前后管道上 设该压力传感器。白面粉的典型数据显示在图8.11中[ 7 ] 。 Figure 8.10 Pressure drop elements and evaluation for bends.弯头压降的组成部分与评估。 Figure 8.1 1 Pressure profile in straight pipeline either side of a steel bend.钢制弯头两边直管上的压力分布图。 The bend was tested in a two inch nominal bore steel pipeline and had a bend diameter, D, to pipe bore, d, ratio of 5:1. The bend was tested in the horizontal plane, with the flour conveyed at a solids loading ratio of about 32. The mean particle size of the flour was 78 micron, and the particle and poured bulk densities were 87 and 30 Ib/ft3 respectively.试验弯头为两英寸口径钢制弯头，弯头直径D与口径d之比为5:1 。弯头为 微米，粒子密度及堆积密度分别是87和水平弯头，所输送面粉的混合比大约是32。面粉的平均粒径为78 30lb/ft3(注:分别为约1400和480kg/m3)。 From Figure 8.1 1 it will be seen that the total pressure drop across the bend was about 2-0 lbf/in2. Since the pressure gradient in the straight pipeline, both before and after the bend was also available, the equivalent length of the bend could be determined. In the case presented this equivalent length was evaluated at about 75 feet. Re-acceleration of the particles may require a significant distance downstream of the bend, particularly if the particles have a large mass and density, and something of the order of a dozen pressure transducers would be required, as shown.从图8.11可以看出弯头的总压降约2.0 lbf/in2 。由于弯头前后压直管道上的压降也可得到，这样就能 够确定弯头的当量长度了。这里估计当量长度约75英尺(注:约23m)。在弯头的下游，粒子的重新加速 可能需要一段有效长度，特别当颗粒质量和密度很大的时候，如图所示需要有12个规律分布的压力传感器。 In practical terms this pressure drop is a little high. With eight such bends in a pipeline it would require the output of a positive displacement blower just to negotiate the bends. The conveying air velocity at the bend was about 3500 ft/min and this is almost double that necessary to convey the flour at a solids loading ratio of 32. 从实际上看这一压降有点偏高。如果管道中有8个这样的弯头，仅仅是克服弯头的阻力就需要 用到容积式风机了。弯头处的输送空气流速约3500 ft/min(注:约18m/s)，这比在混合比为32时输送 面粉所需的风速多出近一倍。 The data was obtained from a test on an instrumented pipeline in a laboratory facility and is used for illustration purposes. Systems, however, are frequently over designed, particularly if the designers are not certain of the minimum conveying air velocity value, and so there is often scope for improving the performance of existing conveying systems as a consequence. 这些数据是从在实验室装置的管道上进行试验所获取的。但是， 系统常常超越设计，尤其是如果设计者没有确定最低输送空气流速值的时候，所以现有的输送系统往往是 有改进余地的。 5.2 Comparative Analysis比较分析 An alternative, and potentially quicker, means of determining the energy loss associated with bends is to compare the conveying performance of two pipelines in which the same material has been conveyed. Ideally both pipelines should be of the same bore and preferably of a similar length and contain a different number of bends of the same geometry. By comparing the performance data of materials conveyed in the two pipelines it is possible to determine the influence of the additional bends. 一种用于确定与弯头相关的能量损失的，并有可能更快的替代办法是，比较在两个管道中输送同样 物料时的输送性能。最理想的情况是:两者的管道口径一样，长度最好相似，几何形状相同的弯头数量不 同。通过比较在这两条管道中输送物料的性能，就有可能确定多出弯头的影响。 Conveying data obtained with barite conveyed through two such pipelines is presented in Figures 8.12a and b. Both pipelines tested were two inch nominal bore and all the bends in the two pipelines had a bend diameter, D, to pipe bore, d, ratio of 24:1. One pipeline was 340 feet long and incorporated nine 90? bends and the other was 330 feet long and incorporated seventeen 90? bends.在这样的两条管道中输送重晶石所获得的数 据显示在图8.12a和8.12b中。这两条实验管道的名义口径是二英寸，而且这两条管道中弯头的弯头直径D与 管道口径d之比为24:1。其中一条管道长340英尺，包括九个90?弯头，而另一条长330英尺，有17个90?弯头。 The bends were uniformly positioned along the length of the pipelines, and there was sufficient length of straight pipeline before every bend to ensure that the material was fully accelerated to its terminal velocity [8]. 弯头沿管道长度的位置一致，而且在每个弯头前有足 够长的直管道，以确保物料已被完全加速到其最终速度[ 8 ] 。 Figure 8.12 Conveying data for barite in two inch bore pipelines of approximately the same length. Pipeline with (a) 9 bends and (b) with 17 bends.在长度相近的两英寸口径管道中输送重晶石的输 送数据。(a)有9个弯头的管道and (b)有17个弯头的管道。 