Experimental and modelling study of hydrogen ignition in CO2 bath gas

Reduced Reaction Mechanisms for Sustainable Aviation Fuel (SAF): Isoparaffinic Alcohol-to-Jet Synthetic Paraffinic Kerosene (AtJ-SPK) and Its Blends with Jet A

“…Selecting “OH” as the ignition signal species considers the following reasons: (1) “CH*” species is removed from the LLNL-AtJ-SPK mechanism in the reduction process (excluded in the reduced mechanism); therefore, it is technically impossible to use this species as the ignition signal for a consistent comparison. (2) “OH” is included in both the reduced and LLNL-AtJ-SPK mechanisms and has been widely used as an indicator of ignition signal in many previous studies. − Overall, the ignition behavior at different temperatures measured in the experiments under stoichiometric and rich conditions could be well reproduced by both the LLNL-AtJ-SPK and reduced mechanisms. Future efforts might be needed to mildly optimize kinetic parameters to eliminate the slight discrepancy at high-temperature conditions.…”

Role of methyldioxy radical chemistry in high‐pressure methane combustion in CO2

“…8 Recently, Harman-Thomas et al 9 studied the performance of four existing chemical kinetic mechanisms for modeling ignition delay time (IDT) of 52 datasets of methane, hydrogen, and syngas combustion at a range of equivalence ratios, pressures, temperatures, and fuel ratios in various concentrations of CO 2 . From this work and Harman-Thomas et al, 10,11 the University of Sheffield (UoS) sCO 2 2.0 mechanism was created and verified for methane, hydrogen, and syngas IDTs. Karimi et al 12 first noted the importance of CH 3 O 2 chemistry in CO 2 at 100 bar and 200 bar and this chemistry was subsequently found to the essential to the creation of UoS sCO 2 1.0.…”

“…It is also well-established that CH 3 O 2 is an important intermediate in low-temperature combustion. 43 The influence of CH 3 O 2 on the IDT was investigated over a pressure 10,11 this could still lead to large errors in chemical kinetic models. Furthermore, there is also a need to populate the current gap in methane IDT data which exists between 40 and 80 bar, to compare the effect of CH 3 O 2 on the IDT across this range where it is predicted to become an important factor.…”

“…Other applications such as the Space-X Raptor engine which operates using a methane fuel in air at over 300 bar, 46 will also be heavily reliant on CH 3 O 2 chemistry and need to have accurate rate coefficients for these reactions to ensure accurate modelling of their combustion. Second, experimental techniques for the high-pressure investigation of CO 2 , such as shock tubes, are often susceptible to non-ideal effects such as bifurcation 10,47 which reduces the available test time, increases the uncertainty, and complicates the analysis. Therefore, by understanding that CH 3 O 2 chemistry is independent of bath gas, any future experimental work can be performed using argon, simplifying the analysis, and reducing the experimental error, if CO 2 would not have a chemical effect on any of the reactions, except for Reaction 1.…”

“…Mechanisms such as FFCM‐1, 21 USC II 18 and GRI 3.0 19 should be restricted to pressures below 50 bar when studying combustion at less than 1200 K. It should also be noted the deep blue may still indicate a pressure difference of almost 20%. Considering the experimental error in shock tubes typically varies from 15% to 25%, 10,11 this could still lead to large errors in chemical kinetic models. Furthermore, there is also a need to populate the current gap in methane IDT data which exists between 40 and 80 bar, to compare the effect of CH 3 O 2 on the IDT across this range where it is predicted to become an important factor.…”