Effect of Hydrogen Addition to Natural Gas on HCCI Engine Emissions Using a Single Zone Thermodynamic Simulation

A wide variety of fuels can be used in HCCI combustion engines. The HCCI combustion process is initiated due to auto-ignition of fuel/air mixture which is dominated by chemical kinetics and there is no flame propagation. Therefore fuel composition has a significant effect on engine performance and emissions and a detailed reaction mechanism is generally essential to analysis HCCI combustion. Computational fluid dynamics (CFD) with detail chemical kinetics could be used to study the HCCI combustion of simple fuels, but for most practical fuels it is computationally too time consuming. Single zone model, on the other hand, permit to have a detailed chemical kinetics modeling for practical fuels and it also gives good results compare to experimental data. In this study the effect of hydrogen addition on methane combustion was investigated using a CHEMKIN single-zone model with detail chemical mechanism in order to investigate combustion phenomena and to analyze emissions and the pressure and temperature distributions in an HCCI engine. Ten different mixture of natural gas-hydrogen with hydrogen ranging from 0 to 90 percent is used. The addition of hydrogen in variable concentrations significantly increases the reactivity of the natural gas blend used (methane–ethane 10:1), particularly under fuel-lean conditions. The results indicate that increasing hydrogen portion decreases CO, CO2 and unburned hydrocarbons while it advances ignition timing and enhances peak pressure and temperature

Keywords:

HCCI , Natural gas , Hydrogen , Thermodynamic modeling