Conveying characteristics for the barite in the pipeline with nine bends are presented in Figure 8.12a and for the pipeline with seventeen bends in Figure 8.12b. Barite was chosen so that a very wide range of conveying conditions could be examined, from low velocity dense phase to high velocity dilute phase. The conveying data has been presented on the same axes for both pipelines, with material flow rates up to 50,000 Ib/h considered for each, and it will be seen that for the pipeline with 9 bends, conveying line inlet air pressures up to 50 lbf/in2 were employed, but this had to be increased to 60 lbf/in2 for the pipeline with 17 bends. The only essential difference between the two pipelines is eight bends and so the difference between the two sets of data can reasonably be attributed to eight bends.在有9个弯头的管道中输送重 晶石的输送特征显示在图8.12a中，有17个弯头的管道的数据显示在图 8.12b中 。选择了重晶石，这样就可 以 检测 工程第三方检测合同工程防雷检测合同植筋拉拔检测方案传感器技术课后答案检测机构通用要求培训 一个非常广泛的输送条件，从低速密相到高速稀相。两条管道的输送数据显示在相同的坐标图中， 每个的物料流量都可高达50,000 lb/h(注:约22.7t/h)，可以看到有9个弯头的管道的输送线进气压力达到 50 lbf/in2，而又17个弯头的管道的压力要增加到60 lbf/in2。两条管道唯一的本质区别是八个弯头，因此两 组数据之间差异可以合理地归因于这八个弯头。 With complete sets of conveying characteristics obtained for the same material conveyed through two pipelines of approximately the same length, but with different numbers of bends, it should be possible to compare the results and determine the influence that the bends have, since the influence of pipe bore and conveying distance have been isolated. The comparison is based on the mass flow rates of the barite achieved for given values of air flow rate and conveying line pressure drop.有了在两条长度相似，而弯头数目不同的管道中输送同样物料所获取的整套输送特性数据， 应该可以对其结果进行比较，并确定弯头所具有的影响，因为管道口径和输送距离的影响已经被排除。比 较是基于在特定的空气流量和输送线压降下所实现的重晶石的质量流量。 A grid was drawn on each set of conveying characteristics and the ratio of the barite flow rates was determined for every grid point. In order to determine whether there is any pattern in the value of this ratio, with respect to conveying conditions, the values corresponding to the grid points have been plotted on the conveying characteristics for the pipeline with 17 bends. These are shown in Figure 8.13.在每套输送特征上都绘制有网格，而且每个网格点的重晶石流量之比已被确定。为了确定在这些 比值下是否有古语输送条件的任何特性曲线，相应网格点的值已被绘制在对应有17个弯头的管道的输 送特性上。这些已显示在图8.13中。 Figure 8.13 Ratio of material flow rates in pipeline with 17 bends, to pipeline with nine bends.在有17个弯头和有9个弯头的管道中物料流量之比。 It will be seen that the material mass flow rates for the line with 17 bends are lower in every case, varying from 88% to 64% of the value obtained with the pipeline with only nine bends. Figure 8.13 shows very clearly that bends have relatively little influence when conveying at very high solids loading ratios with low air flow rates, but have a very significant effect when conveying at low solids loading ratios with high air flow rates. Solids loading ratios have not been shown on Figure 8.13 but this information is available from Figures 8.12a and b. 可以看出，在每一种情况下有17个弯 头的管线的物料质量流量都更低些，为只有9个弯头的管道所达到流量值的88,到64,。图8.13清楚地表明， 当输送混合比极高而空气流量低的时候，弯头的影响相对要小，而当输送混合比低而空气流量高的时候， 弯头的影响非常大。图8.13中没有显示混合比，但这一信息可以从图8.12a和8.12b中获知。 This also shows that no single value can be applied to allow for the influence of bends in a pipeline. An allowance will quite clearly depend on the conveying conditions. Figure 8.13, however, shows that the influence of conveying conditions on the effect of the bends is very uniform and consistent, and so it should be possible to determine a simple relationship between the allowance to be made and some parameter that defines the conveying conditions. 这也表明，没有哪一个值可用于补偿管道中弯头的 影响。补偿量非常明确地取决于输送条件。然而，图8.13表明，输送条件对弯头效应的影响是非常统一和 一致的，因此有可能在补偿量和去定了输送条件的一些参数之间确定一个简单的关系。 5. 2. 1 Equivalent Length当量长度 The next stage in the analysis is to assign an order of magnitude, or value, to the allowance to be made for the bends. For this purpose an equivalent length is probably the best way of allowing for the added resistance. An equivalent length of straight horizontal pipeline in feet is therefore required, so that this can be added to the existing pipeline length to give the total equivalent length of the pipeline [8]. 下一阶段的分析，可以为弯头的补偿量指定一个数量级，或数值。为此，当量长度也许是衡量附加阻 力的最好方法。因此有必要表示为以英尺为单位的水平直管当量长度，这样可以添加到现有的管道长度上， 以得到总管道的当量长度[8] 。 As the equivalent length will vary with conveying conditions it is necessary to superimpose regular grids on the two sets of conveying characteristics, as presented earlier and to evaluate the value at every grid point established. The equivalent length of the bends can be determined with a model that relates material flow rate and equivalent conveying distance for a pneumatic conveying pipeline. Such a model was presented in Chapter 7 with Equation 7.10: 由于当量长度随输送条件而改变，有必要如前面所表示 的那样，在两组输送特性上添加方形网格，以估量每个设定网格点的数值。