1. Sub-millisecond Two-dimensional OH Line Profiles Obtained With A Mhz- rate High Resolution UV Laser Source Mikhail Slipchenko Iowa State University Mechanical Engineering

2. Outline  Spectroscopy in Combustion  Instrumentation  Application to OH PLIF  Fast 2D OH Line Scan

3. Combustion  Fossil fuels account for 85% of world’s 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

4. 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

5. 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

6. 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

7. Pulse-burst laser approach (Based on Lempert and Miles,et. al., AIAA-96-0500, 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

8. Pulse-burst laser layout (Based on Lempert and Miles,et. al., AIAA-96-0500, 1996)

9. Pulse-burst performance 27 mJ/pulse 400 mJ/pulse (Based on Lempert and Miles,et. al., AIAA-96-0500, 1996)

10. OH detection scheme 1064532 SHG 1420 + 763 OPO SFG 313.5 Wavelength, nm P 2 (10)

11. Experimental layout

12. 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

13. OH planar LIF results 4” 20 images – 40 μsec Spacing 47 slpm (Mach 1) 25 slpm15 slpm10 slpm5 slpm

14. Temperature measurements Wavelength, nm P 2 (10) P 2 (10) Doppler broadening

15. Principle of line scan in burst mode 313 nm burst 763 nm seed etalon trace Frequency scan 1064532 SHG 763 + 1420 SFG 313.5 OPO Seed

16. Spectral scanning through OH transition H 2 – Air Flat Flame – 1 Bar 20 Images – 40 μsec Spacing ~0.6 mJ/pulse @ ~313 nm. Hencken burner flame

17. Future direction 2D Temperature at MHz rate Rapid switch between NO lines Time, ms 00.1

18. 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

19. 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

20. End

22. ISU

23. 3d generation pulse-burst Nd:YAG Pulse- Burst Amplifier Power Supply Rack Pulse Slicer AWG

24. Injection-Seeded Optical Parametric Oscillator

25. 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

26. How spectroscopy can help? 300 K 306 310314 nm OH laser induced fluorescence spectrum Laser induced fluorescence (LIF) OHC2C2 CHCH 2 O radicals pollutants NOCO

27. How spectroscopy can help? 500 K 306 310314 nm OH laser induced fluorescence spectrum Laser induced fluorescence (LIF) OHC2C2 CHCH 2 O radicals pollutants NOCO

28. How spectroscopy can help? 1000 K 306 310314 nm OH laser induced fluorescence spectrum Laser induced fluorescence (LIF) OHC2C2 CHCH 2 O radicals pollutants NOCO

29. How spectroscopy can help? 2000 K 306 310314 nm OH laser induced fluorescence spectrum Laser induced fluorescence (LIF) OHC2C2 CHCH 2 O radicals pollutants NOCO

30. How spectroscopy can help? 3000 K 306 310314 nm OH laser induced fluorescence spectrum Laser induced fluorescence (LIF) OHC2C2 CHCH 2 O radicals pollutants NOCO

31. How spectroscopy can help? 3000 K 306 310314 nm OH laser induced fluorescence spectrum Laser induced fluorescence (LIF) OHC2C2 CHCH 2 O radicals pollutants NOCO

33. Outline  Instrumentation development  2D imaging  LIF Spectroscopy in Combustion