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渣漿泵的汽蝕及預(yù)防措施
一、產(chǎn)生汽蝕的機(jī)理及危害
1. 汽蝕的機(jī)理
離心泵內(nèi)的液體在進(jìn)入葉輪葉片之前壓力一直下降，進(jìn)入葉輪葉片后液體獲得能量,壓力升高。泵內(nèi)壓力最低點(diǎn)位于葉片入口附近的k截面處， 若其局部壓力Px小于此處溫度下該液體的飽和蒸氣壓p，液體就要汽化，同時(shí)溶解在該液體中的氣體也逸出，形成大量小氣泡，如圖1-15所示，從而使得液流的過流面積減小，流動(dòng)損失增大，導(dǎo)致泵內(nèi)流量減小,揚(yáng)程變小，效率降低,性能惡化。
當(dāng)氣泡隨液體流到葉輪內(nèi)壓力較高處時(shí),外面液體壓力高于氣泡內(nèi)的壓力，則氣泡會(huì)凝結(jié)潰滅，形成空穴。瞬間，周圍的液體以極高的速度向空穴沖擊，造成液體互相相撞，使局部壓力驟然劇增，有時(shí)可達(dá)數(shù)百個(gè)大氣壓，阻礙液體正常流動(dòng)，嚴(yán)重時(shí)會(huì)造成斷流。
如果這些氣泡在流道壁面附近潰滅，則周圍的液體以極高頻率和速度連續(xù)撞擊金屬表面，金屬表面會(huì)因沖擊、疲芳而剝落。若氣泡內(nèi)還夾雜某些活性氣體(如氧氣等)，它們借助蒸氣凝結(jié)時(shí)放出的熱量(局部溫度可達(dá)200~300C)，對(duì)金屬起電化學(xué)腐蝕作用，這就更會(huì)加快金屬剝落速度。渣漿泵廠家
上述這種液體汽化、凝結(jié)形成高頻沖擊負(fù)荷，造成金屬材料的機(jī)械剝落和電化學(xué)腐蝕的綜合現(xiàn)象統(tǒng)稱為汽蝕現(xiàn)象,通常也稱為空化或空蝕。
Cavitation of slurry pump and preventive measures
1、 Mechanism and harm of cavitation
1. Mechanism of cavitation
The pressure of the liquid in the centrifugal pump has been decreasing before it enters the impeller blade. After entering the impeller blade, the liquid obtains energy and the pressure increases. The lowest point of the pressure in the pump is located at the section K near the blade inlet. If the local pressure PX is lower than the saturated vapor pressure P of the liquid at this temperature, the liquid will vaporize. At the same time, the gas dissolved in the liquid will also escape, forming a large number of small bubbles, as shown in Figure 1-15, so as to reduce the flow area, increase the flow loss, reduce the flow rate and head in the pump, Efficiency is reduced and performance is deteriorated.
When the bubble flows with the liquid to the impeller with high internal pressure, the external liquid pressure is higher than the internal pressure of the bubble, the bubble will condense and collapse, forming a cavity. In an instant, the surrounding liquid impacts the hole at a very high speed, causing the liquid to collide with each other, suddenly increasing the local pressure, sometimes up to hundreds of atmospheric pressure, hindering the normal flow of the liquid, and even breaking the flow.
If these bubbles collapse near the wall of the flow passage, the surrounding liquid continuously impacts the metal surface at a very high frequency and speed, and the metal surface will peel off due to impact and fatigue. If there are some active gases (such as oxygen) in the bubble, they will give off heat (local temperature can be up to 200 ~ 300C) when they condense with the help of steam, which will play an electrochemical corrosion role on the metal, which will accelerate the metal peeling rate. Slurry pump manufacturer
This kind of liquid vaporizes and condenses to form high-frequency impact load, resulting in mechanical peeling and electrochemical corrosion of metal materials, which are collectively referred to as cavitation phenomenon, usually referred to as cavitation or cavitation.
