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渣漿泵流量系數對計算速度的影響
下面研究系數a對只有隔舌斷面高度hg變化時，即泵流量和揚程恒定情況下面積Fs變化時壓水室斷面上速度的影響。這種分析在抽送細固體顆粒固液混合物泵壓水室設計時具有重要意義。在這種情況下，hg 尺寸的選擇，不是根據固體顆粒粒徑，而是根據壓水室內的水力損失和決定其磨損的速度值。
壓水室計算斷面上 A值，因而面積F...隨著系數。值的增大面增大。因為相對比值A/a為恒定值，其參數A與a成正比增大，計算斷面上的流量與a也成正比增大。為了簡化分析，采用壓水室為矩形，于是得到
從這些表達式中看出，參數A與相對比值R3/R2的對數值成正比增大，而計算斷面面積與(R3/R2-1)值成正比增加，即隨著相對流量系數。增大，計算斷面上的液流速度減小，而且在環形壓水室內其平均值最小。
壓力短管喉部斷面面積也隨著a的增大而增大，因而速度u減小。在環形壓水室時，壓力短管喉部液體流速將有最小值。在其他條件相同時，在環形壓水室內特征速度u最小。
知道泵的參數和主要尺寸，就可確定在下列情況下其隔舌斷面高度h不同的壓水室計算斷面上的系數a和速度u：
(1)擴散管喉品固積F與計算斷面面積F,.之比，在各種a值情況下是恒定的(在個別情況下，為簡化分析，可以采用F-F..).。
(2) 盡管水力效率有一定變化，當R,=常數時，水泵揚程H=常數。
(3)在估算普通螺旋形壓水室內流速時，水力效率可以采用清水泵統計資料(在n,相似情況下)。
如來不考慮壓水室斷面尺才變化時泵的水力效率(m) 變化，那么根據表達式(3-3 -5)可以寫為
式中K,一當泵的參數恒定時為常數， 根據式(3-3-4) 計算，K =0.010DxO/B
根據對不同參數和尺寸泵的對應于最高水力效率狀態的關系式U.c= f(a)和ur=f(a)的數值分析結果，得到所研究參數的相似變化(圖3-3-5)。 值a從1增大到1.85，將導致計算斷面上液流平均速度和擴散管入口速度下降(后種速度下降特別大)。如果考慮在最高水力效率狀態時工作，速度Uy和Ur相等，那么對Ug=f(a)來說關系式Ur=f(a)是正確的。這樣，在螺旋形壓水室過渡到環形壓水室時，在壓水室各斷面上速度都將下降。
眾所周知，泵在最佳和大流量狀態工作時，在計算斷面區最大半徑R3 (圖3-3-1上點A)上，觀察到渣漿泵壓水室內磨損穿透。在大多數情況下，決定整個壓水室壽命的這種磨損，與計算斷面上平均速度大小無關，而與半徑R,斷面壁面上速度大小有關。因此，感興趣的是相對流量系數(即壓水室形狀)對泵參數恒定時速度u的影響的分析。
為了簡化起見，在個別情況下，采用E-F... 于是根據式(3-3-5),擴散管喉部速度為
在簡比分析所采用矩形壓水室斯面壁面上的液流速度，根據在對應最高水力效率狀態下工作時這個斷面上的速度矩為常數，則為
在推導速度u3的表達式時，采用了R3=R2+h..=RreM
從圖3-3-5上可知，在壓水室計算斷面外壁上速度也隨著相對流量系數a的增大而減小。
如果采用在各種個斷面上速度相等時，其磨損將近似相同，那么擴散管喉部斷面和計算斷面耐磨性相等的 。條件是速度Ur和..相等，可以寫成下列形式
上述分析指出，甚至在不要求增大隔舌斷面高度的情況下，根據大固體顆粒通過的可能性，為了降低壓水室斷面上的速度，放棄螺旋式壓水室是合理的，同時如下指出那樣，水力損失增加，即降低整臺泵的水力效率。應該注意，因為磨損與液體速度二次方成正比(如下面指出那樣)，降低承受最強烈磨損的壓水室斷面上的速度，是提高渣漿泵體壽命的重要方向之一。渣漿泵廠家
Effect of Flow Coefficient of Slurry Pump on Calculating Speed
Next, the influence of coefficient a on the velocity of the pressure chamber section is studied when only the height of the tongue section changes with hg, that is, the area Fs changes with constant pump flow and head. This analysis is of great significance in the design of pump chamber for pumping fine solid-liquid mixture. In this case, the selection of the size of Hg is not based on the size of solid particles, but on the hydraulic loss in the water chamber and the speed of wear.