可以根据相关的物料流量及气 力输送管道的当量输送距离来确定弯头当量长度的模型。这样一个模型在第7章中用等式7.10来表达: where rhp = mass flow rate of material - Ib/h 这里 =物料的质量流量 – lb/h Le = equivalent length of pipeline – ft Le = 管道的当量长度 - ft and subscripts 1 and 2 refer to different 下标1和2代表同样口径的不同管道 pipelines of the same bore The equivalent lengths of the two pipelines will be:这两条管道的当量长度是: where b = equivalent length of straight 这里b=每个弯头的水平直管当量长度- ft horizontal pipeline per bend - ft Substituting Equation 8.2 into 8.1 and re-arranging gives:把等式8.2代入8.1并重组后得到: It is this ratio that is plotted on Figure 8.13. The only unknown in this equation, therefore, is b. The equivalent length, therefore, will increase in a pattern similar to that shown for the ratios on Figure 8.13. An analysis of the data produced the relationship shown in Figure 8.14. The entire program of test work and analysis was repeated with cement, in place of the barite, and a very similar set of results was obtained. 这是图8.13所绘制的比值 。在这个等式中只有一个未知量，b。因此， 当量长度会按类似图8.13所示比值的模式来增加。对数据分析所得到的关系显示在图8.14中。 整个项目的测试工作和分析，用水泥取代重晶石来重复进行，并获得了一个非常类似的结果。 The correlation is in terms of a single parameter, which is conveying line inlet air velocity, which makes its application very convenient. This would indicate that the location of the bend along the length of the pipeline is only of secondary importance, despite the fact that the conveying air velocity will increase along the length of the pipeline. It might, however, be that the difference in particle velocities across the bends do not vary significantly with their position along the length of the pipeline. 与之相关的是一个单一的参数，这就是输送线进气速度，这使得其 应用非常方便。这表明弯头在沿管道长度上的位置的重要性是其次的，尽管事实上输送空气 流速将沿管道长度而增加。但是，有可能通过弯头的粒子的速度并不会随它们所处的沿管道 长度的位置的不同而有很大的差异。 From Figure 8.14 it will be seen that equivalent lengths of bends can be as low as 5 ft per bend for low velocity dense phase conveying, with conveying line inlet air velocities of 600 ft/min. For dilute phase conveying, however, with a conveying line inlet air velocity of 4000 ft/min, for example, the equivalent length is about 80 ft per bend. The curve continues to rise to higher values of equivalent length with further increase in velocity. 从图8.14可以看出对输送线进气速度为600 ft/min的低 速密相输送，每个弯头的当量长度可低至5英尺(注:约1.5m)。但对输送线进气速度为 4000ft/min(注:约20m/s)的稀相输送，每个弯头的当量长度约为80英尺(注:约24m)。 随速度的进一步增加，曲线继续上升到更大的当量长度值。 Figure 8.14 Influence of conveying line inlet air velocity on equivalent length of long radius 90? steel bends for conveying barite.输送重晶石时，输送线进气速度对长半径90?钢制弯头当量长度的影响。 5.2.1.1 Coefficient of Restitution恢复系数 Although the data in Figure 8.14 relates to barite, the entire process was also carried out with cement, as mentioned above. There were obviously differences in the conveying characteristics between the barite and cement conveyed through the two pipelines but the analysis carried out produced an almost identical result in terms of equivalent length [8]. It is suspected that many other materials will follow this same pattern in terms of equivalent length. However, it is believed that the value of the coefficient of restitution between the particles and the bend wall might well be an additional influencing parameter. 虽然图8.14所示是关于重晶石的数据，如上面所提到的，整 个过程还用水泥进行了同样的实验。通过那两条管道来输送重晶石和水泥的输送特性有着明显的差 异，但以当量长度进行的分析产生了几乎相同的结果[ 8 ] 。人们怀疑，在当量长度上，许多其他材料 将遵循同样的模式。然而，据认为，粒子和弯头壁面间的恢复系数值可能有附加的影响。 If materials having a high value of coefficient of restitution impact against a bend the velocity of the particles on leaving the bend will not be as low as those for materials such as flour, barite and cement. As a consequence the energy loss across the bend will not be as high, particularly for higher velocity flows. This point is considered further, later in this chapter, when the analogous situation of conveying materials through rubber hose is investigated. 如果物料与弯头碰撞后的恢复系数高，那么粒子 离开弯头的速度不会像那些如:面粉、重晶石和水泥等物料的粒子那么低。因此通过弯头的能量损失 不会那么高，特别是对较高速度的流动。这一点在本章后面对通过胶管输送物料的情况进行研究时会 做进一步的讨论。 5.2.2 Pressure Drop压降 An alternative presentation of the data in the form of conveying characteristics is presented in Figure 8.15. The bend loss here is expressed in terms of lbf/in2 per bend. It will be seen that the most significant parameter is air flow rate, and hence conveying air velocity, with losses varying from about '/2 lbf/in2 per bend in low velocity dense phase flow to 2/4 lbf/in2 per bend in high velocity dilute phase flow over the range of air flow rates considered. 