Skip to main content
Article thumbnail
Location of Repository

Laser-induced fluorescence investigation of nitric oxide formation and hydroxyl radicals in a diesel rapid compression machine

By Romain Demory, Cyril Crua and Morgan Heikal


The research presented here aims at providing a deeper understanding of the formation of nitric oxide in diesel combustion. To this end, in-cylinder distributions of nitric oxide (NO) were acquired by laser-induced fluorescence (LIF) in a rapid compression machine at conditions representative of a modern diesel passenger vehicle. In particular, the effects of injection and in-cylinder pressure on NO formation were investigated temporally and spatially to offer new insight into the formation of NO. Excitation and collection strategies were notably fine-tuned to avoid the collection of spurious signal due to oxygen (O2) fluorescence. NO fluorescence was first recorded slightly after the onset of the diffusion flame and until late in the expansion stroke. The early low levels of NO were located on the lean side of the high density of hydroxyl radicals (OH). The absence of NO inside the flame plume could however not be investigated because of the severe attenuation of the laser light attributed to hot CO2 molecules, intermediate species and soot. The formation rate of nitric oxide was found almost constant during the mixing-controlled combustion, the OH densities were restricted to the upstream part of the flame and moved inwards. High OH densities and high soot densities were not found to coexist. Finally, at the end of fuel injection, the spray collapsed on itself thus resulting in high densities of OH and NO throughout. Some of the NO seemed to be formed after the end of apparent combustion, when OH radicals were not detected. The observed fluorescence signal increase was linked to a rapid cooling of the flame plume and the associated freezing of the thermal NO mechanism. Injection pressure was found to influence the location and extent of regions with high densities of NO, but not the overall formation or width of the flame plume. Raising the in-cylinder pressure from 5 MPa to 7 MPa led to a shorter flame penetration and ignition delay with more NO formed early and in the upstream part of the flame. The plume and flame front width were seen to contract with rising in-cylinder pressure, and higher rates of NO formation could be observed as a result of increased air density and local temperatures

Topics: H330 Automotive Engineering
Year: 2010
OAI identifier:

Suggested articles


  1. (1990). A New Look at Oxygen Enrichment: 1) The Diesel Engine," doi
  2. (1992). A review of NOx Formation under Gas-Turbine Combustion,"
  3. A versatile modeling tool for nitric oxide LIF spectra," doi
  4. (1978). An Experimental Study of Diesel Engine Cylinder-Averaged Histories," doi
  5. (2003). Carbon dioxide UV laser-induced fluorescence in high-pressure flames," doi
  6. (2002). Combustion Processes in a Diesel Engine,"
  7. (2008). Combustion structure of free and wall-impinging diesel jets by simultaneous laser-induced fluorescence of formaldehyde, poly-aromatic hydrocarbons, and hydroxides", doi
  8. (1997). Conceptual model of DI diesel combustion based on laser-sheet imaging", SAE 970873, doi
  9. (1994). Cylinder-Averaged Histories of Nitric Oxide in a D.I. Diesel with Simulated Turbocharging," doi
  10. (2007). Diesel combustion: In-cylinder NO concentrations in relation to injection timing", doi
  11. (1996). Effects of Gas Density and Vaporization on Penetration and Dispersion of Diesel Sprays", doi
  12. (2001). Flame Lift-Off on Direct Injection Diesel Sprays Under Quiescent Conditions", doi
  13. (2003). Fuel Effects of Soot Processes of Fuel Jets at DI Diesel Conditions", doi
  14. (2005). Fundamental Investigation of NOx Formation in Diesel Combustion Under Supercharged and EGR Conditions," doi
  15. (2003). Health effects of diesel exhaust," doi
  16. (1997). Laser-Induced Fluorescence Detection of Nitric Oxide in High-Pressure Flames with A-X(0,2) excitation," doi
  17. (2000). Laser-Induced Fluorescence Imaging of NO in a DI Diesel Engine using KrF Excimer Radiation," in Towards Clean Diesel Engines,
  18. (1995). Laser-Induced Fluorescence Measurements of NO and OH Mole Fraction in Fuel-Lean, High-Pressure (1-10 atm) Methane Flames: Fluorescence Modeling and Experimental Validation," doi
  19. (1998). LIF Imaging of Diesel Spray Combustion,"
  20. (1996). LIF Spectroscopy of NO and O2 in High-Pressure Flames," doi
  21. (1999). LIFBASE, Database and spectral simulation for diatomic molecules (v 1.6)," SRI
  22. (2001). Measurements and simulations of in-cylinder UV-absorption in spark ignition and Diesel engines," doi
  23. (2006). Measuring and processing in-cylinder distributions of NO and OH obtained by laser-induced fluorescence in a diesel rapid compression machine," in Applied Laser Techniques to Fluid Mechanics, doi
  24. (1999). Nitric oxide in a diesel engine: laser-based detection and interpretation,"
  25. (1996). OH Radical Imaging doi
  26. (1996). OH Radical Imaging in a DI Diesel Engine and the Structure of the Early Diffusion Flame", doi
  27. (2001). Oxygenates Screening for Advanced Petroleum-Based Diesel Fuels: Part 2. The Effect of Oxygenate Blending Compounds on Exhaust Emissions.", doi
  28. (1994). PLIF Imaging Measurements in High-Pressure Spray Flame Combustion," doi
  29. (1998). PLIF Imaging of NO Formation in a DI Diesel Engine," doi
  30. (2001). Quantitative Laser Diagnostics Studies of the NO Distribution in a DI Diesel Engine with PLN and CR Injection Systems," doi
  31. (2006). Quantitative Laser-Induced Fluorescence Measurements of Nitric-Oxide in a Heavy-Duty Diesel Engine," doi
  32. (2000). Quantitative measurements of nitric oxide in high-pressure (2-5 atm), swirl-stabilized spray flames via laser-induced fluorescence," doi
  33. (2002). Quantitative NO-LIF imaging in high-pressure flames," doi
  34. (1989). Simultaneous Measurement of Raman Scattering and Laser-Induced OH Fluorescence in Nonpremixed Turbulent Jet Flames," doi
  35. Superequilibrium and Thermal Nitric Oxide Formation in Turbulent Diffusion Flames," doi
  36. Technology Development to Meet the Future Demand for Passenger Car Diesel Engines with Lower Emissions and Higher Performance,"
  37. (1946). The Oxidation of Nitrogen in Combustion and Explosions," doi

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.