Influence of jet-jet interactions on the lift-off length in an optical heavy-duty di diesel engine

Clément Chartier*, Ulf Aronsson, Öivind Andersson, Rolf Egnell, Bengt Johansson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

39 Scopus citations


Several investigations have reported that the lift-off length on diesel jets depends strongly on the ambient temperature. The spacing between adjacent jets is thereby expected to influence the lift-off length, as it affects the amount of hot, burned gases present between the jets. Measurements on an 8-hole nozzle in an optical diesel engine showed that the lift-off length can be transient at all times between the start and end of injection. This is attributed to varying in-cylinder temperature and especially to the presence of hot combustion products in the gases entrained into the jets. The effect of inter-jet angle on lift-off length was investigated using symmetric and asymmetric nozzle cups. Decreasing the inter-jet angle produces shorter lift-off length. The lift-off length showed a weaker dependence on the ambient temperature in the engine than predicted by an empirical expression established in a constant-volume combustion vessel. These findings indicate that experiments in such vessels may not capture all features of the conditions in engines. The lift-off length tended to be 15% shorter on the downswirl (leeward) side of the jet. A strong interaction between the effects of the inter-jet spacing and the inlet temperature on the lift-off length was found. All these effects are attributed to the presence of hot gases between the jets.

Original languageEnglish (US)
Pages (from-to)311-318
Number of pages8
StatePublished - 2013
Externally publishedYes


  • Diesel
  • Jet-jet interactions
  • Lift-off length
  • Optical engine
  • Sprays

ASJC Scopus subject areas

  • General Chemical Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Organic Chemistry


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