A study of the homogeneous charge compression ignition combustion process by chemiluminescence imaging

Hultqvist Anders*, Magnus Christensen, Bengt Johansson, Axel Franke, Mattias Richter, Marcus Aldén

*Corresponding author for this work

Research output: Contribution to conferencePaperpeer-review

97 Scopus citations

Abstract

An experimental study of the Homogeneous Charge Compression Ignition (HCCI) combustion process has been conducted by using chemiluminescence imaging. The major intent was to characterize the flame structure and its transient behavior. To achieve this, time resolved images of the naturally emitted light were taken. Emitted light was studied by recording its spectral content and applying different filters to isolate species like OH and CH. Imaging was enabled by a truck-sized engine modified for optical access. An intensified digital camera was used for the imaging. Some imaging was done using a streak-camera, capable of taking eight arbitrarily spaced pictures during a single cycle, thus visualizing the progress of the combustion process. All imaging was done with similar operating conditions and a mixture of n-heptane and iso-octane was used as fuel. Some 20 crank angles before Top Dead Center (TDC), cool flames were found to exist. They appear with a faint structure, evenly distributed throughout the combustion chamber. There was no luminosity recorded between the end of cool flames and the start of the main heat release. Around TDC the main heat release starts. Looking at a macro scale, we find that the charge starts to burn simultaneously at arbitrary points throughout the charge. Since the thermal boundary layer is colder than the bulk of the charge, the local heat release is delayed close to the walls. As a result, the total heat release is slowed down. Ensemble averaged1 images show this wall boundary effect clearly when plotted against CAD. The peak intensity at the main combustion event is one order of magnitude greater than that of the cool flame and the structure is a lot more protruding. Since spontaneous emission imaging is a line-of-sight integration, the flame structure appears a bit smeared. The micro scale structure is very similar from one cycle to another, but there are large variations between cycles on the macro scale.

Original languageEnglish (US)
DOIs
StatePublished - Dec 1 1999
EventInternational Fall Fuels and Lubricants Meeting and Exposition - Toronto, ON, Canada
Duration: Oct 25 1999Oct 28 1999

Other

OtherInternational Fall Fuels and Lubricants Meeting and Exposition
CountryCanada
CityToronto, ON
Period10/25/9910/28/99

ASJC Scopus subject areas

  • Automotive Engineering
  • Safety, Risk, Reliability and Quality
  • Pollution
  • Industrial and Manufacturing Engineering

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