Department of Combustion Physics

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Department of Combustion Physics Gustaf Särner,
PhD-student
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Diagnostic tools for generic diesel research

• Outline
• Thermographic phosphors
• Theoretic overview
• Performed measurements
• Results
• Raman measurement of f and EGR
• Theoretic overview
• Planed measurements

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Thermographic phosphors -Theoretic overview

• Thermographic phosphors
• Ceramic materials doped with rare earth metals
• Phosphorescence properties dependent on
  temperature
• Phosphorescence lifetime decrease with
  temperature
• Phosphorescence spectra changes with temperature
• No pressure sensitivity up to 1 GPa
• Temperature measurements using laser induced
  phosphorescence
• Remote and close to non intrusive measurement
  technique
• TP can be painted on surface using binder
• TP can be seeded in liquid
• Lifetime or spectral intensity ratios used for
  thermometry
• 2D-measurements possible
• Measurement range from cryogenic to 2000 K
  depending on TP used

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Temperature measurements using lifetime method

• Phosphorescence lifetime decrease with
  temperature
• Typical lifetime ??s - ms
• Theoretical lifetime
• Data acquired via PMT or framing camera
• Fitting measured data to theoretic model gives
  lifetime

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Temperature measurements using spectral property
changes

• The fluorescence spectra is temperature dependent
  for some phosphors
• The ratio between two peaks is calibrated to
  temperature

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2D measurements in droplets/spray

• La2O2SEu seeded in water
• Droplet/spray irradiated with laser sheet
  inducing emission in one spatially resolved plane
• Emission lifetime detected with framing camera
  using 7 CCD-chips

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2D measurements in droplets
(Equivalent setup for spray measurements)
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Evaluating data

• Intensity of every pixel compared with its
  corresponding ones on the other CCD-chips
• Exponential curve fitted to the intensity decay
  of each pixel

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TP Results
Room temperature water sprayed in room
temperature air
Warm water droplet falling free in room
temperature air
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Raman Theoretic overview

• Classical explanation
• Molecule in electromagnetic field ? electrical
  dipole momentum ? Reyleigh scattering
• Vibration of molecule ? Raman shift of Reyleigh
  scattering
• Quantum mechanical explanation
• Excitation of electrons to virtual levels from
  all populated ground state vibration levels ?
  deexcitation mostly to the original level
• Sometimes deexitation to other level than
  original ? Raman shift
• Properties of the Raman signal
• Very weak signal
• Intensity laser power
• Intensity l-4
• Intensity p

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Raman diagnostics

• Purpose
• To investigate possibility to measure f and EGR
  non intrusive and spatially resolved in diesel
  engine
• Measurement in one point or along line(s)
• Method
• Excitation with 512 nm
• Penetrates well through unburned gas low
  fluorescence
• High laser powers possible
• Multi-YAG laser system used
• 8 pulses after each other
• Higher laser power (avoiding damaging of optics)
• Pulse stretcher used
• Stretches laser pulse in time using delay loops
• Higher laser powers possible

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Equipment
Spectrometer
Pulse stretcher
Multi-YAG laser
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First signal

• Raman in air
• Single shot
• Integrated signal over about 2 cm
• Signal to noise about 20 100
• Low pressure

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• The end
• Thank you for your attention!