No abstract

Dual fuel combustion exhibits a high degree of complexity due to the presence of different fuels like diesel and natural gas in initially different physical states and a spatially strongly varying mixing ratio. Optimizing this combustion process on an engine test bench is costly and time consuming. Cost reduction can be achieved by utilizing simulation tools. Although these tools cannot replace the application of test benches completely, the total development costs can be reduced by an educated combination of simulations and experiments. A suitable model for describing the reactions taking place in the combustion chamber is required to correctly reproduce the dual fuel combustion process. This is why in the presented study, four different reaction mechanisms are benchmarked to shock tube (ST) and rapid compression machine (RCM) measurements of ignition delay times (IDTs) at pressures between 60 and 100 bar and temperatures between 671 and 1284 K. To accommodate dual fuel relevant diesel-natural gas mixtures, methane–propane–n-heptane mixtures are considered as the surrogate. Additionally, the mechanisms AramcoMech 1.3, 2.0 and 3.0 are tested for methane–propane mixtures. The influence of pressure and propane/n-heptane content on the IDT based on the measurements is presented and the extent to which the mechanisms can reflect the IDT-changes discussed.

No abstract

No abstract

Ignition delays of stoichiometric mixture of 2,5-dimethyltetrahydrofuran/O 2 /inert mixtures were measured at temperatures ranging from 650 to 1300 K in a RCM and in a shock tube. Operating pressures ranged from 10 to 40 bar at higher temperature (ST) and 10 to 20 bar at lower temperatures (RCM). The ignition delay times exhibit a slight deviation from Arrhenius behaviour, and limited low-temperature reactivity. This behaviour is similar to other cyclic ethers studied in comparable conditions namely THF, 2-MTHF and 3-MTHF, where 2,5-dimethylterahydrofuran (2,5-DMTHF) is showing the lowest reactivity of this series of cyclic ethers.Detailed speciation and quantification of the intermediates formed by a stoichiometric 2,5-DMTHF/O 2 /N 2 mixture in the combustion chamber of the RCM was performed at different times between top dead center and the ignition event for T c = 712 K and p TDC = 10 bar. The major fuel specific species observed are 2,5-dimethylfuran, 2,6-dimethyl-1,3-diox-4-ene, hexa-2,5-dione, 1-(2methylcyclopropyl)ethanone, and hex-3-en-2-one.To provide further insight into the kinetics of the oxidation of 2,5-DMTHF, a comprehensive kinetic model was developed and validated upon the acquired experimental data. Reaction pathway analysis and sensitivity analysis give an overview of the oxidation process of 2,5-DMTHF and elucidates the formation of the experimentally observed fuel-specific intermediates.

No abstract

Recently the possibility of hot β-scission pathways gained attention. These reactions give a shortcut during the important fuel consumption phase in combustion processes leading from H-atom abstraction directly to the βscission products without fuel radical thermalization. Methyl formate (MF) was shown to be prone to hot β-scission due to a low β-scission barrier height.

No abstract