Raman spectroscopic studies of the gaseous drag phase in droplet chains and sprays during the evaporation of multi-component fuels

替代燃料有助于提高效率和减少二氧化碳排放。生物混合燃料，如生物柴油或生物乙醇，已经在世界范围内作为替代品。众所周知，点火、燃烧和排放在很大程度上取决于当地的混合条件。因此，有必要更好地了解替代性多组分燃料的蒸发。在本建议的框架内，应测量不同多组分燃料在蒸发过程中液滴链中气态阻力相的组成。通过改变液滴的直径、温度和距离以及环境温度等参数来研究预期的相互作用。该数据库可用于验证组分比蒸发数值模型。研究扩展到在喷雾室中直接喷射汽油。为了实现这些目标，对拉曼多通道设置进行了优化，用于分析气体阻力相，并通过快速触发系统进行扩展，以获得精确的空间和时间分辨率。利用拉曼光谱研究了电池内直径小于100微米的不同多组分燃料液滴的气阻相组成。伴随着这些测量，高速纹影技术被用来确定液滴的速度。随后，测量系统被转移到一个喷雾室。在此基础上，研究了多组分燃料在相应的喷射条件下，压电喷油器喷雾导向直喷过程中的组分比蒸发特性。除其他外，通过测定空燃比验证了混合气形成对点火条件的影响。

Alternative fuels can contribute to improve efficiency and to reduce CO2-emissions. Biogenic blended fuels, such as biodiesel or bioethanol, serve already as substitutes worldwide. It is well-known that ignition, combustion and emissions strongly depend on local mixture conditions. Therefore there is a demand for a better understanding of the evaporation of alternative multi-component fuels.Within the framework of this proposal the composition of the gaseous drag phase in droplet chains during evaporation shall be measured for different multi-component fuels. Expected interactions are studied by varying parameters such as diameter, temperature and distance of droplets as well as the ambient temperature. The data base can serve for validation o numerical models for component specific evaporation. Investigations are extended to gasoline direct injection in a spray chamber. To achieve these objectives, a Raman multipass setup is optimized for the analysis of the gaseous drag phase and extended by a fast trigger system for precise spatial and temporal resolution. Using Raman spectroscopy the gaseous drag phase of different multi-component fuel droplets with diameter less than 100 microns in a cell is examined with respect to its composition. Accompanying these measurements a high-speed schlieren technique is employed to determine the droplet velocities. Subsequently, the measurement system is transferred to a spray chamber. There, the component specific evaporation in a spray-guided direct injection by a piezoelectric injector is characterized for multi-component fuels at application relevant injection conditions. The influence of mixture formation on ignition conditions is verified, amongst others, by the determination of the air-fuel-ratio.