Hydrogen/Diesel Co-Combustion in Compression Ignition Engines Through Hydrogen Ingestion and Direct Hydrogen Injection

Abstract

This dissertation develops, implements, and validates the computational tools necessary for the computational simulation of hydrogen-enhanced Diesel combustion for premixed hydrogen charges ingested into the intake air and for direct injected hydrogen pilot charges into the cylinder. This includes a dual-fuel mechanism, a Lagrangian gaseous injection scheme, an improved spray particle breakup model, an advanced chemical kinetic reaction solver, as well as a complex n-heptane chemical kinetic reaction mechanism consisting of 35 species and 119 reversible reactions capable of describing both premixed and mixing controlled hydrogen/Diesel co-combustion at various fuel concentrations. The results showed that low levels of either hydrogen ingestion and hydrogen direct injection can significantly improve engine efficiency by increasing the kinetic combustion reaction rates though chemical interaction of the Diesel and hydrogen radical pools and specifically though the shared interaction with H2O2, and by delaying the compression ignition timing, which allows for an advancement of the Diesel injection timing. This results in an increase of the premixed combustion phase, which more closely approximates the thermodynamically more efficient Otto cycle.