Diffuse Back-Illuminated Extinction Imaging of Soot: Effects of Beam Steering and Flame Luminosity

This study presents diagnostic development of diffuse back-illuminated extinction imaging of soot. The method provides high temporal and spatial resolution of the line-of-sight optical density of soot (KL) in compression-ignited fuel sprays relevant to automotive applications. The method is subjected to two major sources of error, beam steering effects and broadband flame luminosity effects. These were investigated in detail in a direct injection combustion chamber with diesel fuel, under high and low sooting conditions. A new method for correcting flame luminosity effects is presented and involves measuring the flame luminosity using a separate high-speed camera via a beam splitter. The new method and existing methods are applied and the resulting flame luminosity correction errors are compared. The new method yields 50% lower errors than the most promising method (optical flow method). The impact on KL was investigated, showing that the KL uncertainty when using the optical flow method is unbounded for KL values above 2.7, while the new method has an uncertainty of 0.5 for the maximum KL value of 3.8. The new method yields overall lower uncertainties and is more suited to measuring KL in optical thick conditions. Large refractive index gradients in the path of the incident light cause false attenuation, resulting in ambiguity of the measured KL, referred to as beam steering. A detailed investigation of the beam steering effects caused by the non-uniformities in the diffused light source was performed. A beam steering model was made and qualitatively validated from experiments. The results from the beam steering model showed the importance of having a large collection angle, in order to average out small-scale non-uniformities in the light source. The model also showed that large-scale non-uniformities in the light source could affect the measurement even if the collection angle is large.

• Record URL:
  • https://doi.org/10.4271/2019-01-0011
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/01487191
• Supplemental Notes:
  • Abstract reprinted with permission of SAE International.
• Authors:
  • Bjørgen, Karl Oskar Pires
  • Emberson, David Robert
  • Lovas, Terese
• Conference:
  • International Powertrains, Fuels & Lubricants Meeting
  • Location: Rio De Janeiro , Brazil
  • Date: 2010-5-5 to 2010-5-7
• Publication Date: 2019-1-15

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; References; Tables;
• Serial:
  • SAE Technical Paper
  • Publisher: Society of Automotive Engineers (SAE)
  • ISSN: 0148-7191
  • EISSN: 2688-3627
  • Serial URL: http://papers.sae.org/

Subject/Index Terms

• TRT Terms: Diesel engine exhaust gases; Diesel engines; Flames; Fuel injection; Luminosity factor; Optical density; Optical systems; Particulates
• Uncontrolled Terms: Direct injection system; Soot
• Subject Areas: Environment; Highways; Vehicles and Equipment;

Filing Info

• Accession Number: 01695947
• Record Type: Publication
• Source Agency: SAE International
• Report/Paper Numbers: 2019-01-0011
• Files: TRIS, SAE
• Created Date: Feb 22 2019 5:08PM