A Physically-Consistent Chemical Dataset for the Simulation of N$_2$-CH$_4$ Shocked Flows Up to T=100,000K

TL;DR

This work updates the G"{o}k extrm{c}en chemical dataset to ensure physical consistency across 100-100,000K, improving high-speed shocked flow simulations of N$_2$-CH$_4$ mixtures.

Contribution

The paper introduces an extensively revised chemical dataset for N$_2$-CH$_4$ that remains physically consistent at very high temperatures, enhancing simulation accuracy.

Findings

Updated dataset maintains physical consistency up to 100,000K.

Revised rates improve simulation accuracy for high-speed shock flows.

Dataset provides more reliable predictions compared to original G"{o}k extrm{c}en data.

Abstract

In the previous work carried out in the scope of the \emph{Validation of Aerothermochemistry Models for Re-Entry Applications}, it was verified that the G\"{o}k\c{c}en chemical dataset provided increasingly diverging results from experiments, as one considered shock speeds in excess of 5\kilo\metre\per\second. Namely, for shock velocities between 7 and 9\kilo\metre\per\second, more than one temporal peak in CN Violet radiation were predicted by models considering this kinetic dataset, in contradiction with experiments. This hinted at several of the rates from the dataset not being directly applicable in the temperature range of interest for such applications, often in excess of 10,000\kelvin. Indeed, it has been found that several macroscopic rates from the G\"{o}k\c{c}en chemical dataset reached unphysical values at very high temperatures. Furthermore, many of the ionization rates have been found to be inadequate for the simulation of high-temperature N$_{2}$--CH$_{4}$ shocked flows. Here, we have carried an extensive update of the G\"{o}k\c{c}en chemical dataset, with the aim of at least reaching physically consistent rates for the whole T=100-100,000\kelvin\ temperature range. While it cannot really be claimed that such improved dataset is validated in such an extended temperature range (due to the scarcely available experimental data for such high temperature ranges), it is capable of providing more accurate simulations of high-speed shocked flows for this mixture, when compared to the G\"{o}k\c{c}en chemical dataset.