HCN Update for PyroSim 2021.3 and Free Combustion Calculator Update

Hydrogen cyanide (HCN) reactions were added in FDS 6.7.6 and are supported in PyroSim 2021.3. As part of this update, we have added HCN support in our Combustion Calculator which helps solve the stoichiometric equation to define a reaction. This calculator is provided as a free download with an included tutorial.