图8.15介绍了以输送特性的形式表达数据的另一种方式。这 里弯头损失用lbf/in2/弯头的形式表达。可以看出，最重要的参数是空气流量，也就是输送空气流速。 在所考虑的输送空气流量范围内，损失为从低速密相流动的0.5 lbf/in2到高速稀相流动的2.5 lbf/in2。 Figure 8.15 Influence of conveying conditions on pressure drop for barite conveyed through long radius 90? steel bends. 通过大半径90?钢制弯头输送重晶石时，输送条件对压降的影响。 From the pipeline and conveying parameters for the flour, presented in Figure 8.11, the air flow rate was about 155 ftVmin and the solids loading ratio was given as 32. If this data is plotted on Figure 8.15 for the barite it will be seen that the pressure drop would be about 2 lbf/in2 which is the same value as that reported on Figure 8.11. This is despite the difference in bend geometry. 根据图8.11所示的面粉的输送参数和管 道，空气流量约为155 ft3/min，固气比为32 。如果将这些数据绘制在输送重晶石的图8.15中，可以看 出压降将约为2 lbf/in2，与图8.11报告的一样。尽管弯头的几何形状不一样。 5.2.2.1 Comparative Values比较值 It will be noted that in terms of equivalent lengths the spread of values over the range of conveying conditions considered is of the order of 20:1 from Figure 8.14, but in terms of pressure drop values from Figure 9.15 it is only about 5:1. The values in terms of pressure drop are much closer because pressure gradient values in dense phase are very much higher than those for dilute phase. The use of scaling parameters for evaluating pneumatic conveying system performance and capability is very different from that of summing pressure drop values for individual elements of the pipeline. 应该指出，根据图8.14，所考虑的各种输送条件下，当量长度的比值为20:1，而从图 9.15来看，压降之比只有约5:1。以压降形式表达的值非常接近，因为密相的压力梯度值远高于稀相。 在评估气力输送系统的性能和能力时，使用比例参数所得到的值与各个管道元件加起来的总压降值有 极大的差异。 5.3 Bend Geometry弯头几何形状 The majority of the work reported in this chapter has been undertaken with long radius bends having a D/d ratio of about 24:1. Tests with the wheat flour related to a bend with a D/d ratio of 5:1 but the data agreed quite closely with that for barite in the long radius bends. The influence of bend geometry on the air only pressure drop for bends was considered in Chapter 6 with Figure 6.6 and this is reproduced here in Figure 8.16 for reference. From this it will be seen that it is only with very short radius bends that pressure drops will be high for air only. 本章中大多数实验工作所采用的大曲率半 径弯头的D / d值约为24:1 。用面粉做实验采用的弯头的D / d值为5:1，但数据与重晶石所用的大半径 弯头相当接近。第6章的图6.6介绍了弯头几何形状对弯头的纯空气压降的影响，这里在图8.16中重新 引用，以供参考。从中可以看出，对纯空气而言，只有半径极短的情况下，压降才会很高。 Figure 8.16 Head loss for 90? radiused bends. 90?曲率弯头的压头损失 Bends having a wide range of geometries are employed in pneumatic conveying system pipelines. Short radius bends and tight elbows are cheaper and easier to install than long radius bends. Blind tees are often used in pipelines in which abrasive materials are conveyed. In order to determine the influence of bend radius on pressure drop and conveying performance a program of tests was carried out with a range of bend geometries [9].气力输送系统的管道所采用弯头的几何形状有很多种。短半径弯头和气密 肘管相比大半径弯头更便宜，也更容易安装。在输送研磨物料时，常采用T型盲管。为了确定弯头半径对压 降和输送性能的影响，用各种几何形状的弯头进行了一系列的实验[ 9 ] 。 A pipeline was specially built with a double loop in the horizontal plane, in which the bends at the corners could be replaced. The pipeline included eleven 90? bends and seven of these could be conveniently changed. The pipeline was 165 ft long and of two inch nominal bore. A fine grade of fly ash was used as the conveyed material to ensure that tests could be carried out over as wide a range of conveying conditions as possible. A sketch of the pipeline is given in Figure 8.17 for reference.专门修建了在水平面上双回路管道，转角处的弯头可以更换。管道包括11个90? 弯头，其中的 7个可以很方便地更换。管道长165 ft，名义口径为两英寸。被输送物料为细粉级粉煤灰，以确保可以再广 泛的输送调教下进行测试。图8.17给出了管道的示意图，以供参考。 The central group of seven bends, positioned in the corners of the double loop were arranged so that bends of different geometry could be conveniently incorporated. The location of the bends is indicated on Figure 8.17 and were chosen since there was a reasonable length of straight pipeline before the bend to ensure that the fly ash was accelerated to its terminal velocity before meeting the next bend. 中间一组7个弯头被安排在双回路的拐角处，使得不同几何形状的弯头可方便地换上。图8.17指明了 弯头的位置，在这些弯头前有一段合理程度的直管道，以确保粉煤灰在到达下一个弯头前被加速到其最终 速度。 