A Numerical Exploration of the Combustion of a CH4/H2 Fuel Blend in a Diluted Supercritical CO2 Environment

Abstract

Supercritical CO2 (sCO2) power generation systems have gained popularity in the turbomachinery community in recent years for their high efficiency and compact size owing to the high density of CO2 beyond its critical point. The NET Power sCO2 demonstration plant is the most technologically established direct-fired sCO2 power plant in operation. This paper explores fuel blends ranging from pure natural gas (CH4) to pure hydrogen (H2) for use in the NET Power cycle. In the supercritical regime, CO2 no longer behaves like an ideal gas, and its properties must be determined using existing real gas equations of state (EOS). Following the recommendations of existing literature, the Soave-Redlich-Kwong (SRK) EOS is used to calculate the compressibility factor and the density of the working fluid. The Aramco 2.0 combustion mechanism best models high pressure, high CO2 dilution combustion, but due to the limitations of this study the GRI 3.0 mechanism was used. This work is not able to make suggestions about which fuel blend is best suited for use in the NET Power cycle. However, it confirms that sCO2 requires real gas modeling to capture the behavior of the working fluid beyond its critical point.