介质黏性对渣浆泵性能的影响
    在油气储运工程中，有许多油品的黏度上与清水不同，用离心泵输送这些油品时,因为黏度的增加，使得泵内部的能量损失加大，扬程和流量都要减小，并导致效率下降，而轴功率却增加，泵的特性曲线发生变化，如图1-34所示。当输送液体运动粘度v>20mm2/s时，泵的特性曲线就需要换算，为此应该号虑不同黏度下泵性能的换算方法。
2. 特性曲线换算方法
    目前，还没有成熟的纯理论推导方法能精确地确定出抽送黏性液体的泵性能曲线。常用的换算方法有前苏联国家石油机械研究设计院的标准曲线法、美国水力协会的图线换算法和德国KSB公司的换算方法。其共同特征都是在大量实验的基础上,给出各性能曲线的修正系数图并以此进行换算。
    目前，国内多采用美国水力协会方法进行黏度换算。当已知某离心泵输送20C清水的特性曲线时,利用下列关系式换算成输送黏性液体的特性曲线:

使用本方法时，不需知道离心泵叶轮尺寸，只需知道被输送液体的运动黏度和输送清水时ηmsx工祝点的Q0和Ho (多级泵应取单级叶轮的扬程)，然后利用图1-35或图1-36查出各换算系数，并将换算系数代入式(1-44) 即可。

    使用图1-35或图1-36时，在横坐标上取Q=Q0点作垂线，与H=H0的斜线相交，自交点作水平线与所输送液体的运动黏度为v的斜线相交，从该交点再作垂线与图上方的各换算曲线相交，得到各换算系数。
    应用此法换算范围较宽: (0.6~1.2) Q.，换算误差在v<865mm2/s时不超过士5%，特别当v<400mm2/s时更准确。
    应当注意，该二图只适用于一般结构的离心泵，且在不发生汽蚀的工况下进行换算。它不适用于混流泵、轴流泵，也不适用于含有杂质的非均相液体。此外，图中各曲线不能用外推法延伸使用。
    美国水力协会对世界范围内大量的实验数据进行了分析和研究，给出了近似的换算公式，形成了技术报告，并由国际标准化组织在2005年发布了此报告(ISO/TR 17766-2005)。

根据ISO/TR 17766 的公式计算法对性能曲线进行换算时，公式计算法的适用范围为:介质必须是牛顿型流体;泵只能是离心泵，不适用于混流泵、轴流泵和旋涡泵;运动黏度v= 1~4000mm2/s;比转速ns ≤60;泵有效汽蚀余量NPSH.足够大。
首先引入黏度换算过程参数B,其定义为:

B的范围为B< 40(B≤1时，则设定CH=1,Cq=1)。

流换算系数Co的计算公式为：

扬程换算系数Cu的计算公式为:
效率换算系数C,的计算公式为:
[例1-4]某泵在转速n= 1475r/min输送清水时在4个工况点0. 6Qur w、0. 8QeF-W、1.0QEP-w.1.2QBEP-w的流量、扬程和效率，见表1-4。现用该泵输送原油，密度ρ=956kg/m3，运动黏度vi = 200mm2/s。采用美国水力协会方法对性能参数进行换算(分别采用查图法和公式计算法)。

从图1-35横坐标的流量Qw处垂直向上，直到与给定的扬程Hw相交于一点,从此相交点水平向右或向左,再与原油介质的运动黏度v.i相交，并由此垂直向上，与各换算系数CH、Cq、C,相交，即可得出各换算系数，即Cq=0.93,C,=0.63,CH在4个工况点0.6QsEP-w、0.8QkE w.1. 0QwEP- w.1.2Q w的值分别为0.95 .0. 93.0.91.0.87。泵轴功率P的计算公式为:
                                       P=HQs/367η
    根据式(1- 4)式(1- 50)可计算出输送原油时离心泵的流量.扬程、效率和轴功率，见表

根据ISO/TR 7766的公式计算法对性能曲线进行换算。把Vu = 20mm2/s，Q =139m3/h.N= 1475/min.Hur w= 48m带入式(1- 46)得:
流量换算系数:
    根据公式(1 - 48)计算可求得扬程换算系数CH在4个工况点0. 6QBEP-w、0.8QuEP- w、1. 0QeEP- w、1. 2QEP- w的值分别为0. 930、0. 913、0. 897、0.882。
根据公式(1- 49)计算可求效率换算系数C,为0. 641。渣浆泵
    把流量、扬程、效率的换算系数带入式(1-44)、式(1- 50)可计算出输送原油时离心泵的流量、扬程、效率和轴功率，见表1- 6。

1-5。

Effect of medium viscosity on the performance of slurry pump

In the oil and gas storage and transportation engineering, the viscosity of many oil products is different from that of clean water. When the centrifugal pump is used to transport these oil products, the increase of viscosity will increase the internal energy loss of the pump, reduce the head and flow, and lead to the decrease of efficiency. However, the shaft power increases, and the characteristic curve of the pump changes, as shown in Figure 1-34. When the kinematic viscosity of the conveying liquid V > 20mm2 / s, the characteristic curve of the pump needs to be converted. Therefore, the conversion method of pump performance under different viscosity should be considered.

