Bubbling vs. blow-off – On the relevant mechanism(s) of drop entrainment from oil mist filter media
Bubbling vs. blow-off – On the relevant mechanism(s) of drop entrainment from oil mist filter media
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鼓泡与吹气 â 关于油雾过滤介质中液滴夹带的相关机制
DOI：
10.1016/j.seppur.2015.08.012
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发表时间：
2015
影响因子：
8.6
通讯作者：
Kasper
中科院分区：
文献类型：
--
作者：
Wurster;Kasper
为了阐明流体诱导油雾夹带的机理，并确定油浓度和过滤速度对二次液滴生成速率的影响，对无填料和无填料的玻璃纤维过滤器进行了对比研究。采用两种光学技术，在长时间内，以高时间分辨率，测量了液滴尺寸约为0.5-10 μm和150-2000 μm的范围内，从无填料和无填料的玻璃纤维过滤器中的夹带速率。将这些速率与随时间记录的排油模式进行比较，并与通过吹离分离液滴所需的力的估计值进行比较，与液滴径流进行比较（排水）或在排水膜中形成气泡。（即非润湿性）介质在正常操作期间经历表观润湿性的一次性转变，这是由于从单个液滴到油的膜状流动模式的排水行为的变化。该转变与夹带率的暂时增加（“爆发”）相关。之后，两种类型的介质具有稳态夹带率，其在两个因子内相当，并且主要取决于过滤器的加载速率（这反过来又决定了排水速率），但几乎没有或根本没有过滤速度。总之，排除了吹脱作为一种机制，在现行的操作条件下，无论介质的润湿性如何，都对油夹带有重要贡献。二次液滴是由于破裂气泡的碎片，其形成于介质下游面上的液膜内。初始非粘性介质的夹带破裂也是由于排出油滴上形成的气泡。
A comparative investigation was conducted on wettable and non-wettable glass-fiber filters to clarify the mechanism(s) leading to flow induced entrainment of oil and to determine the influence of oil concentration and filtration velocity on the rate of secondary droplet production. Entrainment rates from a wettable and a non-wettable glass-fiber filter were measured over prolonged periods of time and with high time resolution by two optical techniques covering the drop size regions of about 0.5–10 μm and 150–2000 μm. The rates were compared with oil drainage patterns recorded over time, and with estimates of the forces required to detach drops by blow-off as compared to drop run-off (drainage) or to form air bubbles in a drainage film.It was found that initially oleophobic (i.e. non-wettable) media underwent a one-time transition in apparent wettability during normal operation, due to a change in drainage behavior from individual drops to a film-like flow pattern of oil. The transition was associated with a temporary increase (“burst”) in entrainment rate. After that, both types of media had steady-state entrainment rates that were comparable within a factor of two and depended mostly on the loading rate of the filter (which in turn determines the drainage rate), but showed little or no at all on filtration velocity. In conclusion, blow-off was ruled out as a mechanism contributing significantly to oil entrainment under the prevailing operating conditions, regardless of media wettability. Secondary droplets are due to fragments from bursting air bubbles, which are formed within the liquid film on the downstream face of the media. The entrainment burst of an initially non-wettable medium is also due to bubbles formed on draining oil drops.
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DOI：
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