The pressure chamber calculates the A value on the section, so the area F... With the coefficient. The increasing face of the value increases. Because the relative ratio A/a is constant, its parameter A increases in direct proportion to a, and the calculated cross-section flow also increases in direct proportion to a. In order to simplify the analysis, the pressure chamber is used as a rectangle, and the result is obtained.
From these expressions, it can be seen that the value of parameter A increases in direct proportion to the relative ratio R3/R2, while the calculated cross-section area increases in direct proportion to the value of (R3/R2-1), that is, with the relative flow coefficient. With the increase of pressure, the velocity of liquid flow on the calculated section decreases, and the average value is the smallest in the annular pressure chamber.
The throat section area of pressure short pipe increases with the increase of a, so the velocity u decreases. In the annular pressure chamber, the liquid velocity in the throat of the pressure short pipe will have the minimum value. When other conditions are the same, the characteristic velocity u is the smallest in the annular pressurized water chamber.
Knowing the parameters and main dimensions of the pump, the coefficient a and velocity U of the calculated section of the pressure chamber with different tongue section height h can be determined under the following conditions:
(1) The ratio of the throat volume F of the diffuser to the calculated cross-section area F is constant under various A-values (in some cases, F-F.) can be used to simplify the analysis).
(2) Despite some changes in hydraulic efficiency, when R, = constant, pump head H = constant.
(3) When estimating the flow velocity in a common spiral pressure chamber, the hydraulic efficiency can be calculated by using the statistical data of clean water pumps (in n, similar cases).
If the hydraulic efficiency (m) of the pump is not considered when the section size of the pressure chamber changes, the expression (3-3-5) can be written as follows.
In formula K, when the pump parameters are constant, it is constant. According to formula (3-3-4), K = 0.010DxO/B.
According to the numerical analysis results of the relations U.c= f(a) and ur=f(a) corresponding to the highest hydraulic efficiency state of pumps with different parameters and sizes, the similar changes of the studied parameters are obtained (Fig. 3-3-5). When the value a increases from 1 to 1.85, the average velocity of liquid flow and the inlet velocity of diffuser will decrease (especially the latter). If the velocity U and Ur are equal when working at the highest hydraulic efficiency state, then the relation Ur = f (a) is correct for Ug = f (a). In this way, when the spiral pressure chamber transits to the annular pressure chamber, the velocity will decrease on all sections of the pressure chamber.
It is well known that wear and tear penetration in the pressure chamber of slurry pump is observed on the maximum radius R3 (point A of Figure 3-3-1) of the calculated section when the pump works in the optimum and large flow state. In most cases, the wear that determines the life of the whole chamber has nothing to do with the average velocity on the calculated section, but with the radius R and the velocity on the wall of the section. Therefore, it is interesting to analyze the influence of the relative flow coefficient (i.e. the shape of the pressure chamber) on the velocity u when the pump parameters are constant.
In order to simplify the process, in some cases, E-F is used. According to formula (3-3-5), the throat velocity of the diffuser is 0.
In the simplified comparison analysis, the velocity of liquid flow on the wall of the rectangular pressure chamber is constant according to the velocity moment on the section working at the corresponding maximum hydraulic efficiency.
In deriving the expression of velocity u3, R3 = R2 + h.. = RreM is used.
From Figure 3-3-5, it can be seen that the velocity decreases with the increase of the relative discharge coefficient a on the outer wall of the calculated section of the pressurized water chamber.
If the velocity is equal on all sections, the wear resistance of the throat section and the calculated section of the diffuser will be approximately the same. The condition is that the velocity Ur and... are equal and can be written in the following form
The above analysis points out that it is reasonable to abandon the spiral chamber in order to reduce the speed of the chamber section, even without increasing the height of the tongue section, according to the possibility of passing large solid particles. At the same time, it is pointed out as follows that the hydraulic loss increases, that is to say, the hydraulic efficiency of the whole pump is reduced. It should be noted that because the wear is proportional to the quadratic of the liquid velocity (as indicated below), reducing the speed on the section of the pressure chamber withstanding the strongest wear is one of the important directions to improve the life of the slurry pump body. Slurry Pump Manufacturer
