Shock Tube Design and Fabrication for the Development of a Kinetic Model for Supercritical CO2 Production

Direct-fired supercritical carbon dioxide (sCO2) power cycles offer emissions-free electricity production from the combustion of fossil fuels. Chemical kinetic mechanisms are validated for combustion at lower pressures and much lower CO2 concentrations. The work critically investigates the ability of existing chemical kinetic mechanisms to simulate combustion under these conditions. This is done by investigating ignition delay time (IDT) data recorded using the shock tube experimental technique.

The first key chapter of this Thesis details the development of a new High-Pressure Kinetic Shock Tube (HPST) at the University of Sheffield’s (UoS) Translational Energy Research Centre (TERC). The HPST will be utilised for the research of high-pressure chemical kinetics. The project was delivered in the summer of 2022, with commissioning taking until the end of the year. The HPST will be used in a variety of research projects at the TERC from the combustion of supercritical CO2, ammonia, and synthetic aviation fuels.

Chapter 3 details the development of a new chemical kinetic mechanism for modelling combustion in CO2. The University of Sheffield sCO2 mechanism (UoS sCO2) was developed based on IDT datasets of methane, hydrogen, and syngas. The UoS sCO2 Mechanism was developed and shown through a detailed qualitative analysis to be on average a better fit to the datasets measured for each of the three fuels.

Chapters 4 and 5 focus on the validation of the UoS sCO2 2.0, the second iteration of the mechanism in collaboration with King Abdullah University of Science and Technology (KAUST). Eight IDT datasets for both hydrogen and syngas and ten for methane and methane hydrogen blends were recorded using the KAUST HighPressure Shock Tube between 20 and 40 bar. This data and subsequent modelling analysis are essential to the detailed understanding of the fundamentals of combustion in CO2.