纳米异质粒子对燃油射流喷雾特性的影响

选用平均粒径为20 nm的CeO₂纳米粒子，以油酸为表面活性剂，采用两步法配制质量浓度分别为50与100 mg/L的纳米燃油，分别称为Ce50和Ce100燃油；测量柴油和纳米燃油的密度、黏度和表面张力等基础物性参数；在高压共轨喷雾试验台上拍摄燃油射流喷雾发展过程的影像，应用Matlab软件处理影像，得到喷雾贯穿距和喷雾锥角等特性参数. 结果表明：与柴油相比，Ce50和Ce100纳米燃油的黏度分别增加了2.1%与4.7%，密度和表面张力的增加量较小. 在相同喷射压力下的不同喷雾发展时刻，纳米燃油的油束贯穿距大于柴油，喷雾锥角略小于柴油. 在背压为2 MPa、喷射压力分别为80、120和160 MPa时，与柴油相比，Ce50纳米燃油的喷雾贯穿距分别增加了1.4、1.9和2.4 mm，Ce100纳米燃油的贯穿距分别增加了2.9、2.9和3.7 mm. 随着喷射压力的提高，纳米燃油与柴油在喷雾贯穿距和喷雾锥角上的差异增大. 当燃油喷射背压增加时，油束的贯穿距缩短而喷雾锥角增大，不同质量浓度纳米燃油和柴油的贯穿距和喷雾锥角的差异有所减小.

Effects of nano-scale heterogeneity on fuel jet spray characteristics

Nano fuels with mass concentration of 50 and 100 mg/L was prepared by two-step method, using cerium oxide (CeO₂) nano particles with mean diameter of 20 nm and taking oleic acid as surfactant, which were named as Ce50 and Ce100 fuel. Some basic physical parameters such as density, viscosity and surface tension of fuel blends were measured. The developing process of fuel injection was captured with images on the high-pressure common rail spray measuring system; then the spray penetration length and cone angle were obtained after the spray images being processed with Matlab software. It is revealed that, compared with diesel, the viscosities of Ce50 and Ce100 nano-fuel blends were increased by 2.1% and 4.7%, respectively, while the density and surface tension were augmented slightly. Almost at each moment of the spray proceeding under one specified injection pressure, the nano-fuel exhibits longer spray penetration length and slightly smaller cone angle than diesel. Compared with diesel, the spray penetration of Ce50 Nano-fuel was increased by 1.4, 1.9 and 2.4 mm and the spray penetration length of Ce100 Nano-fuel was increased by 2.9, 2.9 and 3.7 mm, respectively, at the injection pressure of 80, 120 and 160 MPa under the ambient pressure of 2 MPa. With the rise of injection pressure, the differences in both spray penetration length and cone angle between nano-fuel and diesel are magnified. When the ambient pressure increases, the spray penetration is shortened and the cone angle is magnified; the differences of the spray penetration and the cone angle between diesel and nano-fuel with different mass concentrations are reduced.