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渣漿泵與離心泵的工作原理
為了說(shuō)明離心泵的工作原理，先來(lái)看日常生活中的一個(gè)現(xiàn)象。 在雨天打傘，如果用手轉(zhuǎn)動(dòng)傘柄，傘上的水就會(huì)被甩出去，轉(zhuǎn)得越快，雨點(diǎn)甩得越遠(yuǎn)，這是因?yàn)橛晁谛D(zhuǎn)的傘上受到離心力的作用之故。再看另一個(gè)日常生活的現(xiàn)象:水總往低處流，但在醫(yī)院大夫打針時(shí)，抽動(dòng)針筒芯往上提時(shí)能把低處藥液抽入針筒內(nèi)。這是因?yàn)楫?dāng)針筒芯上抽時(shí)，原來(lái)針筒芯占的地方被抽上去后，這塊地方?jīng)]有空氣便形成了真空，而藥面上有大氣壓力的作用，將藥液壓入針筒內(nèi)。在泵中(見(jiàn)圖2-24)，同上面情況一樣,當(dāng)泵的葉輪旋轉(zhuǎn)時(shí)，葉輪葉片將液體
從葉輪甩出去，飛向四周泵體中并引向泵的出口，在此同時(shí)，葉輪中液體甩出去后形成真空，而液面在大氣壓力的作用下，將液體順著吸水管壓入葉輪中，然后又被甩出去。這樣周而復(fù)始，甩出去吸上來(lái)又甩出去，這就是離心泵的工作原理。
再來(lái)討論一下離心泵把低處的水吸上來(lái)時(shí)能吸多高呢?是不是并無(wú)限制呢?如果無(wú)限制，不管井有多深只要加長(zhǎng)吸水管的長(zhǎng)度就能把井中的水吸上來(lái)。但是這是不可能的。我們做一個(gè)實(shí)驗(yàn)，如果將一根長(zhǎng)的玻璃管插入水中，從上部將空氣抽去，如圖2 -25所示。隨著空氣的抽出，水在大氣壓力的作用下沿玻璃管慢慢上升，如果將玻璃管內(nèi)的空氣完全抽出，也就是絕對(duì)真空時(shí)，水上升到10. 33m就不再上升了，這是因?yàn)?/span>: 1個(gè)標(biāo)準(zhǔn)大氣壓=760mmHg= 10.33mH20。這時(shí)玻璃管內(nèi)水柱的壓力與大氣壓力相等了，保持了平衡。同理，如果離心泵葉輪進(jìn)口處也能達(dá)到絕對(duì)真空的話，水沿進(jìn)水管最多也只能上升到10.33m,而不能夠無(wú)限地想吸多高就多高。但是，離心泵進(jìn)口處不可能達(dá)到絕對(duì)真空。這是因?yàn)樗谌~輪中流動(dòng)有流速，進(jìn)水管有水力損失，當(dāng)壓力低到一定程度時(shí)液體會(huì)汽化，泵內(nèi)會(huì)發(fā)生汽蝕等原因。離心泵吸水高度不可能達(dá)到10.33m更不可能超過(guò)10.33m，一般也就4-8m。 各種不同泵而不同，具體能吸多高，需要在泵的樣本中汽蝕余量或允許吸上真空高度來(lái)決定。渣漿泵廠家
Working principle of slurry pump and centrifugal pump
In order to explain the working principle of centrifugal pump, first look at a phenomenon in daily life In rainy days, if you turn the handle of the umbrella by hand, the water on the umbrella will be thrown out. The faster it turns, the farther the raindrop will be thrown out. This is because the rain is affected by centrifugal force on the rotating umbrella. Look at another phenomenon in daily life: water always flows to the lower part, but when the doctor in the hospital injects the needle, he can pump the medicine liquid from the lower part into the needle cylinder when the core of the needle cylinder is pulled up. This is because when the needle cylinder core is drawn up, the original place occupied by the needle cylinder core is drawn up, and there is no air in this place, then a vacuum is formed, and the effect of atmospheric pressure on the drug surface is to hydraulic the drug into the needle cylinder. In the pump (see Figure 2-24), as above, when the impeller of the pump rotates, the impeller blade will turn the liquid
From the impeller, it flies to the surrounding pump body and leads to the outlet of the pump. At the same time, the liquid in the impeller is thrown out and forms a vacuum. Under the action of atmospheric pressure, the liquid surface presses the liquid into the impeller along the suction pipe, and then it is thrown out. This is the working principle of centrifugal pump.
Let's talk about how high the centrifugal pump can suck up the water in the lower part? Is there no limit? If there is no limit, no matter how deep the well is, as long as the length of the suction pipe is lengthened, the water in the well can be sucked up. But it's impossible. In an experiment, if a long glass tube is inserted into the water, the air is extracted from the upper part, as shown in Figure 2-25. With the extraction of air, water rises slowly along the glass tube under the action of atmospheric pressure. If the air in the glass tube is completely extracted, that is, when the absolute vacuum is reached, the water will not rise again when it rises to 10.33m, because: 1 standard atmospheric pressure = 760mmhg = 10.33mh20. At this time, the pressure of the water column in the glass tube is equal to the atmospheric pressure, maintaining a balance. In the same way, if absolute vacuum can be achieved at the impeller inlet of centrifugal pump, the water can only rise to 10.33m along the water inlet pipe at most, instead of infinite suction height. However, it is impossible to reach absolute vacuum at the inlet of centrifugal pump. This is because of the flow velocity of water in the impeller and the hydraulic loss of the water inlet pipe. When the pressure is low to a certain extent, the liquid will vaporize and cavitation will occur in the pump. The suction height of centrifugal pump can not reach 10.33m or more than 10.33m, generally 4-8M The specific suction height of different pumps depends on the NPSH in the pump sample or the allowable suction height. Slurry pump manufacturer
