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

Summary, in English

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.

• Author: Clement Chartier; Ulf Aronsson; Öivind Andersson; Rolf Egnell; Bengt Johansson
• Department/s: Combustion Engines
• Publishing year: 2013
• Language: English
• Pages: 311-318
• Publication/Series: Fuel
• Volume: 112
• Links: http://dx.doi.org/10.1016/j.fuel.2013.05.021
• Document type: Journal article
• Publisher: Elsevier
• Topic: Other Mechanical Engineering
• Keywords: Lift-off length; Jet-jet interactions; Optical engine; Diesel; Sprays
• Status: Published
• ISBN/ISSN/Other: ISSN: 1873-7153