Flow Characteristics Simulation of Biodiesel/N-amyl Alcohol Mixed Fuel Nozzles
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摘要:
为探究混合燃油理化性质差异对柴油机喷嘴内流动特性的影响，以4种不同掺混比的生物柴油/正戊醇为研究对象，采用混合多相流模型，对柴油机喷嘴内的流动情况进行数值模拟分析。结果表明：4种燃油的压力、速度和空化分布特性基本一致；随着正戊醇掺混比例的增加，混合燃油速度和气相体积分数大小在喷孔同一截面处均表现为增加趋势，向生物柴油中掺混一定比例的正戊醇，可以显著降低生物柴油的密度、黏度和表面张力，提高燃油在喷孔内的流动性、促进燃油的空化生成，提升燃油的雾化效果。
Abstract:In order to explore influence of physicochemical properties of mixed fuel on flow characteristics in nozzles of diesel engine, mixed multiphase flow model was used to simulate flow in nozzles of diesel engine with four different mixing ratios of biodiesel/n-amyl alcohol．Results showed that pressure, velocity and cavitation distribution characteristics of four fuels were basically the same．With increase of mixing ratio of n-amyl alcohol, speed of mixed fuel gas phase volume fraction in spray hole size the same cross-section were characterized by increasing trend, biodiesel mixed in certain proportion was n-amyl alcohol and biodiesel could significantly reduce density, viscosity and surface tension, improve fuel in liquidity, promote cavitation generation of fuel, and improve fuel atomization effect．
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Keywords:
- biodiesel oil /
- n-amyl alcohol /
- mixed fuel /
- numerical simulation
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图 4 不同压差下空化分布试验值和仿真值对比
Figure 4. Comparison of experimental and simulation values of cavitation distribution under different pressure differences
图 5 不同压差下质量流量试验值和仿真值对比
Figure 5. Comparison of experimental and simulated mass flow rates under different pressure differences
图 7 4种燃油在不同截面处的压强变化
Figure 7. Pressure variation of four fuels at different cross sections
图 10 4种燃油喷孔内气相体积分数分布
Figure 10. Distribution of gas energy fraction in four fuel injection holes
图 11 4种燃油在不同截面处的气相体积分数变化
Figure 11. Variation of gas phase physical force fraction of four fuels at different cross sections
表 1 燃油物性参数（20 °C）
Table 1. Physical parameters of fuel （20 °C）
物性参数 密度/
（kg·m−3）黏度/
（mPa·s）表面张力/
（10−3N·m−1）饱和蒸
汽压/kPa燃油种类 BD100 871.4 6.24 30.3 1.000 
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表 2 数值模拟边界条件
Table 2. Numerical simulation of boundary conditions
边界条件 数值 喷射压力/MPa 60 环境背压/MPa 1 环境温度/K 293.15
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