CAREER: Modulated Infrared Laser-Induced Fluorescence for Imaging Temperature and Combustion Species in Next-Generation Combustion Systems

Purdue University, West Lafayette IN

Investigators

Abstract

Many next-generation combustion engines (e.g., diesel and gasoline engines) will operate at lower temperatures in order to improve efficiency and reduce pollutant emissions. Unfortunately, the combustion physics governing these engines is not well understood due to a variety of combustion phenomena which strengthen at lower temperatures. Further, our understanding of these processes is significantly limited by our inability to monitor the gas temperature and key molecular species formed throughout the combustion process. The primary goal of this work is to improve our understanding of combustion initiated at lower temperatures through the development and application of new laser diagnostics. Completing this project will provide broadly applicable laser-based imaging diagnostics capable of quantifying gas temperature and key molecular species. This work will produce fundamental datasets describing flame physics and ignition at conditions representative of those found in future engines. This project will support the research and education of numerous doctoral students and the greater scientific community working in the fields of combustion, laser spectroscopy, and optics. This will be achieved through the experimental research program and the development of a new course and interactive web-based tools focused on combustion diagnostics. Combustion in many high-efficiency, low-emissions engines is achieved through a complex combination of autoignition and both cool and hot turbulent flames. These phenomena and the interaction between them are not well understood, in part, due to the lack of diagnostics which can resolve the temperature and species fields across both the low- and high-temperature combustion regimes. Modulated infrared planar laser-induced fluorescence (MIR-PLIF) techniques providing high-speed imaging of temperature and both intermediate and stable combustion products will be developed and applied to bridge this gap. Spectroscopic and kinetic models, capable of quantitatively predicting infrared fluorescence yields and vibrational non-equilibrium in high-temperature gases, will be developed to enable quantitative imaging of molecular species. MIR-PLIF will be used to determine how thermodynamic conditions alter the time-varying structure of both cool and hot turbulent flames, and how cool flames influence high-temperature ignition. Recently developed burner technologies will be utilized and expanded to enable these studies to be conducted across a wide range of conditions that are relevant to next-generation engines. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.