Sub-millisecond Two-dimensional OH Line Profiles Obtained With A Mhz- rate High Resolution UV Laser Source Mikhail Slipchenko Iowa State University Mechanical Engineering Outline Spectroscopy in Combustion Instrumentation Application to OH PLIF Fast 2D OH Line Scan Combustion Fossil fuels account for 85% of worlds energy use, mostly used through combustion Huge effect on environment Search is going on for alternatives to imported oil, from coal to bio-fuels. Combustion research is needed to use these effectively in current infrastructure How spectroscopy can help? Line frequency Line intensity Line width Spectrum can be related to the thermodynamic state of the gas speed pressure concentration temperature OHC2C2 CHCH 2 O radicals pollutants NOCO Importance of spatio-temporal information Turbulent reaction rates are many times faster than laminar reaction Structure of the flame controls the reaction progress Local unsteadiness can lead to combustion inefficiency and pollutants Validation of unsteady combustion models requires spatio-temporal information Time scales Turbulent flames (supersonic) 1 ms 1 s Solid state lasers: up to 500 kHz Turbulent flames (subsonic) 1 sec 1 ms Powerful Pump lasers: up to 200 Hz Laminar flames no dynamics Any light sources Pulse-burst laser approach (Based on Lempert and Miles,et. al., AIAA , 1996) (a) CW laser is sliced into pulse-burst, repeated every 0.1s 0.1s (b) Nd:YAG gain curve (c) Result is high power "burst" of 1~99 pulses 300 s - 2 ms 0.1s 1 s Pulse-burst laser layout (Based on Lempert and Miles,et. al., AIAA , 1996) Pulse-burst performance 27 mJ/pulse 400 mJ/pulse (Based on Lempert and Miles,et. al., AIAA , 1996) OH detection scheme SHG OPO SFG Wavelength, nm P 2 (10) Experimental layout OH planar LIF results 6 mm 1 mm Atmospheric Pressure H 2 -Air Diffusion Flame 4 47 slpm (Mach 1) 25 slpm15 slpm10 slpm5 slpm OH planar LIF results 4 20 images 40 sec Spacing 47 slpm (Mach 1) 25 slpm15 slpm10 slpm5 slpm Temperature measurements Wavelength, nm P 2 (10) P 2 (10) Doppler broadening Principle of line scan in burst mode 313 nm burst 763 nm seed etalon trace Frequency scan SHG SFG OPO Seed Spectral scanning through OH transition H 2 Air Flat Flame 1 Bar 20 Images 40 sec Spacing ~0.6 ~313 nm. Hencken burner flame Future direction 2D Temperature at MHz rate Rapid switch between NO lines Time, ms 00.1 Conclusions For the first time OH planar LIF was obtained using pulse-burst laser system The proof of principle 2D line scan was shown applicable for NO and others Measurements of temperature, velocity and concentration are possible Funding: - Air Force Research Laboratory (James R. Gord) - NASA Langley (Paul Danehy) Collaborators: - Walter Lempert (Ohio State University) - Sukesh Roy and Gary Switzer (Innovative Scientific Solutions, Inc.) Acknowledgments Terry Meyer Joe Miller Jake Schmidt End ISU 3d generation pulse-burst Nd:YAG Pulse- Burst Amplifier Power Supply Rack Pulse Slicer AWG Injection-Seeded Optical Parametric Oscillator UV Output Pump Input UV Mixing Crystal OPO Crystals OPO Output Pump Residual Optical Isolators Beam Dump Seed Laser Beam Dump 763 nm 532 nm 60 mJ/pulse 313 nm 0.6 mJ/pulse How spectroscopy can help? 300 K nm OH laser induced fluorescence spectrum Laser induced fluorescence (LIF) OHC2C2 CHCH 2 O radicals pollutants NOCO How spectroscopy can help? 500 K nm OH laser induced fluorescence spectrum Laser induced fluorescence (LIF) OHC2C2 CHCH 2 O radicals pollutants NOCO How spectroscopy can help? 1000 K nm OH laser induced fluorescence spectrum Laser induced fluorescence (LIF) OHC2C2 CHCH 2 O radicals pollutants NOCO How spectroscopy can help? 2000 K nm OH laser induced fluorescence spectrum Laser induced fluorescence (LIF) OHC2C2 CHCH 2 O radicals pollutants NOCO How spectroscopy can help? 3000 K nm OH laser induced fluorescence spectrum Laser induced fluorescence (LIF) OHC2C2 CHCH 2 O radicals pollutants NOCO How spectroscopy can help? 3000 K nm OH laser induced fluorescence spectrum Laser induced fluorescence (LIF) OHC2C2 CHCH 2 O radicals pollutants NOCO Outline Instrumentation development 2D imaging LIF Spectroscopy in Combustion