Calibration and application of laser-induced fluorescence for liquid-phase thermography

• Grant number: 22/16400-7
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: March 01, 2023
• End date: December 31, 2024
• Field of knowledge: Engineering - Mechanical Engineering - Thermal Engineering
• Principal Investigator: Arthur Vieira da Silva Oliveira
• Grantee: Pedro Stefano Veronese
• Host Institution: Escola de Engenharia de São Carlos (EESC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Associated research grant: 21/01897-0 - Experimental study of droplets impact onto heated walls using combined optical techniques: single droplets, multiple droplets and sprays, AP.JP

Abstract

The study of the temperature distribution in a fluid is fundamental for a solid and global understanding of heat transfer mechanisms and fluid mechanics, with essential impacts in the most diverse areas of engineering, such as automotive (mainly in IC engines), aeronautics, nuclear, microelectronics (more specifically in component cooling), among others. The existing measurement methods, such as thermocouples, provide only local information or measurement averages, precluding a spatial analysis of the phenomenon involved and having a response time that can mask high-frequency transients. With this in mind, there is an effort of the thermal engineering community aimed at the use and development of non-invasive or less invasive measurement techniques (of temperature or other properties), such as the LIF technique (Laser Induced Fluorescence), which intends to be studied and calibrated in the current research project.More specifically, the proposal concerns the selection and calibration of dyes for the 2c (two-color) measurement, aiming at the suppression, in the calculations, of some constants that are difficult to be calculated and/or measured in the laboratory and also to avoid spectral conflicts that disturb the LIF measurement. Hence, the emission curves of all candidate dyes will be obtained and analyzed for experiments foreseen in the FAPESP Young Investigator Grant (2021/01897-0), in which the present Undergraduate Research proposal is linked, which intends to measure the temperature of droplets impacting heated walls. This measurement of the fluorescence emission spectrum will be performed in a cuvette on a heated plate to control the fluid's temperature and thus evaluate the dye's sensitivity to temperature. Furthermore, tests will be performed for different laser powers, allowing the identification of the fluorescence regime in which the system will work: linear, transition and saturated. Finally, after selecting the most appropriate dye for temperature measurement using the available system, a practical application of LIF will be tested to measure the temperature transient of a heated water jet.The execution of the present Undergraduate Research proposal will provide a new competence to the new research group, as it calibrates one of the forms of temperature measurements intended in the project, opening space for the planned master's student to be integrated to the group in the future. It will also develop the undergraduate student as this study introduces him to the technical-scientific environment, especially with an education based on the Scientific Method and skill development with an advanced temperature measurement technique.