渣浆泵的比转速类型和规格

离心泵的类型和规格很多，结构也多种多样，很难对其性能进行综合比较，而且在研制新型泵时，由于泵内流动状况复杂，往往在参照现有泵的基础上进行试验和设计。这样，在有的分类、试验设计和产品系列化方面，就引进了比转速这一概念,用n.表示。
1.比转速表达式
取相似定律的式(1 - 55)及式(1 -56).消去2u.得:
取20C时清水密度ρ= 1000kg/m3，g=9. 81m/s2，有:
式中n----离心泵转速，r/min；
    Q----流量(最高效率下，对于双吸叶轮，取值为叶轮总流量的一半),m/s;

H----扬程(最高效率下 ,对于多级泵应以H/i代入,i为级数),m。
式(1-61)是我国习惯采用的比转速表达式，它是有因次的。在欧美国家习惯用，采用的单位不同,计算值也不同,本质上没有区别。比转速的因次是(m/s)”，它正好是重力加速度因次的3/4次方，因此把比转进除以”，再把转速，汝为角速度，就变为无国次，称为型式数。GB/T 3216 205规定的量式数计算公式为:
比转速和型式数之间的关系为:

比转速是由相似定律导出的综合参数，它是工况的函数，对于同一台泵来说，不同渣浆泵工况就有不同的比转速，应以其设计工况点(或最高效率点)的比转速来代表这台泵的比转速。几何相似的泵在各自最高效率点处的工况相似,因此其比转速相等。比转速不同的泵，其几何形状一定不相似:比转速 相同的泵其几何形状也不一定完全相似。

Specific speed type and specification of slurry pump

There are many types, specifications and structures of centrifugal pumps, so it is difficult to make a comprehensive comparison of their performance. Moreover, in the development of new pumps, due to the complex flow conditions in the pump, tests and designs are often carried out on the basis of referring to the existing pumps. In this way, the concept of specific speed is introduced in some classification, experimental design and product serialization, which is expressed by n.

1. Expression of specific speed

Take the formula (1-55) and formula (1-56) of the similar law, and eliminate 2U

At 20c, the clear water density ρ = 1000kg / m3, g = 9.81m/s2, including:

Where, N - rotating speed of centrifugal pump, R / min;

Q --- flow (under the highest efficiency, for double suction impeller, the value is half of the total flow of impeller), M / S;

H ---- head (under the highest efficiency, H / I shall be substituted for multistage pump, I is the series), M.

Formula (1-61) is the expression of specific speed which is used in our country. It has dimensions. In European and American countries, it is used in different units, and the calculated value is different, so there is no difference in essence. The factor of specific speed is (M / s) ", which is exactly the third fourth power of the factor of gravity acceleration. Therefore, divide the specific speed by", and then turn the speed, Ru, into angular speed, which becomes stateless, called the type number. According to GB / T 3216 205, the calculation formula of the quantity formula is:

The relationship between specific speed and type number is as follows:

Specific speed is a comprehensive parameter derived from the law of similarity, which is a function of working conditions. For the same pump, different slurry pump working conditions have different specific speed. The specific speed of the design working point (or the highest efficiency point) should be used to represent the specific speed of the pump. Pumps with similar geometry have similar working conditions at their highest efficiency points, so their specific speed is equal. The geometry of pumps with different specific speed must be different: the geometry of pumps with the same specific speed may not be exactly similar.