Hi Sudipto,
Mechanisms are typically put online by kinetics groups; I am not aware of a central repository that manages them all.
For the Smooke mechanism: one source may be
https://doi.org/10.1016/S0082-0784(88)80412-0 (although I don't have access at the moment) but there's another version in the Springer book (
Reduced Kinetic Mechanisms and Asymptotic Approximations for Methane-Air Flames); I'm not sure which one you are referring to. Unfortunately I am not aware of a site where Chemkin / CTI files for Smooke can be downloaded. A secondary source lists the PROCI version with 16 species and
46 reactions, while Table II in the Springer text lists 16 species with around 35 reactions. In either version, it should be possible to enter this manually (reaction types should be compatible with CHEMKIN/Cantera).
In general, be careful when going to small (or early) mechanisms - they often are tuned for specific use cases as some compromises are generally necessary. Make sure to spot-check with larger modern mechanisms that your results look reasonable.
-ingmar-