MD3-1: Study of the Effect of Wall Guiding on Direct Diesel Injection by Optical Diagnostics(MD: Measurement and Diagnostics,General Session Papers)
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This paper reports an investigation of the mechanisms of fuel jet interaction with an inclined plate in direct Diesel injection. The analysis is based on the application of optical diagnostics for the study of mixture, auto-ignition and soot formation. The interaction of a jet issuing from a single hole Common Rail Diesel injector with a flat inclined plate is observed in a high pressure, high temperature cell that reproduces the conditions which are typically encountered in the combustion chamber of a Diesel engine during injection. An analysis of the fuel air mixture by Laser Induced Exciplex Fluorescence (LIEF) shows that the presence of the wall significantly affects the mixture structure. Jet impingement on the inclined wall leads to confinement of the jet near the wall in the upstream region. This results in the development of a coherent structure at the jet tip which leads to improved mixing in the jet periphery. Furthermore, the mechanisms of air entrainment in the tail of the jet and near to the injector nozzle are significantly modified to such an extent that the fuel concentration in the upstream zone is very different depending on the configuration tested. A subsequent analysis of the combustion process reveals that the auto-ignition delay increases in the case of the wall impinging jet and that this effect is amplified with the relative angle between the jet and the wall. A combined analysis of the mixture structure by LIEF and of auto-ignition by Laser Induced Fluorescence excited at 355nm (355 LIF) shows that this effect is due to confinement of the jet near to the wall which inhibits auto-ignition and thus results in an increased ignition delay. An analysis of the formation of PAH and soot by LIF 355 and Laser Extinction Method (LEM) respectively reveals that the wall impinging jet has two contradictory effects on soot formation. Improved mixing related to the development of the coherent structure at the jet tip leads to a soot reduction for low incident jet-wall angles. However, this effect is countered by poorer mixing as a result of confinement in the near wall region, leading to an increase in soot concentration when the incident angle is increased.
- 一般社団法人日本機械学会の論文
- 2008-07-28
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- MD3-1: Study of the Effect of Wall Guiding on Direct Diesel Injection by Optical Diagnostics(MD: Measurement and Diagnostics,General Session Papers)