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

Subject Area Hydraulic and Turbo Engines and Piston Engines
Technical Thermodynamics
Term from 2014 to 2021
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 249077371
 
Final Report Year 2022

Final Report Abstract

In this research project, phosphor thermometry for high-temperature applications was further developed for conditions such as those found in IC engines, gas turbines or reactors in process engineering. The main objective was the definition and characterization of novel phosphors that allow a significant increase in signal intensity even at high temperatures. Here, it was possible to draw on the experience of colleagues at i-MEET at FAU and the equipment available there for particle synthesis and characterization, which supported the project. Great progress was made in the phosphor development. Overall, it was found that the interaction of the crystalline host material with the activator ion is a key factor in the development of thermographic phosphors. Some host crystals, in particular (Gd,Lu)AG:Dy, YAG(BN):Dy and YAP:Dy show significant improvements in their luminescence properties compared to the reference phosphor YAG:Dy. The absolute intensity was also increased at high temperatures while the decay time was reduced, with similar temperature sensitivity. In particular, the newly defined thermographic phosphor (Gd,Lu)AG:Dy has great potential to push the limits of gas-phase sensing to higher maximum temperatures. Unfortunately, commercial availability of a larger quantity of these phosphors was not yet available at the time of project completion. A newly created high temperature calibration cell was utilized for extending the calibration range, which was successfully done for the phosphor YAG:Dy,Er. The calibrated temperature range is now slightly higher than for BAM:Eu and LuAG:Ce, which are most commonly used for phosphor thermometry in the gas phase and this temperature range. The newly identified and characterized phosphor SCASN:Eu also covers the temperature range up to 800 K and offers numerous advantages over all other thermographic phosphors discussed here and established so far, mainly due to its excitation spectrum for application in multiphase flows. The decay time method should also be considered for this phosphor in the future, as it is also expected to have high temperature sensitivity. Possible follow-up studies must include particle-based measurements of absorption cross sections and quantum yields for even clearer comparability among phosphors. For this purpose, dispersed particles are required, since cross-sensitivities can occur in bulk materials. Here, in particular the morphology and particle size must also be taken into account, which strongly influences the absorption behavior and also the scattering of the signal. Against this background, the first step is to improve synthesis processes in order to make the particle properties more comparable and, above all, to enable a synthetization of larger quantities. Further development steps should include systematic particle synthesis and also address other applications of this measurement technology in reactive flows such as process engineering reactors. In principle, the newly developed phosphors can also be used for the determination of the surface temperature and also the liquid phase temperature (here especially by using SCASN:Eu) in the medium temperature range.

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