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From quantum mechanics to auto-mechanics

Frontiers in Spectroscopy. Ohio State University, March 2004. Nonlinear Spectroscopy:. From quantum mechanics to auto-mechanics. Lecture Outline. Lecture 1: Linear and Nonlinear Optics Nonlinear spectroscopic techniques Lasers for nonlinear spectroscopy

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From quantum mechanics to auto-mechanics

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  1. Frontiers in Spectroscopy. Ohio State University, March 2004 Nonlinear Spectroscopy: From quantum mechanics to auto-mechanics Paul Ewart

  2. Lecture Outline • Lecture 1: Linear and Nonlinear Optics Nonlinear spectroscopic techniques Lasers for nonlinear spectroscopy • Lecture 2: Basic theory of wave mixing Coherent signal generation Spectral simulation • Lecture 3: Spectroscopy and diagnostics High resolution spectroscopy Combustion diagnostics

  3. DFWM spectroscopy of C2 in oxy-acetylene flame

  4. DFWM spectrum of C2 in oxy-acetylene flame Note: High spectral resolution High signal-to-noise in luminous environment

  5. Simulation of C2 DFWM spectra

  6. Effects of incorrect line position on simulation

  7. Improved line positions from DFWM measurements

  8. DFWM Spectra of C2 in oxy-acetylene flame • Swan band (0,0) Band head • Corrected line positions • Coherent addition

  9. Multiplex DFWM spectroscopy in flames 1 3 2 • Broad laser spectrum overlaps • molecular resonances • 2. Broadband FWM spectrum • recorded on CCD camera • 3. Theoretical spectrum fitted to • find temperature. • C2 spectrum in oxy-acetylene flame

  10. Broadband/Multiplex DFWM spectroscopy of C2

  11. Multiplex FWM thermometry in flames • Time resolved measurement of temperature by single laser shot of broadband modeless laser • Single shot precision of ~4%

  12. 1-D line imaging by FWM Line imaged on Spectrograph slit

  13. Multiplex FWM along a line • Line formed by intersecting planar laser beams • FWM signal is induced by broadband laser • Signal line is mapped onto spectrograph slit • Spatially resolved spectra recorded on CCD camera

  14. Simultaneous measurement of Temperature and Concentration of C2 along a line Spectrum at each position yields temperature T(x) Spectral intensity along line yields concentration

  15. Simultaneous measurement of C2concentration and temperature along 1-D line

  16. DFWM for detection of NOx in a firing s.i. engine

  17. Detection of combustion generated NO in s.i.engine using DFWM • BOXCARS plates: • simple, stable, reproducible • alignment of input laser beams. • Collimated beams in interaction • region minimizes noise from • windows etc.

  18. DFWM spectrum of NO in firing s.i. engine (methane/air)

  19. DFWM spectrum of NO in firing s.i. engine (methane/air) Skip fire 1 in 9 Speed 1200 rpm Ignition timing: 40o BTDC Laser timing: BDC Upper trace: NO absorption (line of sight) Lower trace: DFWM spectrum (space resolved)

  20. LITGS: Laser Induced Thermal Gratings

  21. LITGS in OH in high pressure CH4/air flame Recorded using cw Ar-ion Laser: 1 Watt in ~ 1 ms

  22. Flashlamp pumped dye Laser: 106 Watt in ~ 1 ms

  23. LITGS using long pulse probe NO2:N2 5 bar 300K Temperature precision + 0.1% Pressure precision + 2 %

  24. LITGS in NO2:N2 at 40 bar, 300 K

  25. Simultaneous measurement of Temperature and Pressure along a line using LITGS

  26. Streak image of LITGS signal from line: NO2 in N2 at 2.5 bar 5 mm Position x 0 120 Time nsec Oscillation frequency yields Temperature, T(x) Decay function in time yields Pressure, P(x)

  27. LITGS: Laser Induced Thermal Gratings

  28. TGV, Thermal Grating Velocimetry

  29. TGV in NO2 seeded air flow • Thermal grating written by two beams at 532 nm • Signal read by delayed pulses at 1064 nm from SLM laser • Forward and Back scattered signals are Doppler shifted up and down in frequency by Dn

  30. TGV air flow measurements

  31. Conclusions • Laser Induced Grating techniques: • Temperature CARS • Minor Species, Temperature DFWM • 1-D Concentration and Temp. DFWM • Velocity LITGS • Pressure and Temperature LITGS • 1-D Pressure and Temperature LITGS

  32. Acknowledgements • Karen Bultitude • Rob Stevens • Geraint Lloyd • Radu Bratfalean • Andrew Grant • Duncan Walker • University of Heidelberg PCI • University of Stuttgart, ITV and DLR • EPSRC, British Gas, Rover plc

  33. Potential of LITGS diagnostics • Non-invasive temperature and pressure measurement • Time and space resolved data • Detection of local temperature and pressure • Diagnostics of auto-ignition and engine “knock” Schlieren film of autoignition Courtesy of Prof CWG Sheppard University of Leeds

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