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

Research output: Contribution to journalArticle


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. (C) 2013 Elsevier Ltd. All rights reserved.


Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Other Mechanical Engineering


  • Lift-off length, Jet-jet interactions, Optical engine, Diesel, Sprays
Original languageEnglish
Pages (from-to)311-318
Publication statusPublished - 2013
Publication categoryResearch