渣浆泵抽送悬浮物的特性曲线
一、泵抽送悬浮物时的性能变化
    当悬浮物液流在流道内的流动速度超过那个假定的雷诺数Re具有确定值的速度值时，流动变为自模流动。在这种情况下，抽送悬浮物和清水时的水力摩擦损失是相同的。
    当悬浮物流动时，叶轮流道内水力摩擦损失变化将影响泵内总的水力损失。在具有强烈混合液流即具有混合损失的压水室内，水力损失为自模损失。
    悬浮物在叶轮流道内的流动速度主要与圆周速度有关，在渣浆泵中这种速度相当大。

应该考虑从伪层流状态过渡到自模状态，在假定的雷诺数Re很宽变化范图内发生。如果伪层流状态在Re' <3000时开始，那么自模状态在Re=11000-12000时稳定。在靠近最佳状态，以及一般雷诺数大于对应自模状态值的大多数情况下大流量状态，和只有在小流址状态，在泵一些断面上可能产生与自模状态有显著区别的流动状态。

这样，泵的大多数状态将是自模状态。因此泵过流部件流道内的损失，无论在抽送清水或者抽送悬浮物时将是相同的。
  当很小流量时，流速下降，以至叶轮流道内流动状态从自模转变为紊动或者层流状态，在这种情况下，水力损失远比同样速速时自模状态下损失大(参阅图2-3- 4).
  过流部件流道内水力摩擦损失的增大，将导致小流量时泵扬程特性曲线的“凹陷”现象发生(图3-6-2).在很小流量时，叶轮和压水室之间大量流体进行强烈交换，这就导致紊动或者自模状态发生，杨程略有增加，接近泵抽送为质液体时的扬程。
   悬浮物密度越大，对应自模状态开始的雷诺数Re就越大(在相同悬浮物流速时)，因此，当悬浮物密度增大时，扬程特性曲线在小流量的情况下降低较为明显。
  因为泵抽送清水和悬浮物时理论扬程相同，所以它们的水力功率也与悬浮物和清水的密度有关。轴承和填料函摩擦损失功率，占水力功率的百分数不大。泵抽送悬浮物时圆盘损失功率与抽送清水时圆盘损失功率的比值远大于悬浮物和清水的密度之比。其理由说明如下。在叶轮腔内大部分液体的角速度，一次近似时采用等于叶轮角速度的一半。随着腔内液体到泵轴的距离减小，圆周速度降低。当悬浮物在腔内圆周速度明显减小时，流动状态不再是自模状态。这种现象与所研究两个腔的范围摩擦增大有关。这样，在泵抽送悬浮物时，观察到圆盘摩擦损失增大。这种效应在液体侧向吸入的泵上特别显著，在泵上叶轮后盖是整体的(无穿轴孔)，即存在具有很小圆周速度的很大表面。因此，在这个区域内悬浮物以很小速度旋转。
  根据IO. H莫吉列夫斯基进行的磁铁粉和硅铁悬浮物高液度试验资料，为了考虑圆周摩擦附加损失，必须将泵的功率比泵抽送同样密度均质液体时功率增大10%~12%。因此，如果知道泵抽送清水时的功率No,那么抽送悬浮物时的功率为
  现在我们研究泵抽送悬浮物时汽蚀余R相对于抽送清水时汽蚀余量的变化。
  因为泵在很宽流量范围内扬程特性曲线(很小流量状态除外)，与抽送请时一样，所以，各种损失，特别是叶轮入口损失也与抽送清水时一样。
  现有试验资料证明，与抽送清水泵相比，抽送悬浮物泵的汽蚀特性曲线明显恶化(图8-6-3）泵抽送悬浮物时允许汽蚀余量Oh比抽送清水时汽蚀余量有所增加，其理由说明如下。

物体绕流时，在一定距离上可以观察到流动减速。例如，圆柱绕流时，均匀速度场在圆柱前面5~6倍半径的距离上开始破坏。经常出现物体绕流分流奇点，其速度等于零。
  我们研究在相对运动中叶片入口边绕流。因为抽送磨蚀性固液混合物泵叶轮叶片相对厚度很大，叶片入口段绕流可以看作圆柱表面绕流。在叶轮入口可以观察到悬浮物液流的紊流状态。由于在叶片入口边之前液流减速，液流沿着一些流线的速度降低到临界速度u，在此速度时，液流开始具有不完全破坏结构。因为叶片入口边绕流的分流点(在此点相对速度等于零)处在叶片前面，在这个区域内形成黏塑性流体(图3-6-4)，这种流体已不是牛顿流体。这种流体与塑性体相似，以接近临界速度v的速度运动。
  由于在叶片入口处整个液流发生排挤，这就导致在不是塑性体所占据的液流其余部分内速度增大，其中包括叶片背面上的速度(图3-5-4,点a).因此，在这点速度最大，而压力最小。因为悬浮物液流局部速度比清水(相同流量时)的局部速度增长快，所以泵抽送悬浮物时汽蚀特性曲线恶化。
  在叶片前面点b区域内，由于速度降低，就形成压力很高的区域。压力增量用Ap表示。作用在体积为V.制动部分的悬浮物上的冲量与spf成正比(式中，f为体积V颗粒最大截面面积).在入口边之前压力局部下降，与速度头和叶轮入口相对速度w1有关，可以认为sp=Cpwf/2 (式中，C为比例系数)。

根据动量变化方程式可以认为，

制动颗粒体积与液体流量成正比，即与叶轮入口处的是速度c1成正比，因此，形成塑性体最大截面面积越大，在叶轮入口液流附加排挤就越大。渣浆泵厂家

Characteristic curve of pumping suspended solids

CHANGES IN PERFORMANCE OF PUMPING SUSPENDED MATERIALS

When the velocity of suspended solids flow in the channel exceeds that assumed Reynolds number Re with a fixed value, the flow becomes self-mode flow. In this case, the hydraulic friction loss is the same when pumping suspended solids and clean water.

