Imaging of Laser-induced Fluorescence in a High-pressure Combustor

Recently, we have completed the development of an The ability to obtain quantitative planar laserincorporates a production fuel injector and is capable of induced fluorescence (PLIF) measurements in a highoperating at pressures up to 50 atm with preheated air. pressure combustor would represent a significant This facility allows laser-based imaging techniques to be advance in the application of laser diagnostics to pracperformed at conditions that are representative of gastical combustion systems. To simulate the combustion turbine combustors. environment of a gas-turbine engine, an opticallyaccessible high-pressure combustor has been conPlanar laser-induced fluorescence (PLIF) is a widely structed. The combustor facility incorporates a proused diagnostic technique capable of providing instanduction liquid-fuel injector and a preheated air supply. taneous two-dimensional measurements in flames. In this paper, we demonstrate the feasibility of instanHowever, the application of PLIF techniques to practical taneous OH PLIF measurements in spray flames of combustion devices operated at high pressure remains a heptane and Jet-A fuel at pressures up to 20 atm. Obserchallenge. Examples of such applications include PLIF vations of OH PLIF images at a range of pressures and imaging of fuel concentration in a flame-tube and a overall equivalence ratios are presented. spark-ignition engine. PLIF measurements of OH and Introduction Previous efforts at PSI demonstrated PLIF imaging of To address the demand for increased performance 10 atm in spray flames of heptane, methanol, and and reduced emissions from gas-turbine engines, a ethanol fuels. That work established the quantitative detailed understanding of turbulent combustion extension of linear fluorescence models to high-pressure processes in high-pressure spray flames is essential. environments and exposed interference issues associated Laser diagnostics provide spatially and temporally with PLIF imaging in high-pressure spray flames. Howresolved measurements in reacting flows and have been ever, earlier efforts at PSI were conducted in a comused extensively in atmospheric pressure flames with bustor facility that did not adequately represent the comgaseous fuels. However, the extension of laser-based bustion environment of a gas-turbine combustor. The techniques to practical combustion systems presents a focus of the present work is the demonstration of PLIF significant challenge. The combustion environment in measurements in a more realistic model gas-turbine gas-turbine engines is characterized by elevated combustor. pressures, high thermal loads, liquid-fuel sprays, and the presence of hydrocarbon intermediates. Each of these Optically-Accessible Combustor elements poses a unique challenge for the application of laser diagnostics to gas-turbine engines. At PSI, we are An optically-accessible combustor for PLIF measinvestigating strategies for overcoming these difficulties. urements has been constructed to accept commercial__________ style gas-turbine fuel injectors and to operate at pres*Principal Scientist sures up to 50 atm. One of the challenges associated Principal Research Scientist, Member AIAA with achieving these goals was integrating large † Copyright © by Physical Sciences Inc. Published by the windows into the pressure vessel while maintaining good American Institute of Aeronautics and Astronautics, Inc. structural integrity for high-pressure operation. A with permission. second challenge was presented in the design of the optically-accessible model gas-turbine combustor, which