The group of seven bends, all having the same geometry, were all changed for each test program. Tests were carried out with sets of long radius bends having a bend diameter, D, to pipe bore, d, ratio of 24:1; with short radius bends (D/d = 6); elbows (D/d = 2); and with blind tees. A proportioned sketch of the different bends tested is given in Figure 8.22. 这组七个弯头具有相同的几何形状，在每个测试项目中一起更换。进行 测试的长半径弯头的D/d = 24，短半径弯头D/d = 6，标准弯头D/d = 2;还有T型盲管。图8.22给出测试所用不 同弯头的按比例示意图。 Figure 8.17 Pipeline used for bend geometry tests.用于弯头几何形状实验的管线。 Figure 8.18 Sketch of bends tested.测试所用弯头的示意图。 A complete set of conveying characteristics was obtained with the fly ash conveyed through the pipeline for each of the four different sets of bends. The conveying characteristics obtained with the long radius bends and the blind tees are presented in Figure 8.19. 通过在采用四组不同弯头的管道中输送飞灰，得到了一套完整的输送特性。用 场半径弯头和T型盲管所获得的输送特性显示在图8.19中。 Figure 8.19 Conveying characteristics for fly ash conveyed through the pipeline shown in figure 8.21 having, (a) Long radius bends and (b) blind tees.通过图8.17所示管道输送飞灰的输送特 性，(a)长半径弯头 and (b)T型盲管。 If these two sets of conveying characteristics are compared it will be seen that over a large area of conveying conditions an increase of about 50% in pressure drop is required in the pipeline with blind tees to achieve the same material flow rate in the pipeline with long radius bends. If material flow rates are compared for a given value of conveying line pressure drop it will be seen that the flow rate achieved in the pipeline with blind tees is approximately half of that achieved in the pipeline with long radius bends, particularly at high air flow rates. 如果将这两组输送特性进行 比较，可以看出:在大多数输送工况下，采用T型盲管与采用长半径弯头相比，在同样的物料流量下，压降 增加了约50%。对比给定输送线压降下的物料流量，看以看到;用T型盲管能达到的物料流量是用长半径弯 头时的大约一半，特别是空气流量高的时候。 It must be recalled that these two sets of conveying characteristics relate to the same pipeline, for the 165 ft length of pipeline and four of the bends are exactly the same in each case. These differences, therefore, are due entirely to the change in geometry of only seven of the bends in the pipeline. 必须再次提醒，这两组输送特性所涉及的管道相 同，是165 ft长的管道，且各种场合中都有4个弯头是完全一样的。因此，这些差异完全是由于管道中那七 个弯头形状的变化。 To provide a full comparison of the different sets of bends the conveying characteristics were compared over the entire range of conveying conditions. The comparison was based on the pressure drop required to achieve a specified material flow rate for a given air flow rate. To do this a grid was drawn on each set of conveying characteristics at regular increments of both air and material flow rates, and the conveying line pressure drop at every grid point was noted [9]. 为了提供各组弯头全面的对比，在整个 的输送条件的范围内对其输送特性进行了比较。这个对比是根据需要在给定的空气流量下达到特定的物流 流量时所需的压降来进行的。要做到这一点，在每组输送特性图上的空气与物料流量按规律递增的方向上 绘上网格，并且在每个网格点上标示出了输送线压降[9]。 The results of this analysis are presented in Figure 8.20 with both the blind tees and the short radius bends compared with the long radius bends. The long radius bends have been taken as the datum for reference. 对T型盲管及短半径弯头与长半径弯头对比所得的分 析结果显示在图8.20中。采用长半径弯头作为参照基准。 Figure 8.20 Comparison of performance of long radius bends, (a) With blind tees and (b) short radius bends.与长半径弯头对比的性能，(a) T型盲管 and(b) 短半径弯头。 The numbers on these plots are essentially the ratios of corresponding pressure drops, in terms of a percentage increase, or decrease where there is a negative sign. It will be seen that the pressure drop with the blind tees was about 40% greater than that for the line with the long radius bends, whether for the low velocity dense phase or the high velocity dilute phase conveying of the material. In terms of energy considerations, therefore, blind tees could not be recommended for pneumatic conveying system pipelines with this type of material. 这些图上的数字实质上是相应的压 降比值，按百分比增加，负号代表下降。可以发现，无论是低速密相还是高速稀相输送这种物料，采 用T型盲管的管线的压降要比采用长半径弯头的高出约40%。因此从所需能量方面来看，不建议在这 类物料的气力输送系统管道中采用T型盲管。 A comparison of the short radius with the long radius bends is given in Figure 8.20b and from this it will be seen that there is little difference between the two, although at low values of both air and material flow rates the short radius bends performed better. In terms of bend selection, therefore, long radius bends would only be recommended if there were particular needs for such bends in terms of erosive wear resistance and the minimizing of material degradation. 对比图8.20b中的短半径和长半径 弯头，可以发现两者之间的差距不是太大，尽管在空气和物料流量都较低的时候，短半径弯头的性能 更好些。