Comparative study on the energetic and ecologic parameters of dual fuels (Diesel–NG and HVO–Biogas) and conventional diesel fuel in a CI engine

Abstract

The article presents the results of the experimental research and numerical analysis of a compression ignition (CI) engine adapted for running on dual fuels of different composition (diesel and natural gas, diesel and biogas, biodiesel and natural gas, and biodiesel and biogas). The main goal was to find out the impact of different dual fuels on energy performance and emissions depending on the start of injection (SOI) of diesel and the crank angle degree (CAD). Pure conventional diesel fuel and second generation hydrotreated vegetable oil (HVO) (Neste) was used in the research. Natural gas contained 97 vol. % of methane. Biogas (biomethane) was simulated using a methane and carbon dioxide blend consisting of 60 vol. % of methane and 40 vol. % of carbon dioxide. Dual (liquid and gaseous) fuels were used in the tests, with the energy share of liquid fuels accounting for 40% and gas for 60%. The research results have shown that having replaced conventional diesel fuel with dual fuel, engine’s BTE declined by 11.9–16.5%. The use of methane in the dual fuel blend reduced CO2 volumetric fraction in the exhaust gases by 17–20%, while biomethane increased CO2 volumetric fraction by 10–14%. Dual fuel significantly increased CO and HC emissions, but NOx volumetric fraction decreased by 67–82% and smoke by 23–39%. The numerical analysis of the combustion process revealed changes in the ROHR (Rate of Heat Release) that affected engine efficiency and exhaust emissions was done by AVL (Anstalt für Verbrennungskraftmaschinen List) BOOST program.