A quantitative study of the feasibility of oxygen laser induced fluorescence for engineering gas temperature measurements

The feasibility of using laser induced fluorescence of oxygen (02 LIF) as a temperature diagnostic for engineering gas temperature measurements in general and turbomachinery rigs in particular has been investigated through experiments and analysis. A comprehensive, quantitative error analysis has been performed for the regime of 300-550 K and 1-6 atm. Oxygen ion fluorescence (O+ LIF), saturation, collisional quenching and vibrational relaxation have been identified as the significant error sources, whereas quantum and detector noise are the significant uncertainty sources. The technique precision is limited by quantum and detector noise, and its accuracy is limited by higher-order O+ LIF and saturation processes. For a single-shot measurement, increasing laser fluence reduces uncertainty but increases error. At optimum fluence, the measurement accuracy is equal to the measurement error. The measurement precision may be increased by integrating fluorescence signal from multiple laser shots; the improvement scales as N i /3 . Collisional quenching has been found to be small but not negligible. At 300 K and 1 atm, the measured quenching rate is 5.3 x 109 s-1. The quenching rate scales as P/To7, and neglegting collisional quenching leads to an error of 3 K/atm over the 300-530 K temperature range. The most severe limitation is associated with the vibrational relaxation time. For temperatures above 300 K, the oxygen LIF technique relies on vibrational excitation for temperature sensitivity and may not be used in high-speed flows due to the long vibrational relaxation time of oxygen molecules. For a Mach 1 flow at 500 K and 1 atm, for example, the vibrational relaxation distance is of the order of 1 m. For a Mach 1 flow at 500 K and 1 atm, for example, the vibrational relaxation distance is of the order of 1 m. For temperatures below 250 K, the technique may be used even with high-speed flows as the technique relies on rotational distributions. In conclusion, the oxygen LIF technique is not suitable for use on turbomachinery or other high-speed flows above 300 K because of the long vibrational relaxation time of oxygen. Thesis Supervisor: Alan H. Epstein Supervisor Title: Professor of Aeronautics and Astronautics Director, Gas Turbine Laboratory Acknowledgments First of all, I would like to thank my advisor, Professor Alan H. Epstein, for giving me the opportunity to work on such a challenging project as well as for all his help and advice during my four years at MIT. In addition, I thank Professors C. Forbes Dewey and Edward M. Greitzer, my committee members, for taking the time from their busy schedules to advise me and review my thesis. I gratefully acknowledge the assistance of Dr. Kurt Annen of Aerodyne Research, Inc., with spectroscopy. At the Gas Turbine Laboratory, I would like to thank Dr. Gerald R. Guenette for his help with instrumentation; Messrs. Bill Ames and Jimmy Letendre for their technical assistance in the laboratory; Mr. Viktor Dubrowski for his assistance in the shop; and Mr. Mariano Hellwig for his assistance with electronic equipment. Also, I would like to thank Ms. Holly E. Anderson for her help with purchasing orders and financial affairs. This project was supported by the National Aeronautics and Space Administration (NASA) through the Lewis Research Center, with Dr. Anthony J. Strazisar as technical monitor. Additional funding was provided by ABB. Finally, I would like to thank my father, Mr. Argun Ceyhan, my mother, Mrs. Ayge Ceyhan, and my sister, Ms. Pinar Ceyhan, for their support throughout this project.