Combustion of RME – diesel and NExBTL – diesel blends with hydrogen in the compression ignition engine

Abstract

The article presents the test results of the single cylinder compression ignition engine with common rail injection system operating on biofuels and conventional diesel blends with hydrogen. Two types of liquid fuels were tested: blend of the 7% Rapeseed Methyl Ester (RME) with conventional diesel fuel and Neste Pro Diesel – blend of the 15% Hydrotreated Vegetable Oil (HVO), produced by Neste Oil Corporation with conventional diesel fuel. The purpose of this investigation was to examine the influence of the hydrogen addition to biofuels and diesel blends on combustion phases, autoignition delay, engine performance efficiency and exhaust emissions. Hydrogen fraction was changed within the range from 0 to 43% by energy. Hydrogen was injected into the intake manifold, where it created homogeneous mixture with air. Tests were performed at both fixed and optimal injection timings at low, medium, and nominal engine load. After analysis of the engine bench tests and simulation with AVL BOOST software, it was observed that increasing hydrogen fraction shortened the fuel ignition delay phase and it affected the main combustion phase. Moreover, decrease of carbon monoxide (CO), carbon dioxide (CO2) and smoke opacity was observed with increase of hydrogen amounts to the engine. However, increase of the nitrogen oxide (NOx) concentration in the engine exhaust gases was observed.