A Reduced Kinetics Model for the Oxidation of Transcritical/Supercritical Gasoline Surrogate/Ethanol Mixtures Using Real Gas State Equations

Abstract

Efforts to combat the harmful effects of vehicle emissions on ourenvironment and health include exhaust emissions and fuel efficiencyregulations. One promising solution is direct fuel injection in supercriticalconditions, where the fuel mixture is above critical temperatureand pressure. This study presents a reduced kinetics mechanism (129species and 1015 reactions) utilizing real gas equations to simulate thecombustion of supercritical/transcritical gasoline surrogate/ethanolblends. It was developed by combining two reduced models – aToluene reference fuel (TRF) with a Diisobutylene (DIB) and an ethanolmodel – and validated through simulations of ignition delay time (IDT).The Arrhenius parameters of key reactions for each fuel componentwere modified to improve accuracy. An adjusted Redlich-Kwong cubicstate equation was employed to segregate each surrogate mixturetested as supercritical, transcritical, or subcritical. The new mechanismwas then validated against experimental results using high-pressureconditions and the cubic Peng-Robinson and Redlich-Kwong equationof state parameters. Critical properties of each species were obtainedthrough Joback’s Group Method and the Ambrose-Walton vapor pressureequation. The TRF/DIB/E mechanism results were consistent withshock tube experimental data at high pressure, indicating a potentialfor modeling combustion in ultra-high pressure direct injectionengines.