Development of laser-induced phosphorescence technique for visualisation of temperature and flow fields in IC engines

该项目的目的是发展双色激光诱导磷光技术，用于同时显示内燃机条件下的气体温度和速度场。该技术将用于成像的混合物形成，点火和燃烧。此外，该测量技术可用于基础研究和与能源技术和化学过程技术相关的许多系统的优化。利用具有温度依赖发光信号的惰性YAG:Dy粒子，可以额外用于速度测定。在该项目的第一阶段，通过在荧光粉中添加铒（Er）和镨（Pr）等增敏剂，显著增强了荧光粉颗粒的信号强度。这些优化的荧光粉YAG:Dy:Er和YAG:Dy:Pr适用于1000 K以上的高温测量，并将用于IC发动机条件下的计划研究。然而，为了提高信号强度和在高温下的测量精度，同时减少发光持续时间，进一步修改和改变宿主材料是必要的。在项目的第一阶段，建立了一个流动电池，并进行了磷光的表征和校准，例如根据温度，压力和周围的气相高达720 K。在高于1000 K的温度下进行校准，需要一种新的校准系统。高温标定单元的设计和高温标定是本课题的第二个主要目标。新电池基于多孔介质燃烧器，可为计划的校准测量提供宽温度范围。在优化和校准成功后，测量技术将在内燃机条件下应用，这是该项目的第三个主要目标。同时测量温度场和速度场的可能性将应用于混合物形成和点火过程的研究。为此，可以使用带有火花点火系统的快速压缩机（RCM）。在压缩行程期间进行了测量，以解决温度不均匀性和混合物形成过程中的湍流，并将研究发生在上死点附近的自燃过程。在存在反应性混合物且湍流不是太高的热区域中，自动点火是初始化的。此外，在延迟喷射定时的火花点火集成电路发动机条件下，将详细研究火花塞区域的温度和速度场。局部汽化冷却和由此产生的温度分层以及喷雾引起的湍流将得到解决。因此，循环变化及其对可燃性的影响将被识别。

Aim of the project is the development of the two-colour laser induced phosphorescence technique for simultaneous visualisation of gas temperature and velocity fields under IC engine conditions. The technique will be utilized for imaging of mixture formation, ignition and combustion. Furthermore, this measurement technique can be utilized for fundamental studies and for optimization of many systems related to energy technology and chemical process technology. Inert YAG:Dy particles with a temperature-dependent luminescence signal are utilized, which can be additionally used for velocity determination. In the first phase of the project the signal intensity of the phosphor particles was significantly enhanced by doping additional sensitizers like Erbium (Er) und Praseodymium (Pr) to the phosphors.These optimized phosphors YAG:Dy:Er and YAG:Dy:Pr are applicable for high temperature measurements above 1000 K and will be utilized for the planned studies under IC engine conditions. However, further modifications and variations of the host material are necessary in order to increase signal intensity and thus, measurement accuracy at high temperatures while decreasing the luminescence duration. In the first phase of the project a flow cell was set up and a characterization and calibration of the phosphorescence was conducted e.g. depending on temperature, pressure and surrounding gas phase up to 720 K. For a calibration at temperatures higher than 1000 K, a new calibration system is necessary. The design of the high temperature calibration cell and the high temperature calibration is the second main goal of the project. The new cell is based on a porous media burner enabling a wide temperature range for the planned calibration measurements. After successful optimization and calibration, the measurement technique will be applied under IC engine conditions, which is the third main goal of the project. The possibility of the simultaneous measurement of temperature and velocity fields will be applied for the study of mixture formation and ignition processes. For this purpose, a rapid compression machine (RCM) with a spark ignition system is available. Measurements during the compression stroke for resolving temperature inhomogeneities and turbulent flows during mixture formation are conducted as well as auto-ignition processes will be studied occurring around top dead centre. Auto-ignition is initialized in hot regions in which a reactive mixture is present and where the turbulence is not too high. Furthermore, under spark-ignition IC engine conditions with late injection timing, the region at the spark plug will be studied in detail regarding temperature and velocity fields. The local vaporization cooling and the resulting temperature stratification will be resolved as well as the spray-induced turbulent flow. Thus, the cyclic variation and its influence on ignitability will be identified.