因此在选择弯头上，只有在需要减少冲蚀磨损或尽量避免物料的降级时，才推荐采用长半径 弯头。 A comparison of the elbows with the long radius bends showed an overall increase in percentage ratios of about 15% over those shown on Figure 8.20b for the short radius bends [9]. The data overall, therefore, shows a very close correlation with the data for air only in Figure 8.16, with respect to the influence of bend geometry on pressure drop. 对比图8.20b所示的标准弯头和长半径弯头，压降整体上增加15%左右。因 此，从整体的数据上看，相对于弯头几何形状对压降的影响，图8.16中纯空气的数据与压降有非常密 切的关系。 5.3.1 Pocketed Bends袋形弯头 Bradley [10] undertook a program of tests with a 90? pocketed bend and reported that the pressure drop was only marginally better than that for a blind tee. The pocketed bend was of the vortice variety and was tested in a similar manner to that discussed in relation to Figure 8.11. 布拉德利[10]对一个90?袋形弯头进行测试，并报告说这种弯头的压 降只比T型盲管稍好一点。袋形弯头是涡旋变种，并用与图8.11所讨论的类似方式进行了测试。 5.4 Bend Location弯头位置 The general recommendation is that a reasonable length of straight pipeline should proceed a bend in a pipeline, particularly the first bend in a pipeline following material feed into the pipeline. 一般建议，在管道中弯头的前面要有合理长度的直管段，特别是在喂料 点后的第一个弯头前。 This area in a pipeline is particularly critical because the conveying air velocity is at its lowest and the material is generally fed into the pipeline at zero velocity. Ideally the particles should be accelerated to their terminal velocity. With large and high density particles this requires a relatively long distance. If this is not possible, and particularly if the first bend is a blind tee or pocketed bend, it may be necessary to increase the conveying air velocity to compensate and this, of course, will increase the energy requirements for the system. 之所以对管道的这一部分特别提出要求，是因为这 里的输送气速最低，而且物料通常以零速度喂入管道。 理想情况下，粒子应该加速到其极限速度。 对大尺寸的和高密度的颗粒，这需要一段比较长的距离。如果这不是可能，特别是如果第一个弯头是 一个T型盲管或涡流弯头，可能要增加输送空气流速，以作为补偿，这当然， 会增加系统的能源需求。 By similar reasoning no two bends in the pipeline should be spaced too closely together, particular in the low velocity area in a pipeline.依照类似的道理，管道中的两个弯头不能 靠的太近，特别是在管道的低速区。 Long radius bends are also to be avoided if the first bend must feed vertically up. The problem here is analogous to inclined pipelines. A long radius bend in a horizontal to vertically up orientation will have a significant section of pipeline on an incline, and a higher conveying air velocity may be required for material to negotiate such a geometry.如果第一个弯头必须垂直向上，也应避免长半径弯头。这里的问题类似于 倾斜管道。一个长半径弯头用于水平转向垂直向上，将有很大一段管道位于斜面上，为了克服这种几 何形状，可能需要较高的输送空气速度。 6 PIPELINE MATERIAL管道材料 Although all the data so far has related to the pneumatic conveying of materials through steel pipelines, not all pipelines are made of steel. Rubber hose is widely used in pneumatic conveying systems, both for pipeline and bends, and in systems where a degree of natural flexibility is required, such as in vacuum off-loading and mobile systems. 虽然迄今所有的数据都是关于通过钢管气力输送物料的，但并非所有的管道都是钢制 的。在系统需要有一定程度的自然挠性的时候，橡胶软管被广泛用于气力输送系统，包括管道和弯头， 例如在真空卸货和移动系统中。 By virtue of its natural resilience rubber hose can often be used to particular effect in reducing erosive wear with abrasive materials and in minimizing degradation with friable materials. As a pipeline material it is particularly suited to the conveying of certain sticky and cohesive materials. 由于橡胶软管的自然恢复能力，在减少研磨物料的冲 蚀磨损和尽量避免易碎物料降级的场合中，橡胶软管往往起到特定的效果。由于管道材料，是特别适 合某些输送粘性和粘性材料。 For the off-loading of ships, that have self-discharging facilities, high pressures are generally employed in order to keep the discharge time to a minimum. With materials such as cement, conveying air pressures up to 100 psig can be utilized, and hose is available that will meet this requirement. 对于具有自卸装置的船舶卸货，通常采用高压以达 到尽快的卸货。 对如水泥这些物料，可以利用的输送空气压力高达100 psig，所采用的软管应满足这 一要求。 A particular application is the transfer of drilling mud powders, such as barite, bentonite and oil well cement, from supply boats onto off-shore drilling platforms. As materials have to be off-loaded from boats in rough seas, a long length of hose is used to connect the discharge system on the boat with the fixed pipeline on the drilling rig.一个特定的应用是从补给船向海上钻井平台输送钻井泥浆，如重晶石粉，膨润土和 油井水泥。由于物料要从汹涌的海洋上卸下，要有一段长的胶管用于连接船上的卸料系统与钻井平台 上的固定管道。 