固液混合物液流参数对磨损的影响

    下面分析混合物液流各个参数对零件磨损的影响。首先，研究固体颗粒浓度的影响。固体颗粒与表面接触的数量越多，零件表面磨损就越快，即零件磨损与固体颗粒浓度成正比。但是，在颗粒与被磨损表面接触时，固体颗粒反射回去并形成遮盖层，妨碍部分固体到达磨损的表面。
    根据下列理由来估价遮盖层对磨损过程的影响。
    研究其底面积为F而高度等于混合物液流速度w的棱柱，被包括在棱柱体积内的固体颗粒数量为
    另一方面，假定固体颗粒之间平均距离为b.得到同核柱体积内颗粒数最为
    在混合物液流中固体颗粒之间平均重高6= T.而颗粒在单位液流断面积上的分布密度为
    例如，如果研究面积为F叶片表面的混合物液流绕流，那么在表面上可以布置固体颗粒的数量，由此，可得到

    在磨损开始瞬时，所有A固体颗粒都可能落在面积F的表面上；同时其中一部分颗粒从这个表面上反射回去并与混合物液流一起运动颗粒相撞，即产生被磨损表面的掩盖层。在第一次反射后，一部分到达磨损表面的新颗粒将不等于A，而是A（1-n）

式中，n为反射颗粒与眼混合物液流运动的下一部分颗粒相撞的概率。在第三部分颗粒加入时，它们与数量为A(1-0)口的反射颗粒相遇，并且则有A-A(1- 0)Q-A(1-0+n4)的颗粒到达磨损表面。
    在i部分颗粒接近所研究表面时，到达表面的颗粒数量n=A(1-n+n*-n*+0+..-).
    当i趋于无限大时，数列将趋于n=A/(1+a>，这时颗粒在混合物中的数量和落到磨损表面上颗粒数量之间的关系为=1/(1+0)。
    下面确定从磨损表面反射的固体颗粒与运动液流中所含颗粒相撞的概率。

计算指出，如果所有反射颗粒(采用球形)最大截面的总面积等于所研究面积的0.48倍，那么遮盖层相当大，使混合物液流中所含的颗粒不能落在磨损表面上。于是，混合物运动液流中的颗粒和从表面上反射的颗粒之间相撞概率为

因此，零件线性磨损与0.4P/(0.4+P2n)成正比，这一点已由B.N.卡尔林、A.n.斯切尼金和E. I.札尔尼茨基用安放在流体中的柱体试祥和叶轮叶片的试验所证实。
由式(3-7-1)可以看出，混合物对泵零件的磨损慢于固体颗粒浓度的增加，下面研究浓度增加对泥沙的数量有何影响，在泵零件磨损相同时，泵可以输送的泥沙数量。令易磨损件如叶轮的线性磨损量等于A.So，于是aSo值与比值0. 4/(0. 4+ p/a)和磨损时间to成正比，即

因为以足够的精度可以用P2/3代替比值0.4P/(0.4+P2/3),所以OS,≈kP2/2no，由泵输送泥沙的体积为
    假定在固液混合物中固体颗粒浓度P1=0.1,通过泵泥沙的数量Vn,于是在输送浓度P的固液混合物时，通过泵泥沙数量增加为Vr/Vπ= VP/0. I,即在浓度增大时，在零件磨损相同的情况下可以输送较大量的泥沙。在浓度从0.1增大到0.25时，所输送泥沙量可以增加36%。
但是，应该注意，实际上固体颗粒浓度的提高，通常与泵的流量减少有关，即输送固体物料实际数量较少。

  下面研究所输送固体颗粒度即颗粒直径对零件磨损的影响。

    叶轮叶片前缘(入口边)扭曲和绕流，可以认为与圆柱绕流相似，所以对于估价泥沙粒度对磨损的影响，可以采用用本篇第二章第四节的资料。在其他条件相同的情况下，固体颗粒落在磨损表面上的数量越多，零件磨损就越快。在式(3-7-1)中，颗粒相对数量用系数确定，其数值与颗粒相对尺寸有关，即与颗粒直径和叶片厚度的比值有关，参阅本篇第二章第四节。
  根据式(3-7-1),表面线性磨损与混合物液流速度三次方有关。这与颗粒动能有关，在其作用下产生磨损。动能与混合物液流速度二次方成正比，而参与磨损的颗粒数量与泵的流量或者速度一次方成正比。因此，在泵的流量(或者在任意流道中的流量)变化时，例如在流道断面变化时，磨损与液流速度二次方成正此。这些情况已被很多试验所证实。渣浆泵厂家

Effect of Liquid Flow Parameters of Solid-liquid Mixture on Wear

Next, the influence of various parameters of liquid flow of mixture on the wear of parts is analyzed. Firstly, the influence of solid particle concentration is studied. The more solid particles contact with the surface, the faster the surface wear of parts, that is, the wear of parts is proportional to the concentration of solid particles. However, when the particles contact the worn surface, the solid particles reflect back and form a covering layer, which prevents some solids from reaching the worn surface.