2. Conversion method of characteristic curve

At present, there is no mature theoretical derivation method to accurately determine the performance curve of the pump pumping viscous liquid. The commonly used conversion methods are the standard curve method of the National Petroleum Machinery Research and Design Institute of the former Soviet Union, the chart line conversion algorithm of the American Hydraulic Association and the conversion method of KSB company of Germany. The common feature is that on the basis of a large number of experiments, the correction coefficient diagrams of each performance curve are given and converted.

At present, the method of American Hydraulic association is widely used in viscosity conversion in China. When the characteristic curve of 20c clear water delivered by a centrifugal pump is known, it can be converted into the characteristic curve of viscous liquid delivered by the following formula:

When using this method, it is not necessary to know the impeller size of the centrifugal pump, only the kinematic viscosity of the delivered liquid and Q0 and ho of η MSX working point when delivering clean water (the lift of single-stage impeller should be taken for multi-stage pump), then use figure 1-35 or figure 1-36 to find out each conversion coefficient, and substitute the conversion coefficient into equation (1-44).

When using figure 1-35 or figure 1-36, take point q = Q0 on the abscissa as the vertical line, intersect with the oblique line of H = H0, and self intersection point as the horizontal line intersects with the oblique line of the kinematic viscosity of the liquid delivered as v. from this intersection point, make the vertical line intersect with each conversion curve above the figure to obtain each conversion coefficient.

The conversion range is wide: (0.6 ~ 1.2) Q. the conversion error is less than ± 5% when V < 865mm2 / s, especially when V < 400mm2 / s.

It should be noted that the second drawing is only applicable to the centrifugal pump of general structure, and the conversion is carried out under the condition of no cavitation. It is not suitable for mixed flow pump, axial flow pump, and heterogeneous liquid containing impurities. In addition, the curves in the figure cannot be extended by extrapolation.

The American Hydraulic association has analyzed and studied a large number of experimental data in the world, given approximate conversion formulas, and formed a technical report, which was issued by the international organization for Standardization in 2005 (ISO / TR 17766-2005).

When the performance curve is converted according to the formula calculation method of ISO / TR 17766, the application scope of the formula calculation method is: the medium must be Newtonian fluid; the pump can only be centrifugal pump, which is not suitable for mixed flow pump, axial flow pump and vortex pump; the kinematic viscosity v = 1 ~ 4000mm2 / S; the specific speed ns ≤ 60; the effective NPSH of the pump is large enough.

Firstly, parameter B of viscosity conversion process is introduced, which is defined as:

The range of B is B < 40 (when B ≤ 1, set ch = 1, CQ = 1).

The calculation formula of flow conversion coefficient CO is:

The calculation formula of head conversion coefficient Cu is as follows:

The calculation formula of efficiency conversion coefficient C is:

[example 1-4] see table 1-4 for the flow, lift and efficiency of 0.6qur W, 0.8qef-w and 1.0qep-w.1.2qbep-w at four operating points when the speed of a pump is n = 1475r / min to deliver clean water. The pump is now used to transport crude oil with density ρ = 956kg / m3 and kinematic viscosity VI = 200mm2 / s. The performance parameters are converted by the method of American Hydraulic Association (using the method of looking up the chart and the method of formula calculation respectively).

From the flow QW in the abscissa of Fig. 1-35, it is vertically upward until it intersects with the given lift HW at a point, from which it is horizontally right or left, and then intersects with the kinematic viscosity V.I of the crude oil medium, and then vertically upward, intersects with each conversion coefficient ch, CQ, C, to obtain each conversion coefficient, that is, CQ = 0.93, C, = 0.63, The values of CH at four operating points are 0.6qsep-w, 0.8qke w.1.0qwp-w.1.2qw, respectively, 0.95.0.93.0.91.0.87. The calculation formula of pump shaft power P is:

P=HQs/367 ETA

According to formula (1-4) (1-50), the flow, head, efficiency and shaft power of the centrifugal pump can be calculated when delivering crude oil, as shown in table

According to the formula calculation method of ISO / TR 7766, the performance curve is converted. Take Vu = 20mm2 / s, q = 139m3 / h, n = 1475 / min, HuR w = 48m into the formula (1-46)

Flow conversion factor:

According to the formula (1-48), the values of head conversion coefficient ch at four working points, 0.6qbep-w, 0.8qep-w, 1.0qeep-w and 1.2qep-w, are 0.930, 0.913, 0.897 and 0.882 respectively.

According to the formula (1-49), the efficiency conversion coefficient C is 0.641. Slurry pump

Take the conversion coefficient of flow, head and efficiency into formula (1-44) and formula (1-50) to calculate the flow, head, efficiency and shaft power of centrifugal pump when delivering crude oil, as shown in table 1-6.

1-5.