Road trucks and rail tankers are most conveniently off-loaded through lengths of flexible rubber hose, whether the vehicles are self off-loading or not. In these applications it would be impractical to use rigid metal pipelines because of the time required to achieve the necessary alignment. An unknown quantity, however, is whether the pressure drop for rubber hose will be any different from that of steel pipeline. 公路卡车和铁路车厢最方便的卸货是通过柔性橡胶软管，无论是不是自卸货。在这些 应用中使用硬金属管道将是不切实际的，因要实现必要的调整时间。但是，一个未知量是:橡胶管压 降是否和钢管有所不同。 6.1 Pipeline Pressure Drop管道压降 In order to determine whether there is any difference in conveying performance between steel and rubber hose a program of tests was specifically undertaken. A 140 ft long pipeline of two inch bore steel pipeline that incorporated five 90? bends was used. 为了确定钢管和橡胶软管的输送性能是否有任何差异，特别进行了一系列的测试。采 用了一段长140 ft，口径为两英寸，包括5个90?弯头的钢管。 Oil well cement was conveyed through this pipeline and its conveying characteristics were obtained. A 140 ft length of two inch bore rubber hose line was then strapped to the steel pipeline. By this means exactly the same routing and bend geometries were replicated. The oil well cement was then conveyed through this pipeline and its conveying characteristics were obtained.通过这条管道输送油井水泥，并得到了它的 输送特性。一段长140 ft的两英寸口径橡胶软管绑在钢管。通过这种方法，复制出完全相同的走向和 弯头的几何形状。然后通过这条管道输送油井水泥，并获得了它的输送特性。 The two sets of conveying characteristics are presented in Figure 8.21. Oil well cement, like ordinary portland cement, is capable of being conveyed in dense phase and at low velocity and so the two sets of data cover a very wide range of conveying conditions. Tests were carried out with air supply pressures up to about 28 lbf/in2 gauge and so, as the pipeline was relative short, solids loading ratios up to about 200 were achieved. 这两组输送特性列于图8.21中。油井水泥和普通硅酸盐水泥一样，能够以 低速密相输送，因此这两组数据涵盖了十分广泛的输送条件范围。试验的供气压力约28 lbf/in2(表压)， 因为管道相对较短，可以达到约200的固气比。 Figure 8.21 Conveying characteristics for oil well cement conveyed through 140 ft long pipeline of two inch bore of different materials, (a) Steel pipe and (b) rubber hose line.通过不同材料的两英 寸管径，长140英尺的管道输送油井水泥的输送特性，(a) 钢管 and (b) 橡胶软管。 From the two sets of conveying characteristics it will be seen that the nature of the curves is very different. With the steel pipeline there is a distinct pressure minimum point in the pressure drop curves. Conveying performance appears to be similar at low values of air flow rate but are widely different at high values of air flow rate. 从这两组输送特性可以看出曲线的形态有很大的不同。钢管的压降曲线上有一个明显 的压力最低点。空气流量低的时候输送性能的表现类似，但空气流量高时有很大的不同。 In order to compare the performance of the oil well cement in the two pipelines a grid was drawn on each of the sets of conveying characteristics, in much the same way as reported above for the program undertaken with bends of different geometry. The ratio of pressure drops for corresponding air and material flow rates were evaluated. The results of this exercise are presented in Figure 8.22. 为了比较这两条管线 输送油井水泥的性能，在两组输送特性图上都绘制了网格，采取了与前面报告的对不同几何形状 弯头测试程序相同的方式。对相应的空气和物料流量下压降的比率进行了评价。这一结果显示在 图8.22中。 From Figure 8.22 it will be seen that there is a gradual increase in pressure drop for the rubber hose line, compared with that for the steel pipeline, with increase in air flow rate. The lines of constant percentage increase drawn on Figure 8.22 slope in the same way as the lines of constant velocity on the conveying characteristics, as illustrated on Figure 7.4, and so it is clearly a conveying air velocity effect. In dense phase flow at very low velocities there is little or no difference between the two pipeline materials, but with higher velocity dilute phase flow the pressure drop for flow through the rubber hose line is 50% greater than that through the steel pipeline. 从图8.22可以看出，相对于钢管，随空气流量的增加，橡胶软管的压降 逐渐增加。像图7.4中输送特性图上恒定速度线一样，图8.22中恒定百分比线以同样的斜率向上， 所以显然是输送空气流速产生的效果。以非常低的速度密相流动时，两种管道材料间很少或没有 区别，但具有更高的速度稀相流动时，通过橡胶管流动的压降比钢管高50,。 Figure 8.22 Comparison of pressure drop data for steel and rubber hose lines.钢管与橡胶软管的压降数据的对比。 The program of tests was repeated with another drilling mud powder (barite) and a similar set of results was obtained [11].用另一中钻井泥浆粉(重晶石)进行重复测试，得到了类似 的一组结果 [11]。 