[ ( ) ] ρ dk = x μ + μ t k + G i σ x k + G b - ρε - Y M 1 k i ε ρ dε = x μ + μ t ε i [ ( ) σ x ] + ε i ε C 1ε k G k + C 3ε G b - C 2ε ρ ε2 2 k

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Download "[ ( ) ] ρ dk = x μ + μ t k + G i σ x k + G b - ρε - Y M 1 k i ε ρ dε = x μ + μ t ε i [ ( ) σ x ] + ε i ε C 1ε k G k + C 3ε G b - C 2ε ρ ε2 2 k"

顿翎昝
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2013 8 32 8 Mechanical Science and Technology or Aerospace Engineering August Vol. 32 2013 No.

1 Mechanical Science and Technology or Aerospace Engineering August Vol No. 8 李德镇, 韩振南为了改善柴油机 D6114 喷油嘴 291 DLLA150 FC PV01 内部燃油流动状况, 使喷入气缸内的燃油达到较好的雾化质量, 在原有喷嘴基础上, 针对喷嘴结构参数长径比喷嘴入口过渡圆角及喷孔锥角设计了 9 种方案在 CFD( 计算流体动力学 ) 软件中建立了喷嘴内部流场的三维模型, 对整个流场区域进行了流体动力学模拟计算分析了喷嘴结构参数对喷孔内部空化程度湍动能及流速的影响, 得出 : 随着长径比 ( L /D) 的减小, 燃油在喷孔中的空化程度增强, 湍动能减小, 流速增加 ; 随着过渡圆角与直径比 ( r /D) 的增大, 喷孔内部流体空化程度增强, 流速增大, 湍动能减弱 ; 随着喷孔锥角 ( θ) 的增大, 喷孔内燃油空化程度加强, 湍动能减弱雾化质量 ; 结构参数 ; 三维模型 ; 空化程度 ; 湍动能 TK A Inluence o Nozzle Structure Parameters on Flow Characteristic in Three-dimensional Flow Field Simulation Li Dezhen Han Zhennan College o Mechanical Engineering Taiyuan University o Technology Taiyuan Abstract In order to improve the internal uel low conditions in the nozzle 291 DLLA150 FC PV01 o the diesel engine D6114 and make uel sprayed into the cylinder to obtain good atomization quality nine schemes were designed based on the nozzle structure parameters length-diameter ratio the round angle-radius o nozzle inlet and oriices angle. Three-dimensional model o the internal nozzle low ield was established and simulated using the CFD Computational Fluid Dynamics sotware. The inluence o spray nozzle structure parameters on hole internal cavitation degree turbulent kinetic energy and low velocity was analyzed. The results show that with the decreasing o length-diameter ratio L /D the cavitation degree o uel in the oriice and the velocity will increase but the turbulent kinetic energy will decrease with the increasing o round angle-radius to diameter ratio r /D the cavitation degree o uel in the oriice and the velocity will also increase while the turbulent kinetic energy will descrease with the increasing o oriices angle θ the cavitation degree o uel in the oriice will increase and the turbulent kinetic energy will decrease. Key words atomization diesel engines engine cylinders kinetic energy oriices turbulent low cavitation computational luid dynamics computer simulation low ields uels mathematical models nozzles three dimensional two phase low velocity atomization quality structure parameters three-dimensional model cavitation degree turbulent kinetic energy PM lidezhen@ 163. com zhennan - han@ hotmail. com HC

8 1135 [ ( ) ] ρ dk = x μ + μ t k + G i σ x k + G b - ρε - Y M 1 k i ε ρ dε = x μ + μ t ε i [ ( ) σ x ] + ε i ε C 1ε k G k + C 3ε G b - C 2ε ρ ε2 2 k Payri R G k G b Y M 1 Som S KH-ACT 6 k 2 μ t = ρc

2 [ ( ) ] ρ dk = x μ + μ t k + G i σ x k + G b - ρε - Y M 1 k i ε ρ dε = x μ + μ t ε i [ ( ) σ x ] + ε i ε C 1ε k G k + C 3ε G b - C 2ε ρ ε2 2 k Payri R G k G b Y M 1 Som S KH-ACT 6 k 2 μ t = ρc μ 3 ε Fluent α v = α l n 0 3 πr3 4 n 0 D DLLA 150 R FC PV01 CFD d 4 dα v α l n 0 3 πr 3 ( ) = 1 + ρ + α 5 g ρ v - ρ g ρ + α g ρ l - ρ g n πr3 2 p R - p p R > p dr = 槡 3 ρ p - - p R Berwerk p R < p 槡 3 ρ1 ρ ρ v ρ l Hiroyasu p R p Hanetal 4 2 Pro /E 291 DLLA150 FC PV / Fluent Fluent k-ε k 1 2