The effect of the covering layer on the wear process is evaluated for the following reasons.

A prism with a base area of F and a height equal to the liquid velocity W of the mixture is studied. The number of solid particles included in the volume of the prism is as follows.

On the other hand, it is assumed that the average distance between solid particles is B. The maximum number of particles in the volume of the same core column is obtained.

The average weight of solid particles in liquid flow of mixture is 6= T, while the distribution density of particles in the cross section of liquid flow is 6= T.

For example, if the flow of liquid mixture over the surface of F blade is studied, the number of solid particles can be arranged on the surface, from which the number of solid particles can be obtained.

At the beginning of wear, all A solid particles may fall on the surface of area F. At the same time, some of them reflect back from the surface and collide with particles moving along with the liquid flow of the mixture, that is to say, a covering layer on the worn surface is formed. After the first reflection, a portion of the new particles reaching the worn surface will not be equal to A, but A(1-n)

In the formula, n is the probability of collision between the reflecting particles and the next part of the fluid flow of the eye mixture. In the third part, when the particles are added, they meet with the reflective particles whose number is A (1-0), and the particles of A-A (1-0) Q-A (1-0+n4) reach the wear surface.

The number of particles reaching the surface n=A (1-n+n*-n*+0+. -) when part I particles approach the studied surface.

When I tends to be infinite, the sequence tends to n=A/(1+a>), and the relationship between the number of particles in the mixture and the number of particles falling on the worn surface is equal to 1/(1+0).

Next, the probability of collision between the solid particles reflected from the worn surface and the particles contained in the moving fluid flow is determined.

It is pointed out that if the total area of the maximum cross section of all reflecting particles (spherical) is equal to 0.48 times of the studied area, the covering layer is quite large, so that the particles contained in the liquid flow of the mixture can not fall on the worn surface. Thus, the probability of collision between particles in the moving liquid flow of a mixture and particles reflecting from the surface is zero.

Therefore, the linear wear of parts is proportional to 0.4P/(0.4+P2n), which has been confirmed by the tests of B.N. Karlin, A.n. Schenickin and E.I. Zarnitzky on cylinders and impeller blades mounted in fluids.

Formula (3-7-1) shows that the wear rate of the mixture on the pump parts is slower than that of the solid particle concentration. Next, the influence of the increase of the concentration on the amount of sediment is studied. When the wear of the pump parts is the same, the amount of sediment that can be transported by the pump. The linear wear of wearable parts such as impellers is equal to A. So the aSo value is proportional to the ratio of 0.4/(0.4+p/a) and the wear time to.

Because the ratio of 0.4P/(0.4+P2/3) can be replaced by P2/3 with sufficient accuracy, the volume of sediment transported by pumps is 0.4P/(0.4+P2/3), so OS, kP2/2no.

Assuming the solid particle concentration P1 = 0.1 in the solid-liquid mixture and the amount of sediment through the pump Vn, the amount of sediment through the pump increases to Vr/Vpi= VP/0.I in the solid-liquid mixture with the concentration P, i.e. when the concentration increases, a large amount of sediment can be transported under the same wear condition of parts. When the concentration increases from 0.1 to 0.25, the sediment transported can increase by 36%.

However, it should be noted that, in fact, the increase of solid particle concentration is usually related to the decrease of pump flow, that is, the actual quantity of solid material conveyed is less.

The influence of solid particle size conveyed, i. e. particle diameter, on the wear of parts is studied below.

The distortion and flow around the leading edge (entrance) of impeller blade can be considered to be similar to that around a cylinder. Therefore, the data in Section IV of Chapter II of this chapter can be used to evaluate the effect of sediment particle size on wear. Under the same other conditions, the more solid particles fall on the worn surface, the faster the parts wear. In formula (3-7-1), the relative number of particles is determined by the coefficient. Its value is related to the relative size of particles, i.e. the ratio of particle diameter to blade thickness. See Section 4 of Chapter 2 of this chapter.

According to formula (3-7-1), the linear wear of the surface is related to the cubic velocity of liquid flow in the mixture. This is related to the kinetic energy of particles, which causes wear and tear under the action of particles. Kinetic energy is proportional to the quadratic square of the liquid flow velocity of the mixture, and the number of particles involved in wear is proportional to the flow rate or the first square of the velocity of the pump. Therefore, when the flow rate of the pump (or the flow rate in any channel) changes, such as when the cross-section of the channel changes, the wear and liquid flow velocity quadratic square here. These conditions have been confirmed by many experiments.