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渣漿泵水力損失與水力效率
水力損失發(fā)生在泵的吸水室、葉輪流道、壓水室中。水力損失可分為三種情況:①液體流經(jīng)泵的吸水室、葉輪流道、壓水室時(shí)與壁面發(fā)生的沿程摩擦損失;②發(fā)生在上述流道的突然擴(kuò)大、縮小、轉(zhuǎn)彎等的局部阻力損失;③當(dāng)運(yùn)行工況發(fā)生改變時(shí)發(fā)生在葉片進(jìn)口及出口的撞擊損失。
沿程摩擦阻力損失及局部阻力損失可按水力學(xué)中的計(jì)算方法來(lái)進(jìn)行計(jì)算。但是迄今為止還無(wú)法精確的計(jì)算，通過(guò)上述分析可以看出降低流道表面粗糙度，清理打磨流道，流道面積變化均勻，避免過(guò)大的擴(kuò)散等，可以減小水力損失。葉片進(jìn)口的沖擊損失，在設(shè)計(jì)流量下，液流角與葉片安放角是一致的，撞擊損失較小。但當(dāng)泵不在設(shè)計(jì)流量工作時(shí)，液流角與葉片安放角不再一致，撞擊損失較大，如圖2-38所示。葉輪出口的水力損失，當(dāng)泵在設(shè)計(jì)流量工作時(shí)，葉輪出口處的流速與壓水室中液體流速基本相等，不會(huì)產(chǎn)生很大的損失，而當(dāng)偏離設(shè)計(jì)流量工作時(shí)，兩者的流速不再相等，從而產(chǎn)生較大的損失。所以選用泵時(shí)，應(yīng)盡量在設(shè)計(jì)工況下(即高效區(qū))工作，否則會(huì)增加泵的水力沖擊損失。
水力效率:
ηh=H/H+△H=H/HT
式中 H----泵的有效揚(yáng)程;
Ht----泵的理論揚(yáng)程。
四、泵的效率η
泵的總效率η即為泵的機(jī)械效率、容積效率和水力效率的乘積。渣漿泵廠家
Hydraulic loss and efficiency of slurry pump
The hydraulic loss occurs in the suction chamber, impeller passage and pressure chamber of the pump. The hydraulic loss can be divided into three situations: ① the friction loss along the wall when the liquid flows through the suction chamber, impeller passage and pressure chamber of the pump; ② the local resistance loss when the passage expands, shrinks and turns suddenly; ③ the impact loss at the inlet and outlet of the blade when the operation conditions change.
Friction loss along the way and local resistance loss can be calculated according to the calculation method in hydraulics. However, up to now, it has not been able to calculate accurately. Through the above analysis, it can be seen that reducing the surface roughness of the runner, cleaning and polishing the runner, uniform change of the runner area, avoiding excessive diffusion, etc., can reduce the hydraulic loss. Under the design flow rate, the angle of liquid flow is the same as the angle of blade setting, and the impact loss is smaller. However, when the pump is not working at the design flow, the liquid flow angle is no longer consistent with the blade setting angle, and the impact loss is large, as shown in figure 2-38. When the pump is working at the design flow, the flow velocity at the outlet of the impeller is basically the same as that of the liquid in the water pressure chamber, which will not cause great loss. When the pump is working at the design flow, the flow velocity of the two is no longer equal, which will cause great loss. Therefore, when selecting the pump, we should try to work in the design condition (i.e. high efficiency area), otherwise, it will increase the hydraulic impact loss of the pump.
Hydraulic efficiency:
ηh=H/H+△H=H/HT
Where h is the effective head of the pump;
HT ---- theoretical head of pump.
IV. pump efficiency η
The total efficiency η of the pump is the product of the mechanical efficiency, volumetric efficiency and hydraulic efficiency of the pump. Slurry pump manufacturer
