Understanding the effects of doping a regular E10 gasoline with EHN in an HCCI engine: Experimental and numerical study

Abstract

In this study, the effects of doping a regular E10 gasoline with 2-ethlyhexyl nitrate (EHN) are investigated under homogeneous charge compression ignition conditions. Experiments are performed in a 1-liter single-cylinder engine fueled with both straight and EHN-doped E10 gasoline. Numerical studies are performed with an internal combustion engine single-zone reactor utilizing detailed chemical kinetic mechanism with EHN and NOx chemistry and a surrogate fuel. The kinetic model reproduces the experimental data well for the straight fuel at high initial temperature (TBDC) conditions, whereas the low temperature heat release (LTHR) is under-predicted. Adding EHN reduces the required TBDC, while EHN thermal decomposition rate has to be significantly reduced to accurately reproduce the experimental result, by preventing over-estimation of EHN effect and LTHR. EHN decomposition generates NO2 and 3-heptyl radicals. Using the well-matched mechanism, the numerical results indicate that among the product of EHN decomposition, NO2 decreases the autoignition reactivity whereas the production of 3-heptyl radical is the main source for enhancing the low-to-intermediate chemistry by which OH production is accelerated. The production of 3-heptyl radical is highly sensitive to the EHN decomposition reactions. Despite the reactivity enhancement, increase in NOx emission is observed when the fuel-doping increases.