机械科学与技术 1136 3 第 32 卷内随着 L / D 的减小即喷孔直径的增大气相体积分数变大湍动能增强速度相应提高模型网格划分及边界条件的设定物理模型采用 D6114 柴油机的喷油嘴 291 DLLA150 FC PV01 在 Gambit 中建立各个模型并进行网格划分流动区域使用结构化网格进行划分为了提高计算精度对流动条件变化较大的

3 机械科学与技术第 32 卷内随着 L / D 的减小即喷孔直径的增大气相体积分数变大湍动能增强速度相应提高模型网格划分及边界条件的设定物理模型采用 D6114 柴油机的喷油嘴 291 DLLA150 FC PV01 在 Gambit 中建立各个模型并进行网格划分流动区域使用结构化网格进行划分为了提高计算精度对流动条件变化较大的喷孔入口处和壁面附近的网格适当的加密图 3 模型网格数为主要是六面体图 3 流动区域网格划分示意图网格经检测网格扭曲率 Skewness 85% 保证了求解计算中的精度其它方案在建模和网格划分中采用了相同的方法网格扭曲率 Skewness = max θ θ θ ( 180 θ max θ min θ ) 7 式中 θ max 为网格的最大角度 θ min 为网格的最小角度 θ 为网格的平均角度 Skewness 用来判断网格质量的好坏一般要求其值小于 97% 针对所有方案在 Fluent 模拟求解计算中采用了相同的进口压力 118 MPa 和出口压力 1. 1 MPa 针阀升程都为 mm 采用标准 k-ε 模型设定 Turbulence kinetic energy和 Turbulence dissipation rate 项采用 2 阶迎风格式差分计算其余参数使用 1 阶迎风 7 格式模拟结果的对比与分析长径比对喷嘴内部燃油空化程度湍动能及流速的影响 5 4 3时图 4a 分别列出了长径比 L / D 等于 6 的喷孔内部空化程度及流速特性的情况对比图由气相体积分数分布图可以看出随着喷嘴直径的增大气相体积分数增加即喷嘴内燃油空化程度增强从图 4b 中能够直观的看出喷嘴内部空化程度随 L / D 变化的发展趋势长径比 L / D 越小空化现象越明显沿喷孔径向方向的空化区域越宽相比过小的喷嘴直径不利于空化现象的产生即发生空化现象的区域较窄从速度矢量图可以看出流速也随着 L / D 的减小相应增加原因是喷孔直径变大减少了壁面对流体流动的约束降低了对其动能的损耗结合图 4a 和图 4b 可以得出在一定范围图4 不同 L / D 对喷嘴内部燃油流动性能的影响

4 r /D 5 r /D r /D r D 5a r /D b r /D r /D = 3 r /D r /D 5b r /D 5a 5b 4. 3 θ θ 6a θ b θ = 80 6a 6b 5 r /D

5 L /D 2 r /D 3 θ 6 θ 1 Payri R Salvador F J Gimeno J et al. Diesel nozzle geometry inluence on spray liquid-phase uel penetration in evaporative conditions J. Fuel ~ Som S Ramirez A I Longman D E et al. Eect o nozzle oriice geometry on spray combustion and emission characteristics under diesel engine conditions J. Fuel ~ J ~ 21 4 Martinez L Benkenida A Cuenot B. A model or the injection boundary conditions in the context o 3D simulation o diesel spray methodology and validation J. Fuel ~ D Fluent M J ~ 36 8 Payri F Payri R Salvador F J et al. A contribution to the understanding o cavitation eects in Diesel injector nozzles through a combined experimental and computational investigation J. Computers and Fluids ~ J ~ 140

CFDesign 2 1 CFDesign CFDesign CAD ~ r /min mm 1

CFDesign 2 1 CFDesign CFDesign CAD ~ r /min mm 1 33 3 Vol 33 No 3 2012 6 Journal of Jinan University Natural Science Jun 2012 1 2 2 1 2 528436 CFDesign CFDesign TQ430 6 + 64 A 1000-9965 2012 03-0316 - 07 Numerical simulation for gas and liquid particles