When the suspension flow moves, the change of hydraulic friction loss in impeller passage will affect the total hydraulic loss in the pump. In a pressurized water chamber with strong mixing fluid flow, i.e. mixing loss, the hydraulic loss is self-model loss.

The velocity of suspended solids in impeller passage is mainly related to the circumferential velocity, which is quite large in slurry pump.

Consideration should be given to the transition from pseudo-laminar state to modelling state, which occurs in the hypothetical Reynolds number wide variation paradigm. If the pseudolaminar flow begins at Re'< 3000, the self-model state is stable at Re=11000-12000. In most cases when the Reynolds number is greater than the corresponding self-model state value, the flow state with large flow rate may be significantly different from the self-model state on some sections of the pump in the condition of small flow location.

In this way, most of the state of the pump will be self-model state. Therefore, the loss in the passage of the flow passage of the pump components will be the same whether it is pumping clean water or suspended solids.

When the flow rate is very small, the flow velocity decreases, so that the flow state in the impeller passage changes from a model to a turbulent or laminar flow state. In this case, the hydraulic loss is much greater than that in the self-model state at the same speed (see Figure 2-3-4).

The increase of hydraulic friction loss in flow passage of flow passage components will lead to the "depression" phenomenon of pump head characteristic curve at small flow rate (Figure 3-6-2). At very small flow rate, a large amount of fluid is exchanged intensively between impeller and pressure chamber, which leads to turbulence or self-modelling, and the Yang-Cheng increases slightly, approaching pumping as liquid mass. Lift of body time.

The Reynolds number Re at the beginning of self-model state increases with the increase of suspended matter density (at the same suspended material flow rate). Therefore, when the suspended matter density increases, the head characteristic curve decreases obviously under the condition of small flow rate.

Because the theoretical lift of pumping clear water and suspended solids is the same, their hydraulic power is also related to the density of suspended solids and suspended solids. The friction loss power of bearings and stuffing box accounts for a small percentage of hydraulic power. The ratio of disc loss power to disc loss power in pumping suspended solids is much larger than that in pumping clear water. The reasons are as follows. In the first approximation, the angular velocity of most liquid in the impeller chamber is equal to half of the angular velocity of the impeller. The circumferential velocity decreases as the distance between the liquid in the cavity and the pump shaft decreases. When the circumferential velocity of suspended solids in the cavity decreases significantly, the flow state is no longer self-modeled. This phenomenon is related to the increase of friction in the range of the two cavities studied. In this way, when the suspended matter is pumped by the pump, it is observed that the friction loss of the disc increases. This effect is particularly significant in lateral liquid suction pumps, where the impeller back cover is integral (without perforation), i.e. there is a large surface with a small circumferential velocity.  Therefore, the suspended matter rotates at a very small speed in this area.

According to IO. H. Mogilevski's high liquid test data of magnet powder and ferrosilicon suspension, in order to consider the additional loss of circumferential friction, the power of the pump must be increased by 10%~12% compared with that of pumping homogeneous liquid with the same density. Therefore, if the power of pumping clear water is known to be No, then the power of pumping suspended solids is zero.

Now we study the change of cavitation residual R in pumping suspended solids relative to that in pumping clean water.

Because the pump head characteristic curve in a wide flow range (except for very small flow state) is the same as when pumping, so all kinds of losses, especially the impeller inlet loss, are the same as when pumping clean water.

The available test data prove that the cavitation characteristic curve of pumping suspended solids pump is worse than that of pumping clean water pump (Figure 8-6-3). The allowable cavitation allowance Oh of pumping suspended solids is higher than that of pumping clean water. The reasons are as follows.

The deceleration of flow can be observed at a certain distance when an object flows around it. For example, when a cylinder flows around it, the uniform velocity field begins to destroy at a distance of 5 to 6 times the radius in front of the cylinder.  Singularities of flow diversion around objects often occur, and their velocities are equal to zero.

We study the flow around the blade inlet in relative motion. Because the relative thickness of impeller blade of pumping abrasive solid-liquid mixture pump is very large, the flow around the blade inlet can be regarded as the flow around the cylinder surface. Turbulence of suspended solids can be observed at the inlet of impeller. Because the liquid flow decelerates before the blade inlet, the velocity of the liquid flow along some streamlines decreases to the critical velocity U. At this velocity, the liquid flow begins to have an incomplete destruction structure. Because the shunt point (where the relative velocity is equal to zero) of the flow around the blade inlet is in front of the blade, viscoplastic fluid is formed in this area (Fig. 3-6-4), which is no longer Newtonian fluid. This fluid is similar to the plastic body and moves at a speed close to the critical velocity v.

Because of the squeezing of the whole flow at the blade entrance, the velocity in the rest of the flow, which is not occupied by the plastic body, increases, including the velocity on the back of the blade (Fig. 3-5-4, point a). Therefore, the velocity is the highest at this point and the pressure is the lowest. Because the local velocity of suspended solids flow increases faster than that of clear water (at the same flow rate), the cavitation characteristic curve deteriorates when suspended solids are pumped.

In front of the blade