6.2 Coefficient of Restitution恢复系数 It is suspected that the coefficient of restitution between the particles and the pipeline wall plays an important part. Rubber, being resilient, will have a lower coefficient of restitution for impacting particles than steel. If the rubber absorbs more of the energy of impact of the particles than the steel, a greater pressure drop will result with the rubber pipeline, due to having to re-accelerate the particles from a lower velocity. This is why the pressure drop for flow through the rubber hose is greater than that through the steel pipeline, and since pressure drop increases with 2(velocity), this is why it increases with increase in conveying air velocity [11]. 人们怀疑是粒子与管壁间 的恢复系数起到了重要的作用。橡胶具有弹性，与粒子碰撞时，相对钢管有更低的恢复系数。如果橡 胶管比钢管吸收更多碰撞能量，那么粒子就要从更低的速度重新加速。这就是为什么通过橡胶管流动 的压降要大于钢管的原因，由于压降的增加与速度的平方成正比，这就是为什么它随输送空气流速增 加而增加的原因[11]。 7 EQUIVALENT LENGTH当量长度 Scaling, whether for system design or for undertaking a review of alternative conveying systems for a given duty, is generally undertaken in two stages. The first stage is to scale to the length and routing required and the second is to scale with respect to pipeline bore. Scaling with respect to length and pipeline routing is usually in terms of an equivalent length of the pipeline. The equivalent length incorporates vertical lift and bends, as well as horizontal pipeline, and is expressed in terms of horizontal length. A factor of two is suggested for a scaling parameter for vertically upward sections of pipeline. Equivalent lengths for bends were presented in Figure 8.14.无论是系统设计或对特定负荷下替代输送系统的审查，按比例缩放一般分为两个阶段进行。 第一阶段是按长度和所需走向进行缩放，第二阶段按管径进行缩放。对于长度和管道走向的缩放通常是按 管道的当量长度来计算。当量长度包括了垂直提升，弯头以及水平管道，并水平长度来表示。建议垂直向 上的管道部分比例参数取二。图8.14显示了弯头的当量长度。 For non radiused bends and tight elbows an additional allowance will have to be made. An additional allowance will also have to be made for rubber hose, but the data given here can be used in estimating appropriate values. Although the information presented relates to particular conveyed materials it must be appreciated that at this point in time there is no universal solution to the problem of designing pneumatic conveying systems and for determining the conveying capability of a pipeline. Different materials will behave differently, as was illustrated with total pipeline systems in Chapter 4. 对于非半径弯头及肘管。对橡胶软管也要有额外的裕度，但这里给出的 数据可以用来估算适当的值。因为现有的资料都是关于特定的物料的，在这个时刻，在设计气力输送系统 和确定管道输送能力时没有普遍适用的解决问题的办法。不同的物料的表现将有所不同，如同在第4章总管 道系统中所描述的那样。 REFERENCES 1. P. Marjanovic. An investigation of the behavior of gas-solid mixture flow properties for vertical pneumatic conveying in pipelines. PhD Thesis. Thames Polytechnic (now The University of Greenwich) London. 1984. 2. D. Mills, J.S. Mason, and P. Marjanovic. The influence of product type on dense phase pneumatic conveying in vertical pipelines. Proc Pneumatech 2, pp 193-210. Canterbury. Sept 1984. 3. D. Mills. Measuring pressure on pneumatic conveying systems. Chem Eng, Vol 108, No 10,pp 84-89. Sept 2001. 4. J. Firstbrook. Operation and development of the pneumatic coal transportation system. Proc Pneumotransport 5. BHR Group Conf. London. April 1980. 5. T.J. Sheer, R. Ramsden, and M. Butterworth. The design of pipeline systems for transporting ice into deep mines. Proc 3rd Israeli Conf for Conveying and Handling of Paniculate Solids, pp 10.75-80. Dead Sea. May/June 2000. 6. D. Mills. A review of the research work of Professor Predrag Marjanovic. Proc 4th Int Conf for Conveying and Handling of Paniculate Solids. Budapest. May 2003. 7. M.S.A. Bradley and D. Mills. Approaches to dealing with the problem of energy losses due to bends. Proc 13lh Powder and Bulk Solids Conf. pp 705-715. Chicago. May 1988. 8. P. Marjanovic, D. Mills, and J.S. Mason. The influence of bends on the performance of a pneumatic conveying system. Proc 15th Powder and Bulk Solids Conf. pp 391- 399. Chicago. June 1990. 9. D. Mills and J.S. Mason. The influence of bend geometry on pressure drop in pneumatic conveying system pipelines. Proc 10th Powder and Bulk Solids Conf. pp 203- 214. Chicago. May 1985. 10. M.S.A. Bradley. Pressure losses caused by bends in pneumatic conveying pipelines: effects of bend geometry and fittings. Proc 14th Powder and Bulk Solids Conf. pp 681- 694. Chicago. May 1989. 11. P. Marjanovic, D. Mills, and J.S. Mason. The influence of pipeline material on the performance of pneumatic conveying systems. Proc Pneumatech 4. pp 453-464. Glasgow. June 1990. 12. D. Mills. Using rubber hose to enhance your pneumatic conveying process. Powder and Bulk Engineering, pp 79-87. March 2000.