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渣漿泵的比轉(zhuǎn)速類型和規(guī)格
離心泵的類型和規(guī)格很多，結(jié)構(gòu)也多種多樣，很難對(duì)其性能進(jìn)行綜合比較，而且在研制新型泵時(shí)，由于泵內(nèi)流動(dòng)狀況復(fù)雜，往往在參照現(xiàn)有泵的基礎(chǔ)上進(jìn)行試驗(yàn)和設(shè)計(jì)。這樣，在有的分類、試驗(yàn)設(shè)計(jì)和產(chǎn)品系列化方面，就引進(jìn)了比轉(zhuǎn)速這一概念,用n.表示。
1.比轉(zhuǎn)速表達(dá)式
取相似定律的式(1 - 55)及式(1 -56).消去2u.得:
取20C時(shí)清水密度ρ= 1000kg/m3，g=9. 81m/s2，有:
式中n----離心泵轉(zhuǎn)速，r/min；
Q----流量(最高效率下，對(duì)于雙吸葉輪，取值為葉輪總流量的一半),m/s;
H----揚(yáng)程(最高效率下 ,對(duì)于多級(jí)泵應(yīng)以H/i代入,i為級(jí)數(shù)),m。
式(1-61)是我國習(xí)慣采用的比轉(zhuǎn)速表達(dá)式，它是有因次的。在歐美國家習(xí)慣用，采用的單位不同,計(jì)算值也不同,本質(zhì)上沒有區(qū)別。比轉(zhuǎn)速的因次是(m/s)”，它正好是重力加速度因次的3/4次方，因此把比轉(zhuǎn)進(jìn)除以”，再把轉(zhuǎn)速，汝為角速度，就變?yōu)闊o國次，稱為型式數(shù)。GB/T 3216 205規(guī)定的量式數(shù)計(jì)算公式為:
比轉(zhuǎn)速和型式數(shù)之間的關(guān)系為:
比轉(zhuǎn)速是由相似定律導(dǎo)出的綜合參數(shù)，它是工況的函數(shù)，對(duì)于同一臺(tái)泵來說，不同渣漿泵工況就有不同的比轉(zhuǎn)速，應(yīng)以其設(shè)計(jì)工況點(diǎn)(或最高效率點(diǎn))的比轉(zhuǎn)速來代表這臺(tái)泵的比轉(zhuǎn)速。幾何相似的泵在各自最高效率點(diǎn)處的工況相似,因此其比轉(zhuǎn)速相等。比轉(zhuǎn)速不同的泵，其幾何形狀一定不相似:比轉(zhuǎn)速 相同的泵其幾何形狀也不一定完全相似。
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.
