幂律流体椭圆形射流破碎的试验研究
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摘要
基于高速摄影光学试验平台,通过使用4个椭圆度不同的喷孔与两种工质,研究了幂律流体椭圆形射流形貌与破碎的特征.结果表明:与水不同,椭圆孔产生的"轴转换"不稳定现象在幂律液体中整体衰退明显;液体射流速度较小时,椭圆度对破碎长度的影响较小,而后随着射流速度的增大(小于33 m/s),椭圆度对射流破碎的促进作用逐渐增强.轴转换波长与射流速度呈现线性关系,幂律液的波长增长率随着椭圆度的增大而增大.通过试验数据修正了幂律流体椭圆射流形貌模型,并分析了椭圆度、韦伯数、表观雷诺数对于射流不稳定性的影响.
Based on a high-speed photographic optical experimental platform,the characteristics of elliptical jet morphologies and power-law fluid fractures were studied using four nozzles with different ellipticities and two working fluids. The results showed that,compared with that in water,the axis-switching phenomenon produced by the elliptical hole was significantly degenerated in the power-law fluid. Ellipticity exerted a slight influence on the breakup length at a low jet velocity but gradually promoted jet fractures with increasing jet velocity(<33 m/s). A linear relationship was found between the axis-switching wavelength and jet velocity,and the wavelength growth rate of the power-law liquid increased with increasing ellipticity. The experimental data were used to modify the elliptical jet topography model of power-law fluids. Whereas increases in ellipticity,Weber number,and apparent Reynolds number promoted jet instability,increases in power index,consistency coefficient,and surface tension coefficient suppressed this instability.
Based on a high-speed photographic optical experimental platform,the characteristics of elliptical jet morphologies and power-law fluid fractures were studied using four nozzles with different ellipticities and two working fluids. The results showed that,compared with that in water,the axis-switching phenomenon produced by the elliptical hole was significantly degenerated in the power-law fluid. Ellipticity exerted a slight influence on the breakup length at a low jet velocity but gradually promoted jet fractures with increasing jet velocity(<33 m/s). A linear relationship was found between the axis-switching wavelength and jet velocity,and the wavelength growth rate of the power-law liquid increased with increasing ellipticity. The experimental data were used to modify the elliptical jet topography model of power-law fluids. Whereas increases in ellipticity,Weber number,and apparent Reynolds number promoted jet instability,increases in power index,consistency coefficient,and surface tension coefficient suppressed this instability.
引文
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[3]任晓华,张磊,任泽昱,等.基于多组分蒸发模型的柴油喷雾燃烧的LES研究[J].燃烧科学与技术,2018,24(6):528-534.Ren Xiaohua,Zhang Lei,Ren Zeyu,et al.Large eddy simulation of diesel spray combustion based on a multicomponent vaporization model[J].Journal of Combustion Science and Technology,2018,24(6):528-534(in Chinese).
[4]Sharma P,Fang T.Spray and atomization of a common rail fuel injector with non-circular orifices[J].Fuel,2015,153:416-430.
[5]郗大光,龚允怡,彭志军,等.椭圆孔射流的雾化问[J].内燃机学报,1996,14(4):370-377.Xi Daguang,Gong Yunyi,Peng Zhijun,et al.Atomization of a liquid jet from an elliptical orifice[J].Transactions of CSICE,1996,14(4):370-377(in Chinese).
[6]Kasyap T V,Sivakumar D,Raghunandan B N.Breakup of liquid jets emanating from elliptical orifices at low flow conditions[J].Atomization&Sprays,2008,18(7):645-668.
[7]Kasyap T V,Sivakumar D,Raghunandan B N.Flow and breakup characteristics of elliptical liquid jets[J].International Journal of Multiphase Flow,2009,35(1):8-19.
[8]Wang F,Fang T.Liquid jet breakup for non-circular orifices under low pressures[J].International Journal of Multiphase Flow,2015,72:248-262.
[9]Rajesh K R,Sakthikumar R,Sivakumar D.Interfacial oscillation of liquid jets discharging from non-circular orifices[J].International Journal of Multiphase Flow,2016,87:1-8.
[10]Bechtel S E,Cooper J A,Forest M G,et al.A new model to determine dynamic surface tension and elongational viscosity using oscillating jet measurements[J].Journal of Fluid Mechanics,1995,293:379-403.
[11]Gu S,Wang L,Dls H.Instability evolution of the viscous elliptic liquid jet in the Rayleigh regime[J].Physical Review E,2017,95(6):063112.
[12]Amini G,Dolatabadi A.Axis-switching and breakup of low-speed elliptic liquid jets[J].International Journal of Multiphase Flow,2012,42:96-103.
[13]Chen R,Wilson M,Leong Y K,et al.Preparation and rheology of biochar,lignite char and coal slurry fuels[J].Fuel,2011,90(4):1689-1695.
[14]Natarajan V P,Suppes G J.Rheological studies on a slurry biofuel to aid in evaluating its suitability as a fuel[J].Fuel,1997,76(14):1527-1535.
[15]Abdullah H,Mourant D,Li C Z,et al.Bioslurry as a fuel.3.Fuel and rheological properties of bioslurry prepared from the bio-oil and biochar of mallee biomass fast pyrolysis[J].Energy&Fuels,2010,24(10):5669-5676.
[16]陈良勇,段钰锋,刘猛,等.水煤浆真实流变特性的研究[J].动力工程学报,2008,28(5):753-758.Chen Liangyong,Duan Yufeng,Liu Meng,et al.True rheological behavior of coal-water slurry[J].Journal of Power Engineering,2008,28(5):753-758(in Chinese).
[17]Bechtel S E,Youssef N T,Forest M G,et al.NonNewtonian viscous oscillating free surface jets,and a new strain-rate dependent viscosity form for flows experiencing low strain rates[J].Rheologica Acta,2001,40(4):373-383.