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hystrath / hyStrath

Hypersonic / Rarefied gas dynamics code developments (GPL-3.0)
https://hystrath.github.io/
GNU General Public License v3.0
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Reference for reverse rate constants for Jachimowski-1992 mechanism #115

Open iainsymthe opened 2 years ago

iainsymthe commented 2 years ago

The reference provided for the Jachimowski mechanism in hTCReactionsJ92 // C. J. Jachimowski // An Analysis of Combustion Studies in Shock Expansion // Tunnels and Reflected Shock Tunnels // NASA TP-3224 // 1992

https://ntrs.nasa.gov/api/citations/19920019131/downloads/19920019131.pdf only has the forward rates. Can you provide a reference for the reverse rates?

vincentcasseau commented 2 years ago

As far as I remember, the forward rates and the equilibrium constants were given in this paper. Since we didn't have the capability to simply provide the equilibrium constant to model the reverse reaction, we plotted the evolution of the backward reaction versus T using forward and Keq data in python and found a set of modified Arrhenius coefficients that fit best this profile.

iainsymthe commented 2 years ago

Thanks, Vincent.  I had put in the link of the publication in my previous note and as you can see that publication does not have the equilibrium constants.  The forward rates are in Table II along with the units and the  third body coefficients.  Does hy2Foam now have the capability to compute equilibrium rate constants like chemFoam does now? ThanksIain On Tuesday, August 23, 2022 at 08:23:24 AM CDT, Vince @.***> wrote:

As far as I remember, the forward rates and the equilibrium constants were given in this paper. Since we didn't have the capability to simply provide the equilibrium constant to model the reverse reaction, we plotted the evolution of the backward reaction versus T using forward and Keq data in python and found a set of modified Arrhenius coefficients that fit best this profile.

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vincentcasseau commented 2 years ago

@jimmyjohnh do you remember how the equilibrium constants were computed in your python script?

Does hy2Foam now have the capability to compute equilibrium rate constants like chemFoam does now?

Not yet unfortunately.

iainsymthe commented 2 years ago

If one were to compare chemFoam with hTCReactionsJ92 (with specified reverse rate coefficient) with a chemFoam computed reverse rates (user provides only Jachimowski-1992 forward rates) - the results are very different - both in terms of ignition delay and final peak temp. I tried a case with stoic H2-air mixture at 2K and 5 atm as the initial temp and pressure. With the current set-up with hy2Foam not being able to calculate reverse rates based on the law of mass action (as in chemFoam) users are limited to using the mechanisms given in chemDicts - one cannot use other chemkin mechanism files as they usually don't come with reverse rates.