Quantitative Study Of Spray Structure And Characteristics Of Multi-component Fuel Under High-load Like Conditions Of Heavy Duty Diesel Engine By Plief Technique

New engine combustion technologies, including HCCI (homogeneous charge compression ignition) combustion and Low-Temperature Combustion (LTC), rely on deep understanding to the diesel spray development. Because of the complexity and variety of the diesel fuel as well as the limitation of optical diagnosis technique, researchers have to employ surrogate fuel, including single or multi-component fuel, to quantitatively investigate the diesel spray development. However, the surrogated fuel employed to quantitatively study the spray structure and characteristics so far under the heavy-duty-diesel-engine like conditions was single-component fuel with lower viscosity compared with commercial diesel fuel. With the aim to understand the diesel spray development more accurately, this work investigated the liquid and vapor phase concentration and temperature distribution of multi-component surrogated fuel, which had a similar viscosity with #2 light diesel fuel, under high-load like conditions of heavy duty diesel engine (950 K, 60 kg/m3 for ambient temperature and density). The injection pressure and nozzle hole diameter were 180 MPa and 0.10 mm respectively. Afterwards, the effect of fuel viscosity on spray structure and characteristics at ignition timing were studied, which laid a foundation for combustion control by changing fuel properties.It was found that the sprays of single-component fuel comprised an intact core, a liquid-droplet core (LDC), a vapor-rich core (VRC), a low-temperature core (LTCore), a spray head and a lean sheath. The development of the spray featured three stages according to the spray structure parameters. By increasing the resolution of the equivalence ratio, it was further found that the micro-distribution of equivalence ratio was extremely heterogeneous with various islands of equivalence ratio in a stratified equivalence ratio zone, and the three stages were well correlated with the distribution of equivalence ratio.The observation of the spray development of multi-component fuel showed that the spray of multi-component also featured three stages as single-component spray developed. However there were apparent differences between the inner structures of the two kind of fuel, which were resulted from the effect of fuel viscosity. The fuel viscosity mainly influenced evaporation, and the increase of fuel viscosity led to distinct decrease of evaporation rate, thereby inducing a series of changes of inner structures of sprays. Meanwhile, the effect of fuel viscosity on macroscopic characteristics of sprays could be negligible.It was observed that increasing fuel viscosity could effectively improve the homogeneity of the spray head at ignition timing, while restricted the development of rich region (Φ>2 in this case). It was also found that concentration of VRC was more homogeneously distributed with lower temperature of LTcore at ignition as fuel viscosity increased. Additionally, the strategy of higher fuel viscosity reduced the fuel mass of overly rich mixturesΦ>2, and enhanced lean premixed mixtures of 0<Φ<1, which is favorable for reduction soot but unfavorable for inhibition of NO formation.