Numerical investigation of the impact of gas composition on the combustion process in a dual-fuel compression-ignition engine

This study discusses the model of operation of a dual-fuel compression-ignition engine, powered by gaseous fuel with an initial dose of diesel fuel as the ignition inhibitor. The study used a zero dimensional multiphase mathematical model of a dual-fuel engine to simulate the impact of enhancing Natural Gas (NG) with other gases on the combustion process. The model simulated the thermodynamic parameters of the gas mixture in the cylinder of a dual-fuel (NG/Diesel), turbocharged, four cylinder CRDI (Common-Rail Direct Injection) engine. The tests discussed herein were conducted for steady state engine operation, for partial load and constant consumption of gaseous fuel. In the discussed tests, carbon dioxide and higher hydrocarbons (ethane and propane) were used as additions to NG. It has been shown that a change of gas composition has a significant impact on the combustion process and parameters of operation of a dual-fuel engine. The combustion of gas additives largely determines the combustion of both the main component of gaseous fuel and the initial dose of diesel fuel. The addition of higher hydrocarbons to methane can improve engine performance by as much as 6% with additions of higher carbon amounting to 20% of total fuel volume. Also, it has been shown that changes of gas composition significantly impact the ignition delay of the initial diesel dose. (C) 2016 Elsevier B.V. All rights reserved.