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相似理論在渣漿泵中的應(yīng)用描述和計(jì)算
由于液體在離心泵中的流動(dòng)過程十分復(fù)雜，很難依靠理論方程來描述和計(jì)算，一般多采用試驗(yàn)的方法進(jìn)行研究，因此需要使用流體力學(xué)中的相似原理來指導(dǎo)試驗(yàn)并把試驗(yàn)結(jié)果應(yīng)用到實(shí)際問題中。相似原理為離心泵的相似設(shè)計(jì)、試驗(yàn)研究和性能換算等方面提供了可靠的理論依據(jù)。
一、離心泵相似條件
要保證液體在兩泵中流動(dòng)相似，必須滿足兩泵幾何相似、運(yùn)動(dòng)相似和動(dòng)力相似。在本節(jié)論述過程中，將兩臺(tái)要進(jìn)行性能換算的離心泵分別稱為模型泵和原型泵，并用右上角打撇的參數(shù)表示模型泵的參數(shù)。
(1)幾何相似。幾何相似是指模型泵和原型泵通流部分的幾何形狀相似，即對(duì)應(yīng)的線性尺才之比等于比例常數(shù)A.(a. = D:/D.也稱比例縮放系效)，對(duì)應(yīng)的葉片幾何角和葉片數(shù)均相等。
(2)運(yùn)動(dòng)相似。運(yùn)動(dòng)相似是指流體在泵內(nèi)流動(dòng)過程中.兩泵的對(duì)應(yīng)點(diǎn)上同名流動(dòng)速度的比值相等，并等于速度比例常數(shù)λ.同時(shí)同名速度的方向角也相等。
(3)動(dòng)力相似。動(dòng)力相似是指兩泵對(duì)應(yīng)點(diǎn)上作用的同名力之比相等，并等于力比例常數(shù)不，同名力的方向相同。對(duì)離心泵而言，不需要所有的力之比都相等，僅保證黏性力和慣性力之比相等即可，即兩泵的雷諾數(shù)Re相等就是動(dòng)力相似的充要條件。因?yàn)殡x心泵中雷諾數(shù)一般大于105,此時(shí)流動(dòng)阻力和運(yùn)動(dòng)狀況已不隨Re而變化，自動(dòng)滿足動(dòng)力相似的要求。渣漿泵
因此，對(duì)Re>105的兩泵的相似條件是:幾何相似和進(jìn)口運(yùn)動(dòng)相似。符合上述相似條件的泵稱為相似泵。
Application description and calculation of similarity theory in slurry pump
Because the flow process of liquid in centrifugal pump is very complex, it is difficult to describe and calculate by theoretical equation. Generally, experimental method is used to study, so it is necessary to use the similarity principle of hydrodynamics to guide the test and apply the test results to practical problems. The similarity principle provides a reliable theoretical basis for similar design, experimental research and performance conversion of centrifugal pump.
1、 Similar conditions of centrifugal pump
In order to ensure that the flow of liquid in the two pumps is similar, it is necessary to meet the geometric similarity, motion similarity and dynamic similarity of the two pumps. In this section, the two centrifugal pumps to be converted are called model pump and prototype pump respectively, and the parameters of model pump are represented by the parameters of skimming in the upper right corner.
(1) Geometric similarity. Geometric similarity refers to the geometric similarity of the flow passage parts of the model pump and the prototype pump, that is, the ratio of the corresponding linear scale is equal to the scale constant A. (A. = D: / d. also known as the scale factor effect), and the corresponding blade geometric angle and blade number are equal.
(2) Movement is similar. Motion similarity refers to the fact that the ratio of the flow velocity of the same name at the corresponding point of the two pumps is equal, and it is equal to the velocity ratio constant λ. At the same time, the direction angle of the same name velocity is also equal.
(3) Similar dynamics. Dynamic similarity refers to the fact that the ratio of the forces acting on the corresponding points of two pumps with the same name is equal and equal to the constant of the force proportion, and the direction of the forces with the same name is the same. For centrifugal pumps, it is not necessary to make the ratio of all forces equal, only to make sure that the ratio of viscous force and inertia force is equal, that is, the Reynolds number Re of the two pumps is equal, which is the necessary and sufficient condition for the dynamic similarity. Because the Reynolds number in the centrifugal pump is generally greater than 105, the flow resistance and the motion state do not change with Re, and automatically meet the requirements of dynamic similarity. Slurry pump
Therefore, the similarity condition of two pumps with re > 105 is that the geometry is similar to the inlet motion. The pumps that meet the above similar conditions are called similar pumps.
