Exploring the Oxy-Fuel Combustion in Spark-Ignition Engines for Future Clean Powerplants

Abstract

In the context of the CO2 challenge, oxy-fuel combustion in internal combustion engines (OFC-ICE) arises as a promising technology for carbon capture and almost zero-NOx solutions. Although the literature shows some experimental and theoretical works on OFC-ICE, there is a lack of systematic studies dealing with dilution strategies or where nonsynthetic exhaust gases recirculated (EGR) is used. Using a combination of zero-dimensional (0D)-one dimensional (1D) and computational fluid dynamics modeling and experimental measurements, dilution with oxygen (λ>1) and real EGR in a single-cylinder spark-ignition OFC-ICE is here assessed, considering thermo-mechanical limitations and knocking. Results show that an EGR strategy is more appropriate than O2 dilution. A slightly poor mixture near stoichiometric conditions, with EGR rates around 70%, reduces NOx more than 99%, and CO and unburned hydrocarbons up to 90% with respect to the conventional internal combustion engines. It is concluded that OFC-ICE has a lower knocking propensity, thus allowing to increase the compression ratio to partially compensate for the expected efficiency diminution to about 4% points.