Measurements of Major Species in a High Pressure Gas Turbine Combustion Simulator Using Raman Scattering

A flashlamp-pumped dye laser was modified to produce 80mJ/pulse, narrowband output at 532 nm suitable for pumping of Raman active transitions of the major combustion species CO2, H2O, N2, and O2. Simultaneous measurements of multiple species were obtained in atmospheric pressure methane-air flames, demonstrating absolutely quantitative measurements of species mole-fraction. Comparisons with Q-switched Nd:YAG laser pumping showed that higher fluences, and concomitantly higher Raman signals, were possible with the long-pulse flashlamp-pumped dye laser. A series of measurements in Physical Sciences Inc.’s (PSI) Gas Turbine Combustion Simulation Facility compared the Nd:YAG laser to the dye laser using both heptane and Jet-A fuels at pressures up to 15 atm. A commercial GE CFM-56 fuel injector was used to accurately simulate the aero-thermo-chemical environment of a practical gas turbine combustor. Measurements obtained with the low pulse energy flashlamp pumped dye laser suggest that improved laser performance should achieve ~ 1% mole-fraction accuracy of the major combustion species.