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液滴沖擊不同浸潤性壁面的數(shù)值分析
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“十二五”國家科技支撐計劃資助項目(2012BAD30B01)、 國家自然科學(xué)基金資助項目(51006031)和中央高?;究蒲袠I(yè)務(wù)費專項資金資助項目(15CX06052A、13CX02078A)


Numerical Analysis of Droplet Impact on Surfaces with Different Wettabilities
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    摘要:

    采用復(fù)合水平集和流體體積法并綜合考慮傳熱和接觸熱阻的作用,建立了液滴碰撞水平壁面數(shù)值模型,并實驗驗證了模型的準(zhǔn)確性。通過分析計算結(jié)果,探索了壁面浸潤性對液滴撞壁過程的影響,揭示了液滴撞壁流動傳熱及飛濺機(jī)制,并建立了液滴飛濺臨界條件理論判據(jù)。數(shù)值結(jié)果表明:液滴鋪展系數(shù)的碰撞速度效應(yīng)明顯,碰撞速度越大,液滴的鋪展系數(shù)越大,但液滴達(dá)到最大鋪展系數(shù)所需無量綱時間與碰撞速度不相關(guān);碰撞速度越大,液滴撞壁收縮幅度越大,壁面浸潤性對鋪展系數(shù)的影響越小。液體內(nèi)部壓力梯度是液滴鋪展邊緣產(chǎn)生射流和斷裂的主要原因;Rayleigh-Plateau不穩(wěn)定性和毛細(xì)波是射流頸部收縮和破碎飛濺的關(guān)鍵因素。

    Abstract:

    In order to explore the mechanism of fuel droplet impact on surface in diesel engine small-size combustor, a numerical model was developed using coupled level set and volume of fluid method including heat transfer and contact resistance. This model was verified by using experiments. The effect of wettabilities and the mechanism of droplet fluid and heat transfer as well as splashing during spreading were obtained according to results analysis. The theoretical condition of splashing is developed based on energy conservation equation. The results show that when the droplet contacts with the surface, it presents surface oscillation, spread and splash as the impact velocity increases. Spreading factor is closely related to impact velocity, the higher the impact velocity is, the larger the spreading factor is. The dimensionless time of maximum spreading factor is uncorrelated to impact velocity, the higher impact velocity is, the larger contraction is. The effect of wettabilities on spreading factor decreases with increasing impact velocity. The pressure gradient inside droplet is the main factor resulting in droplet spreading, breakup and splashing. Rayleigh-Plateau instability and capillary wave results in the shrink, breakup and splash from the liquid sheet. The conclusions are significant to spray control technology.

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李大樹,仇性啟,鄭志偉,崔運靜,馬培勇.液滴沖擊不同浸潤性壁面的數(shù)值分析[J].農(nóng)業(yè)機(jī)械學(xué)報,2015,46(7):294-302. Li Dashu, Qiu Xingqi, Zheng Zhiwei, Cui Yunjing, Ma Peiyong. Numerical Analysis of Droplet Impact on Surfaces with Different Wettabilities[J]. Transactions of the Chinese Society for Agricultural Machinery,2015,46(7):294-302.

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  • 收稿日期:2014-09-19
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  • 在線發(fā)布日期: 2015-07-10
  • 出版日期: 2015-07-10
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