Numerical investigation on hydrogen-diesel dual-fuel engine improvements by oxygen enrichment

Hydrogen-diesel dual fuel (HDDF) technology is one approach available to improve the performance and reduce carbon-based emissions of compression ignition (CI) engines. Unfortunately, when operated at partial and low loads, HDDF engine configurations suffer from poor fuel utilization, combustion efficiency and ignition delay. As partial load application is increasingly important to performance of hybrid power systems, this paper explores the use of oxygen enrichment to improve HDDF performance outside of conventional load applications.

In this paper, a numerical model was first developed and validated for HDDF combustion using experimental data. This model was subsequently applied to study the influences of oxygen enrichment on engine performance and emission characteristics. Furthermore, the Exhaust Gas Recirculation (EGR) was implemented as a secondary control for NO_x emission reduction. For this configuration the results showed that oxygen enrichment (between 21% and 27% by volume) into the intake manifold led to an improved combustion efficiency and reduced carbon-based emissions. The brake thermal efficiency (BTE) increased by 1.6% and the brake specific energy consumption decreased by 4%. Across the emissions spectrum, soot emission reduced by 72%, whereas NO_x emission increased by 63% without using the EGR technique. By combining oxygen enrichment and EGR strategies, a considerable reduction of 79% in NO_x and an increase of 2.6% in BTE was observed for the oxygen concentration of 27% and EGR rate of 24% compared to a conventional HDDF operation with 45% HES ratio.