Examination of the ignition delay period in gas-fueled diesel engines

Changes in the physical and chemical processes during the ignition delay period of a gas-fueled diesel engine (dual-fuel engine) due to the increased admission of the gaseous fuels and diluents are examined. The extension to the chemical aspects of the ignition delay with the added gaseous fuels and the diluents into the cylinder charge is evaluated using detailed reaction kinetics for the oxidation of dual-fuel mixtures at an adiabatic constant volume process while employing n-heptane as a representative of the main components of the diesel fuel. In the examination of the physical aspects of the delay period, the relative contributions of changes in charge temperature, pressure, physical properties, pre-ignition energy release heat transfer and the residual gas effects due to the admission of the gaseous fuels are discussed and evaluated. It is shown that the introduction of gaseous fuels and diluents into the diesel engine can substantially affect both the physical and chemical processes within the ignition delay period. The major extension of the delay is due to the chemical factors, which strongly depend on the type of gaseous fuel used and its concentration in the cylinder charge.Nous avons examin\ue9 les changements qui surviennent dans les processus physiques et chimiques au cours du d\ue9lai d?allumage d?un moteur mixte essence-diesel, attribuables \ue0 l?admission accrue de combustibles gazeux et de diluants. On \ue9value l?extension aux aspects chimiques du d\ue9lai d?allumage avec les combustibles gazeux et les diluants ajout\ue9s \ue0 la charge du cylindre en utilisant une cin\ue9tique de r\ue9action d\ue9taill\ue9e pour l?oxydation de m\ue9langes mixtes \ue0 un processus adiabatique \ue0 volume constant tout en employant le n-heptane comme \ue9l\ue9ment repr\ue9sentatif des principaux \ue9l\ue9ments constituants du carburant diesel. Dans le cadre de l?examen des aspects physiques du d\ue9lai, on note et \ue9value les contributions relatives des changements dans la temp\ue9rature de charge, de la pression, des propri\ue9t\ue9s physiques, du transfert de chaleur de la lib\ue9ration d?\ue9nergie pr\ue9alable \ue0 l?allumage et des incidences des gaz r\ue9siduels qui sont attribuables \ue0 l?admission des combustibles gazeux. Il est d\ue9montr\ue9 que l?introduction de combustibles gazeux et de diluants dans le moteur diesel peut influer substantiellement tant sur les processus physiques que sur les processus chimiques \ue0 l?int\ue9rieur du d\ue9lai d?allumage. L?extension majeure du d\ue9lai est attribuable aux facteurs chimiques, lesquels sont fortement tributaires du type de carburant gazeux employ\ue9 et de sa concentration dans la charge du cylindre.Peer reviewed: YesNRC publication: Ye